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1
Baynham, Mark Kevin. "Gibberellin plant growth hormones." Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328329.
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Pharmawati, Made, and mikewood@deakin edu au. "A study of the natriuretic peptide hormone system in plants." Deakin University. School of Biological and Chemical Sciences, 1999. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060727.145040.
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In this study, both physiological and cellular effects are elicited by natriuretic peptides (NPs), a novel type of plant hormone. It was found that rat ANP (rANP) influenced stomatal opening movement in Tradescantia sp., where a significant increase in stomatal opening was observed in the presence of 1 µM rANP. Furthermore, this effect is mediated by cGMP, a (putative) second messenger of NPs. Two inhibitors of guanylyl cyclase, LY 83583 and methylene blue, inhibited rANP-induced stomatal opening. In contrast, stomatal opening is induced in a concentration dependent manner by the cell permeant cGMP analogue 8-Br-cGMP. In addition it was found, that like in animals, the secondary structure of rANP is essential for rANP responses. Linearised rANP is biologically inactive.
Since ANP elicit plant responses, an attempt was made to isolate NP analogues from plants. A protocol for partially purifying NP from plants was developed. It was found that two fractions eluted from an immunoaffinity chromatography column (0.5 M KCI eluted fraction and 0.75 M KCI eluted fraction) were biologically active.
The level of cGMP in response to NPs was also tested. It is suggested that the receptor of NP is specific since only 0.75 M KCI eluted fractions increased cGMP levels in Zea mays root stele tissue. rANP did not elicit an effect on cGMP levels in this tissue and LY 83583 did not affect this response. It is therefore argued that a plant specific biologically active NP system is present in the stele and it is predicted that NPs modulate solute movement in this tissue.
NPs also influence K+, Na+ and H+ fluxes in Zea mays root stele. Increase in both K+ and Na+ uptake were observed after 30 min., while H+ flux shifted immediately toward influx in the presence of both 0.5 and 0.75 KCI eluted fractions. Finally, a model is proposed for the effect of NPs on solute movement and its signalling system in plants.
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Bastian, René. "Characterisation of AtPNP-A - a novel arabidopsis thaliana gene with role in water and salt homeostasis." Thesis, University of the Western Cape, 2009. http://hdl.handle.net/11394/2818.
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Philosophiae Doctor - PhDPlant natriuretic peptides (PNPs) are a novel class of extracellular, systemically mobile molecules that elicit a number of plant responses important in homeostasis and growth. Natriuretic peptides were first identified in vertebrates where they play a role in the regulation of salt and water balance. Subsequent experimental investigations have identified the presence of a natriuretic peptide hormone system in plants. While PNPs have been implicated in various physiological responses such as stomatal guard cell movements and regulation of net water uptake, its biological role has remained elusive. Here we have used co-expression and promoter content analysis tools to understand the biological role of the Arabidopsis thaliana PNP (AtPNP-A). The analysis of AtPNP-A and its co-expressed genes revealed that genes annotated as part of the systemic acquired resistance (SAR) pathway were over-represented, thus suggesting that AtPNP-A may function as a component of plant defense responses and specifically, SAR. The results further show that AtPNP-A shares many characteristics with pathogenesis related (PR) proteins in that its transcription is strongly induced in response to pathogen challenges, thus implying a newly described role for AtPNP-A in pathogen attack. Additional tissue expression analysis also indicated distinct localization of PNP activity in sepals and transcriptional meta-analysis showed that AtPNP-A may play a role in starch breakdown. Therefore, together with the finding that AtPNP-A plays a role in regulating phloem transport, we also hypothesize that AtPNP-A may play a role in phloem unloading in sepals to assist processes such as seed formation in plants. In plants, the second messenger, guanosine 3’,5’-cyclic monophosphate (cGMP) mediates a whole range of important processes including salinity tolerance, disease resistance, drought tolerance and responses to light. Since PNPs regulate water and salt homeostasis via a cGMP-dependent signaling pathways, it is thus important to analyse the transcriptome induced by the second messenger (cGMP) in Arabidopsis thaliana to give a better understanding of its mechanism of action. This study was also supplemented by the analysis of the gibberellic acid (GA) dependent transcriptome, since cGMP also plays a role its transcription pathway. This data analysis, together with promoter content investigation, revealed that genes upregulated after cGMP treatment and down-regulated in the GA insensitive mutant (ga1-3) were enriched with a GA response element (GARE), while no GARE enrichment were observed in genes up-regulated in the ga1-3 mutant. These findings suggest that GARE is indicative of GA-induced and cGMP-dependent transcriptional up-regulation. Gene ontology analysis confirmed previous reports that cGMP is involved in ion homeostasis and indicated that the transcriptional cGMP response is bi-polar in the sense that both genes up- and down-regulated in response to cGMP is involved in cation transport. Additionally, ab initio analysis of genes transcriptionally dependent on cGMP identified CHX8 as a hub gene and promoter content of CHX8 co-expressed genes show enrichment of the GARE motif. The fact that CHX8 has its highest expression levels during male gametogenesis and pollen tube growth, together with our findings, suggest that GA-induced and cGMP- dependent genes may play a key role in ion and water homeostasis in the male gametophyte. Finally, we propose that the type of analysis undertaken here can yield new insights into gene regulation networks and inform experimental strategies to unravel complex transcription regulatory systems under different developmental and stimulus specific conditions.
South Africa
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Woods, S. L. "Analysis of plant hormones involved in potato dormancy." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384566.
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Leung, Ching-man. "Characterization of two auxin-induced ACC synthase genes in tomatoes." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36748845.
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Veerappan, Vijaykumar. "Molecular and genetic analysis of the function of cis-cinnamic acid in arabidopsis thaliana /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202004%20VEERAP.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 78-85). Also available in electronic version. Access restricted to campus users.
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McCoy, Mark Christopher. "The effects of phytohormones on growth and artemisinin production in hairy root cultures of artemisia annua l." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0529103-162012/.
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Herrington, Edward John. "Light quality effects on in vitro shoot proliferation of Spiraea nipponica." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28809.
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The work on Spiraea in vitro shoot cultures was done to determine the feasibility of using light quality to modify endogenous phytohormone balances to decrease apical dominance. Such an effect would enable a reduction in the high levels of exogenous cytokinin benzyladenine (BA) applied in culture and thus reduce potential side-effects.
The Spiraea in vitro light quality response was characterized by examining the effects of different light wavelengths on growth. A mixture of red/FR induced rates of shoot proliferation with 0.25 mg/1 BA that were as high as rates obtained under white light with 0.5 mg/1 BA. Shoot quality, as determined by the proportion of shoots 1 cm or longer (useful shoots), was highest under red/FR light. The lowest shoot proliferation rate was observed under blue light. When light wavelengths intermediate between blue and red light (green, yellow, and orange) were applied to explants only minor growth modifications occurred. Green light did not inhibit shoot initiation but inhibited shoot elongation at the 0.5 mg/1 BA level.
The efficacy of the light source-filter combinations in the first experiment was studied in two further experiments. With the three light sources (tungsten filament, fluorescent, and metal halide) together with a blue filter, results supported the putative blue light inhibitory effect suggested in the first light quality experiment. Under the red filter, the tungsten filament source induced the highest shoot number means at both
BA levels used (0.25 and 0.5 mg/1).
Two factors may have contributed to the red/FR effect observed in the first experiment; the time under an incubation light regime before transfer to the treatment regime, and the photon fluence rate of each regime. In the subsequent study to examine these factors, shoot initiation was optimized at the lower BA levels of 0.25 and 0.4 mg/1 when cultures under low fluence red/FR were transferred after four weeks to white light of a higher fluence for one more week.
