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1
Lee, Ming-Yi. "XvERD15, an early-responsive gene to stress from Xerophyte viscosa." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4287.
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Includes bibliographical references (leaves 44-54).Genes that are upregulated in the early response to stress are not well understood. ERD15 (early-responsive to dehydration) in Arabidopsis and its homologues in various other plants have been shown to be upregulated within I hr post-exposure to dehydration and high salinity stress treatments. There is however limited literature on the functionality of ERD15. A cDNA showing homology to ERD15 was isolated from a library generated by low temperature stress treatment of Xerophyta viscosa and was subsequently named XvERD15.
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Thompson, Iris Lee. "Agricultural Systems in Babati : Zea mays and its alternatives." Thesis, Södertörn University College, School of Life Sciences, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-2660.
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This paper aims to give an understanding on the aspects that influences the choice of cropsand agricultural methods in Babati, Tanzania. Drought is a reoccurring problem in this part ofTanzania, which affects a majority of the towns’ farmers. This fact is likely to affect thechoice of crop as well as the limitations when it comes to the choices in cultivation. But thechoice itself has implications on its surrounding and can be affected by the surrounding. Tounderstand the circumstances, a wider picture will be depicted and an evaluation of thegeography of Babati and on its climate conditions. The results from this study suggest thatlack of crop rotation pose as a problem that should be studied. Furthermore, green manurefrom legumes and plants like Tithonia could be a less expensive alternative but can stillfunction as an effective fertilizer. Concerning the drought issue the study can not concludethat drought resistant crops would have any big improving effects. Nevertheless there is someevidence advocating that it could be apart of the solution in terms of avoiding some of thenegative effects brought on by drought.
3
Dace, Halford. "Metabolomics of desiccation tolerance in Xerophyta humilis." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9111.
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Includes bibliographical referencesResurrection plants are unique in the ability to survive near complete water loss in vegetative tissues without loss of viability. In order to do so, they employ multifaceted strategies which include structural adaptations, antioxidant and photoprotective mechanisms, and the accumulation of proteins and metabolites that stabilise macromolecules. A full understanding of the phenomenon of vegetative desiccation tolerance will require a systems view of these adaptations at the levels of the genome, the control of gene expression, and the control of metabolic pathways. This dissertation reports a high-throughput metabolomic analysis of the changes that occur in vegetative tissues of resurrection plant Xerophyta humilis during dehydration. A combination of chromatography, mass spectrometry and nuclear magnetic resonance revealed numerous primary and secondary metabolites in the plant. Multivariate statistics identified a subset of metabolites that were significantly up- or down-regulated in response to water deficit stress. These metabolites both confirmed existing observations about the metabolic response of X. humilis to drying and revealed compounds not previously known to be associated with this response. Desiccation-associated metabolites were mapped onto known biochemical pathways, to generate hypotheses concerning possible regulatory schemes in the stress response, inviting deeper investigation in future.
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Lyall, Rafe. "Regulation of desiccation tolerance in Xerophyta seedlings and leaves." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22853.
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A small, diverse group of angiosperms known as resurrection plants display vegetative desiccation tolerance and can survive loss of up to 95% of cellular water, a feat only seen in the seeds and pollen of other angiosperms. Xerophyta humilis is a resurrection plant native to Southern Africa that has been the target of previous transcriptomic and proteomic studies into the mechanisms of plant desiccation tolerance. The aim of this study was to investigate the hypothesis that vegetative desiccation tolerance is derived from the networks that control desiccation tolerance in seeds and germinating seedlings in angiosperms, particularly the epigenetically silenced seed maturation genes. Germinating seedlings of X. humilis and the related resurrection plant X. viscosa were found to be VDT from the earliest stages of germination, and exhibited the characteristic vegetative trait of poikilochlorophylly as seen in mature leaves. The X. humilis desiccation transcriptome comprising 76,768 distinct gene clusters was successfully assembled from sequencing samples at five relative water contents (100%, 80%, 60%, 40% and 5%) to identify the networks activated in response to water loss. Desiccation was associated with successive waves of transcription factor induction, as well as widespread down-regulation of histone modification enzymes. Many seed-specific genes, such as late embryogenesis abundant (LEA) proteins, seed storage proteins and oleosins, were induced in vegetative tissue. LEA transcripts in particular were highly up-regulated during desiccation, and the large number of distinct LEA transcripts (over 150) suggests possible LEA gene expansion in Xerophyta compared to desiccation-sensitive plants. Components of the PYL/SnRK2/ABF ABA-signalling pathway were also induced, although the ABF transcription factors activated in response to desiccation were most similar to those induced by drought in A. thaliana rather than seed maturation. Of the canonical seed master regulators (such as the LEC1/ABI3/FUS3/LEC2 network and ABI5) only three ABI3 transcripts were expressed, all of which encoded proteins lacking the seed motif-binding B3-domain. The results of this study suggest that vegetative desiccation tolerance in X. humilis is not associated with re-activation of seed master regulators in vegetative tissue, but may instead involve activation of seed genes by vegetative drought response regulators.
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Fan, Cynthia. "Characterisation of two desiccation-linked dehydrins from Xerophyta humilis." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22723.
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In response to abiotic stresses, organisms throughout the plant kingdom, as well as microorganisms and micro-animals such as nematodes or tardigrades, have been observed to express Late Embryogenesis Abundant (LEA) proteins as protective mechanisms. However, despite two decades of research, little is understood about their physiological functions and this has led to extensive nomenclature, with a large amount of redundancy. The primary reason for this lack of insight into LEA protein functions is their highly hydrophilic and intrinsically disordered nature. Intrinsically disordered proteins (IDPs) cannot be studied using conventional methods of structural analyses such as X-ray crystallography and, therefore, alternative techniques are required. A combination of transgenic and in vitro studies have also shown that LEA proteins are most likely to behave as molecular chaperones by binding water and ions, preventing macromolecular aggregation and protecting enzymatic activity during dehydration. This study characterized two dehydrins that were expressed during dehydration in the desiccation tolerant plant, Xerophyta humilis. From a transcriptome analyses on X. humilis, cDNA for the two dehydrins were obtained. These sequences were first analysed using various in silico tools in order to identify putative dehydrin-specific characteristics. Subsequently, these two dehydrins were cloned and expressed for production of recombinant dehydrin protein. These proteins were then analysed in terms of structural and functional characteristics. Structurally, through the use of circular dichroism in an in vitro system, both dehydrins demonstrated the shift towards being increasingly alpha-helical when placed in environments of decreasing water content. The role of these two dehydrins in stabilizing enzymes during dehydration was subsequently investigated using citrate synthase (CS) and lactate dehydrogenase (LDH). The preservation of enzyme activity was observed in both CS and LDH. This preservation of enzyme activity was further maintained by the presence of trehalose. Anti-aggregation roles were also investigated, however, neither dehydrin demonstrated significant ability to minimize the aggregation of LDH. This study hopes to establish a pipeline for characterizing LEA proteins using structural and functional assays in order to provide alternative means of LEA protein classification.
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Onyemata, Ezenwa James. "Structural and functional studies of XvPrx2, a type II peroxiredoxin protein from the resurrection plant xerophyta viscosa." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/5206.
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Philosophiae Doctor - PhDXvPrx2 is a 1-Cys-containing member of the Prx5 subfamily of peroxiredoxins isolated from the resurrection plant Xerophyta viscosa. It is reported to be up-regulated during periods of desiccation and to protect nucleic acids and cellular proteins from oxidative damage through scavenging of reactive oxygen species, suggesting that it may play a role the desiccation tolerance of X. viscosa (Govender, 2006). Members of the Prx5 subfamily have previously been reported to occur as non-covalent homodimers associating across an A-type interface. PrxD from Populus tremula, a close homologue of XvPrx2, forms disulphide bonds with glutathione (glutathionylation) resulting in the unfolding of the Cp-loop and α2-helix and disruption of the homodimer, on the basis of which glutathionylation has been proposed as a physiological mechanism for regeneration of all members of the Prx5 subfamily (Noguera-Mazon, et al., 2006b).
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Chireshe, Nyaradzo. "Stomatal control during dessication in the resurrection plant Xerophyta humilis." Bachelor's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/24964.
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Stomatal apertures on leaves of the resurrection plant Xerophyta humilis were monitored microscopically in order to characterize stomatal regulation during a dehydration time course. In addition, the effect of exogenous application of the stress hormone ABA on stomatal regulation was followed. X humilis stomatal regulation appears to be initially similar to that typical of desiccation sensitive plants, but differed in that stomata did not all close at once but at a slower rate to control the drying rate of the plant, this gave time for protection mechanisms to be laid down. The signal hormone ABA was found to have strong stomatal control on the adaxial surfaces of leaves but weak control on the abaxial leaf surfaces, thus it is difficult to say that ABA regulates the process until RWC of below 50%, where stomatal apertures open as a result of shrinkage of guard cells due to loss of water.
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Ellick, Tamaryn Lorean. "Investigation of XvSap promoters from the resurrection plant, Xerophyta viscosa." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10452.
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Includes bibliographical references.The XvPSap1 promoter derived from Xerophyta viscosa has been demonstrated to be stress-inducible during dehydration in transgenic Nicotiana tabacum, black Mexican sweetcorn cells and Zea mays. To improve this promoter, for future applications in crop biotechnology, four shortened promoters, XvSap1D, E, F and G were generated by mutagenesis. The generated promoters had circa 50% reduction in size and contained the 5' proximal and 3' distal regions of the XvPsap1 promoter with the internal region removed. The shortened promoters displayed no significant sequence homology to any other known plant promoter, besides XvPSap1. In addition to the shortened promoters, a newly discovered full length XvPSap2 promoter, showing a 56.41% homology with XvPSap 1 was also assessed in this study.
