Role of enzymes in glyoxylate cycle in transgenic 'KDML 105' rice Oryza sativa L. overexpressing OsCam1-1 under salt stress

Abstract

The previous study reported that the transcriptome profiling of the KDML 105 rice overexpressing OsCam1-1 widely affected the expression of genes involved in several cellular processes including the genes associated with the glyoxylate cycle, which exhibited up-regulation in KDML 105 overexpressing OsCam1-1 under salt stress. In this study, we focused on the role of the glyoxylate cycle in transgenic KDML 105 rice under salt stress. The phenotypes as follows: fresh weight and dry weight of shoot & root, SPAD value, activities of isocitrate lyase, and malate synthase; sugar, and starch contents, and total lipid content were investigated at 0, 2, 4, 6 days after salt stress treatment and compared to the wild type KDML105. The results showed that the KDML 105 rice overexpressing OsCam1-1 better maintained fresh weight, dry weight of shoot, and SPAD value than wild type. Furthermore, the isocitrate lyase and malate synthase activities of transgenic rice overexpressing OsCam1-1 were higher than wild type in the youngest fully expanded leaf at day 2 while the second youngest leaf has higher isocitrate lyase activity than wild type at day 6. The transgenic rice overexpressing OsCam1-1 exhibited lower contents of sugars (sucrose, glucose, and fructose) and starch especially from the second youngest leaf than wild type suggesting that they may be metabolized or mobilized under salt stress better than the wild type. Moreover, transgenic rice also exhibited somewhat lower unsaturated fatty acid contents than wildtype. These results indicated that the glyoxylate cycle of which its key enzymes were enhanced by the overexpression of OsCam1-1 gene, probably helps maintain and balance carbon source and energy metabolism in rice under salt stress condition.