Overexpression of IbMIPS1 gene enhances salt tolerance in transgenic sweetpotato

Myo-inositol-1-phosphate synthase (MIPS) is a key rate limiting enzyme in the de novo biosynthesis of myo-inositol in plants. In the present study, the IbMIPS1 gene was introduced into sweetpotato cultivar Xushu 18 and the transgenic plants exhibited significantly enhanced salt tolerance compared with the wild-type (WT). Overexpression of IbMIPS1 up-regulated the salt stress responsive genes, including myo-inositol monophosphatase (MIPP), pyrroline-5-carboxylate synthase (P5CS), pyrroline-5-carboxylate reductase (P5CR), psbA, phosphoribulokinase (PRK), and superoxide dismutase (SOD) genes, under salt stress. Inositol and proline content, SOD and photosynthesis activities were significantly increased, whereas malonaldehyde (MDA) and H2O2 contents were significantly decreased in the transgenic plants. These findings suggest that the IbMIPS1 gene may enhance salt tolerance of sweetpotato by regulating the expression of salt stress responsive genes, increasing the content of inositol and proline and enhancing the activity of photosynthesis.