Transcriptomics Analysis of Rice Overexpressing the Calcium Sensor OsCaM1-1 Revealed Its Effects on Carbohydrate Metabolism Under Salt Stress

Overexpression of the Ca²⁺-modulated calmodulin gene, OsCam1-1 was previously shown to confer a better salt-tolerant ability to the transgenic rice (Oryza sativa L). Transcriptome profiles of the three-week old transgenic rice seedlings grown under salt stress (150 mM NaCl) for four hours compared with those of the wild type by RNA Seq revealed 1,725 differentially expressed salt-responsive genes. GO Enrichment analysis has shown that genes involved in carbohydrate metabolic process, response to abiotic stress, and regulation of transcription were enriched in the OsCam1-1-overexpressing transgenic rice. Expression of differentially expressed genes involved with carbohydrate metabolism including b-amylase, aconitase, isocitrate lyase, and malate synthase was verified by real-time RT-PCR. Genes encoding isocitrate lyase and malate synthase, two key enzymes in the glyoxylate cycle, were found highly expressed under salt stress in all three independent transgenic rice lines. Higher expression levels of isocitrate lyase were observed in either senesced or young leaf of the transgenic seedlings grown under salt stress. Compared with wild type, the transgenic seedlings exhibited higher levels of starch after 3 and 5 days and higher levels of sucrose after 3 days under salt stress. Taken together, these results suggest that OsCaM1-1 may enhance salt-tolerant ability by altering carbohydrate metabolism in rice grown under salt stress.