Project description:Plants and rhizosphere microbes rely closely on each other, with plants supplying carbon to bacteria in root exudates, and bacteria mobilizing soil-bound phosphate for plant nutrition. When the phosphate supply becomes limiting for plant growth, the composition of root exudation changes, affecting rhizosphere microbial communities and microbially-mediated nutrient fluxes. To evaluate how plant phosphate deprivation affects rhizosphere bacteria, Lolium perenne seedlings were root-inoculated with Pseudomonas aeruginosa 7NR, and grown in axenic microcosms under different phosphate regimes (330 uM vs 3-6 uM phosphate). The effect of biological nutrient limitation was examined by DNA microarray studies of rhizobacterial gene expression.
Project description:Arsenic (As) bioavailability in the rice rhizosphere is influenced by many microbial interactions, particularly by metal-transforming functional groups at the root-soil interface. This study was conducted to examine As-transforming microbes and As-speciation in the rice rhizosphere compartments, in response to two different water management practices (continuous and intermittently flooded), established on fields with high to low soil-As concentration. Microbial functional gene composition in the rhizosphere and root-plaque compartments were characterized using the GeoChip 4.0 microarray. Arsenic speciation and concentrations were analyzed in the rhizosphere soil, root-plaque, porewater and grain samples. Results indicated that intermittent flooding significantly altered As-speciation in the rhizosphere, and reduced methyl-As and AsIII concentrations in the pore water, root-plaque and rice grain. Ordination and taxonomic analysis of detected gene-probes indicated that root-plaque and rhizosphere assembled significantly different metal-transforming functional groups. Taxonomic non-redundancy was evident, suggesting that As-reduction, -oxidation and -methylation processes were performed by different microbial groups. As-transformation was coupled to different biogeochemical cycling processes establishing functional non-redundancy of rice-rhizosphere microbiome in response to both rhizosphere compartmentalization and experimental treatments. This study confirmed diverse As-biotransformation at root-soil interface and provided novel insights on their responses to water management, which can be applied for mitigating As-bioavailability and accumulation in rice grains.
Project description:Phosphate (Pi) deficiency severely affects crop yield. Modern high yielding rice genotypes are sensitive to Pi deficiency whereas traditional rice cultivars are naturally compatible to low Pi ecosystems. However, the underlying molecular mechanisms for low Pi tolerance in traditional genotypes remain largely elusive. To delineate the molecular mechanisms for low Pi tolerance, two contrasting rice genotypes - Dular (low Pi tolerant) and PB1 (low Pi sensitive) - have been selected. Comparative morphophysiological, global transcriptome and lipidome analyses of root and shoot tissues of both genotypes raised under Pi deficient and sufficient conditions revealed the potential low Pi tolerance mechanisms of traditional genotype. Most of the genes associated with enhanced internal Pi utilization (phospholipid remobilization) and modulation of root system architecture (RSA) are highly induced in traditional rice genotype, Dular. Higher reserve of phospholipid and greater accumulation of galactolipids under low Pi in Dular indicated its better internal Pi utilization. Furthermore, Dular also maintained better root growth than PB1 under low Pi resulting in larger root surface area due to increased lateral root density and root hair length. Genes involved in enhanced low Pi tolerance of traditional genotype can be exploited to improve the low Pi tolerance of modern high yielding rice cultivars.
Project description:To understand expression of candidate gene located on QTLs for phosphate sensitivity traits under low P using NtPT1-transgenic rice with increased Pi uptake efficiency and gene expression profile at the V3-stage seedling through the 60K Rice Whole Genome Microarray
Project description:In response to bacterial infection, early transcriptional re-programming occurs in the host plant. We used microarrays to analyse the global transcriptomic response to Xoo. infection in a resistant rice cultivar (IR24). This was analysed in parallel with microarrays examining Xoo infection in a susceptible rice cultivar (IRBB21) as well as in response to Xoc [GSE19239], viral [GSE11025], parasite [GSE10373] and fungal [GSE7256, GSE18361] infections in rice, in order to identify common and distinct responses to biotic stress.
