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:Purpose: To identify conserved and novel miRNAs in date palm and, most importantly, to identify miRNAs that could play a role in salt tolerance Methods: we generated sRNA libraries from the leaves and roots of NaCl-treated and untreated seedlings of date palm,then Deep sequencing of these four sRNA libraries,last The bioinformatics analysis,further validated using semi-quantitative PCR (qPCR). Results: Deep sequencing of these four sRNA libraries yielded approximately 251 million reads. The bioinformatics analysis has identified 153 homologs of conserved miRNAs, 89 miRNA variants, and 180 putative novel miRNAs in date palm. Expression profiles under salinity revealed differential regulation of most miRNAs in date palm. In leaves, all of the identified miRNAs were affected by the salinity treatment, and the majority (75%) of them were upregulated, whereas in roots, only 33% of the miRNAs were upregulated, but 44% of them were downregulated, while the remaining miRNAs (22%) were unaffected by the treatment. The salt responsiveness of some of these miRNAs was further validated using semi-quantitative PCR (qPCR). Some of the predicted targets for the identified miRNA include genes with known functions in plant salt tolerance, such as potassium channel AKT2-like proteins, vacuolar protein sorting-associated protein, and calcium-dependent and mitogen-activated proteins. As one of the first cultivated trees in the world with a wide range of abiotic stress tolerance, date palm contains a large population of conserved and nonconserved miRNAs that function at the posttranscriptional level. Conclusions: This study provided insights into miRNA-mediated gene expression that are important for adaptation to salinity in date palms.