Glyphosate, a known promoter of IAA oxidation, was used to investigate the presumed effect of lowered IAA-cytokinin interactions. Two types of responses to glyphosate occurred, each one dependent on the glyphosate concentration. At the lower glyphosate level (0.087 mg/1), cultures under both light regimes with 0.25 mg/1 of BA, showed a strong inhibition of shoot initiation. This inhibitory effect was overcome in cultures with 0.5 mg/1 of BA and an overall stimulatory response occurred as shoot initiation rates were as much as four-fold higher than in the previous experiments. For both BA levels, changes in shoot number were greater under white light than under red/FR. At the higher glyphosate level (0.2 67 mg/1), the shoot initiation rates were greater than glyphosate-free controls for both BA levels under white light although under red/FR the rates were virtually unchanged from controls. The glyphosate effect investigated for Spiraea cultures appears to be influenced by the levels of the cytokinin BA resulting in pleiotropic effects which depend on the specific concentrations of each component.Land and Food Systems, Faculty of
Graduate
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Wai, King-ming. "Purification and characterization of beta-cyanoalanine synthase from rice (Oryza sativa)." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23234581.
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Hove, Runyararo Memory. "Evolutionary development and functional role of plant natriuretic peptide (PNP)-B." Thesis, University of Fort Hare, 2009. http://hdl.handle.net/10353/155.
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Plant natriuretic peptides (PNP) are novel peptides which, like in vertebrates, have been shown to have a function associated with water and salt homeostasis. Two PNP-encoding genes have been identified and isolated from Arabidopsis thaliana, namely; AtPNP-A and AtPNP-B. In this study, the focus was on PNP-B, which has not been extensively studied. Bioinformatic analysis was done on the AtPNP-B gene. This included the bioinformatic study of its primary structure, secondary structure, tertiary structure, transcription factor binding sites (TFBS) and its relation to other known proteins. The AtPNP-B gene was shown to be a 510 bp long, including a predicted 138 bp intron. AtPNP-B was also shown to have some sequence similarity with AtPNP-A and CjBAp12. The TFBS for AtPNP-B and OsJPNP-B were compared and they comprised of TFBS that are related to water homeostasis and pathogenesis. This suggested two possible functions; water stress and homeostasis and a pathogenesis related function for PNP-B. Following bioinformatic analysis, the heterologous expression of the AtPNP-B was attempted to investigate whether the AtPNP-B gene encoded a functional protein and to determine the functional role of PNP-B. However, expression was unsuccessful. An evolutionary study was then carried out which revealed that there were some plants without the intron such as, rice, leafy spurge, oilseed rape, onion, poplar, sugar cane, sunflower and tobacco. These plants would therefore be used for expression and functional studies in the future. The evolutionary studies also revealed that PNP-B had a relationship with expansins and the endoglucanase family 45. Other PNP-B related molecules were also obtained from other plant genomes and therefore used in the construction of a phylogenetic tree. The phylogenetic tree revealed that AtPNP-B clustered in the same group as CjBAp12 while AtPNP-A had its own cluster group. There were also other PNP-B like molecules that clustered in the same group as expansins (α- and β-). Thus, we postulate that, like PNP-A, PNP-B also has a possible function in water and salt homeostasis. However, due to the clustering iii of AtPNP-B into the same group as CjBAp12, a possible role of PNP-B in pathogenesis-related response is also postulated.
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Hays, Dirk B. "The role of plant hormones in Brassica napus embryo development." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20742.pdf.
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Williams, James Timothy. "Total Synthesis of Bacterial Carbohydrates and Plant-derived Glycopeptide Hormones." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15508.
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Glycosylation is one of the most abundant post-translational modifications that can modify the structure of peptides and proteins and occurs after ribosomal synthesis. Post-translational modifications further diversify the cellular proteome and are implicated in a diverse number of biological activities. Over 70% of eukaryotic proteins are believed to be glycosylated. However, many pathogenic bacteria and viruses also glycosylate proteins, which is implicated in host-recognition, host- infection or host-invasion. It has recently been shown that, plants glycosylate secreted peptide hormones to facilitate survival messenger systems and control their root growth. This thesis describes chemical approaches to the synthesis of bacterial and plant carbohydrates and glycoproteins with a view to elucidating the structural and functional role(s) of glycosylation Chapter 1 describes the total synthesis of pseudaminic acid, a unique, nine-carbon carbohydrate implicated as a virulence factor in Gram-negative bacteria. We successfully synthesised pseudaminic acid from the commercially-available sialic acid. The synthetic route provides a means to access homogenous glycopeptides incorporating pseudaminic acid for the future development of vaccines and diagnostics. Chapter 2 describes investigations into the role that glycosylation plays in secreted peptide hormones in plants. A library of arabinosylated glycopeptide hormones found in plantswere successfully synthesised. These are now being assessed in biological studies to elucidate the molecular messenger systems to understand the role of arabinosylation on peptide hormone activity.
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Yuan, Kun Wysocka-Diller Joanna Singh Narendra K. "Functional and genetic analysis of plant transcription factors involved in the plant growth under various environmental conditions." Auburn, Ala, 2008. http://repo.lib.auburn.edu/2007%20Fall%20Dissertations/Yuan_Kun_37.pdf.
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Athmani, Salah. "Synthesis of cytokinin analogues." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304608.
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Rogers, Jennifer Jacqueline Mavis. "Mutational analysis of the maize auxin binding protein, ABP1." Thesis, University of the West of England, Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249341.
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Ward, Jane Louise. "Probing the mechanism of gibberellin 20-oxidase and a structure-activity study of methyl jasmonate and related derivatives." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361109.
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Harrison, Polly A. "Partial synthesis of selected gibberellins." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294577.
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Oakeley, Edward James. "Promoter analysis of auxin-binding protein genes from Zea mays L. and Fragaria x ananassa." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260811.
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Taylor, Catherine. "A mechanism of action of strigolactone." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709140.
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Garnaat, Carl William 1957. "PHYTOHORMONAL REGULATION OF 3-HYDROXY-3-METHYLGLUTARYL COENZYME A REDUCTASE IN PLANT CELL CULTURES (ABSCISIC ACID, MEVINOLIN)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276793.
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Zhang, Tao. "Regulation of EGY1 gene expression by environmental factors and developmental cues /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202005%20ZHANG.
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Balasubramanian, Rajagopal. "Harlequin (hlq) : an arabidopsis mutant that ectopically expresses Dc3-GUS and shows defects in cell wall morphogenesis /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202003%20BALASU.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 197-236). Also available in electronic version. Access restricted to campus users.
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Xing, Ti. "Hormone binding in plants." Thesis, De Montfort University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280511.
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偉景明 and King-ming Wai. "Purification and characterization of beta-cyanoalanine synthase from rice (Oryza sativa)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225275.
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Feys, Bart Julienne Frans. "Towards positional cloning of COI1, an arabidopsis gene controlling the response to coronatine and methyl jasmonate." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317974.
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Weir, A. J. "#alpha#-ketogutarate dependent gibberellin hydroxylases and plant growth regultion." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233760.
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Ververidis, Philippos. "Characterisation and partial purification of the enzyme responsible for ethylene synthesis from 1-aminocyclopropane-1carboxylic acid in plant tissues." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303175.
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Hoffman, Sister Angela. "Hormonal regulation of cell development and polyphenol biosynthesis in cultured Populus trichocarpa cells /." Full text open access at:, 1989. http://content.ohsu.edu/u?/etd,220.