9
Ndima, Tozama Beauty. "Gene expression associated with drought tolerance in Xerophyta viscosa Baker." Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4309.
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Bibliography: leaves 89-100.Herophyta viscosa (Baker) is a monocytyledonous resurrection plant that can tolerate extremes of dessication. Upon rewatering, it rehydrates completely and assumes its full physiological activities. Studies on changes in gene expression associated with dehydration stress tolerance were conducted. A cDNA library constructed from m RNA isolated from dehydrated (85%, 37% and 5% relative water content) X. viscosa leaves, was differently screened. Of the 192 randomly selected cDNAs screened, 30 showed higher expression levels when X. viscosa was dehydrated while 20 showed lower expession. XVLEA, XVDH and XVLEC represent three cDNAs that were upregulated during dehydration stress. XVLEA showed the highest identity at the amino acid level with a late embryogenesis abundant protein, LEA29G, from Gossipium hirsutum (30%) and LEA D-29 from cotton (50%). XVDH exhibited significant identity to dehydrin proteins from Arabidopsis thaliana (45%) and Pisum sativum (43%) at the amino acid level. It encodes a glycine-rich protein (27kDa) which is largely hydrophilic and contains a hydrophobic segment at the C-terminus. XVLEC showed 28% identity and 50% similarity to a lectin-like protein from Arabidopsis thaliana. Southern blot analysis confirmed the presence of the three cDNAs in the X.viscosa genome. Both XVLEA and XVDH transcripts were highly expressed during dehydration- (37% RWC) and rehydration (4%, 32%, 72% RWC) treatment of the plant ͌ 1.0kb was observed. However, with XVDH a transcript of ͌ 1.0 kb and 1.09 kb were observed. XVDH transcripts accumulated in X. viscosa plants in response to low temperature, heat and dehydration stresses, as well as to exogenous supply of abscisic acid, ethylene and methyl jasmonate. Localization studies of the XVDH encoded protein showed that XVDH is located in the plasma membrane-cell wall region.
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Gabier, Hawwa. "Label-free proteomic analysis of Xerophyta schlechteri leaf tissue under dehydration stress." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33783.
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Most higher plants cannot withstand severe water loss, except for a small group of angiosperms called resurrection plants. They can survive severe water loss without the loss of viability by employing mechanisms that aid them in desiccation tolerance. Desiccation tolerance in resurrection plants is a complex and multifaceted phenomenon and allows the plant to implement various strategies for survival. The focus of this study was a label-free proteomic analysis of Xerophyta schlechteri, a monocotyledonous and poikilochlorophyllous resurrection plant, in response to desiccation. The study investigated some of the physiological, morphological and biochemical changes of X. schlechteri leaf tissue in response to dehydration followed by proteomic analyses using a spectral counting approach. The differentially expressed proteins were identified and quantified and then subjected to gene ontological analyses to identify relevant biological processes involved in desiccation tolerance. The proteomic data was finally correlated to and validated using metabolomic analyses. X. schlechteri was subjected to a controlled dehydration stress treatment, in which changes in the relative water content (RWC) of leaf tissues, the associated changes in processes outlined above and further expanded on below, were determined. Three physiological stages were tentatively identified, namely, the early response to drying (ERD) which represents ~ 80 - 70% RWC (1.61 gH2O g ̄ˡ dwt -1.5 gH2O g ̄ˡ dwt), a mid-response to drying (MRD) represented by ~ 60 - 40% RWC (1.5 gH2O g ̄ˡ dwt -1.0 gH2O g ̄ˡ dwt) and a late response to drying (LRD), represented by ~ 40 - 10% RWC (1.0 gH2O g ̄ˡ dwt - 0.5 gH2O g ̄ˡ dwt). Morphological changes in the late stages of drying were marked by loss of green chlorophyll, increased purple anthocyanin production and leaf folding along the midrib with the abaxial surface exposed to light. Chlorophyll content analyses showed a significant decrease in chlorophyll content in the dehydrated leaf tissue as compared to the fully hydrated state. Biochemical assays to measure the activity of enzymatic antioxidants, namely, ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) were done at selected RWC points. There was a significant increase in antioxidant enzyme activity for APX, CAT, GR and SOD in the dehydrated plant tissue. The label-free proteomics approach utilized, identified a total of 3125 unique proteins in the X. schlechteri leaf tissue across the dehydration treatment of which a combined 517 proteins were significantly differentially expressed in response to drying. Amongst the differentially expressed proteins, 253 proteins were upregulated, and 264 proteins were downregulated. This was followed by functional analyses and classification of gene ontologies using bioinformatics tools such as Blast2GO, MapMan and KEGG. This allowed the identification of certain biological processes and pathways involved in the X. schlechteri desiccation response. Key biological processes and molecular processes were differentially expressed across the drying stages, these included photosynthesis, cellular respiration and antioxidant activity, respectively. The proteomic analysis was complemented and validated using metabolomics approaches based on GC MS/MS and LC/MS. The abundance of specific sugars, sugar alcohols, fatty acids, organic acids, phytohormones and amino acids of X. schlechteri during desiccation were investigated. Sugars such as raffinose and sucrose are known to play a protective role in desiccation and were found to be abundant in MRD and LRD leaf tissue while, L-histidine, an amino acid which plays a critical role in plant growth, was found to be more abundant in LRD tissue as compared to MRD. The phytohormone abscisic acid, invoked in desiccation tolerance was found to be abundant at LRD and less abundant at ERD. The metabolomic data suggested that the regulation of metabolites was towards reducing possible toxic metabolites while increasing the expression of metabolites that help and protect plant cell integrity from the negative effects of desiccation. The use of a label-free proteomics approach complemented with metabolomics allowed the identification and validation of biological processes and pathways potentially involved in establishing desiccation tolerance in X. schlechteri. As far as we are aware, this is the first label-free proteomic analysis of X. schlechteri in response to dehydration.
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Radermacher, Astrid Lillie. "Desiccation-driven senescence in the resurrection plant Xerophyta schlechteri (Baker) N.L. Menezes." Doctoral thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31708.
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Drought-induced senescence is a degenerative process that involves the degradation of cellular metabolites and photosynthetic pigments and uncontrolled dismantling of cellular membranes and organelles. Angiosperm resurrection plants display vegetative desiccation tolerance and avoid drought-induced senescence in most of their tissues. Developmentally older tissues, however, fail to recover during rehydration and ultimately senesce. Comparison of the desiccation-associated responses of older senescent tissues (ST) with non-senescent tissues (NST) will allow for understanding of mechanisms promoting senescence in the former and prevention of senescence in the latter. In the monocotyledonous resurrection plant Xerophyta schlechteri (Baker) N.L.Menezes, leaf tips senesce following desiccation, whereas the rest of the leaf blade survives. This study characterised structural, metabolic and transcriptional changes in ST and NST at varying water contents during desiccation and rehydration. Light and transmission electron microscopy was used to follow anatomical and subcellular responses, and metabolic differences were studied using gas chromatography-mass spectrometry and colorimetric metabolite assays. These results show that drying below 35% relative water content (0.7 gH2O/g dry mass) in ST resulted in the initiation of age-related senescence hallmarks and that these tissues continue this process after rehydration. Analysis of the transcriptome was done using RNA-Seq, which was subject to differential expression analysis and network analysis to elucidate the potential mechanisms for senescence regulation in this species. Significantly increased transcription of senescence associated genes was observed in the air dry sampling point, indicating that initiation of cellular death occurred below 20% RWC. Network analysis based on Pearson correlation revealed a high degree of clustering of these genes, suggesting co-regulation. The majority of these genes had two enriched motifs in their upstream regions, identified as binding sites for WRKY and other transcription factors. A model integrating these observations is presented, with insights into how senescence is initiated in ST and repressed in NST.
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Waters, Robyn. "Molecular characterisation of the "LEAome" in the resurrection plant Xerophyta humilis (Baker)." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20012.
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Studies on resurrection plants and other anhydrobiotic organisms, have shown that Late Embryogenesis Abundant (LEA) proteins are expressed upon the onset of desiccation and are therefore inferred to be associated with the desiccation tolerance response. To date, despite some 25 years of research on these proteins, there is still very little understanding of the physiological function(s) of the majority of LEAs. This is because they lack tertiary structure in the hydrated state, making assigning of physiological roles difficult.
This MSc study was undertaken to investigate the gene expression of a set of 21 putative LEAs during dehydration and subsequent rehydration stress, in the resurrection plant Xerophyta humilis (Baker). Recombinant proteins were expressed for 3 of the LEA genes from this set in order to perform structural studies and to ascertain their LEA status. These studies were conducted with the purpose of shedding light on the role of LEAs in desiccation tolerance, to add to the ever-growing transcriptomic and proteomic data, and to the current knowledge of these enigmatic proteins. Quantitative real-time gene expression (qPCR) analysis was conducted on the set of 21 full length X. humilis cDNA clone nucleotide sequences, with similarities to late embryogenesis mRNA sequences, derived from a study conducted by Collett et al., (2004). Expression analysis was conducted in both leaves and roots, across a dehydration and rehydration profile of X. humilis. Of this total group of 21 full length cDNA clones, three LEAs; XhLEA2-3 and XhLEA2-6 (two putative Group 2 LEA genes) and XhLEA3-5 (a putative Group 3 LEA gene), were chosen for cloning and expression studies. cDNAs of these XhLEAs were cloned into a modified bacterial expression vector and recombinant protein expression was attempted in E. coli.
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Shen, Arthur Yen-Hsiang. "The transcriptome response of leaves of the resurrection plant, Xerophyta humilis to desiccation." Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13009.