Project description:Determining how a bacterial pathogen responds to its host and other bacterial species by altering gene expression is key to understand its pathogenesis and environmental adaption. Here, we used RNA-Seq to comprehensively and quantitatively assess the transcriptional response of the rice bacterial pathogen Acidovorax avenae subsp. avenae strain RS-1 cultivated in vitro, in vivo and in co-culture with rice rhizobacterium Burkholderia seminalis R456. Results revealed a surprisingly large number of regulatory differences between these conditions indicating adaptation of A. avenae subsp. avenae to specific ecological conditions. In particular, a number of potential virulence factors such as type 3 secretion system proteins were specifically expressed under in vivo conditions, whereas genes whose protein products are involved in inter-bacterial interaction such as auxin efflux carrier, small mechanosensitive ion channel protein, and ureidoglycolate hydrolase were among those specifically up-regulated under co-culture conditions. In addition, global genomic analysis of strain RS-1 identified 406 putative non-coding (nc) RNA genes. Interestingly, 8 ncRNA genes that were uniquely expressed under in vivo may be linked to pathogenicity while 4 ncRNA genes that were uniquely expressed under coculture conditions may be involved in adaption to co-cultivation with B. seminalis. Expression data obtained by RNA-Seq were also confirmed for selected genes by quantitative real-time PCR and two-dimensional gel electrophoresis as well as knockout analysis. Aaa strain RS-1 and B. seminalis strain R456 was isolated from diseased rice plants (Li et al., 2011; Xie et al., 2011) and rice rhizosphere (Zhang et al., 2007; Li et al., 2011), respectively, in our previous studies, and were stored in 20-30% sterile glycerol at -80°C. The samples of Aaa strain RS-1 for in vitro and in vivo analysis were prepared as described before (Ibrahim et al., 2012). The co-culture analysis of Aaa strain RS-1 with B. seminalis strain R456 were conducted according to Ruiz et al. (2009) and Di Cagno et al. (2009). Briefly, Aaa strain RS-1 and B. seminalis strain R456 was inoculated and incubated in chambers of a double culture vessel apparatus separated by a 0.4-μm membrane filter (Millipore Isopore™). In order to avoid the possible contamination during in vivo and co-culture operation, all bacterial samples were further confirmed based on the sequence analysis of 16S-rRNA (Li et al., 2011). Then samples were processed for RNA harvesting, mRNA purification and cDNA synthesis.
Project description:Background and study aims
Colorectal cancer (CRC) is one of the most commoncancers among humans worldwide. Recent studies demonstrated that the composition of the bacterial community in the human gut, as well as inflammation occurring in the gut, are some of the factors that modify the risk of an individual to develop CRC. The human gut is home to more than 1000 bacterial species, including health-promoting species and disease-causing species.
The consumption of rice bran, a by-product of rice milling, was previously shown to positively modify bacterial composition in the gut among healthy adults. The protective effect of a long-term rice bran consumption against CRC among individuals known to have higher risk of CRC, such as older individuals who are regular smokers and having a family history of CRC, needs to be established.
This study aims to investigate whether the implementation of a 24-week dietary programme involving rice bran consumption among adults at high risk of CRC is feasible, and whether it has any effect in inducing a health-promoting modification of the bacterial community, as well as a reduction of inflammation, in the gut of these individuals.
Who can participate?
Chinese adults of either gender, who are aged 50 or above and are categorised to be in the high risk CRC group by the Asian-Pacific Colorectal Screening tool, in which classification is based on age, smoking status and family history of CRC.
What does the study involve?
After the recruited subjects were screened for eligibility of study participation and written informed consent had been obtained from them, they were randomly assigned into either Group A or Group B. Participants in Group A were given packets of rice bran and were asked to consume 30 grams of the rice bran at 24-hour intervals for 24 weeks. Participants in Group B were given packets of rice powder that has similar appearance and colour as the rice bran, and were asked to consume 30 grams of the rice powder, also at 24-hour intervals for 24 weeks. All participants were asked to provide a stool sample and blood sample at various time points during the study, namely just before rice bran consumption, as well as 6 weeks, 12 weeks and 24 weeks after the start of rice bran consumption. Laboratory tests were conducted on these samples. All participants were also instructed to complete a log book, detailing the date and time of rice bran or rice powder intake each day, and the amount consumed. The participants also completed a faecal diary where they documented the frequency of egestion, and the shape and amount of stool egested each day, as well as the occurrence of any abdominal discomfort or pain.