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Katsir, Leron J. "Biochemical characterization of the COI1-JAZ receptor for jasmonate." Diss., Connect to online resource - MSU authorized users, 2008.
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Kaliff, Maria. "Genes, hormones and signalling pathways implicated in plant defence to Leptosphaeria maculans /." Uppsala : Dept. of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/2007119.pdf.
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Ruzvidzo, Oziniel. "Plant Natriuretic Peptides - Elucidation of the Mechanisms of Action." Thesis, University of the Western Cape, 2009. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5854_1285860491.
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Several lines of cellular and physiological evidence have suggested the presence of a novel class of systemically mobile plant molecules that are recognized by antibodies generated against vertebrate atrial natriuretic peptides (ANPs). Functional characterization of these immunoanalogues, referred to as immunoreactive plant natriuretic peptides (irPNPs) or plant natriuretic peptides (PNPs), has shown that they play important roles in a number of cellular processes crucial for plant growth and maintenance of cellular homeostasis. Although the various biological roles of PNPs in plants are known, their exact mode of action remains elusive. To elucidate the mechanisms of action for these immunoanalogues, we have prepared a biologically active recombinant PNP from Arabidopsis thaliana (AtPNP-A) and the biological activity was demonstrated by showing its ability to induce water uptake into Arabidopsis thaliana protoplasts. In addition, the molecule was shown to downregulate photosynthesis while at the same time up-regulating respiration, transpiration as well as net water uptake and retention capacities in the sage Plectranthus ecklonii. Further analysis of the recombinant AtPNP-A indicated that the peptide can induce systemic response signalling though the phloem. A recombinant Arabidopsis wall associated kinase-like protein (AtWAKL10) that has a domain organization resembling that of vertebrate natriuretic peptide (NP) receptors was also partially characterized as a possible receptor for the recombinant AtPNP-A. Vertebrate NP receptors contain an extracellular ligand-binding domain and an intracellular guanylate cyclase (GC)/kinase domain and signal through the activity of their GC domain that is capable of generating intracellular cGMP from GTP. The structural resemblance of AtWAKL10 to vertebrate NP receptors could suggest a functional homology with receptor molecules and it is conceivable that such a receptor may recognize PNPs as ligands. The characterization of the recombinant AtWAKL10 showed that the molecule functions as both a GC and a kinase in vitro. This strengthened the suggestion that AtWAKL10 could be a possible AtPNP-A receptor especially considering the fact that AtPNP-A applications to plant cells also
trigger cGMP transients. Furthermore, a bioinformatic analysis of the functions of AtPNP-A and AtWAKL10 has inferred both molecules in plant pathogen responses and defense mechanisms, thus indirectly functionally linking the two proteins.
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Simancas, San Martín Bárbara. "Importancia de la vitamina E y los jasmonatos en la respuesta de las plantas ante la distinta disponibilidad de fósforo." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462069.
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El fósforo es un macroelemento esencial para el desarrollo y crecimiento de todas las plantas. Sin embargo, el fósforo inorgánico (Pi), forma asimilable por las plantas, es cada vez más escaso en los suelos naturales y es el limitante más importante para las plantas en suelos calcáreos. La deficiencia del Pi afecta enormemente al estado fisiológico de la planta, activando sus mecanismos de respuesta al estrés. Por ello, la presente tesis se centrará fundamentalmente en el papel de la vitamina E, potente antioxidante en plantas, y en la producción de jasmonatos, hormonas de respuesta a estrés, ante la distinta disponibilidad de Pi.
En la presente tesis se observó que la vitamina E (siendo el α-tocoferol la forma más abundante en hojas) juega un papel importante en el control de la longevidad de las plantas y sus efectos dependen de la disponibilidad de Pi. En concreto, el α-tocoferol incrementó la longevidad y previno la senescencia de las plantas en condiciones control, exceso de Pi o de disponibilidad leve de Pi, mientras que aceleró la senescencia ante una deficiencia muy severa de Pi. Por otro lado, observamos que la vitamina E participa activamente en la señalización celular. La vitamina E afecta, a través del control de la peroxidación lipídica, a la síntesis de diversas hormonas que derivan de hidroperóxidos lipídicos, como los jasmonatos que participan directamente en la señalización celular. Además, la deficiencia en α-tocoferol conlleva una reprogramación transcripcional de numerosos factores de transcripción relacionados con el crecimiento y las defensas químicas (muchos de ellos asociados a la síntesis de etileno), lo cual se observó tras el análisis de 1.880 factores de transcripción en la planta modelo Arabidopsis thaliana. De modo que la presencia o ausencia de α-tocoferol cambia la expresión de muchos factores de transcripción esenciales para el desarrollo y crecimiento de la planta. Además, la vitamina E tiene una papel importante en la regulación del metabolismo de ácidos grasos y puede ayudar al intercambio de señales del cloroplasto al núcleo, sugiriendo que la vitamina E influye en la señalización retrógrada. También se ha abordado el estudio del efecto del priming, o efecto memoria ante un estrés reiterado, debido a que en la naturaleza los estreses y las deficiencias nutricionales suelen ser recurrentes. En nuestros estudios se han observado efectos del priming en los niveles de transcripción de 45 factores de transcripción fuertemente asociados con el crecimiento y estrés. Además, la exposición reiterada de la deficiencia de Pi o priming, ha producido un gran incremento de α-tocoferol, remarcando la idea del papel fundamental que desempeña frente a la distinta disponibilidad de Pi.
Por otro lado, nos hemos centrado en el papel de los jasmonatos, hormonas vegetales de respuesta a estreses bióticos y abióticos. Los mutantes deficientes en vitamina E estudiados, con menor crecimiento que las plantas con α-tocoferol, sintetizan mayores cantidades de jasmonatos, sugiriendo un compromiso (trade-off) entre activar los mecanismos de fotoprotección y su crecimiento, con la capacidad de activar las defensas bióticas o químicas en la planta. Resulta curioso que las plantas deficientes en vitamina E presenten especialmente valores más altos de ácido 12-oxo-fitodienoico (OPDA), precursor del resto de jasmonatos. Dicho incremento del OPDA también se observó en la ortiga (Urtica dioica), fundamentalmente en plantas hembras. Ello sugiere que, además de ser el precursor de los jasmonatos, el OPDA podría desempeñar un papel defensivo y específico en plantas hembras de ortigas y en plantas de Arabidopsis deficientes en vitamina E. Nuestros resultados muestran además un marcado dimorfismo sexual secundario en términos de fotoinhibición, estrés oxidativo y fotoprotección en la ortiga junto a cambios en el sex-ratio según la disponibilidad de Pi.Phosphorus is a macroelement essential for the development and growth of all plants. Phosphorus deficiency causes many symptoms in plants, activating their stress response mechanisms. The response of stress in plants is usually based on the level of antioxidants produced and the synthesis of endogenous hormones. We studied the role of vitamin E, an important antioxidant in plants, and the production of jasmonates, a stress response hormone, in response to phosphorus availability. Vitamin E played an important role in controlling longevity, depending on the phosphorus availability. α-Tocopherol increased longevity and prevented senescence in plants under control conditions, excess phosphorus or mild phosphorus starvation. However, α-tocopherol accelerated senescence under severe phosphorus deficiency. Furthermore, vitamin E deficiency increased jasmonates levels, suggesting a trade-off between activating the mechanism of photoprotection and the activation of biotic or chemical defences in plant. A reduced growth and photoprotection in vitamin E mutant´s favours the capacity to synthesize chemical defences, such as jasmonates under abiotic stress conditions, thus suggesting again, a trade-off between growth, photoprotection and chemical defences. Conversely, vitamin E plays a major role in the regulation of fatty acid metabolism and could help transfer signals from chloroplast to the nucleus, suggesting vitamin E influences retrograde signalling. In addition, there are effects of priming on the transcript levels of 45 genes encoding, transcriptions factors mainly associated with growth and stress in wild-types plants in response to low phosphorus availability. Therefore, it appears α-tocopherol not only protects plants from photo-oxidative stress under phosphorus availability, but also controls defence-related transcriptional reprogramming and hormonal modulation. On the other hand, an increased nutrient availability in the soil can alleviate photoinhibition and photo-oxidative stress in the leaves of drought stressed nettle plants, especially in females. Sexratio increased under reduced phosphorus availability, increasing the number of females over males, probably because females are the most vulnerable gender under stress conditions. Females enhanced 12-oxo-phytodienoic acid contents under reduced phosphorus availability. This increase was, however, not accompanied by increases in other jasmonates, thus suggesting specific defensive roles for 12-oxo-phytodienoic acid in females.