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Includes bibliographical references.In angiosperms, desiccation tolerance, a genetic trait that enables tissues to survive loss of more than 95% of cellular water is widely observed in the seeds, but is only found in the vegetative tissues of a small group of species known as the resurrection plants. Xerophyta humilis is a small resurrection plant indigenous to Southern Africa. In this study, the hypothesis that vegetative desiccation tolerance is derived from an adaptation of seed desiccation tolerance was tested by characterizing changes in the transcriptome of X. humilis leaves during desiccation. The mRNA transcript abundance of a set of 1680 X. humilis genes was analyzed at 6 different stages of water loss in the leaves of X. humilis. Functional enrichment analysis showed that genes that were down-regulated during desiccation were over-represented with genes involved in photosynthesis, cellular developmental processes, as well as transcription regulator activity. Three distinct clusters of up-regulated genes were identified. The earliest set of up-regulated genes were enriched with genes associated with the turnover of proteins and the simultaneous synthesis of proteins required for protection. Enrichment also included genes associated with lipid body synthesis, as well as the transport of storage proteins to vacuoles. Two groups of late desiccation up-regulated genes were also identified, their expression only increased at later stages of desiccation and remained high in the desiccated leaves.
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Neumann, Alexis Joy. "Characterisation of galactinol synthase II (XvGolSII) from the resurrection plant Xerophyta viscosa (Baker)." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/6623.
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The monocotyledonous Xerophyta viscosa belongs to a unique group of angiosperms known as resurrection plants. These plants possess a number of unique characteristics which allow them to survive and cope for extended periods with extreme abiotic stresses such as dehydration and cold stress. It is therefore of great interest to understand and elucidate the various molecular mechanisms which are specifically regulated in response to abiotic stress by identifying genes and proteins which may contribute to abiotic stress tolerance. These genes could potentially be utilized in the development of crops with improved tolerance to abiotic stresses. The aim of this study was to preliminarily characterize XvGolSII, a galactinol synthase, which had been isolated from a X. viscosa cold stress cDNA library. In this study, the XvGolSII cDNA was sequenced and both the nucleic and amino acid sequence analysed through in silico analysis. The XvGolSII cDNA sequence was shown to be 1434 bp in length, with an open reading frame (ORF) of 1018 bp. This ORF encodes a 339 amino acid protein with a molecular weight of 38.7 kDa, containing a characteristic hydrophobic carboxyterminal pentapeptide, APSAA. Recombinant XvGolSII protein was successfully expressed in E. coli BL21 cells using the pET29b expression vector. The recombinant XvGolSII protein showed in vitro galactinol synthase activity via an activity assay using HPAEC-PAD, where it produced galactinol from the substrates myo-inositol and UDPgalactose. Subcellular localisation examination, using an XvGolSII-YFP fusion protein, indicated localisation to the cell membrane of onion epidermal cells. Quantitative real time PCR analysis showed XvGolSII to be significantly down-regulated during dehydration stress while mildly up-regulated during the early stages of cold stress, though the latter increase was not significant. Western blot analyses did not detect XvGolSII in total protein extracted from X. viscosa leaf tissue during dehydration and rehydration treatments, using polyclonal antibodies generated from the XvGolSII recombinant protein. This study successfully characterized XvGolSII at the molecular level and provides a basis for further investigation of the role of XvGolSII in abiotic stress tolerance.
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Ngubane, Nqobile A. C. "Cloning and characterisation of LEA1-EM genes in the resurrection plant, Xerophyta humilis." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4312.
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Includes abstract.Includes bibliographical references (leaves 75-86).
The presence and expressIon patterns of orthologues of LEA group 1 genes has been characterised in the resurrection plant, Xerophyta humilis. The group I LEAs (Em I and Em6) were first identified as proteins that were abundantly and specifically expressed during the desiccation and germination phase of angiosperm seed development. The group I LEA genes are characterised by the presence of one or more tandemly repeated 20-amino acid motifs that are particularly rich in Gly residues.
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Walford, Sally-Ann. "Isolation and characterisation of an Hsp90 homologue from the resurrection plant Xerophyta viscosa." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/20194.
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Bibliography: pages 128-163.Prior to this study, a eDNA library of dehydrated Xerophyta viscosa was differentially screened and several genes were found to be upregulated during dehydration. One of these cDNAs was found to share a high degree of sequence identity with the ER-Iocated Hsp90 or Grp94 family of proteins (hereafter referred to as XVGrp94) and forms the basis of this work. The XVGrp94 eDNA was found to be truncated at the 5· terminus and a full length eDNA was isolated using SMART-RACE™ (§witching Mechanism gt 5' end of RNA Iranscript- Random ~mplification of Complementary .!;rids). This eDNA was sequenced and appeared to be a representative of the Hsp90 family of genes. The putative gene contained an ORF (Open Reading frame) potentially coding for an 812 amino acid protein with a calculated size of 92.83 kDa. It shares 85% homology with other Hsp90s from plants and it contains several characteristic features of these proteins. Additionally, it contains the ER (endoplasmic reticulum) targeting and retention signals. Southern blot analysis confirmed the presence of the gene in the X. viscosa genome possibly as a member of a family of closely related genes. Northern blot analysis revealed a transcript size of 2.8 kb, however, expression patterns of the transcript could not be established. Western blot analysis showed that the XVGrp94 concentration increased significantly in response to heat and dehydration, and a slight increase was observed in response to conditions of high salt, but no response was seen in response to high light, cold or exogenous ABA (abscisic acid) application. The XVGrp94 open reading frame was cloned into the pProEX HTa expression vector and expressed in E. coli, but purification of the recombinant protein was not successful.
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Loffell, D. A. "Aspects of the physiology of the resurrection plant Xerophyta Humilis under different environmental conditions." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/7724.
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Bibliography: leaves 92-100.Xerophyta humilis is a resurrection monocot that is able to survive drying of its tissues to an air-dry state. in order to assess the alidity of laboratory-based experimentation, and the results obtained from such studies, a comparison of aspects of X. humilis physiology under different environmental conditions was undertaken. Analyses of chlorophyll fluorescence, gas exchange parameters, pigment concentrations and electrolyte leakage were performed on plants dehydrated under laboratory conditions differing with respect to light intensity ("high light" (ca. 1400 ųmol.m-². s-¹) and "low light" (ca. 400 ųmol. m-². s-¹)). Physiological parameters were also examined during rehydration under high and low light laboratory conditions, and natural field conditions. Plants maintained fully hydrated for some time were also examined under laboratory conditions for the occurrence of rhythmic patterns in their daily physiology, and for any evidence of acclimatisation to the different environments.
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Dennis, Timothy James. "The functional analysis of XhLEA3-2 - a LEA_4 from the resurrection plant, Xerophyta humilis." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27094.
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Climate change is a pressing reality in the current era. Changing environmental conditions and limited water availability are associated with the loss of arable land in areas where farming has traditionally thrived. Thus, linked to climate change, is the risk of a global food shortage. Resurrection plants are phenomenal in that they are able to survive extended periods of drought in a state of anhydrobiosis and then resume full metabolism upon rehydration. These plants serve as models to scientists and genetic engineers who hope to replicate, to a degree, the 'resurrection phenomenon' in drought sensitive crop species. The ability of resurrection plants to survive drought needs to be studied on a molecular level if it is to be implemented in transgenic crops. Currently, the molecular mechanisms of desiccation tolerance are only somewhat understood, and considerable investigation is still required. Xerophyta humilis is a monocotyledonous resurrection plant in which one of the responses to extreme water loss is the upregulation of several Late Embryogenesis Abundant (LEA) genes. The protein products of these genes, called LEA proteins, are known to be correlated with abiotic stress tolerance in plants, invertebrates and microorganisms. However, the precise molecular mode(s) of action of LEA proteins are still poorly understood. In this study, a group LEA_4, LEA protein, which we have termed XhLEA3-2, shown to be transcriptionally upregulated during desiccation of the resurrection plant X. humilis, has been characterized. A bioinformatic, predictive analysis was performed to detect any LEA-like characteristics of XhLEA3-2. Recombinant XhLEA3-2 was produced in Escherichia coli, purified, and used to generate XhLEA3-2 specific antibodies for expression analyses. The ability of XhLEA3-2 to function as a molecular chaperone was assessed using a lactate dehydrogenase (LDH) enzyme stability assay. Transgenic expression of XhLEA3-2 in E. coli and tobacco was also investigated. In summary, this thesis demonstrates that XhLEA3-2: has typical LEA protein properties according to bioinformatic analyses, has two close homologs in X. viscosa, is present in dry X. humilis leaf tissue, has homologs present in dry X. viscosa leaf tissue, has some molecular chaperone activity, can protect E. coli from desiccation but not from osmotic stress, and can be transiently expressed in tobacco.
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Chopera, Denis Rutendo. "Molecular characterization of XvlNO1, a myo-inositol 1-phosphate synthase gene from Xerophyta viscosa." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4249.
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Includes bibliographical references.Myo-inositol I-phosphate synthase (INO 1) catalyses the conversion of glucose-6-phosphate to myo-inositol I-phosphate, which is subsequently dephosphorylated to myo-inositol. Myo-inositol is a precursor for a number of important metabolites that include membrane components, storage molecules, phytohormones and a variety of osmoprotectants. Xerophyta viscosa Baker (Family Velloziaceae) is a monocotyledonous angiosperm which has the ability to resume full physiological function after desiccation. The full-length cDNA for INO1 from X viscosa was isolated using the RACE technique.
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Proctor, Jessica Diane. "The functional characterisation of the XhABFA transcription factor from the resurrection plant Xerophyta humilis." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/32973.
