Transcriptome of rice oryza sativa L. over-expressing OsCam1-1 gene and characterization of salt stress-responsive isocitrate lyase gene

Abstract

The previous study of OsCam1-1 showed that the transgenic KDML105 rice over-expressing OsCam1-1 was more tolerant to salt stress than the wild type, so to investigate the role of calmodulin encoded by OsCam1-1 in the salt-responsive mechanism, the transcriptome approach using RNA-seq technique was applied. Transcriptome profile of the transgenic KDML105 rice over-expressing OsCam1-1 under 4 hr of salt stresss (150 mM NaCl) revealed that several cell processes were affected; signaling, hormone-mediated regulation, transcription, secondary metabolism, stress responses, lipid metabolism, glycolysis, TCA cycle, glyoxylate cycle, photosynthesis, and carbohydrate metabolism. Photosynthesis rate and stomatal conductance at day 3 and 5 of salt stress treatment were repressed by OsCam1-1 effect. The sucrose and starch contents, the products of photosynthesis, were higher in the transgenic rice at day 3 and 5 of salt stress treatment. According to the gene expression study by transcriptomics and qRT-PCR, the gene encoding a key enzyme in glyoxylate cycle, isocitrate lyase (ICL), was enhanced by the effect of OsCam1-1 over-expression under salt stress. ICL was hypothesized to involve in salt tolerance mechanism by OsCam1-1 regulation. Thus, OsICL was functionally characterized using gene complementation approach. OsICL was transferred into the Aticl Arabidopsis mutant and wild type for generating revertant and OsICL overexpression line respectively, in order to compare their salt stress response with wild type and the Aticl mutant line. The results showed that the Aticl mutant had significantly lower germination rate, fresh weight, and dry weight than wild type, revertant, and OsICL over-expression lines under salt stress, suggesting that OsICL was a salt tolerance gene in rice.