Project description:Rhizobia are soil bacteria that induce nodule formation on leguminous plants. In the nodules, they reduce dinitrogen to ammonium that can be utilized by plants. Besides nitrogen fixation, rhizobia have other symbiotic functions in plants including phosphorus and iron mobilization and protection of the plants against various abiotic stresses including salinity. Worldwide, about 20% of cultivable and 33% of irrigation land is saline, and it is estimated that around 50% of the arable land will be saline by 2050. Salinity inhibits plant growth and development, results in senescence, and ultimately plant death. The purpose of this study was to investigate how rhizobia, isolated from Kenyan soils, relieve common beans from salinity stress. The yield loss of common bean plants, which were either not inoculated or inoculated with the commercial R. tropici rhizobia CIAT899 was reduced by 73% when the plants were exposed to 300 mM NaCl, while only 60% yield loss was observed after inoculation with a novel indigenous isolate from Kenyan soil, named S3. Expression profiles showed that genes involved in the transport of mineral ions (such as K+, Ca2+, Fe3+, PO43-, and NO3-) to the host plant, and for the synthesis and transport of osmotolerance molecules (soluble carbohydrates, amino acids, and nucleotides) are highly expressed in S3 bacteroids during salt stress than in the controls. Furthermore, genes for the synthesis and transport of glutathione and γ-aminobutyric acid were upregulated in salt-stressed and S3-inocculated common bean plants. We conclude that microbial osmolytes, mineral ions, and antioxidant molecules from rhizobia enhance salt tolerance in common beans.
Project description:Cold tolerance of crop plants influences survival and productivity under low-temperature conditions. Elucidation of molecular mechanisms underlying low temperature tolerance could be helpful in breeding. In this study, based on transcriptome and metabolomic analysis, we successfully identified a number of candidate genes and metabolites involved in key biological pathways during cold stress response. During cold stress, a total of 22335 differentially expressed genes were detected in each group (093Cvs120C, 093Tvs120T, 093Cvs093T, 120Cvs120T), of which 12978 were up-regulated and 9357 were down-regulated. A total of 18,166 metabolites were detected and 7,670 metabolites were annotated, among which 654 were secondary metabolites with significant differences. Under cold stress, the petC gene in both common bean cultivars was down-regulated, which led to the decrease of photosynthetic efficiency. Transcriptome and metabolome results under cold stress showed that the synthesis pathways of various unsaturated fatty acids including alpha-linolenic acid were significantly up-regulated and their contents were enriched. In addition, leukotriene-A4 hydrolase in the catabolic pathway of 120 arachidonic acid was inhibited under cold stress. Furthermore, the content of arachidonic acid was increased. A variety of amino acids in both 093 and 120 were enriched under cold stress, which was beneficial to the resistance of bean to osmotic stress caused by cold stress. However, in addition to a few amino acids that were enriched together, 093 was mainly positively charged and 120 was negatively charged among the amino acids that were enriched differently. This is an interesting phenomenon that needs to be further studied. In addition, under cold stress, we found that genes in multiple metabolic pathways, including ABA, GA, JA and other hormone metabolism pathways, were differentially expressed in 093 and 120.
Project description:Paraburkholderia phymatum belongs to the β-subclass of proteobacteria. It has recently been shown to be able to nodulate and fix nitrogen in symbiosis with several mimosoid and papillionoid legumes. In contrast to symbiosis of legumes with α-proteobacteria, very little is known about the molecular determinants underlying the successful establishment of this mutualistic relationship with β-proteobacteria. In this study, we analyzed RNA-seq data of free-living P. phymatum growing under nitrogen replete and limited conditions, the latter partially mimicking the situation in nitrogen deprived soils. Among the genes up-regulated under nitrogen limitation, we found genes involved in exopolysaccharide production and motility, two traits relevant for plant root infection. Next, RNA-seq data of P. phymatum grown under free-living conditions and from symbiotic root nodules of Phaseolus vulgaris (common bean) were generated and compared. Among the genes highly up-regulated during symbiosis, we identified an operon encoding a potential cytochrome o ubiquinol oxidase (Bphy_3646-49). Bean root nodules induced by a cyoB mutant strain showed reduced nitrogenase and nitrogen fixation abilities suggesting an important role of the cytochrome for respiration inside the nodule. Analysis of mutant strains for RNA polymerase transcription factor rpoN (σ54) and its activator NifA indicated that – similar to the situation in α-rhizobia – P. phymatum RpoN and NifA are key regulators during symbiosis with P. vulgaris.