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Vegetative desiccation tolerance (VDT), the ability to survive loss of up to 95% of cellular water in leaves and roots, is rare amongst vascular plants. However, the trait has evolved multiple times in a small, diverse group of angiosperms collectively known as “resurrection plants”. The physiological, morphological and metabolic changes that take place during VDT have been well characterised. However, in stark contrast, the underlying regulatory mechanisms that activate the VDT programme are not well understood. A widely held view is that VDT in resurrection plants may have arisen by a genetic reprogramming of the seed maturation pathways common to the vast majority of angiosperms. In Arabidopsis thaliana, the activation of seed maturation genes is regulated by the canonical LAFL (LEC1, ABI3, FUS3 and LEC2) network of transcription factors (TFs). However, thus far there is limited evidence to indicate that the LAFL network itself regulates VDT in resurrection plants, though downstream components of this network (such as the ABI3 regulon) are active. Recently, in a transcriptomic study of the resurrection plant Xerophyta humilis, it was found that the LAFL TFs are induced during seed maturation but not during vegetative desiccation. Instead, members of the ABF family of TFs, which are associated with the vegetative abiotic stress response, were strongly upregulated, particularly XhABFA. This finding supports an alternative hypothesis: namely that the activation of VDT in X. humilis has evolved by the rewiring of the transcriptional network that controls the abiotic drought stress response in desiccation sensitive plants. The aim of this study was to investigate whether XhABFA is able to bind to the promoters of and activate the expression of three genes, XhPER1, XhECP63 and XhDSI-1VOC, which are seed-specific in desiccation sensitive plant species but are upregulated in X. humilis leaves as they desiccate. Two experimental approaches were taken in order to determine this: transient expression of XhABFA in A. thaliana protoplasts transfected with promoter:firefly luciferase reporter constructs, and a Yeast One-Hybrid analysis. A. thaliana protoplasts expressing XhABFA displayed significantly greater firefly luciferase activity than protoplasts transfected with the empty vector, indicating that XhABFA can drive transcription from the promoters of these three canonical seed genes. This is the first evidence of activation of seed-specific genes in desiccating leaves by a “vegetative” abiotic stress TF and suggests that components of the drought stress response may be important in activating VDT in X. humilis. This finding may help shed light on our understanding of the regulatory networks underpinning VDT in angiosperm resurrection plants.
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Myers, Marleen. "Molecular genetics of the floral response in Xerophta humilis." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4306.
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Ginbot, Zekarias Gebremedhin. "Characterization of two, desiccation linked, Group 1 LEA proteins from the resurrection plant Xerophyta humilis." Doctoral thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10523.
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Studies on resurrection plants and other anhydrobiotic organisms show expression of Late Embryogenesis Abundant (LEA) proteins associated with desiccation tolerance. However, the precise role of these proteins has not been described. This study was undertaken to investigate expression, structure and function of XhLEA1-4S1 and XhLEA1-1S2, Group 1 LEA proteins from Xerophyta humilis, in order to shed light on their role in desiccation tolerance. Complementary DNA (cDNA) of these XhLEAs were cloned into bacterial expression vectors and the recombinant proteins expressed in E. coli. Antibodies were generated and used in determination of expression conditions and immunolocalization studies.
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Govender, Kershini. "Characterisation of XvPrx2 : a type II peroxiredoxin isolated from the resurrection plant Xerophyta viscosa (Baker)." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4268.
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Includes bibliographical references.Knowledge of the biochemical and molecular mechanisms by which plants tolerate environmental stresses is necessary for genetic engineering approaches to improve crop performance. A unique feature of resurrection plants, such as Xerophyta viscosa, is their ability to cope with severe water loss of greater than 90%. A full-length cDNA library was synthesised from a cold stressed X viscosa plant. Sequencing and BLAST analysis revealed the identity of sixty genes. A type 2 peroxiredoxin (XvPrx2) was selected for further analyses as it was observed, by northern analyses, to be stress-inducible. The XvPrx2 protein was confirmed to be involved in the stress response by Western analyses. The XvPrx2 gene, which displays highest identity to a rice orthologue, has an open reading frame of 162 amino acids, and codes for a hydrophilic polypeptide of 162 residues with a predicted molecular weight of 17.5 kDa. The XvPrx2 polypeptide displays significant identity with other plant type II Prxs, with an absolutely conserved amino acid sequence proposed to constitute the active site of the enzyme (PGAFTPTCS). The XvPrx2 protein has a single cataly1ic cysteine residue at position 51 similar to Prxs from Oryza sativa and Candida boidinii. A mutated protein (XvV76C) was generated by converting the valine at position 76 to a cysteine resulting in a conformational change as determined by limited proteolysis. An in vitro DNA protection assay showed that, in the presence of either XvPrx2 or XvV76C, DNA protection occurred. In addition, an in vivo assay showed that increased protection was conferred on cell lines over-expressing either XvPrx2 or XvV76C. Several upstream promoter regions were identified for the XvPrx2 gene using the splinkerette method. Southern and two dimensional gel analyses revealed that multiple XvPrx2 homologues exist within the X viscosa genome. These homologues have similar pI values to Arabidopsis orthologues. Immuno-cytochemical data revealed that XvPrx2 is localised to the chloroplast, however, this could be attributed to cross reactivity with a chloroplastic homologue. Using YFP technology, the protein was observed to be expressed in the cytosol, and this location is supported by the absence of an upstream targeting signal in the XvPrx2 sequence. The XvPrx2 activity was maximal with DTT as electron donor and HzOz as substrate with t-BOOH being the next preferred. Using Trx£. coli a 2-15 fold lower enzyme activity was observed. The XvPrx2 activity with GSH was significantly lower and Grx had no measurable effect on this reaction. The XvV76C protein displayed significantly lower activity compared to XvPrx2 for all substrates assessed. Enzymatic kinetic parameter values determined for XvPrx2 using DTT as electron donor and HzOz as substrate were: Km = 45 IlM, V max = 278 Ilmol min-I.mg-I protein, kcat 6.173 x 103 s-1 and kcaJKm = 0.136 X 103 IlM-1.s-l. Based on knowledge-based models of XvPrx2 and XvV76C no structural differences were observed between the two molecules.
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Sattar, Shakiera. "Molecular characterisation of the lateral organ boundaries gene (XvLOB) from the resurrection plant Xerophyta viscosa." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11087.
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The aim of this study is to preliminary characterise XvLOB, a LOB domain containing gene, which has been isolated from a dehydration stress library in X. viscosa. In this study the gene was isolated and cloned, the DNA and amino acid sequences were analysed by in silico analysis, the recombinant XvLOB protein expressed, subcellular localisation examined and both the transcript and protein expression levels in response to dehydration was investigated.
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Milborrow, Evan. "Non-coding RNA networks regulating leaf vegetative desiccation tolerance in the resurrection plant Xerophyta humilis." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29437.
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Common to orthodox seeds, desiccation tolerance (DT) is exceedingly rare in the vegetative tissues of modern angiosperms, being limited to a small number of "resurrection plants". While the molecular mechanisms of DT, as well as the transcription factors regulating the seed and vegetative DT programmes, have been identified, very little is known with regards to the role of regulatory noncoding RNAs (ncRNAs). To investigate the presence and roles of possible ncRNA players, RNA-Seq was performed on desiccating Xerophyta humilis leaves and a bioinformatic pipeline assembled to identify the potential decoy lncRNAs and miRNAs present. Interaction mapping was performed, identifying a number of small regulatory networks each regulating a small subset of the desiccation transcriptome. Predicted networks were screened for function related to DT and expression consistent with functional regulatory interactions. Of the predicted networks, two appear highly promising as potential regulators of key DT response genes. The results indicate that differentially expressed (DE) desiccation response ncRNAs are present in the vegetative tissues of X. humilis and likely play a key role in the regulation of DT. This suggests that ncRNAs appear to play a more important role in DT than previously thought, and may have facilitated the evolution of vegetative DT through reprogramming of seed DT programs in vegetative tissues.
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Rossetto, Estela de Sousa. "Aspectos celulares de folhas de Xerophyta plicata Spreng. (Velloziaceae), durante os processos de dessecação e revivescencia." [s.n.], 1992. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315426.
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Orientador: Mary Anne Heidi DolderDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Xerophyta plicata Spreng. (Velloziaceae) é uma Angiosperma brasileira tolerante à dessecação, que ocorre em afloramentos do RJ ao RN. Embora não perca as folhas nos períodos elas ficam amarelas, encolhidas, dobradas e torcidas. Quando a agua volta, as folhas se distendem e voltam a ficar verdes. As células do mesofilo sobrevivem aos ciclos de saída e de entrada de agua por meio de alterações ultra-estruturais responsaveis pela manutenção da viabilidade celular. Essas alterações parecem processos degradativos limitados, que mantém remanescentes das estruturas vitais. A utilização de solução fixadora não aquosa previne a ocorrência de artefatos de técnica nas folhas secas, que são muito reativas à agua¿Observação: O resumo, na íntegra poderá ser visualizado no texto completo da tese digital
Abstract: Xerophyta plicata Spreng.(Velloziaceae) is a Brazilian desiccation tolerant Angiosperm that occurs in granitic rock outcrops from Rio de Janeiro State to Rio Grande do Norte State. Although leaves do not fall during the drought periods, they become yellow, shrinked, folded and twisted. When water is available again, leaves distend and retake the green colour. Mesophyll cells survive the water inlet and outlet cycles by means of ultrastructural changes that are responsable for maintaining their viability. These changes are similar to limited degradative processes in which remnants of the vital structures are preserved. The use of a non-aqueous fixative solution for dry tissues prevent the occurrency of fixation artefacts in these that are very reactive to water....Note: The complete abstract is available with the full electronic digital thesis or dissertations
Mestrado
Mestre em Biologia Vegetal
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Walford, Sally-Ann. "Activation of seed-specific genes in leaves and roots of the desiccation tolerant plant, Xerophyta humilis." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4349.