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Subramanian, Senthil. "Short blue root (sbr), an arabidopsis mutant that ectopically over-expresses and ABA- and auxin-inducible transgene Dc3-GUS and has defects in the cell wall /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202002%20SUBRAM.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 238-266). Also available in electronic version. Access restricted to campus users.
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Cherif, Hayett. "EFFECT OF IBA AND DMSO ON IMPROVING BENCHGRAFT RESPONSE OF VITIS CHAMPINI 'DOG-RIDGE' ROOTSTOCK." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275367.
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Björklund, Simon. "Plant hormones in wood formation : novel insights into the roles of ethylene and gibberellins /." Umeå : Dept. of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200781.pdf.
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Guinn, Gene, and Donald L. Brummett. "Irrigation and Nitrogen Effects on Plant Hormones, Boll Retention, and Growth of Fruiting Branches." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/204460.
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An experiment was conducted in Phoenix in 1986 to determine effects of water and N deficits on ABA and IAA concentrations in young bolls and their abscission zones in relation to boll retention, and to determine the effects of N on growth of fruiting branches through the season. Water deficit decreased boll retention, decreased the concentration of free IAA in bolls and their abscission zones, and increased ABA in bolls and abscission zones. But, the concentration of ester IAA increased with water deficit (in contrast to free IAA). Because ester IAA resists degradation during stress, it may facilitate recovery when stress is relieved and some of it is converted to free IAA. N-deficiency symptoms were mild and did not appear early in the season. N had no effect on the ABA and IAA contents of bolls and their abscission zones, and had only a small effect on growth of fruiting branches. The N test is to be repeated in 1987 when N deficiency should be more severe.
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Campos, Marcelo Lattarulo. "Controle hormonal da defesa à herbivoria em tomateiro." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-19052009-081547/.
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Apesar de sua elevada importância econômica mundial, o cultivo do tomateiro é classificado como de alto risco devido à infestação da cultura por um grande número de pragas e doenças. Esse problema leva tal cultura a depender amplamente da aplicação de agroquímicos que, além de elevaram o custo de produção, são potenciais causadores de danos ambientais e do aparecimento de outras pragas e doenças. Observando o problema mais detalhadamente, pode-se perceber que uma grande parcela das perdas advém dos danos causados por artrópodes herbívoros, os quais são capazes de se alimentar de diversas partes da planta, causando, geralmente, perda de produtividade. Apesar disso, o tomateiro apresenta mecanismos de defesa naturais contra tais pragas, como tricomas e aleloquímicos, que agem intoxicando os artrópodes, dificultando sua movimentação e/ou alterando varias fases de seu desenvolvimento. A busca por genótipos de tomateiro com maior densidade de tricomas e elevado teor de aleloquímicos é hoje considerado um hot spot de pesquisa, devido ao benefício que trariam como redução do custo de produção e maior produtividade. Sabese que vários hormônios vegetais estão ligados a geração de caracteres anti-herbivoria, mas, atualmente, um grande foco vem sendo dado somente ao ácido jasmônico, devido ao seu claro papel na formação de tricomas, aleloquímicos, inibidores de proteases, dentre outros. Visando mostrar a importância de uma abordagem multi-hormonal nesse tipo de estudo, o presente trabalho teve como objetivo avaliar quais hormônios vegetais estão envolvidos com a formação de vários caracteres anti-herbivoria em tomateiro, como densidade de tricomas e teor de aleloquímicos e inibidores de protease. Para tal, fez-se uso da um grande número de mutantes hormonais introgredidos na cultivar Micro-Tom (a qual apresenta diversas facilidades de trabalho como porte reduzido e rápido ciclo de vida). Demonstrou-se que, apesar do ácido jasmônico ser extremamente importante na formação de tais caracteres, outros hormônios também atuam fortemente em tal papel. Etileno, giberelinas e auxina alteram de forma indireta a densidade de tricomas em tomateiro, através de alteração na área de células epidérmicas. O ácido jasmônico é um forte regulador positivo da formação de tricomas, do aleloquímico zingibereno e da formação de inibidores de protease. De forma antagônica, brassinosteróides parecem controlar negativamente a densidade de tricomas, a produção de zingibereno e inibidores de protease. Interessantemente, observou-se que esse controle negativo efetuado por brassinosteróides acontece através de um controle na via do ácido jasmônico, o qual foi comprovado pela produção de duplos mutantes. Resultados obtidos em testes com o herbívoro polífago Spodoptera frugiperda e com a praga de tomate Tuta absoluta (traça-do-tomateiro), bem como de análise de expressão gênica comprovaram a importância do ácido jasmônico, brassinosteróides e sua interação na defesa a herbivoria. Os resultados aqui apresentados sugerem que o foco para futuros estudos da formação de mecanismos anti-herbivoria em tomateiro deve ser voltado não só para o ácido jasmônico como para brassinosteroides e para suas ações antagônicas.Even though the cultivation of tomato has a high economical importance, this culture is classified as being of elevated risk because of it common infestation by pests and diseases. This problem makes this culture greatly dependent of the application of several agrochemicals, which leads to increase in cost of production, environmental damages and also facilitating the appearance of new pests and diseases. Looking carefully to the problem, it is possible to conclude that a great part of tomato losses are caused by herbivory-arthropods, which are capable of feeding of several parts of the plant, causing, generally, losses in the productivity. However, tomato has natural defense mechanisms against those pests, for example trichomes and allelochemicals, which act poisoning the arthropods, hindering their movement through the plant and/or altering steps of their development. The search for tomato genotypes with great density of trichomes and elevated levels of allelochemicals is nowadays being considered as a hot spot of research, because of the benefits it would provide (for example: a decrease in the cost of production and also a higher productivity). Although it is believed that many plant hormones are involved in the generation of anti-herbivory traits, a great focus has been given only to jasmonic acid because of it clear action in the formation of those traits, such as trichomes, allelochemicals, proteinase inhibitors and many others. The present work objective was to evaluate which hormones are involved in the formation of anti-herbivory traits such as trichome density and allelochemicals and proteinase inhibitors content. For this reason, we made use of several hormonal mutants already introgressed in the Micro-Tom cultivar (which presents benefits as small size and fast life cycle). It was showed that jasmonic acid is an important hormone in the formation of these traits, but other phytohormones also play important roles. Ethylene, gibberellins and auxin alters trichome density indirectly, by altering the area of epidermal cells and thus cell number. Jasmonic acid is a positive regulator of trichome formation, the allelochemicals zingiberene content and also in the formation of proteinase inhibitors. However, brassinosteroids acts by negatively controlling all of those. Interestingly, we observed that this negative control happens through the control of jasmonic acid pathway, a hormonal interaction that was proved by double-mutant analysis. Results obtained in tests with the polyphagous insect Spodoptera frugiperda and the tomato specific pest Tuta absoluta (tomato pinworm) and also with qPCR showed the importance of jasmonic acid, brassinosteroid and their interaction in herbivory defense. Our data suggest that future studies about the formation of antiherbivory traits should be analyzed by focusing the functions not only of jasmonic acid but also brassinosteroid and their antagonist functions.
