Project description:Roots make the first contact with the soil environment and are the first responders of stress. These root behaviors are quantifiable and adaptive. The response of rice varieties in mechanical and salinity stress was measured in a novel experimental setup that mimics the soil environment. We analyzed the response of roots by means of SAC (Stress Adaptation Coefficient) in 28 rice varieties that include high-yield salt tolerant varieties as well as geographically isolated native rice varieties. cDNA microarray of IR64 root-tip shows about 6000 common transcripts to be differentially regulated among the two stresses and common pathways were identified. Overall, our study indicates that there is an important commonality in the molecular basis of salt and mechanical stress and presents an easy-to-perform early establishment stress screen for rice varieties.
Project description:The aim of this study was to minimize the number of candidate genes responsible for salt tolerance between a pair of rice varieties (CSR27 and MI48) with contrasting level of salt tolerance by bulked segregant analysis of their recombinant inbred lines. Microarray analysis of RNA extracted from the tolerant and susceptible parents without and with stress showed 798 and 2407 differentially expressed genes, respectively. The number of differentially expressed genes was drastically reduced to 70 and 30, by pooling the RNAs from ten extreme tolerant and ten extreme susceptible RILs due to normalization of irrelevant differentially expressed genes between the parents.
Project description:The aim of this study was to minimize the number of candidate genes responsible for salt tolerance between a pair of rice varieties (CSR27 and MI48) with contrasting level of salt tolerance by bulked segregant analysis of their recombinant inbred lines. Microarray analysis of RNA extracted from the tolerant and susceptible parents without and with stress showed 798 and 2407 differentially expressed genes, respectively. The number of differentially expressed genes was drastically reduced to 70 and 30, by pooling the RNAs from ten extreme tolerant and ten extreme susceptible RILs due to normalization of irrelevant differentially expressed genes between the parents. RNA from CSR27, MI48, tolerant bulk and susceptible bulk grown under control and salt stress conditions were analysed in two different biological replications (A and B) making total sixteen samples
Project description:A submergence tolerant indica rice cultivar FR13A, was also reported to withstand salt stress and proven in our experiments. The mechanism of tolerance is yet to be studied by forward genetics approach. However, it is known that salt stress tolerance is governed by several QTLs and not by a single gene. To understand the mechanism of such a complex mechanism of salt tolerance we selected, two indica rice genotypes namely, I) FR13A, a tolerant indica variety and ii) IR24, a susceptible genotype for this study. We used the 22K rice Oligoarray from Agilent technologies to study the transcript profile in the leaves of the two contrasting rice genotypes under constitutive and salt stress conditions at seedling stage. Keywords: Mechanism of salt tolerance
Project description:The aim of this study is to assess natural variation in transcriptional responses to salt stress in rice. We utilized a diversity panel (RDP1) described in Zhao et al 2011. Eight day old rice seedlings were subjected to a gradual 6 dS·m-1 salt stress for a period of 24h. RNA seqeuncing was performed on shoot tissue using Illumina HiSeq 2500.
Project description:The aim of this study was to characterize the tissue tolerance mechanisms of rice under salt stress. Our preliminary experiment identified a japonica rice landrace Shuzenji-kokumai (SZK), which is considered to be tissue-tolerant because it can maintain better growth than salt-sensitive rice while having a high Na+ concentration in the shoots under salt stress. These mechanisms differ from those of most salt-tolerant rice varieties, which have low Na+ concentrations in the shoots. We compared the physiological and molecular characteristics of SZK with those of FL478, a salt-tolerant variety, and Kunishi, a salt-sensitive variety. Under salt stress conditions, SZK accumulated high levels of Na+ in roots, leaf sheaths, and leaf blades, which were almost as high as those in the salt-sensitive Kunishi. Simultaneously, SZK maintained better growth and physiological status, as determined by its higher dry weight, lower electrolyte leakage ratio, and lower malondialdehyde concentration. OsNHX1 and OsNHX2 were up-regulated in the leaf sheaths of SZK, suggesting that Na+ is compartmentalized in the vacuole to avoid Na+ toxicity. In contrast, FL478 showed up-regulation of OsHKT1;5 and OsSOS1 in the roots, which exclude Na+ from the shoots. RNA-seq analysis showed that 4623 and 1998 differentially expressed genes (DEGs) were detected in the leaf sheaths and leaf blades of SZK, respectively. Among them, the HSP (heat shock protein) gene expression was highly up-regulated only in SZK, indicating that SZK protects against the protein damage caused by Na+ toxicity. Our findings suggest that SZK has atypical survival mechanisms under salt-stress conditions. These mechanisms offer potential traits for improving salt tolerance in rice.