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Includes abstract.Includes bibliographical references (leaves 131-169).
The ability of tissues to survive almost complete loss of cellular water is a trait found throughout the plant kingdom. While this desiccation tolerance is common in seeds of most angiosperms it is rare in their vegetative tissues. Xerophyta humilis (Bak.) Dur and Schintz belongs to a small group of resurrection angiosperms and it possesses the ability to withstand extreme desiccation of greater than 90% in both its seeds and vegetative tissues and return to active metabolism upon rehydration. We have tested the hypothesis that vegetative desiccation tolerance in angiosperms has evolved as an adaptation of seed desiccation tolerance.
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Bajic, Jelena. "Exploring the longevity of dry Craterostigma wilmsii (homoiochlorophyllous) and Xerophyta humilis (poikolichlorophyllous) under simulated field conditions." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4240.
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Includes bibliographical references (p.143-164).In the field C. wilmsii (homoiochlorophyllous) and X humilis (poikilochlorophyllous) plants do not experience drought longer than two and six months, respectively. In this study longevity of dry C. wilmsii and X. humilis plants was investigated for up to 10 months under four different sets of conditions. Some conditions resembled those under which the two species would experience drought in the field, but also included those that resemble the accelerated aging conditions used in seed studies.
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Bresler, Andries Petrus. "Molecular characterisation of XvVTC2, a gene coding for a GDP-L-galactose phosphorylase from Xerophyta viscosa." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/12376.
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Includes bibliographical references (leaves 100-108).Climate change is predicted to have a negative impact on world food security in the next 40 years. Resurrection plants can withstand highly variable and harsh climatic conditions. This makes them ideal candidates to elucidate possible mechanisms which can be used to adapt crop plants to tolerate variable climatic conditions associated with climate change.
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Cooper, Keren. "The effect of drying rate on the resurrection species Craterostigma wilmsii (homoiochlorophyllous) and Xerophyta humilis (poikilochlorophyllous)." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/6244.
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Bibliography: leaves 90-98.Craterostigma wilmsii and Xerophyta humilis are angiosperm resurrection species that employ different strategies in dealing with desiccation and the related light stress. C. wilmsii is homoiochlorophyllous in that it retains its chlorophyll throughout dehydration, while X. humilis, a poikilochlorophyllous resurrection plant, breaks down its photosynthetic apparatus during drying.
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Kamies, Rizqah. "A methodological investigation into the roots of the resurrection plant, Xerophyta viscosa, for further proteomic analyses." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10955.
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In order to conduct proteomic analysis on the hydrated root tissues of the resurrection plant, Xerophyta viscosa Baker, aeroponically grown plant roots were subjected to various proteomic techniques. Three protein extraction methods were investigated, of which one method, was the most suited in isolating total protein from the root tissues of X. viscosa.
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Conrad, Nailah. "Characterization of XVEF and XvCaM : two calcium-binding proteins isolated from the resurrection plant Xerophyta viscosa." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4251.
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Includes bibliographical references.Xerophyta viscosa (Baker) is a resurrection plant with the ability to survive desiccation and rehydrate upon watering with minimal tissue damage. XVEF was isolated by differential screening of aX viscosa dehydration stress cDNA library. Reconstruction of the full length XVEF cDNA was conducted utilizing overlap extension PCR. XVEF codes for a putative calcium-binding protein and sequence analysis indicated that it has a 708 bp ORF corresponding to a protein with a molecular mass of26.95 kDa, has a conserved calcium-binding EF-hand motif, potential phosphorylation sites, a pI of 6.49 and a putative conserved transmembrane domain spanning residues 90-107. Northern blot analyses of total RNA indicated that XVEF transcript increased 48 hours after 100/-lM ABA application and was present between 12 and 48 hours in response to a low temperature stress (4°C). A second gene, XvCaM, was isolated from a low temperature (4°C) cDNA stress library. Sequence analysis indicates that it has a 450 bp ORF corresponding to a 16.39 kDa protein, a pI of 3.90 and potential phosphorylation sites. It apparently encodes a calcium-binding protein with putatively three EF-hands which showed the highest similarity to plant calmodulins. XVCAM was heterologously expressed in E. coli as a fusion protein with a 6X His-tag and it was shown to be a functional protein that binds Ca2+ by utilizing a 45CaCh overlay assay. Northern blot analyses of XvCaM using total RNA under low (4°C) and high temperature treatment (42°C) showed constitutive expression levels of the transcript. Under the dehydration/rehydration treatment transcript levels decreased between 40% R WC dehydration and 26% RWC rehydration. The northern blot conducted with polysomal RNA isolated from 150 mM NaCI treatment also showed constitutive expression. Western blot analyses using anti-XVCAM polyclonal antibodies showed that the protein accumulated at 24 hours during the NaCI stress and at 15% RWC (dry) to 40% RWC (rehydration) during the dehydration/rehydration stress. The northern and western analyses results suggest that XVCAM undergoes post-translational modifications and XvCaM mRNA is possibly stored for rapid recovery processes upon rehydration. These results indicate that XVEF and XvCaM are possibly calcium-binding proteins most likely involved in modulating stress-responsive calcium-signaling cascades.
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SILVA, Silvia Roberta Santos. "Adaptações morfoanatômicas de herbáceas em resposta a condições xéricas." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18351.
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CAPES
Espécies vegetais que ocorrem na Caatinga estão submetidas ao clima semiárido que se caracteriza por altas temperaturas, baixa precipitação e elevadas taxas de transpiração, que favoreceram o desenvolvimento de adaptações morfoanatômicas, ecológicas e fisiológicas. Esse ambiente xérico abriga inúmeras plantas conhecidas como xerófitas, cujos caracteres xeromórficos estão envolvidos principalmente com o estresse hídrico. Na maioria das vezes, o estrato herbáceo, considerado efêmero, é negligenciado quanto à sua investigação em detrimento das espécies que se mantém na paisagem, como as arbustivas e arbóreas, tendo sua biologia pouco explorada e consequentemente pouco compreendida quanto às estratégias de sobrevivência em ambientes xéricos como a caatinga. Assim, esse trabalho objetivou caracterizar morfoanatomicamente espécies de herbáceas identificando caracteres adaptativos típicos e como estes podem ser influenciados pela dificuldade de obtenção de água motivada pela distância do curso de água em três áreas classificadas em: AA-curso de água ausente, AT-curso de água temporário, AP-curso de água permanente. As espécies estudadas apresentaram características xeromórficas típicas, as quais conferem vantagem adaptativa em ambientes semiáridos, tais como a presença de: cutícula espessa, parênquima paliçádico com várias camadas incluindo mesofilo isobilateral, um indumento denso marcado pela presença de muitos tricomas, cristais de oxalato de cálcio, aumento da região cortical radicular, variações na atividade cambial e densidade de elementos de vaso e fibras xilemáticas. O índice de plasticidade fenotípica apresentou maiores valores para as espécies perenes indicando ajustamento às condições ambientais. Entretanto, os caracteres xeromórficos sofrem poucas alterações significativas nas diferentes áreas estudadas, porém, esses parâmetros foram relevantes para compreender o comportamento das herbáceas no ambiente e podem servir de base para novos estudos envolvendo herbáceas e xerófitas de modo geral. No mais, aspectos como variações cambiais associados à ultraestrutura de organelas e parede celular de tecidos distintos, pode ser a chave para a compreensão de respostas à disponibilidade hídrica nas áreas aqui estudadas.
Plant species that occur in the Caatinga are subject to the semiarid climate characterized by high temperatures, low rainfall and high transpiration rates, which favored the development of morphoanatomic, ecological and physiological adaptations. This xeric environment covers numerous plants known as xerophytes, whose xeromorphic characters are mainly involved with water stress. In most cases, the herbaceous stratum, considered ephemeral, is neglected as its research to the detriment of species that remains in the landscape, such as shrub and tree, with its unspoilt biology and therefore little understood about the survival strategies in environments xeric such as Caatinga. So, This study aimed to feature morphological and anatomically herbaceous species identifying typical adaptive characters and how these can be influenced by the difficulty of obtaining water driven by the distance of the watercourse in three areas classified as: AA – no water course, AT- temporary water course and AP-permanent water course. The species present typical xeromorphic characteristics which confer adaptive advantage in semi-arid environments, such as the presence of: a thick cuticle, palisade parenchyma with multiple layers including isobilateral mesophyll, a dense indumentum marked by the presence of many trichomes, calcium oxalate crystals, increased root cortical region, variations in foreign exchange activity and density of vessel elements and xylem fiber. The phenotypic plasticity index shows higher values for perennial species indicating adjustment to environmental conditions. However, xeromorphic characters suffer few significant changes in the different areas studied, however, these parameters are relevant to understanding the behavior of herbaceous on the environment and provide the basis for new studies involving herbaceous and in general xerophytes. Therefore, aspects such as currency fluctuations associated with ultra organelles structure and cell wall distinct tissues, may hold the key to understanding responses to water availability in the areas studied here.
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Davis, Emily. "Molecular characterization of ALDRXv4, an aldose reductase orthologue isolated from xerophyta viscosa, in response to abiotic stress." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4254.
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Tawouokam, Jean Bernard. "Attempt to express the Xerophyta viscose stress-responsive gene, Xvcor, in yeast with view to functional analysis." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/4338.