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Zhang, Xunzhong. "Influence of Plant Growth Regulators on Turfgrass Growth, Antioxidant Status, and Drought Tolerance." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30739.
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A series of studies were conducted to examine the antioxidant status, drought and disease tolerance, and growth response to foliar application of soluble seaweed (Ascophyllum nodosum) extracts (SE) and humic acid (HA; 25% active HA or 2.9% active HA) in tall fescue (Festuca arundinacea Schreb), Kentucky bluegrass (Poa pratensis L.) and creeping bentgrass (Agrostis palusttis Huds.) grown under low (-0.5 MPa) and high (-0.03 MPa) soil moisture environments.
Foliar application of humic acid (2.9 % active HA) at 23.7 and 47.4 l/ha improved leaf water status, shoot and root development in tall fescue, Kentucky bluegrass and creeping bentgrass grown under drought. Humic acid (2.9% active HA) at 15.5 l/ha or SE at 326 g/ha significantly reduced dollarspot incidence and improved turf quality in creeping bentgrass.
Drought stress induced an increase of antioxidants alpha-tocopherol and ascorbic acid concentrations in the three turfgrass species. In the experiment with Kentucky bluegrass, drought stress increased beta-carotene concentration, but did not significantly influence superoxide dismutase (SOD) activity.
Foliar application of humic acid (25% active HA) at 5 l/ha and/or SE at 326 g/ha consistently enhanced alpha-tocopherol and ascorbic acid concentrations, leaf water status, and growth in the three cool-season turfgrass species grown under low and high soil moisture environments. In the experiment with Kentucky bluegrass, application of HA at 5 l/ha plus SE at 326 g/ha also increased beta-carotene content and SOD activity under low and high soil moisture environments. There were close positive correlations between the antioxidant status and shoot or root growth in the three turfgrass species regardless of soil moisture levels.
The antioxidant SOD activity, photosynthetic capacity in terms of Fvm690, and chlorophyll content in terms of Fm730/Fm690 exhibited a seasonal fluctuation in endophyte [Neotiphodium coenophialum (Morgan Jones and Gams) Glenn, Bacon, Price and Hanlin] -free and endophyte-infected tall fescue. Application of SE enhanced SOD activity, photosynthetic capacity, and chlorophyll content in tall fescue, especially at 4 weeks after SE treatment. The SOD activity, photosynthetic capacity and chlorophyll content were not significantly influenced by the endophyte infection. A close positive correlation between SOD and photosynthetic capacity during the summer was found in endophyte-free and endophyte-infected tall fescue.Ph. D.
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Dorans, Alison M. I. "The role of endogenous signals in defence and resistance responses of tomato." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265659.
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Leung, Ching-man, and 梁靜雯. "Characterization of two auxin-induced ACC synthase genes in tomatoes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36748845.
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SCHEERENS, JOSEPH CARL. "HORMONAL CONTROL OF SEX EXPRESSION IN BUFFALO GOURD (CUCURBITA FOETIDISSIMA HBK.)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187938.
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Seven field experiments and two in-vitro studies were performed to elucidate hormonal control of staminate flowering in gynoecious and monoecious buffalo gourd (Cucurbita foetidissima HBK.) sex types. Objectives included development of techniques effecting staminate induction on gynoecious phenotypes which normally produce abortive stamenless male buds. Natural and synthetic growth regulants shown to modify sex expression in other cucurbits were surveyed for their masculinizing potential. Several compounds exogenously-applied to apical meristems elicited changes in shoot morphology. However, only aminoethoxyvinylglycine (AVG, an ethylene synthesis inhibitor) effected staminate induction on gynoecious segregates. Growth rate, patterns of female flowering or ontogeny of stamenless buds differentiated prior to treatment were not influenced by AVG. AVG was applied at various dosages (0-500 ppm) and produced male buds on all replicates treated at levels of 125 ppm or higher. The mean number of staminate buds induced varied linearly with dosage and averaged from 0-7.5 male flowers/shoot. A control model for staminate induction mediated by endogenous ethylene was advanced and potential benefits of this phenomenon to breeding efforts and/or to hybrid seed production were discussed. Ethephon (an ethylene releasing compound) was applied at various dosages to monoecious plants in anticipation of simulating the gynoecious phenotype. Although morphological changes were evident (i.e. reduction in shoot growth rate and floral initiation, increase in floral bud abortion and tissue senescence), ethephon failed to reduce staminate flowering or increase differentiation of antherless buds as expected. Dosage levels employed and/or confounding environmental factors may have contributed to the lack of staminate inhibition. During in-vitro studies, indirect evidence for ethylene-mediated control of male flowering was obtained by staminate proliferation in buds of gynoecious explants treated with silver nitrate (an inhibitor of ethylene action) and by formation of stamenless buds on monoecious explants treated with ethephon. However, low levels of floral induction under culture conditions employed rendered these results inconclusive. An incidental study of segregation ratios among AVG-facilitated self- and cross-pollination progeny upheld the supposition for monogenic inheritance of gynoecy in buffalo gourd.
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Junior, Celso Gaspar Litholdo. "Identificação e expressão de genes da biossíntese do jasmonato na interação entre Theobroma cacao e Moniliophthora perniciosa." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-10122009-100915/.
