Academic literature on the topic 'Rudimentary glumes'

Based on morphological study and corroborated by unpublished molecular phylogenetic analyses, five grass species of high-mountain grasslands in Mexico, Central and South America, Agrostis bacillata, A. exserta, A. liebmannii, A. rosei, and A. trichodes, are transferred to Podagrostis and bring the number of species of this genus recognized in the New World to ten. The name Apera liebmannii is lectotypified and epitypified. We provide an updated genus description for Podagrostis, and updated species descriptions, images, and notes on the new combinations. The diagnostic characteristics differentiating Podagrostis from Agrostis are: a) palea that reaches from (2/3) ¾ to almost the apex of the lemma; b) florets that usually almost equal the length of the glumes or are at least ¾ the length of the glumes; c) rachilla extension present and emerging from under the base of the palea as a slender short stub (rudimentary or up to 1.4 mm long, sometimes obscure in most florets in P. rosei), smooth or scaberulous, glabrous or distally pilulose (hairs < 0.3 mm long); d) lemmas usually awnless, sometimes with a short straight awn 0.2–0.6 mm long, inserted medially or in the upper 1/3 of the lemma, not surpassing the glumes (awn well-developed, straight or geniculate and inserted in lower 1/3 of lemma, not or briefly surpassing glumes in P. rosei). We include a generic key to distinguish the species of Podagrostis from other similar genera in Latin America and a key to distinguish the species of Podagrostis now accepted as occurring in these areas.

Seedling vernalization was more effective than seed vernalization in promoting flowering of downy brome (Bromus tectorumL. # BROTE). Vernalizing imbibed downy brome caryopses at 3 C for 0 to 30 days did not induce rapid flowering when the caryopses were planted. Downy brome seedlings were exposed for 30 days to six photoperiod/temperature treatments. After subsequent transfer to long days, plants from the short-day/3 C treatment flowered within 30 days. Flowering was delayed or was absent in treatments with higher temperatures or long days. The shoot apex increased in volume during the short-day/3 C vernalization period. Two days following vernalization, floral initiation had occurred. By day 5, lateral organs had proliferated. Rudimentary glumes and lemmas were visible by day 8.

SUMMARYFloral organ development influences plant reproduction and crop yield. The mechanism of floral organ specification is generally conserved in angiosperms as demonstrated by the ‘ABC’ model. However, mechanisms underlying the development of floral organs in specific groups of species such as grasses remain unclear. In the genus Oryza (rice), a spikelet consists of a fertile floret sub-tended by a lemma, a palea, two sterile lemmas and rudimentary glumes. To understand how the lemma is formed, a curve-shaped lemma-distortion1 (ld1) mutant was identified. Genetic analysis confirmed that the ld1 mutant phenotype was due to a single recessive gene mutation. Using a large F2 population, the LD1 gene was mapped between markers Indel-7-15 and Indel-7-18, which encompassed a region of 15·6 kilo base pairs (kbp). According to rice genome annotations, two putative genes, LOC_Os07g32510 and LOC_Os07g32520, were located in this candidate region. However, DNA sequencing results indicated only 1 base pair (bp) substitution (T⇨C) was found in LOC_Os07g32510 between the wild-type and the ld1 mutant. Thus LOC_Os07g32510, encoding a DNA binding with one zinc finger (DoF) containing protein, was the candidate gene for LD1. Further analysis showed that mutation of the amino acid cysteine (C) to arginine (R) was likely to lead to zinc finger protein deactivation. Phylogenetic and conservation analysis of the gene from different species revealed that cysteine was critical to LD1 function. As a new gene controlling lemma development, the study of LD1 could provide insights into rice floral organ formation mechanisms.