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Bibliography: leaves 24-29.Low temperature is one of the environmental factors that cause substantial crop losses in the world. Recent advances in the study of plants native from temperate regions, have established that cold acclimation is regulated at the gene expression leveL To study the function ofaXerophyta viscosa cold responsive protein that accumulates in plant cells under various environmental stresses, we have cloned the Xerophyta viscosa cold-responsive cDNA gene designed Xvcor, into a less complex host, Saccharomyces cerevisiae with the purpose of carrying out in vivo functional analysis. Sequence analysis showed that Xvcor encodes a 264 amino acid residue protein (Garwe et al 2002). The Hydropathy plot indicated that the XVCOR protein is highly hydrophobic and contains 6 transmembrane domains (Garwe et al 2002). In order to achieve high-level expression of Xvcor, the gene was placed under the control of a strong promoter (Phosphoglycerate kinase). Reverse-transcription PCR amplification revealed that the Xvcor transcript accumulated in yeast cells. However, SDS-PAGE analysis could not detect the predicted 29.6 kDa recombinant protein, suggesting that the translation might be hampered. Tests designed to measure the enhancement of stress tolerance between the recombinant and the control showed similar growth performance, confirming the absence of recombinant protein. A computer search for codon usage showed that the codon usage bias in Xvcor was low compared with that of highly expressed genes of S. cerevisiae. Together, these results suggest that the codon usage in Xvcor could influence its expression in yeast.
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Brown, Carly. "A comparison of some potential indicators of desiccation-tolerance in 2 Poikilochlorophyllous Xerophyta species and Homiochlorophyllous Craterostigma wilmsii." Bachelor's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/24762.
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Three possible indicators of desiccation-tolerance in ang10sperms: sucrose accumulation and hexose sugar flux, an increase in hexokinase activity, and accumulation of LEA-like proteins, were investigated and compared during dehydration between two moncotyledonous poikilochlorophyllous resurrection angiosperm species; Xerophyta schlecterii and Xerophyta humilis, and a dicotyledonous homiochlorophyllous resurrection species, Craterostigma wilmsii. Comparisons were also made with Xerophyta viscosa, using data from Whittaker et al, (2001). Soluble sugar concentrations and hexokinase activities were also examined during rehydration of the three species. Sucrose was accumulated during dehydration in all species examined. However, C. wilmsii had completed sucrose accumulation by the intermediate stages of drying, whereas Xhumilis exhibited a late accumulation. It was not clear if Xschlecterii exhibited late sucrose accumulation due to high standard deviations in the results. C. wilmsii accumulated higher sucrose levels than the two poikilochlorophyllous species. During rehydration the sucrose concentrations dropped in all three species, and was probably being used as an energy source for the resumption of metabolism. Glucose and fructose concentrations were relatively constant during dehydration in all three species, and did not appear to be contributing greatly to sucrose accumulation. This was further confirmed by the low levels of activity of hexokinase found in all three species during dehydration and rehydration, which suggests that the channelling of glucose and fructose into sucrose biosynthesis is not being upregulated during dehydration. C. wilmsii had an increased level of hexokinase late in dehydration, that may have been in preparation for the rapid rehydration experienced by this homiochlorophyllous species, where hexokinase would need to rapidly channel glucose and fructose into metabolism. There was not an increase in activity at the period of highest sucrose accumulation in this species. The activity of hexokinase was relatively constant throughout dehydration and rehydration for Xschlecterii, as it was for Xhumilis. Glucose and fructose levels dropped slightly in C. wilmsii during rehydration but remained relatively constant in the two poikilochlorophyllous species. The presence of LEA-like proteins was found in all three species, although the bands were very faint for X viscosa and Xhumilis. In Xschlecterii the bands were clear in the dehydrated leaf sample, but were faint or absent in the hydrated sample. It is possible that the proteins in this species were upregulated or induced by drying. A protein common to all three species in dehydrated and hydrated samples was observed between the 22.5 kDa and the 15.3 kDa molecular markers.
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Abdalla, Kamal O. "Analysis of the nuclear proteome of the resurrection plant Xerophyta viscosa (Baker) and its response to dehydration stress." Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/4233.
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Xerophyta viscosa Baker (family Velloziaceae) can survive extremes of dehydration (desiccation), down to 5% relative water content (RWC) and resumes full physiological activity within 80 h of rehydration. A thorough understanding of this phenomenon may provide further insight into possible mechanisms for improving drought tolerance in other plants. In this respect a comprehensive analysis of the nuclear proteome of this plant and its response to dehydration stress at 35% RWC was carried out. The RWC at 35% represents a distinct phase of the dehydration process where induction of late protection mechanisms is initiated and is a characteristic of desiccation tolerant species. We optimized nuclei isolation and nuclear protein extraction protocols and successfully employed these protocols to isolate highly purified nuclei and subsequently nuclear proteins from fully hydrated and dehydrated X. viscosa leaf samples. The integrity of the purified nuclei was confirmed with light and fluorescent microscopy. The nuclei were uniform spheres, approximately 5 μm in size. The purity and enrichment of the nuclear proteins were confirmed by chlorophyll assay and Western blot analysis. The nuclear proteins were investigated using two-dimensional (2D) and isobaric tags for relative and absolute quantitation (iTRAQ) technologies. Using the 2DE approach, a total of 438 proteins spots were reproducibly detected and analysed of which 18 protein spots were shown to be up-regulated in response to dehydration. These proteins contained both regulatory and functional proteins. The largest category comprised five novel protein factors and two proteins with unassigned functions. The second category comprised proteins involved in gene regulation and signal transduction. The third category comprised stress responsive proteins with chaperone type activities. Other categories include proteins involved in energy metabolism, protein degradation and translation. These results demonstrate that dehydration was controlled by multiple genes within the plant nucleus and X. viscosa may possess its own specific nuclear proteins that are involved in desiccation stress. In addition we comprehensively analyzed the nuclear proteome of X. viscosa using iTRAQ with two-dimensional liquid chromatography and tandem mass spectrometry to complement the data obtained from the 2DE approach. Using iTRAQ, we reproducibly University of Cape Town identified 128 proteins with confidence ¥ 95% (Ï < 0.05). Sixty six percent of the identified proteins showed consistent expression levels. The remaining 34% proteins showed significant changes in expressions. Of the latter, 23% were shown to be up regulated in response to dehydration stress. The remaining 11% were shown to be down regulated. The nuclear proteins of X. viscosa up-regulated in response to dehydration stress showed a coordinated response involving both regulatory and functional proteins and were implicated in diverse cellular functions. The characteristic feature of the X. viscosa nuclear proteins is the high level of stress molecules among the dehydration responsive proteins with evident functions in defense mechanisms compared to down regulated proteins and proteins showing consistent expression levels. These results demonstrate that enhanced defense capacity is crucial to desiccation tolerance and strongly support the notion that late dehydration responsive proteins are involved in protection of the cellular structures during dehydration. Proteins showing consistent expression levels during dehydration most likely maintain the minimum viability in cells under all conditions or may be indirectly associated with desiccation tolerance. Down-regulated proteins are likely important for plant survival under normal growth conditions. The proteins up-regulated in response to dehydration stress were assumed to be associated directly with the acquisition of desiccation tolerance. The up-regulated proteins were further categorized into nine functional groups to gain more insight into their roles in desiccation tolerance. The largest group was shown to be involved in gene regulation and signal transduction (36%), which reflects the role of the nucleus in gene expression and regulation. The second group included stress responsive molecules such as antioxidants, molecular chaperones and compatible solutes (33%). This reflects the importance of strong defense systems in preventing lipid peroxidation, protein aggregation, membrane leakage and maintaining the integrity of cellular structures during dehydration and in the dried state. The third group contained proteins involved in nucleocytoplasmic transport (10%). This might reflect the capacity of this plant to control the movement of molecules to and from the nucleus during dehydration and the importance of this process in adaptation to dehydration stress. The fourth group contained proteins involved in protein translation (7%). Proteins categorized to other functions, include proteins with miscellaneous and unknown functions. Proteins with unknown functions were considered to be X. viscosa nuclear-specific proteins. There was good correlation between the up-regulated proteins identified by 2-DE and iTRAQ approaches. In conclusion, this study revealed that X. viscosa nuclear proteome was responsive to dehydration stress and desiccation tolerance is University of Cape Town genetically encoded. Secondly, X. viscosa relies on readily inducible protection to combat desiccation and desiccation tolerance is controlled by multiple genes within the plant nucleus. Thirdly, the protective mechanisms of desiccation tolerance utilized by X. viscosa appear to involve signal perception genes and modulating gene expression of appropriate genes encoding protective molecules including antioxidants, molecular chaperones, compatible solutes, proteins of translation and degradation machinery, proteins with miscellaneous functions and novel protein factors. Lastly, proteins are crucial to desiccation tolerance allowing X. viscosa to possess a unique stress tolerance with versatile and coordinated actions to provide protection for its cellular structures during desiccation and in the dried state. To our best knowledge this is the first study to provide insight into the nuclear (organellar) proteome of a desiccation tolerant plant.
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Oduor, Okoth Richard. "Functional Analysis of the Novel Stress- Inducible XVPSAP promoter isolated from Xerophya Viscosa." Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/4314.
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Gardner, Michael Jack. "Resources for the investigation of the desiccation tolerance mechanisms of the roots of Xerophyta humilis (Bak) Dur and Schinz." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/4263.
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Bibliography: leaves 119-150.Although roots play an integral role in the sensing and amelioration of environmenatl stresses, there are no reports that specifically detail their involvement in the desiccation tolerance mechanisms of resurrection plants. Very lttle is known about even the genral anatomy and physiology of the roots of plants such as X. humilis, and almost nothing about the molecular responses that confer their ability to survive desiccation. This report details foundational studies of the functional anatomy and large-scale molecular responses of the roots during dehydrtion and rehydration.
