トウモロコシ種子における炭素と窒素の代謝を同期させることによる栄養価と収量ポテンシャルの向上におけるZmPEPCK2

Maize (Zea mays L.) is the world's third most important staple crop, serving as a crucial source of both dietary energy and protein. The carbon and nitrogen contents in developing kernels fundamentally determine grain quality, influencing both nutritional value and processing characteristics. However, increasing nitrogen content in maize kernels without compromising yield remains a major challenge in breeding programs. Here we report that phosphoenolpyruvate carboxykinase 2 (PEPCK2) functions as a key regulator enhancing nitrogen sink strength, with its maternal expression level determining carbon and nitrogen accumulation in progeny kernels. Genetic analyses revealed that variations in the PEPCK2 promoter and coding regions were strongly associated with yield- and quality-related traits. Through genetic manipulation, we demonstrated that PEPCK2 overexpression increased ear length by 18.7%, kernel weight by 22.3%, and protein content by 31.5%, while knockdown reduced these parameters by 15.2%-21.4% without affecting vegetative growth. Biochemical characterization showed that PEPCK2 catalyzes the conversion of oxaloacetate to phosphoenolpyruvate, enhancing flux through the tricarboxylic acid cycle 2.3-fold and facilitating the conversion of amino acids' carbon skeletons into starch while efficiently recycling nitrogen for protein synthesis. Our findings establish PEPCK2 as a master regulator that simultaneously enhances both nutritional quality and yield potential in maize. The conservation of this carbon-nitrogen coordination mechanism points to promising applications for improving cereal crops through targeted metabolic engineering.