Burkholderia glumae causes rice (Oryza sativa) bacterial panicle blight, which is an increasingly economically important disease worldwide. As the first B. glumae strain isolated from patients with chronic infections, AU6208 has been reported as an opportunistic clinic pathogen. However, our understanding of the molecular mechanism underlying human pathogenesis by B. glumae remains rudimentary. In this study, we report the complete genome sequence of the human-isolated B. glumae strain AU6208 and compare this to the genome of the rice-pathogenic B. glumae type strain LMG 2196T. Analysis of the average nucleotide identity demonstrated 99.4% similarity between the human- and plant-pathogenic strains. However, the phenotypic results from this study suggest a history of niche adaptation and divergence. In particular, we found 44 genes were predicted to be horizontally transferred into AU6208, and most of these genes were upregulated in conditions that mimic clinical conditions. In these, the gene pair sbnAB encodes key enzymes in antibiotic biosynthesis. These results suggest that horizontal gene transfer in AU6208 may be responsible for selective advantages in its pathogenicity in humans. Our analysis of the AU6208 genome and comparison with that of LMG 2196T reveal the evolutionary signatures of B. glumae in the process of switching niches from plants to humans.

Pseudosasa was confirmed as polyphyletic by recent phylogenetic analyses, with Chinese species of Pseudosasa distantly related to those from Japan. Among the Chinese species of Pseudosasa, Pseudosasa pubiflora is a morphologically unique as well as taxonomically problematic species endemic to South China, of which the generic designation is still uncertain. Molecular analyses based on both plastid and nuclear genomic data demonstrated that this species is closest to the recently published genus Sinosasa. Morphologically, the two are somewhat similar to each other in flowering branches developing at the nodes of every order of branches, raceme-like units of inflorescence with 3–5 short spikelets, each spikelet with few florets including a rudimentary one at the apex, and each floret with 3 stamens and 2 stigmas. However, P. pubiflora is very different from Sinosasa species in many reproductive and vegetative characters, such as the morphology of paracladia (lateral spikelet “pedicels”), the absence or existence of pulvinus at the base of paracladia, the relative length of the upper glume and the lowest lemma, the shape of lodicules and primary culm buds, the branch complement, the morphology of nodes, culm leaves and dried foliage leaf blades, and the number of foliage leaves per ultimate branchlet. The morphological and molecular evidence warrants recognition of a new genus to accommodate this unique species, which is here named Kengiochloa. After consulting related literature and examination of herbarium specimens or specimen photos, a taxonomic revision of K. pubiflora and its synonyms was made, and it was confirmed that four names, viz. P. gracilis, Yushania lanshanensis, Arundinaria tenuivagina and P. parilis, should be merged with K. pubiflora, while Indocalamus pallidiflorus and Acidosasa paucifolia are distinct species.

Fibrin has been used clinically for wound coverings, surgical glues, and cell delivery because of its affordability, cytocompatibility, and ability to modulate angiogenesis and inflammation. However, its rapid degradation rate has limited its usefulness as a scaffold for 3D cell culture and tissue engineering. Previous studies have sought to slow the degradation rate of fibrin with the addition of proteolysis inhibitors or synthetic crosslinkers that require multiple functionalization or polymerization steps. These strategies are difficult to implement in vivo and introduce increased complexity, both of which hinder the use of fibrin in research and medicine. Previously, we demonstrated that additional crosslinking of fibrin gels using bifunctionalized poly(ethylene glycol)-n-hydroxysuccinimide (PEG-NHS) slows the degradation rate of fibrin. In this study, we aimed to further improve the longevity of these PEG-fibrin gels such that they could be used for tissue engineering in vitro or in situ without the need for proteolysis inhibitors. It is well documented that increasing the salinity of fibrin precursor solutions affects the resulting gel morphology. Here, we investigated whether this altered morphology influences the fibrin degradation rate. Increasing the final sodium chloride (NaCl) concentration from 145 mM (physiologic level) to 250 mM resulted in fine, transparent high-salt (HS) fibrin gels that degrade 2–3 times slower than coarse, opaque physiologic-salt (PS) fibrin gels both in vitro (when treated with proteases and when seeded with amniotic fluid stem cells) and in vivo (when injected subcutaneously into mice). Increased salt concentrations did not affect the viability of encapsulated cells, the ability of encapsulated endothelial cells to form rudimentary capillary networks, or the ability of the gels to maintain induced pluripotent stem cells. Finally, when implanted subcutaneously, PS gels degraded completely within one week while HS gels remained stable and maintained viability of seeded dermal fibroblasts. To our knowledge, this is the simplest method reported for the fabrication of fibrin gels with tunable degradation properties and will be useful for implementing fibrin gels in a wide range of research and clinical applications.