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Beckett, Megan. "Investigation into the role of volatile organic compounds, and abscisic in stomatal regulation, in the resurrection plant Xerophyta humilis." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10102.
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The findings presented in this study give evidence for an ABA-mediated stomatal closure in response to initial dehydration of X. humilis, however, from 60% RWC onwards, stomata were observed to open again. This supplies further support for the hypothesis that resurrection plants actively lose water once protection is accumulated in order to minimize ROS activity and put a stasis on unregulated metabolism.
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McDonald, Zac Eliot. "Sucrose Phosphate Synthase activity and gene expression in relation to dehydration induced sucrose accumulation in the resurrection plan Xerophyta Humilis." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4295.
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Marais, Saberi. "XvVHA-c``1- a novel stress responsive V-ATPase subunit c`` homologue isolated from the resurrection plant Xerophyta viscosa Baker." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/4291.
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Tshabuse, Freedom. "Characterization of membrane lipids and, Changes therein during desiccation and rehydration of the resurrection plant Xerophyta humilis (Bak) Dur and Schinz." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28121.
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Drought is the primary challenge facing agricultural productivity and food sustainability productivity in Africa and many parts of the world. Very few higher plants, including crop plants, can survive periods of extended water loss. However, a small group of angiosperms, termed resurrection plants are able to lose up to 95% of their cellular water content in vegetative tissue upon extended periods of water, remain in an air-dry for months to years and regain full metabolic activity in the same tissue upon re-watering. The aim of this study was to investigate the changes in acyl chain composition within the major glycerophospholipids (in total and chloroplast suspension) and galactolipids (chloroplast suspension) at different stages of dehydration and rehydration treatments in the resurrection plant Xerophyta humilis (Bak) Dur and Schniz. This was done in order to ascertain their roles during acquisition of desiccation tolerance in X. humilis. The galactolipids and glycerophospholipids acyl chain compositions were determined by multiple reaction monitoring (MRM) mass spectrometry. The glycerophospholipids profiles from total leaves and roots lipid extracts showed an increased representation of unsaturated molecular species such as 18:3/18:3 (in leaves) and 18:3/18:2 (in leaves and roots) during dehydration, with a decrease in saturated and mono-saturated molecular species such as 16:0/16:0. Rehydration was associated with the opposite trend. Furthermore, increased representation of molecular species with unusual fatty acids were observed during dehydration, with the odd-numbered fatty acids such as 15:0, 17:0 and 19:0 increasing during dehydration and decreasing during re-watering. On the other hand, the 23:0 and 25:0 fatty acids decreased during dehydration and increased upon rehydration. Within the chloroplast profiles, the galactolipids (i.e. monogalactosyldiacylglycerolipids and digalactosyldiacylglycerolipids) showed maintenance of 18:3/18:3 and 18:3/18:2 molecular species during dehydration and rehydration. The phosphatidylglycerolipids profiles in the chloroplast, together with the uncommon chloroplastic glycerophospholipids such as phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol also showed an increase in the unsaturated molecular species during dehydration and decrease upon rehydration. Taken together, our data suggest that water deficit in X. humilis roots and leaves induce fatty acid unsaturation, as well as production of uncommon fatty acids. These unsaturated fatty acids may aid in maintaining membrane integrity during dehydration. This study shows that changes in lipid composition are part of the desiccation tolerance strategies used by X. humilis.
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Viana, Aline. "Morfologia e anatomia foliar de espécies de angiospermas com ocorrência nos campos de areais do bioma pampa." Universidade Estadual do Oeste do Paraná, 2018. http://tede.unioeste.br/handle/tede/3800.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
(Morphology and foliar anatomy of angiosperm species occurring in the sand fields of the Pampa biome). Part of the vegetation in the southwest of Rio Grande do Sul (RS) is classified as sand fields, phytophysiognomy of the Pampa with sandy soils, susceptible to the natural process of sandstone, intensified by anthropic action. This process has contributed to a reduction in the biological diversity of the biome and is even more worrisome for species with restricted occurrence and/or the threat of extinction. The objective of this work was to characterize the leaf blade morphoanatomy of 20 angiosperm species of the sand fields, of which 8 are considered endangered, seeking to identify strategies that allow adaptation to the rural environment. To this end, individuals from different populations of each species were collected in sand-field regions of the Pampa biome. Leaf blades in frontal view were analyzed using scanning electron microscopy (SEM), light microscopy (LM), and transverse sections (TS) in LM. Microchemical tests were also performed in TS observed in LM. It was observed that, although they belong to distinct phylogenetic groups, many of the studied species share characteristics which can be interpreted as adaptive strategies, such as trichomes covering the entire leaf surface, stomata on both sides, compact mesophyll, druses, secretory channels, phenolic compounds, and mucilage. We conclude that these species, occurring in sand-field regions, have characteristics that confer adaptation to dry environments and/or water deficits. In this way, we emphasize the importance of the creation of conservation units in the sand-field region, aiming to preserve these species.
(Morfologia e anatomia foliar de espécies de angiospermas com ocorrência nos campos de areais do bioma pampa). Parte da vegetação do sudoeste do Rio Grande do Sul (RS) é classificada como campos de areais, fitofisionomia do Pampa que ocorre sobre solos arenosos, suscetíveis ao processo natural de arenização, intensificado pela ação antrópica. Esse processo tem contribuído para a redução da biodiversidade do bioma, sendo ainda mais preocupante para espécies com ocorrência restrita e/ou ameaçadas de extinção. Nesse contexto, esse trabalho teve como objetivo caracterizar a morfoanatomia da lâmina foliar de 20 espécies de angiospermas dos campos de areais do RS, das quais oito são consideradas ameaçadas de extinção, buscando identificar estratégias adaptativas ao ambiente campestre. Para isso, indivíduos de diferentes populações de cada espécie foram coletados nos municípios de Alegrete, Manoel Viana e São Francisco de Assis, RS. Lâminas foliares em vista frontal foram analisadas com microscópio eletrônico de varredura (MEV) e microscopia de luz (ML) e em secção transversal (ST) em ML, e testes microquímicos das ST. Foi possível observar que, apesar de pertencerem a grupos filogenéticos distintos, muitas das espécies estudadas compartilham características, que podem ser interpretadas como estratégias adaptativas, destacando-se: tricomas tectores cobrindo toda a superfície foliar, estômatos em ambas as faces, mesofilo compacto, drusas, canais secretores, compostos fenólicos e mucilagem. Concluímos que essas espécies com ocorrência aos campos de areais possuem características adaptativas ao ambiente seco e/ou para déficits de água. Dessa forma, ressaltamos a importância da criação de unidades de conservação na região dos campos arenosos, visando à preservação dessas espécies.
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Mowla, Shaheen B. "Molecular characterization of XvPer1, a novel antioxidant enzyme from the resurrection plant Xerophyta viscosa, and AC3, a LEA-like protein from Arabidopsis thaliana." Thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6728.
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By differential screening of a cDNA library of the resurrection plant Xerophyta viscosa, a cDNA termed XvPer I was isolated for its over-expression under dehydration stress. Analysis of the cDNA sequence indicated a hydrophilic protein of a predicted Mw of 24.2 kDa with high identity to plant l-Cys peroxiredoxins, a novel antioxidant enzyme. Southern blot analysis revealed that XvPer I was most probably a single copy gene. The polypeptide sequence had significant identities (-70%) with other recently identified plant I-Cys peroxiredoxins with an absolutely conserved active site (PVCTTE). The protein sequence also had a putative bipartite nuclear localization signal.
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Wiesner, Lubbe. "Isolation and characterisation of antiplasmodial compounds from Xerophyta species and the bioavailability, metabolic and efficacy evaluation of 9-0-acetylhydnocarpin in a mouse model." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/3304.
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Maredza, Alice T. "Isolation of the aldose reductase gene (XvAld1) from the resurrection plant Xerophyta viscosa, and characterisation of the gene product and transgenic plants expressing the gene." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/4292.
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Includes abstract.Includes bibliographical references (leaves 170-209).
The Xerophyta viscosa aldose reductase cDNA (XvAld1) was isolated from a dehydration library. Gene transcripts that are upregulated during stress are normally involved in protection and/ or adaptation, leading to stress tolerance. The genomic organisation of XvAld1 was characterised using Southern blot analysis and DNA sequencing. The results revealed more than one copy of the gene with a complex banding pattern that was partially resolved by sequencing. The sequencing of PCRamplified genomic clones showed that the gene is organised into nine exons and eight introns spanning ~2.9 kb. The observed nucleotide differences between the sequenced clones could reflect polymorphisms between different copies of the gene. An 870-bp clone of the 5′ untranslated region, matching the 5′ leader sequence on the XvAld1 cDNA was analysed for cis-acting response elements. Many of the sequence motifs matched those for hormonal regulation, organ specific expression, dehydration, high or low temperature responses, light and phytochrome responsiveness, wounding, as well as G-box, CAAT and TATA-boxes.
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Peters, Shaun W. "XvGoIS, a galactinol synthase is transcriptionally upregulated under water deficit : the role of raffinosaccharides in abiotic stress tolerance in the resurrection plant Xerophyta viscosa (Baker)." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4318.
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Includes bibliographical references (leaves 84-102).As part of an ongoing project to genetically manipulate maize for increased abiotic stress tolerance, we have isolated and identified a number of genes from the resurrection plant Xerophyta viscosa (Baker) that are differentially expressed during water deficit. A cDNA was isolated from a library constructed from the leaves of water stressed X viscosa plants, which showed high identity to galactinol synthase (GoIS) enzymes from a variety of plant species. GolS is fundamental to the biosynthesis of raffinose family oligosachharides (RFOs), sucrosyl carbohydrates that are unique to plants and implicated in carbon translocation and abiotic stress tolerance. We subsequently designated this cDNA XvGoIS.