Project description:Common bean (Phaseolus vulgaris L.) is the most consumed grain legume in developing countries in Latin America and Sub-Saharan Africa1. Like other legumes, common bean seeds are rich in protein, carbohydrates, fibers and other health-promoting phenolic compounds thus being vital for food security and income source for local small farmers2. Seed quality traits depend on accumulation of various storage molecules during the seed development (SD) process and influenced by the genotype and adaptive changes to environment3. Concerning common bean, there is still a lack of a deeper molecular knowledge of SD that is hampering the development of new biotech approaches for seed trait modulation and could timely address challenges of agriculture or industry. Our present work aims to unravel the molecular mechanisms underlying SD using a proteomic approach. To achieve this goal, we characterized SD in terms biomass, seed length and weight in the genotype SER16, one of the most promissory drought-resistant release of the CIAT-CGIAR. Seed samples were collected at the 4 main SD stages: Late-Embryogenesis (10 days after anthesis, d.a.a.), Early (20 d.a.a.) and Late Maturation (30 d.a.a.) and Desiccation (40 d.a.a.). The analysis of bean proteome was conducted using a gel-free proteomic analysis (LC-MS/MS) under the scope of EU-FP7-PRIME-XS project. A total of 410 unique proteins were differentially expressed throughout the 4 major seed development stages, in which most of the identified proteins belong in the ‘protein metabolism’ (31,98%) functional category, that includes synthesis, regulation, folding. Other functional categories are represented such as carbohydrate and lipid metabolism (11,26%) and stress/defense and redox metabolism (11,04%). We identified 93 proteins were unique to the first (10-20 d.a.a.), 22 to the second (20-30 d.a.a.) and 40 to the last (30-40 d.a.a.) phase transition, reflecting the major biological processes occurring at this specific seed developmental stage. This study will contribute to reveal key metabolic pathways and mechanisms with potential role in modulating common bean seed development and quality traits.
Project description:Common bean (Phaseolus vulgaris L.) is a relevant crop cultivated over the world, largely in water insufficiency vulnerable areas. Since drought is the main environmental factor restraining worldwide crop production, efforts have been invested to amend drought tolerance in commercial common bean varieties. However, scarce molecular data are available for those cultivars of P. vulgaris with drought tolerance attributes. As a first approach, Pinto Saltillo (PS), Azufrado Higuera (AH), and Negro Jamapa Plus (NP) were assessed phenotypically and physiologically to determine the outcome in response to drought on these common bean cultivars. Based on this, a Next-generation sequencing approach was applied to PS, which was the most drought-tolerant cultivar to determine the molecular changes at the transcriptional level. The RNA-Seq analysis revealed that numerous PS genes are dynamically modulated by drought. In brief, 1005 differentially expressed genes (DEGs) were identified, from which 645 genes were up-regulated by drought stress, whereas 360 genes were down-regulated. Further analysis showed that the enriched categories of the up-regulated genes in response to drought fit to processes related to carbohydrate metabolism (polysaccharide metabolic processes), particularly genes encoding proteins located within the cell periphery (cell wall dynamics). In the case of down-regulated genes, heat shock-responsive genes, mainly associated with protein folding, chloroplast, and oxidation-reduction processes were identified. Our findings suggest that secondary cell wall (SCW) properties contribute to P. vulgaris L. drought tolerance through alleviation or mitigation of drought-induced osmotic disturbances, making cultivars more adaptable to such stress. Altogether, the knowledge derived from this study is significant for a forthcoming understanding of the molecular mechanisms involved in drought tolerance on common bean, especially for drought-tolerant cultivars such as PS.
Project description:TIFY is a large plant-specific transcription factor gene family. A subgroup of TIFY genes named JAZ (Jasmonate-ZIM domain) has been identified as repressors of jasmonate (JA)-regulated transcription in Arabidopsis and other plants. JA signaling is involved in many aspects of plant growth/development and in the defense responses to biotic and abiotic stresses. Here we identified the TIFY genes (designated as PvTIFY) from the legume common bean (Phaseolus vulgaris) and functionally characterized PvTIFY10C as a transcriptional regulator. Twenty-three genes from the PvTIFY gene family were identified through whole genome sequence analysis. Most of these were induced upon methyl-JA elicitation. We selected PvTIFY10C as a representative JA-responsive PvTIFY gene for further functional analysis. Transcriptome analysis via microarray hybridization using the designed Bean Custom Array 90K was performed in transgenic roots of composite plants with modulated -RNAi-silencing or over-expression- PvTIFY10C gene expression. Data were interpreted using Mapman adapted to common bean. Microarray differential gene expression data were validated by real-time qRT-PCR expression analysis. Comparative global gene expression analysis revealed opposite regulatory changes in processes such as RNA and protein regulation, stress response and metabolism in silenced vs. over-expressing roots. These data point to transcript reprogramming -mainly repression- orchestrated by PvTIFY10C. In addition we found that several PvTIFY genes as well as genes from the JA biosynthetic pathway responded to P-deficiency. Relevant P-responsive genes that participate in carbon metabolic pathways, cell wall synthesis, lipid metabolism, transport, DNA, RNA and protein regulation, signaling, were oppositely-regulated in control vs. PvTIFY10C silenced roots. These data indicate that PvTIFY10C regulates, directly or indirectly, gene expression of some P-responsive genes something that could be mediated by JA-signaling. Our work contributed to the functional characterization of PvTIFY transcriptional regulators in common bean, an agronomically important legume. Members from the large PvTIFY gene family are important global transcriptional regulators that could participate as repressors of the JA signaling pathway. In addition we propose that the JA-signaling pathway that involves PvTIFY genes might play a role in regulating the plant response / adaptation to P-starvation.