Studies on meristem identity regulators in Rice (Oryza sativa), a model plant for cereal crops have revealed how meristem identity and transitions are controlled, bearing implications for crop yield improvement. We were interested in exploring the function of OsULTRAPETALA1 (OsULT1), whose Arabidopsis homolog is a TrxG Factor, in rice inflorescence and spikelet/floret organ development. OsULT1 is a direct downstream target of floret meristem identity and development transcriptional regulator OsMADS1 (Khanday et al., 2016). The aim of this thesis is to functionally characterize OsULT1 by raising transgenic rice plants with ubiquitous knockdown and other lines that are overexpressors of OsULT1. In the dsRNAi-OsULT1 knockdown transgenics, we observed reduced plant height, panicle branching, and delay in flowering time. Interestingly, the pUbi-OsULT1 overexpression transgenics showed a converse phenotype of precocious flowering. Histological studies on young branching inflorescence meristem from the dsRNAi-OsULT1 knockdown transgenics and wild-type plants, was done to understand the onset of developmental abnormalities during panicle development. We observed an increase in the number of lateral organs made from the spikelet meristem; this could be due to a delay in SM to FM transition. These data suggest OsULT1 to be a heterochronic factor regulating meristem progression. Histological analyses of young spikelets showed a homeotic conversion of sterile lemma to a lemma-like organ. In floral meristem of knockdown plants, reduced palea and altered stamen number were noted. We quantified expression levels of some selected well-studied spikelet meristem regulators. qRT-PCR done on RNA from pooled dsRNAi-OsULT1 panicle tissues (Early-stage: 0.1 to 0.3cm and Late-stage: 0.4 to 2cm) and compared to similarly staged wild-type panicles. We found OsMADS1 and OsIDS1 transcript levels to be up-regulated and down-regulated respectively in the dsRNAi-OsULT1 transgenics compared to the wild-type. This could relate to the sterile lemma and rudimentary glume phenotypes observed in the affected knockdown spikelets. Since chromatin modifiers lacking DNA-binding domain recruit TF’s to target genes, we tested the possibility of protein interaction between OsULT1 and OsMADS1 using the yeast two-hybrid assay. This assay confirmed the interaction between OsULT1 and OsMADS1, thus raising the prospect of such a TF–Chromatin factor complex regulating downstream target gene expression by modulation of the histone modification status of the gene loci relevant for SM and FM development. We surveyed the abundance of repressive and activating histone marks in two developmental stages in wild-type panicle tissues as an attempt to correlate histone marks with transcript abundance. We observed as expected an inverse correlation between the expression levels of OsMADS34 and OsMADS22 and the abundance of the H3K27me3 mark at these two loci. We then evaluated the chromatin status at the genes which are differentially expressed in the dsRNAi-OsULT transgenics like OsMADS1, OsIG1, and OsIDS1. The results of the ChIP-qPCR analysis to assess the abundance of histone marks indicate a complex relationship between chromatin marks and transcript abundance. For future in-depth studies of gene targets in specific stages of SM and FM, we have standardized Laser Capture Micro-dissection of specific rice wild-type panicle meristems for transcriptomic studies in these recessed difficult to access tissues. Preliminary data indicate sets of transcripts that could be specific to Primary Branch Meristem (PBM), Secondary Branch Meristem (SBM), and Floral Meristem (FM). Overall, we have used reverse genetics tools to elucidate the functions of a predicted Trithorax-Group factor OsULT1 in spikelet meristem transient maintenance, its lateral organ development, and effects on floret organ numbers. The implications of the studies support the published hypothesis that ancestral rice species had three-fertile floret per spikelet (Ren et al., 2020; Zhang et al., 2017), instead of the one floret per spikelet in seen in extant species. The work in this thesis highlights the important role of chromatin modifiers like the Trithorax factors in rice panicle development.