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Silva, Guilherme de Lira Sobral. "Morfometria e composiÃÃo quimÃca-bromatolÃgica da pornunÃa (Manihot sp.) em funÃÃo da densidade de plantio e adubaÃÃo fosfatada." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11509.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorNos Ãltimos anos, vÃrias pesquisas foram desenvolvidas na regiÃo SemiÃrida do Nordeste Brasileiro, no intuito de conhecer as potencialidades, tanto na produÃÃo como na qualidade de suas forragens. Como exemplo, a pornunÃa (Manihot sp.) na adiÃÃo de fonte de proteÃna no arraÃoamento de animais. Avaliou-se um modelo para a estimativa da Ãrea foliar, morfometria, composiÃÃo quÃmico-bromatolÃgica e mineral da pornunÃa (Manihot sp.) em funÃÃo da densidade de plantio e adubaÃÃo fosfatada. O experimento foi conduzido em sistema de sequeiro, no perÃodo de maio 2010 a outubro de 2011. Adotou-se o delineamento em blocos casualizados, em esquema fatorial 4 x 4, com trÃs repetiÃÃes, sendo 4 espaÃamentos (1,5 x 1,5; 1,5 x 2,0; 2,0 x 2,0 e 2,5 x 2,0 metros) e 4 doses de fÃsforo (0,0; 56,66; 113,32 e 169,98 gramas/covas de superfosfato simples). Foram marcadas 192 plantas, sendo 4 por parcelas para avaliaÃÃes morfomÃtricas (altura da planta, nÃmero de ramos, diÃmetro de caule e nÃmero de folhas), quÃmico-bromatolÃgica e mineral (folhas, hastes e pool). No estudo do modelo para estimativa da Ãrea foliar, foram coletadas 3 folhas por planta, num total de 144, para determinaÃÃo da AF utilizando o mÃtodo direto (AFReal), medidor de Ãrea foliar tipo esteira (Li-Cor 3100) e por meio das dimensÃes lineares. O crescimento da pornunÃa, em termos de altura da planta, nÃmero de ramos, diÃmetro de caule e nÃmero de folhas depende da distribuiÃÃo temporal dos pulsos de precipitaÃÃo, principalmente o nÃmero de folhas da planta. Dentre as variÃveis de crescimento avaliadas, o nÃmero de folhas da planta à o mais sensÃvel Ãs variaÃÃes da disponibilidade de Ãgua no solo e distribuiÃÃo da chuva na estaÃÃo chuvosa e, como consequÃncia nÃo hà efeito do espaÃamento de plantio nem da adubaÃÃo fosfatada sobre esta variÃvel. A densidade de plantio e a adubaÃÃo fosfatada nÃo influenciam o nÃmero de rebrotaÃÃes, folhas e diÃmetro da pornunÃa quando cultivada em sequeiro. Em condiÃÃes de sequeiro, o espaÃamento de plantio e a adubaÃÃo fosfatada nÃo interferem (p>0,05) na composiÃÃo quÃmico-bromatolÃgica das folhas e do pool da pornunÃa, em termos de MS, PB, FDN, CHOT e CNF a exceÃÃo do teor de EE do pool. Pelo contrario, o espaÃamento de plantio e a adubaÃÃo fosfatada afetam (p<0,05) na composiÃÃo quÃmico-bromatolÃgica das hastes, a exceÃÃo do CHOT. A adubaÃÃo fosfatada e o espaÃamento de plantio influenciam os teores de magnÃsio e fÃsforo nas hastes e fÃsforo no pool da pornunÃa. A Ãrea foliar da pornunÃa determinada pelo medidor Li-Cor 3100 à cerca de 10% inferior em comparaÃÃo ao mÃtodo AFReal. O modelo que melhor se ajusta para a estimativa da Ãrea foliar foi do tipo potencial a partir das dimensÃes morfolÃgicas se aproximarem mais quando se usa o produto da largura pelo comprimento da folha, independente do seu tamanho.
In recent years, several studies have been developed in the semiarid region of Northeast Brazil, in order to know the potential, both in production and in the quality of the fodder. As an example, pornunÃa (Manihot sp.) used as addition of a protein source in animal feeding. It was evaluated a model for leaf area estimation, morphology, chemical composition and mineral of the pornunÃa (Manihot sp.) in function of planting density and phosphorus fertilization. The experiment was conducted under rainfed system in the period from May 2010 to October 2011. It was adopted a randomized block design in a factorial 4 x 4 with three replications and four spacings row (1,5 x 1,5; 1,5 x 2,0; 2,0 x 2,0 and 2,5 x 2,0 meters) and four levels of phosphorus (0,0; 56,66; 113,32 and 169,98 grams/pits superphosphate). 192 plants were marked, being 4 by plots for morphological (plant height, number of branches, stem diameter and number of leaves), bromatological and mineral (leaves, stems and pool). In the model studies to estimate leaf area were collected 3 leaves per plant, for a total of 144 leaves, to determine the AF using the direct method (AFReal), leaf area meter (Li-Cor 3100) and by linear dimensions. The growth of pornunÃa in terms of plant height, number of branches, stem diameter, leaf number depends on the temporal distribution of precipitation pulses, particularly the number of leaves. Among the growth variables evaluated, the number of leaves of the plant is the most sensitive to changes in soil water availability and rainfall distribution during the rainy season and as a consequence there is no spacing row or phosphorus fertilization effect on this variable. Planting density and phosphorus fertilization did not influence the number of regrowth, leaves and diameter of the plant when it is grown in rainfed. Under rainfed conditions, the planting space and phosphorus fertilization do not interfere (p> 0.05) in the chemical composition of the leaves and the pool of pornunÃa, in terms of DM, CP, NDF, CHOT and NFC, with exception of EE content in the pool. Rather, the spacing row and phosphorus fertilization affect (p <0.05) the chemical composition of the stems, with the exception of CHOT. The phosphorus fertilization and planting spacing influence the levels of magnesium and phosphorus in the stems and phosphorus in the pool of the pornunÃa. The pornunÃa leaf area determined by the meter Li-Cor 3100 is about 10% lower compared to the AFReal method. The model that best fits to estimate the leaf area was the potential type from the morphological dimensions, when it gets closer if using the product of the width by length of the sheet, regardless of its size.
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Pontes, Rodrigo Corrêa. "Avaliação fitogeográfica dos relictos xerófitos em afloramentos rochosos no campestre do divino, Santa Maria/RS." Universidade Federal de Santa Maria, 2017. http://repositorio.ufsm.br/handle/1/12162.
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The present study aims to identify and evaluate the areas of ecological refuges with xerophytic species, present in the locality of Campestre do Divino, Santo Antão district, Santa Maria municipality, central region of the State of Rio Grande do Sul, southern Brazil, through an environmental analysis of botanical, climatic, geological and geomorphological aspects. The research was developed through field data collection. Atmospheric variables were obtained through reading instruments. Geomorphological observations were performed together with the survey of the xerophytic species considered relictual, relating their presence with the climate, geomorphology and geology of the study area. It was also sought to analyze the anthropic impacts when it was identified. With the data collected in the field, the areas of these xerophytic refuges were georeferenced and later thematic maps were elaborated for a better understanding of the geographic distribution. Based on the Pleistocene Refugia Theory and with data obtained in the field, an environmental analysis was carried out where it was possible to verify that the presence of these xerophytic elements present an intrinsic pedological relation, guaranteeing that the study area always contained an open phytophysiognomy. These islands of endemism are represented by relictual species belonging to the families Bromeliaceae, Cactaceae and Orchidaceae, bioindicators of paleoclimatic events of intense aridity established in the Quaternary. Sheltered in rocky outcrops and litholic neosols, these endemic and endangered floristic elements, have maintained their survival processes, lingering in our landscape in adverse climatic conditions.O presente estudo busca identificar e avaliar as áreas de refúgios ecológicos com espécies xerófitas, presentes na localidade de Campestre do Divino, distrito de Santo Antão, Município de Santa Maria, região central do Estado do Rio Grande do Sul, sul do Brasil, através de uma análise ambiental dos aspectos botânicos, climáticos, geológicos e geomorfológicos. A pesquisa foi desenvolvida por meio de coletas de dados a campo. Variáveis atmosféricas foram obtidas através de instrumentos de leitura. Observações geomorfológicas foram realizadas conjuntamente com o levantamento das espécies xerófitas consideradas relictuais, relacionando a sua presença com o clima geomorfologia e geologia da área de estudo. Também se buscou analisar os impactos antrópicos quando este foi identificado. Com os dados coletados a campo, as áreas desses refúgios xerófitos foram georreferenciadas e posteriormente foram elaborados mapas temáticos para um melhor entendimento da distribuição geográfica. Embasado pela Teoria dos Refúgios Pleistocênicos e com dados obtidos em campo, realizou-se uma análise ambiental onde pôde-se constatar que a presença desses elementos xerófitos apresentam uma relação intrínseca pedológica, garantindo que a área de estudo sempre conteve uma fitofisionomia aberta. Essas ilhas de endemismo são representadas por espécies relictuais pertencentes às famílias Bromeliaceae, Cactaceae e Orchidaceae, bioindicadoras de eventos paleoclimáticos de intensa aridez firmados no Quaternário. Refugiados em afloramentos rochosos e neossolos litólicos, esses elementos florísticos endêmicos e ameaçados de extinção, mantiveram seus processos de sobrevivência, perdurando em nossa paisagem em condições climáticas adversas.