2005.Large-scale gene expression analysis of barley and rice under salinity stress

2005.Large-scale gene expression analysis of barley and rice under salinity stress

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ABSTRACT

Salinity stress imposes significant yield restriction on irrigated and rainfed agricultural systems. Rice is one of the most economically important crop species which is salt-sensitive. A related cereal, barley, has significant morphological and developmental similarity with rice but is among the most salt-tolerant crop species. In an effort to identify genes which may be involved in adaptation of rice and barley to salinity stress we have conducted large-scale gene expression analysis in species. Identification of components that distinguish the response of barley from that of rice, and of tolerant genotypes from sensitive ones, could improve our understanding of tolerance mechanisms. Such an understanding is necessary for efforts to improve salinity tolerance of rice. We performed transcriptional profiling of a barley genotype, Morex, under salinity stress at three time points over a short duration. Considerably different sets of genes were induced by salinity stress at the three time points, indicating the dynamic nature of the transcriptome. Genes related to jasmonic acid (JA) biosynthesis and known to be JA-responsive were induced by salinity stress in barley. In an effort to elucidate the role of JA in salinity response of barley, we characterized the performance and gene expression of barley plants which were pretreated with JA before salinity stress. Phenotypic characterization of pretreated plants indicated that JA partial ameliorated salinity stress by JA as evident in increased photosynthetic performance and decreased Na+ accumulation in shoot tissue. Transcriptional profiling was further extended to rice genotypes which differed in salt-tolerance at early vegetative stage and reproductive stage. These studies revealed that different genotypes induced strikingly different set of genes in response to salinity. One key feature was that the sensitive genotypes induce a much larger set of genes in response to salinity relative to tolerant lines. One of the approaches used to identify genes with a potential role in salinity adaptation was to co-localize responsive genes with known salinity tolerance quantitative trait loci (QTL). This approach resulted in identification of a cation transporter which was later reported to be the gene responsible for significant variation in salinity tolerance of rice. Such an integrated approach of combining genetic information with large-scale genomics data has potential use in crop improvement  .