Project description:Dongxiang wild rice (Oryza rufipogon Griff.) is the progenitor of cultivated rice (Oryza sativa L.) and is well known for its superior level of tolerance against cold, drought and diseases. To date, however, little is known about the salt-tolerant character of Dongxiang wild rice. To elucidate the molecular genetic mechanisms of salt-stress tolerance in Dongxiang wild rice, the Illumina HiSeq 2000 platform was used to analyze the transcriptome profiles of the leaves and roots at the seedling stage under salt stress compared with those under normal conditions. The analysis results for the sequencing data showed that 6,867 transcripts were differentially expressed in the leaves (2,216 up-regulated and 4,651 down-regulated) and 4,988 transcripts in the roots (3,105 up-regulated and 1,883 down-regulated). Among these differentially expressed genes, the detection of many transcription factor genes demonstrated that multiple regulatory pathways were involved in salt stress tolerance. In addition, the differentially expressed genes were compared with the previous RNA-Seq analysis of salt-stress responses in cultivated rice Nipponbare, indicating the possible specific molecular mechanisms of salt-stress responses for Dongxiang wild rice. A large number of the salt-inducible genes identified in this study were co-localized onto fine-mapped salt-tolerance-related quantitative trait loci, providing candidates for gene cloning and elucidation of molecular mechanisms responsible for salt-stress tolerance in rice.
Project description:A submergence tolerant indica rice cultivar FR13A, was also reported to withstand salt stress and proven in our experiments. The mechanism of tolerance is yet to be studied by forward genetics approach. However, it is known that salt stress tolerance is governed by several QTLs and not by a single gene. To understand the mechanism of such a complex mechanism of salt tolerance we selected, two indica rice genotypes namely, I) FR13A, a tolerant indica variety and ii) IR24, a susceptible genotype for this study. We used the 22K rice Oligoarray from Agilent technologies to study the transcript profile in the leaves of the two contrasting rice genotypes under constitutive and salt stress conditions at seedling stage. Experiment Overall Design: We used Agilent rice gene chips (G4138A) to investigate the transcript level changes in rice plant tissues during salt stress treatment. We used two contrasting rice genotypes (FR13A tolerant and IR24 susceptible) differing in salt stress response. Plants were grown in growth chambers and treated with 150 mM salt concentration at 14th DAS. Sampling was done in both constitutive and treated plants at 3 time points. Two replications of microarray experiments were carried out by hybridizing the RNA from tolerant samples against the susceptible lines on the same slide.
Project description:Soil salinity is a major production constrain for agricultural crops, especially in Oryza sativa (rice). Analyzing physiological effect and molecular mechanism under salt stress is key for developing stress-tolerant plants. Roots system has a major role in coping with the osmotic change impacted by salinity and few salt-stress-related transcriptome studies in rice have been previously reported. However, transcriptome data sets using rice roots grown in soil condition are more relevant for further applications, but have not yet been available. The present work analyzed rice root and shoot physiological characteristics in response to salt stress using 250 mM NaCl for different timepoints. Subsequently, we identified that 5 day treatment is critical timepoint for stress response in the specific experimental design. We then generated RNA-Seq-based transcriptome data set with rice roots treated with 250 mM NaCl for 5 days along with untreated controls in soil condition using rice japonica cultivar Chilbo. We identified 447 upregulated genes under salt stress with more than fourfold changes (p value < 0.05, FDR < 0.05) and used qRT-PCR for six genes to confirm their salt-dependent induction patterns. GO-enrichment analysis indicated that carbohydrate and amino-acid metabolic process are significantly affected by the salt stress. MapMan overview analysis indicated that secondary metabolite-related genes are induced under salt stress. Metabolites profiling analysis confirmed that phenolics and flavonoids accumulate in root under salt stress. We further constructed a functional network consisting of regulatory genes based on predicted protein–protein interactions, suggesting useful regulatory molecular network for future applications.
Project description:Iron (Fe) toxicity is a major challenge for plant cultivation in acidic water-logged soil environments, where lowland rice is a major staple food crop. Only few studies addressed the molecular characterization of excess Fe tolerance in rice, and these highlight different mechanisms for Fe tolerance in the studied varieties. Here, we screened 16 lowland rice varieties for excess Fe stress growth responses to identify contrasting lines, Fe-tolerant Lachit and -susceptible Hacha. Hacha and Lachit differed in their physiological and morphological responses to excess Fe, including leaf growth, leaf rolling, reactive oxygen species generation, Fe and metal contents. These responses were mirrored by differential gene expression patterns, obtained through RNA-sequencing, and corresponding GO term enrichment in tolerant versus susceptible lines. From the comparative transcriptomic profiles between Lachit and Hacha in response to excess Fe stress, individual genes of the category metal homeostasis, mainly root-expressed, may contribute to the tolerance of Lachit. 22 out of these 35 metal homeostasis genes are present in selection sweep genomic regions, in breeding signatures and/or differentiated during rice domestication. These findings will serve to design targeted Fe tolerance breeding of rice crops.