Project description:The turf grass Sporobolus virginicus is halophyte and has high salinity tolerance. To investigate the molecular basis of its remarkable tolerance, we performed Illumina high-throughput RNA sequencing on roots and shoots of a S. virginicus genotype under normal and saline conditions. The 130 million short reads were assembled into 444,242 unigenes. A comparative analysis of the transcriptome with rice and Arabidopsis transcriptome revealed six turf grass-specific unigenes encoding transcription factors. Interestingly, all of them showed root specific expression and five of them encode bZIP type transcription factors. Another remarkable transcriptional feature of S. virginicus was activation of specific pathways under salinity stress. Pathway enrichment analysis suggested transcriptional activation of amino acid, pyruvate, and phospholipid metabolism. Up-regulation of several unigenes, previously shown to respond to salt stress in other halophytes was also observed. Gene Ontology enrichment analysis revealed that unigenes assigned as proteins in response to water stress, such as dehydrin and aquaporin, and transporters such as cation, amino acid, and citrate transporters, and H(+)-ATPase, were up-regulated in both shoots and roots under salinity. A correspondence analysis of the enriched pathways in turf grass cells, but not in rice cells, revealed two groups of unigenes similarly up-regulated in the turf grass in response to salt stress; one of the groups, showing excessive up-regulation under salinity, included unigenes homologos to salinity responsive genes in other halophytes. Thus, the present study identified candidate genes involved in salt tolerance of S. virginicus. This genetic resource should be valuable for understanding the mechanisms underlying high salt tolerance in S. virginicus. This information can also provide insight into salt tolerance in other halophytes.
Project description:Sprobolus virginicus is a halophytic C4 grass found in worldwide from tropical to warm temperate regions. A Japanese genotype showed a salinity tolerance up to 1,500 mM NaCl, a three-fold higher concentration than seawater salinity. To identify key genes involved in the regulation of salt tolerance in S. virginicus, random cDNA libraries were constructed from salt-treated leaves, and were introduced into Arabidopsis for salt tolerant plant screening. Eight independent transgenic lines were found to be more salt tolerant than wild type from the screen of 3011 lines on the medium containing 175 mM NaCl. Among the selected lines, two contained cDNAs encoding glycine-rich RNA-binding proteins (GRPs). To identify transcriptomic change in the GRP-transgenic line, we performed microarray analysis of the transgenic line and WTunder salt stress.