Project description:Drought is one of the major environmental factors limiting biomass and seed yield production in agriculture. In this research we focused on plants from Fabaceae family, which have a unique ability for establishment of symbiosis with nitrogen-fixing bacteria, and are relatively susceptible to water limitation. We present the changes in nitrogenase activity and global gene expression occurring in Medicago truncatula and Lotus japonicus root nodules during water deficit. Our results prove a decrease in the efficiency of nitrogen fixation as well as extensive changes in plant and bacterial transcriptomes shortly after watering cessation. We show for the first time that not only symbiotic plant component, but also Sinorhizobium meliloti and Mesorhizobium loti bacteria residing in the root nodules of M. truncatula and L. japonicus, respectively, adjust their gene expression in response to water shortage. Although our results demonstrate that both M. truncatula and L. japonicus root nodules are susceptible to water deprivation, they indicate significant differences in plant and bacterial response to drought between tested species, which may be related to various type of root nodules formed by these species.
Project description:We studied potentially amyloidogenic proteins (e.g. protein forming polymers and complexes that are resistant to treatment with ionic detergents) in root nodules formed by two lines of garden pea (P. sativum L.): Sprint-2 (Fix+ phenotype) and Sprint-2Fix- (sym31) (Fix- phenotype) inoculated with the Rhizobium leguminosarum bv. viciae RCAM1026 root nodule bacteria. The Fix+ phenotype is characterized by effective (ability to fix nitrogen) root nodules formation. The Fix- line is a descendant of the Fix+ line and forms ineffective root nodules (unable to fix nitrogen) with undifferentiated bacteroids. We demonstrated the presence of both plant and bacterial proteins in detergent resistant fractions, including previously identified amyloid proteins RopA and RopB of R. leguminosarum and vicilin of P. sativum L.
Project description:The secretion of metabolites by plant roots is a key determinant of microbial growth and colonisation. We have used Pisum sativum and its natural symbiont Rhizobium leguminosarum (it can form N2 fixing nodules on pea roots) to study the natural metabolites secreted by roots. To do this root secretion was harvested from pea plants grown under sterile conditions. This root exudate was then concentrated and used as a sole carbon and nitrogen source for growth of the bacteria in the laboratory. These bacteria were harvested in mid-exponential growth and RNA extracted for microarray analysis. As control cultures the bacteria were grown on 30 mM pyruvate as a carbon source and 10 mM ammonium chloride as a nitrogen source and RNA extracted. Two colour microarrays were performed using root exudate cultures versus pyruvate ammonia grown cultures. This was done in biological triplicate.
Project description:12plex_medicago_2014_02 - nar nodule vs root transcriptome - which are the genes differentially expressed in alfalfa spontaneous (non rhizobium-infected) nodules vs. control roots? - biological material: aeroponically grown cuttings of a Medicago sativa (alfalfa) accession that produces empty nodules when nitrogen-starved. Samples for transcriptome comparison: isolated NAR nodules (10 days post N-starvation) vs. roots of the same plants (pools of 3 roots).
Project description:Rhizobia are soil bacteria that can enter into complex symbiotic relationships with legumes, where rhizobia induce the formation of nodules on the plant root. Inside nodules, rhizobia differentiate into nitrogen-fixing bacteroids that reduce atmospheric nitrogen into ammonia, secreting it to the plant host in exchange for carbon. During the transition from free-living bacteria to bacteroids, rhizobial metabolism undergoes major changes. To investigate the metabolism of bacteroids and contrast it with the free-living state, we quantified the proteome of unlabelled bacteroids relative to 15N-labelled free-living rhizobia. The data were used to build a core metabolic model of pea bacteroids for the strain Rhizobium leguminosarum bv. viciae 3841.
Project description:Background: The soil environment is responsible for sustaining most terrestrial plant life on earth, yet we know surprisingly little about the important functions carried out by diverse microbial communities in soil. Soil microbes that inhabit the channels of decaying root systems, the detritusphere, are likely to be essential for plant growth and health, as these channels are the preferred locations of new root growth. Understanding the microbial metagenome of the detritusphere and how it responds to agricultural management such as crop rotations and soil tillage will be vital for improving global food production. Methods: The rhizosphere soils of wheat and chickpea growing under + and - decaying root were collected for metagenomics sequencing. A gene catalogue was established by de novo assembling metagenomic sequencing. Genes abundance was compared between bulk soil and rhizosphere soils under different treatments. Conclusions: The study describes the diversity and functional capacity of a high-quality soil microbial metagenome. The results demonstrate the contribution of the microbiome from decaying root in determining the metagenome of developing root systems, which is fundamental to plant growth, since roots preferentially inhabit previous root channels. Modifications in root microbial function through soil management, can ultimately govern plant health, productivity and food security.