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A doença vassoura-de-bruxa do cacaueiro (Theobroma cacao L.), causada pelo basidiomiceto Moniliophthora perniciosa consiste numa importante enfermidade e apenas o uso de variedades resistentes representa uma solução econômica e ambientalmente viável. Os hormônios vegetais são imprescindíveis na rede de sinalização envolvida na resposta contra uma grande variedade de estresses bióticos e abióticos, sendo bem reconhecido o papel crucial do ácido salicílico (AS), etileno (ET) e os jasmonatos (JA) na interação planta-patógeno. O mecanismo de resistência observado em T. cacao contra o fungo hemibiotrófico M. perniciosa parece não envolver resposta de hipersensibilidade mediada pela sinalização por AS, e caracteriza-se pela menor incidência de sintomas e atenuação do crescimento micelial no material resistente. A resposta regulada por JA e/ou ET é determinada pela contenção e redução da colonização de tecidos infectados pelo patógeno, com atenuação dos sintomas manifestados, e está associada com a indução e produção de inibidores de protease, enzimas líticas da parede de fungos e enzimas do metabolismo secundário e cujo os genes demonstraram indução diferencial em amostras inoculadas com M. perniciosa. Recentemente, foi demonstrada a produção de AS pelo fungo M. perniciosa, o que poderia estar associado a um desarranjo hormonal na planta, auxiliando o pátogeno no processo infectivo. A partir destas evidências este trabalho teve como hipótese que JA e/ou ET estaria regulando a interação T. cacao e M. perniciosa. Sabe-se que a transcrição de genes codificantes das enzimas da via de biossíntese de JA é induzida por aplicação exógena de metil-jasmonato (MJ) e por patógenos, assim para verificar a participação de JA na resposta de defesa de cacau, seqüências de genes que codificam para enzimas da via de biossíntese foram identificadas, classificadas e confirmados sua identidade por seqüenciamento. A indução e expressão quantitativa destes, além dos genes Samsi, Accox, Pal, Jaz e Della, foram avaliadas entre o acesso susceptível à M. perniciosa (\'P7\') e o resistente (\'CAB 214\') de T. cacao, em experimentos de aplicação de indutores (AS, ET e MJ) e inoculação com M. perniciosa. As análises de expressão gênica relativa por RT-qPCR foram conduzidas e a resposta dos genes de biossíntese de JA, quando tratado com MJ no \'P7\' pareceu ser mais intensa e mais específica, enquanto que o acesso \'CAB 214\' apresentou resposta com menor intensidade, porém com resposta mais precoce, demonstrando que o mecanismo de regulação positiva pela aplicação exógena de MJ também ocorre em T. cacao. Em relação à inoculação, os resultados de expressão gênica sugerem uma diferença na resposta transcricional dos genes analisados sob inoculação de M. perniciosa entre o \'P7\' e o \'CAB 214\' onde os transcritos de Aos, Kat, Samsi e Jaz apresentaram elevação significativa somente no \'CAB 214\' em comparação ao \'P7\'. Em acessos resistentes, como \'CAB 214\', o efeito de AS produzido pelo fungo poderia não estar surtindo efeitos antagônicos, como indicado pelo aumento transcricional de Aos, gene codificador da principal enzima envolvida na biossíntese de JA, e embora os demais genes da via estejam sendo reprimidos, muito possivelmente a sinalização da resposta de defesa do acesso resistente \'CAB 214\' seja desencadeada por JA, devido ao papel central de AOS na sua biossíntese, e de maneira sinérgica ET estaria participando do mecanismo de resposta, indicado pela alta indução de Samsi no acesso resistenteWitches broom disease of cacao (Theobroma cacao L.), caused by the basidiomycete Moniliophthora perniciosa is an important disease and the use of resistant varieties is the only economic and environmental long-term solution. Plant hormones are essential in the signaling network involved in the response against a variety of biotic and abiotic stresses. It is well recognized the crucial role of salicylic acid (SA), ethylene (ET) and jasmonate (JA) in plant-pathogen interactions. The mechanism of resistance observed in Theobroma cacao against M. perniciosa does not appear to involve hypersensitivity response mediated by AS signaling, and it is characterized by lower incidence of symptoms and reduction of mycelial growth in resistant material. The response regulated by JA and/or ET is determined by the growth inhibition and a reduction of the colonization of infected tissues by the pathogen, together with an attenuation of symptoms. It is also associated with an induction and production of the protease inhibitors, lytic enzymes and enzymes of secondary metabolism and the genes enconding these enzymes have shown differential expression patterns in samples inoculated with M. perniciosa. It has been recently demonstrated that the production of AS by the fungus M. perniciosa could be associated with a hormonal disorder in the plant, which could therefore help the pathogen in the infective process. Considering this, the hypothesis that JA and/or ET would regulate the interaction of T. cacao with M. perniciosa was formulated in order to be tested by this research work. It is known that the transcription of genes encoding the enzymes of the JA biosynthesis pathway is induced by exogenous application of methyl jasmonate (MJ) and by pathogen, thus, in order to verify the involvement of JA in defense response of cocoa, sequences of genes that encode the enzymes of the JA biosynthesis pathway were isolated, identified, classified and had their identity confirmed by sequencing, and relative quantitative gene expression were evaluated in susceptible \'P7\' and resistant \'CAB 214\' plants of T. cacao. In addition genes Sams, Accox, Pal , Jaz and Della, were evaluated in experiments with application of inducers (AS, ET and MJ) and inoculation with M. perniciosa. Analysis of relative gene expression by RT-qPCR were conducted and \'P7\' seems to have the expression of jasmonate biosynthesis genes in a more intense and more specific manner when treated with MJ, while \'CAB 214\' shows an earlier yet lower response suggesting that the mechanism of positive regulation by the exogenous application of MJ also occurs in T. cacao. For the inoculation, the gene expression results suggest a difference in the transcriptional response from inoculation with M. perniciosa between \'P7\' and \'CAB 214\' in T. cacao. The effect of AS produced by the fungus may not have antagonistic effects in resistant materials such as \'CAB 214\', as indicated by the increase of the transcription of Aos gene that encodes the main enzyme involved in JA biosynthesis, so the defense responses of \'CAB 214\' is possibly triggered by JA signaling, because the central role of AOS in its biosynthesis, and may be part of synergistic ET signaling, indicated by high Samsi expression in resistance material
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Wang, You. "Development of yeast-based methods to screen for plant cytokinin-binding proteins." Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060123.141512/index.html.
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Norberg, Åke. "Isolation and characterization of regulatory peptides and bioactive compounds /." Stockholm : Karolinska institutet, 2004. http://diss.kib.ki.se/2004/91-7349-882-3/.
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Robles, Linda Marie. "Characterization of EER4 and SAR1 in relation to their role in ethylene signaling and dampening responses." Diss., [Riverside, Calif.] : University of California, Riverside, 2010. http://proquest.umi.com/pqdweb?index=0&did=2019848141&SrchMode=2&sid=3&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1274116478&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2010.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed May 17, 2010). Includes bibliographical references. Also issued in print.
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Bergonci, Tábata. "Análise funcional dos peptídeos RALF em Arabidopsis: avaliação do efeito do hormônio brassinolide em plantas superexpressoras e silenciadas para os genes AtRALF1 e AtRALF34." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-29052012-104800/.
