Reduced inositol content and altered morphology in transgenic potato plants inhibited for 1D‐myo‐inositol 3‐phosphate synthase

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Abstract
Summary: Myo ‐inositol is a precursor of many plant metabolites, including polyols, cell wall components and phosphoinositides. The first committed step in the de novo myo ‐inositol synthetic pathway is catalysed by the enzyme 1D‐ myo ‐inositol 3‐phosphate synthase (MIPS; EC 5.5.1.4 ), which converts D‐glucose 6‐phosphate to 1D‐ myo ‐inositol 3‐phosphate. Suppression of MIPS activity by an antisense RNA approach in transgenic potato ( Solanum tuberosum L.) plants to below 20% of the wild‐type level in leaves resulted in strongly reduced levels of inositol, galactinol and raffinose (approximately 7%, 5% and 12%, respectively, of wild‐type values). In contrast, increases were observed for concentrations of hexose phosphates (up to 1.7‐fold), sucrose (twofold) and starch (two‐ to fourfold). Transgenic plants exhibited reduced apical dominance, altered leaf morphology, precocious leaf senescence and a decrease in overall tuber yield. These observations indicate a crucial role for myo ‐inositol in plant physiology and development.