Abstract
SummaryStarch is the most important form of energy storage in cereal crops. Many key enzymes involved in starch biosynthesis have been identified. However, the molecular mechanisms underlying the regulation of starch biosynthesis are largely unknown. In this study, we isolated a novel floury endosperm rice (Oryza sativa) mutant flo16 with defective starch grain (SG) formation. The amylose content and amylopectin structure were both altered in the flo16 mutant. Map‐based cloning and complementation tests demonstrated that FLO16 encodes a NAD‐dependent cytosolic malate dehydrogenase (CMDH). The ATP contents were decreased in the mutant, resulting in significant reductions in the activity of starch synthesis‐related enzymes. Our results indicated that FLO16 plays a critical role in redox homeostasis that is important for compound SG formation and subsequent starch biosynthesis in rice endosperm. Overexpression of FLO16 significantly improved grain weight, suggesting a possible application of FLO16 in rice breeding. These findings provide a novel insight into the regulation of starch synthesis and seed development in rice.
Highlights
Starch, large biopolymers of glucose, is the most important form of carbohydrates for most organisms
Our results demonstrated that FLO16 is important for starch biosynthesis and seed development in rice
These results suggest that the flo16 mutant is defective in plant growth and development and that changes in starch metabolism extend beyond the endosperm
Summary
Many key enzymes involved in starch biosynthesis have been identified. The molecular mechanisms underlying the regulation of starch biosynthesis are largely unknown. We isolated a novel floury endosperm rice (Oryza sativa) mutant flo with defective starch grain (SG) formation. The ATP contents were decreased in the mutant, resulting in significant reductions in the activity of starch synthesis-related enzymes. Our results indicated that FLO16 plays a critical role in redox homeostasis that is important for compound SG formation and subsequent starch biosynthesis in rice endosperm. Overexpression of FLO16 significantly improved grain weight, suggesting a possible application of FLO16 in rice breeding. These findings provide a novel insight into the regulation of starch synthesis and seed development in rice
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