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A exemplo do que ocorre em animais, peptídeos hormonais em plantas desempenham papéis importantes no crescimento, desenvolvimento e defesa. RALF é um peptídeo hormonal ubíquo em plantas que foi primeiramente isolado de folhas de tabaco. Embora não se saiba exatamente sua função, as informações até agora existentes apontam para um envolvimento com aspectos básicos da biologia celular, provavelmente alongamento celular. Peptídeos RALF em Arabidopsis são encontrados em uma família multigênica de 37 membros. Plantas transgênicas superexpressando o AtRALF1 sob o controle do forte promotor constitutivo 35S, mostram um fenótipo semi-anão e inibição do crescimento das raízes. Um fenótipo semelhante também foi observado quando o AtRALF23 foi superexpresso. O AtRALF23, ao contrário do AtRALF1, tem sua expressão inibida por brassinosteróides. Esses fatos sugerem que diferentes peptídeos hormonais RALF, apesar de convergirem para a mesma função, apresentam uma relação individualizada com outros hormônios. O objetivo desse trabalho foi contribuir para a determinação da função dos peptídeos RALF em plantas e para o esclarecimento da inter-relação existente entre eles e os demais hormônios vegetais. Para tal, selecionou-se as isoformas AtRALF1 e AtRALF34 com base em semelhança/dessemelhança estrutural e padrão de expressão. Plantas silenciadas e com altos níveis de expressão para ambos os genes foram obtidas e avaliadas. A construção gênica AtRALF1-GFP foi inserida em Arabidopsis sob o controle do promotor 35S e foi observada fluorescência no retículo endoplasmático, complexo de Golgi e apoplasto. Genes anteriormente reportados como induzidos em plantas 35S:AtRALF1 foram validados e utilizados em experimentos com o AtRALF1 e o brassinolide. O conjunto dos resultados sugere um efeito antagônico do peptídeo AtRALF1 com relação ao efeito do brassinolide no alongamento de hipocótilos e raízes. Plantas com altos níveis de AtRALF1 são resistentes a aplicação exógena de brassinolide, não exibindo as respostas características do hormônio esteróide. O antagonismo entre os dois hormônios também foi sugerido pela análise da expressão de genes que são induzidos por AtRALF1 e brassinolide.Like in animals, plant peptide hormones play important roles in growth, development and defense. RALF is a peptide hormone ubiquitous in plants that was first isolated from tobacco leaves. Although its function has not been established, the information gathered so far suggest its involvement with basic aspects of cellular biology, probably cellular elongation. RALF peptides in Arabidopsis are found in a multigene family of 37 members. Transgenic plants overexpressing AtRALF1 under the control of the strong constitutive promoter 35S, show a semi-dwarf phenotype and root growth inhibition. A similar phenotype was also observed when AtRALF23 was overexpressed. AtRALF23, as opposed to AtRALF1, is inhibited by brassinosteroids. These facts suggest that different RALF peptide hormones, despite the convergence to the same function, show a unique relationship with other hormones. The goal of this work was to contribute to the determination of the function of RALF peptides in plants and to clarify the inter-relationship between RALF and the other plant hormones. With that in mind, the isoforms AtRALF1 and AtRALF34 were selected based on primary structure similarity/dissimilarity and pattern of gene expression. Plants with high levels of expression or silenced for both genes were obtained and evaluated. The gene construct AtRALF1-GFP was introduced in Arabidopsis under the control of the 35S promoter and fluorescence was observed in the endoplasmic reticulum, Golgi apparatus and apoplast. Genes previously reported as induced in 35S:AtRALF1 plants were validated and used in AtRALF1 peptide and brassinolide experiments. Taken together our results suggest an antagonistic effect of the peptide AtRALF1 regarding the elongation effect of brassinolide in hypocotyls and roots. Plants with high levels of AtRALF1 are resistant to exogenously applied brassinolide, and do not show typical responses to the steroid hormone. The antagonism between the two hormones was also suggested by the gene expression analysis of the AtRALF1 and brassinolide inducible genes.
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Wheelhouse, Nicholas Mark. "The effect of amino acids on growth hormone action in ovine hepatocytes." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=185765.
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Many of the anabolic effects of growth hormone (GH) are indirect, occurring through GH-stimulated production of insulin-like growth factor-I (IGF-I) by the liver. As well as being GH regulated, plasma IGF-I concentrations have been demonstrated to be dependent upon protein nutrition, with low protein diets being associated with reduced plasma IGF-I concentrations. This effect cannot be reversed by GH, suggesting that liver sensitivity to GH is impaired. To investigate the mechanisms through which protein supply affects GH sensitivity, primary cultures of ovine hepatocytes were grown in defined media. In a first experiment the media contained various fractions (0.2, 1.0, 5.0) of portal vein amino acid concentrations in fed sheep. In the second 24h incubation period, unstimulated IGF-I secretion was highly sensitive the concentration of amino acids in the media, with significantly greater release of basal IGF-I in 5x compared to either 1x (P<0.05) or 0.2x amino acid containing media. In a second series of experiments the effects of specific amino acid depletions was examined. Methionine depletion of 0.2x portal amino acid concentrations ablated the GH response second 24h of culture without affecting basal IGF-I release. By comparison 3H-leucine incorporation into secreted protein, following 20 hours of culture in defined media was significantly reduced in 0.2x aa (P<0.01) and 1.0x aa (P<0.05) media compared with 5.0x aa media, however secretory protein synthesis was unaffected by methionine depletion to 0.2x portal concentrations. The results suggest that amino acid availability regulates both basal and GH stimulated IGF-I release in ovine hepatocytes. Furthermore reducing methionine concentrations in the culture media to 0.2x portal concentrations diminishes GH response without compromising protein secretion.
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Santos, Valdinei Moreira dos. "Agrochemicals on growth and hormonal relations of \'Micro-Tom\' and Arabidopsis roots under water deficit conditions." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-06012017-171318/.
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The increasing concerns launched by debates about climate changes added to the uncontrolled growth of world population have opened a market to natural inputs for a more sustainable agriculture. Taking those concerns together, it is very important to think in advance in terms of finding solutions to increase the food production, with improved quality and in a supposed changing environment. Natural substances such as seaweed biostimulants are coming up as inputs for crops yield and abiotic stress tolerance enhancement with increasing use in agriculture. In this scene, it is important to understand effects and mode of action of these substances on plant physiology to permit the development of consistent products and guarantee the delivery of solutions to growers that assist them in solving their needs. Therefore, this research was carried out aiming to understand the role of agrochemicals (classical plant growth regulators and seaweed biostimulants) on root development and hormonal relations of tomato \'Micro-Tom\' and Arabidopsis under water deficit conditions. Ascophyllum nodosum extracts (ANE) ability to stimulate endogenous hormonal responses in conditions of drought and osmotic stress was tested. We carried out experiments with two plant models: one is classically used in plant science studies and the other, a crop-like plant model whose scientific findings can be applied for several crops. We used tomato hormonal mutants and reporter lines grown in conditions of drought stress to study the effects of plant growth regulators and seaweed extracts on root growth and hormonal responses, respectively. Additionally, we tested in vitro the effects of these substances on root growth of Arabidopsis seedlings under osmotic stress conditions. The root development of tomato and Arabidopsis was negatively affected by the presence of water deficit caused by drought and osmotic stress, respectively. Gibberellins biosynthesis inhibitors only affected the root growth of gibberellin-deficient mutant (gib-3). Extracts of the same seaweed presented different effects on root growth of Arabidopsis seedlings and hormonal responsiveness in roots of tomato, possibly due to variability in their compositions. ANE A and B show opposite effects on root growth. ANE A promotes root growth, whereas ANE B shows inhibitory effects. These substances seem to have little influence on auxin responses in roots, however, they alter the balance between abscisic acid and ethylene under drought conditions. The standardization of the composition of seaweed extracts complemented with studies on their physiological and molecular effects in crops is crucial for the establishment of these agricultural inputs as one of the solutions for current and future requirements of food production.As crescentes preocupações oriundas a partir dos atuais debates sobre mudanças climáticas somadas ao descontrolado crescimento da população mundial têm dado espaço para o uso de insumos agrícolas naturais, objetivando sustentabilidade na agricultura. Diante de tais preocupações, é importante pensar antecipadamente e encontrar maneiras de aumentar a produção e a qualidade de alimentos, em um ambiente de supostas mudanças climáticas. Substâncias naturais, como bioestimulantes à base de alga, estão ganhando relevância como melhoradores da produtividade e tolerância a estresses abióticos com crescentes usos na agricultura. Diante desse cenário, é importante compreender os efeitos e modos de ação dessas substâncias na fisiologia das plantas para permitir o desenvolvimento de produtos consistentes e garantir aos produtores soluções que atendam às suas necessidades. Portanto, este estudo foi realizado com o objetivo de entender o papel de agroquímicos (reguladores vegetais clássicos e biostimulantes à base da alga) sobre o desenvolvimento radicular e relações hormonais do tomateiro \'Micro-Tom\' e Arabidopsis sob condições de estresse hídrico. Foi testada a habilidade de extratos Ascophyllum nodosum (ANE) em estimular respostas hormonais em condições de seca e estresse osmótico. Foram realizados experimentos com duas plantas-modelo: Arabidopsis que é largamente utilizada em estudos científicos de plantas e o tomateiro \'Micro-Tom\', uma planta-modelo mais adequada para estudos aplicados à agricultura sob condições tropicais. Foram utilizados mutantes hormonais e linhas-repórter de tomate cultivadas em condições de seca para o estudo dos efeitos dos reguladores vegetias e extratos de alga no crescimento radicular e respostas hormonais, respectivamente. Além disso, foram testados in vitro os efeitos dessas substâncias no crescimento radicular de plântulas de Arabidopsis em condições de estresse osmótico. O desenvolvimento radicular do tomateiro e Arabidopsis foi negativamente afetado pela ocorrência do déficit hídrico causado por seca e estresse osmótico, respectivamente. Inibidores de giberelinas afetaram apenas o crescimento radicular do mutante com baixo nível endógeno giberelinas (gib-3). Extratos da mesma espécie de alga apresentaram diferentes efeitos no crescimento radicular de plântulas de Arabidopsis e resposta hormonal em raízes de tomateiro. ANE A e B aprensenta efeitos opostos no desenvolvimento de raízes. ANE A promove o crescimento radicular enquanto ANE A inibe. ANEs pouco influenciam as respostas auxínicas, contudo, essas substâncias alteram o balanço entre entre ácido abscísico e etileno sob condições de estresse hídrico por seca. A padronização da composição de extratos de alga somada aos estudos sobre os seus efeitos fisiológicos e moleculares em culturas é crucial para o estabelecimento desses insumos agrícolas como uma das soluções para as necessidades atuais e futuras da produção de alimentos.
