A <i>myo</i>‐inositol‐1‐phosphate synthase gene, <i>Ib<scp>MIPS</scp>1</i>, enhances salt and drought tolerance and stem nematode resistance in transgenic sweet potato

<jats:title>Summary</jats:title><jats:p><jats:italic>Myo</jats:italic>‐inositol‐1‐phosphate synthase (<jats:styled-content style="fixed-case">MIPS</jats:styled-content>) is a key rate limiting enzyme in <jats:italic>myo</jats:italic>‐inositol biosynthesis. The <jats:italic><jats:styled-content style="fixed-case">MIPS</jats:styled-content></jats:italic> gene has been shown to improve tolerance to abiotic stresses in several plant species. However, its role in resistance to biotic stresses has not been reported. In this study, we found that expression of the sweet potato <jats:italic>Ib<jats:styled-content style="fixed-case">MIPS</jats:styled-content>1</jats:italic> gene was induced by NaCl, polyethylene glycol (<jats:styled-content style="fixed-case">PEG</jats:styled-content>), abscisic acid (<jats:styled-content style="fixed-case">ABA</jats:styled-content>) and stem nematodes. Its overexpression significantly enhanced stem nematode resistance as well as salt and drought tolerance in transgenic sweet potato under field conditions. Transcriptome and real‐time quantitative <jats:styled-content style="fixed-case">PCR</jats:styled-content> analyses showed that overexpression of <jats:italic>Ib<jats:styled-content style="fixed-case">MIPS</jats:styled-content>1</jats:italic> up‐regulated the genes involved in inositol biosynthesis, phosphatidylinositol (<jats:styled-content style="fixed-case">PI</jats:styled-content>) and <jats:styled-content style="fixed-case">ABA</jats:styled-content> signalling pathways, stress responses, photosynthesis and <jats:styled-content style="fixed-case">ROS</jats:styled-content>‐scavenging system under salt, drought and stem nematode stresses. Inositol, inositol‐1,4,5‐trisphosphate (<jats:styled-content style="fixed-case">IP</jats:styled-content><jats:sub>3</jats:sub>), phosphatidic acid (<jats:styled-content style="fixed-case">PA</jats:styled-content>), Ca<jats:sup>2+</jats:sup>, <jats:styled-content style="fixed-case">ABA</jats:styled-content>, K<jats:sup>+</jats:sup>, proline and trehalose content was significantly increased, whereas malonaldehyde (<jats:styled-content style="fixed-case">MDA</jats:styled-content>), Na<jats:sup>+</jats:sup> and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> content was significantly decreased in the transgenic plants under salt and drought stresses. After stem nematode infection, the significant increase of inositol, <jats:styled-content style="fixed-case">IP</jats:styled-content><jats:sub>3</jats:sub>, <jats:styled-content style="fixed-case">PA</jats:styled-content>, Ca<jats:sup>2+</jats:sup>, <jats:styled-content style="fixed-case">ABA</jats:styled-content>, callose and lignin content and significant reduction of <jats:styled-content style="fixed-case">MDA</jats:styled-content> content were found, and a rapid increase of H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> levels was observed, peaked at 1 to 2 days and thereafter declined in the transgenic plants. This study indicates that the <jats:italic>Ib<jats:styled-content style="fixed-case">MIPS</jats:styled-content>1</jats:italic> gene has the potential to be used to improve the resistance to biotic and abiotic stresses in plants.</jats:p>