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Abad, Juan Carlos Guerrero. "Identificação da subtilase responsável pelo processamento do prepopeptídeo AtRALF1 em Arabidopsis thaliana." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-09022012-162000/.
Full textAbstract:
Desde a década de 90, uma nova família de moléculas de origem protéica e com características hormonais vem sendo estudada em plantas. Esse grupo de novas moléculas, coletivamente chamado de peptídeos hormonais, está envolvido com defesa, reprodução, crescimento e desenvolvimento. RALF, que é um desses novos peptídeos, é ubíquo em plantas e está envolvido com desenvolvimento vegetal. Em Arabidopsis existem 34 genes semelhantes ao RALF (AtRALFs). Nosso grupo mostrou que AtRALF1 é processado de um precursor maior por uma subtilase. Arabidopsis possui 56 subtilases, o objetivo deste trabalho é identificar a subtilase responsável pelo processamento do AtRALF1. Predição da localização subcelular e análise da expressão in silico, ambas confirmadas por análise da expressão por RT-PCR e fusões proteicas com a proteína verde fluorescente, permitiram reduzir para sete o número de subtilases candidatas. Cruzamentos entre mutantes nocaute ou plantas de baixa expressão por RNAi dessas sete subtilases com plantas superexpressoras do AtRALF1 identificaram as subtilases AtSBT6.1 (At5g19660) e AtSBT5.3 (At2g04160) como prováveis envolvidas no processamento do prepropeptídeo AtRALF1.Since the 90s, a new family of molecules of protein origin and with hormone characteristics has been studied in plants. This group of new molecules, collectively named peptide hormones, is involved in defense, reproduction, growth and development. RALF, one of these peptides, is ubiquitous in plants and is involved in plant development. In Arabidopsis there are 34 RALF-like genes (AtRALFs). Our group has shown that AtRALF1 is processed from a larger precursor by a subtilase. Arabidopsis has 56 subtilases, our goal is the identification of the specific subtilase that is responsible for the AtRALF1 processing. Prediction of subcelular localization and in silico gene expression analysis, both confirmed by RT-PCR expression analysis and chimeric proteins with green-fluorescent protein, allowed the reduction of the initial 56 candidates to only 7 subtilases. Crosses between knockout mutants or RNAi plants expressing low levels of subtilases with overexpressors of AtRALF1 identified the subtilases AtSBT6.1 (At5g19660) and AtSBT5.3 (At2g04160) as potentialy involved in the prepropeptide AtRALF1 processing.
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Vilarrasa, Blasi Josep. "Spatial analysis of brassinosteroid signaling in the stem cell niche of Arabidopsis primary root = Caracterització molecular de la funció de BRI1 en les cèl•lules mare de lʼarrel dʼArabidopsis." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/277540.
Full textAbstract:
The present PhD thesis work reports the molecular and genetic dissection for the role of plant steroid hormones Brassinosteroids (BRs) in root growth and development of Arabidopsis thaliana (Arabidopsis). A genetic, physiological and cellular analysis of existing BR mutants, together with the discovery of a novel pathway for the control of BR mediated stem cell divisions.
The results presented here provide experimental evidence for a role of BRs in stem cell homeostasis in the primary root of Arabidopsis. Specifically, BRs promote columella stem cell differentiation and the division of a set of low mitotic cells called quiescent center (QC) that maintain the surrounding stem cells. Using a microgenomic approach, a novel BR signaling component, BRAVO (Brassinosteroids at Vascular and Organizing Centre) has been identified that is specifically expressed in the stem cells. BRAVO encodes a R2-R3 MYB transcription factor (MYB56) that acts as a negative regulator of BRmediated QC divisions. This study uncovers a fine example of negative regulation model; BRAVO is directly repressed and interacts with BES1 creating a molecular switch that controls QC divisions.
The work carried out during this PhD thesis shed light to a new function of brassinosteroids in the regulation of stem cells. BRAVO provides plasticity to the stem cells to response to DNA damage, and at the same time robustness to ensure QC function upon damage. The control of plant stem cell homeostasis is pivotal to understand plant adaptation to environmental changing conditions and provides a new mechanism to understand plants life span.Aquesta tesi doctoral té com a objectiu principal investigar els efectes de les hormones vegetals esteroides, Brassinosteroids (BRs), durant el desenvolupament de lʼarrel primària dʼArabidopsis thaliana (Arabidopsis). Per tal dʼassolir aquest objectiu hem realitzat una caracterització genètica, fisiològica i anàlisi cel•lular de mutants de BRs. Així mateix, sʼha descobert una nova ruta de senyalització que controla les divisions de les cèl•lules mare mediades per BRs, Els nostres resultats experimentals mostren com els BRs controlen la homeòstasi de les cèl•lules mare de lʼarrel. En concret, els BRs promouen la diferenciació de les cèl•lules mare de la columel•la i la divisió dʼun grup de cèl•lules mitòticament inactives que actuen en el manteniment de les cèl•lules mare, el centre quiescent (QC). Mitjançant un abordatge microgenòmic hem identificat un nou element de la ruta de senyalització dels BRs específic de les cèl•lules mare, BRAVO (Brassinosteroids at Vascular and Organizing Centre). BRAVO és un factor de transcripció R2R3 de la família MYB (MYB56), que actua com a regulador negatiu de les divisions de QC. Els nostres resultats mostren un model de regulació negativa, on BES1 reprimeix directament i interacciona amb BRAVO, creant un interruptor molecular que controla les divisions del QC. El treball realitzat durant aquesta tesis doctoral permet proposar una nova funció dels BRs en el control de les cèl•lules mare. BRAVO dóna plasticitat a les cèl•lules mare per a poder respondre al dany sobre lADN, així com robustesa per evitar-lo. El control de la homeòstasi de les cèl•lules mare en plantes és vital per entendre lʼadaptació dʼaquests organismes sèssils i la longevitat que presenten algunes espècies.