Suppressing ASPARTIC PROTEASE 1 prolongs photosynthesis and increases wheat grain weight

The elongation of photosynthesis, or functional staygreen, represents a feasible strategy to propel metabolite flux towards cereal kernels. However, achieving this goal remains a challenge in food crops. Here we report the cloning of wheat CO 2 assimilation and kernel enhanced 2 ( cake2 ), the mechanism underlying the photosynthesis advantages and natural alleles amenable to breeding elite varieties. A premature stop mutation in the A-genome copy of the ASPARTIC PROTEASE 1 ( APP-A1 ) gene increased the photosynthesis rate and yield. APP1 bound and degraded PsbO, the protective extrinsic member of photosystem II critical for increasing photosynthesis and yield. Furthermore, a natural polymorphism of the APP-A1 gene in common wheat reduced APP-A1’s activity and promoted photosynthesis and grain size and weight. This work demonstrates that the modification of APP1 increases photosynthesis, grain size and yield potentials. The genetic resources could propel photosynthesis and high-yield potentials in elite varieties of tetraploid and hexaploid wheat. Suppressing wheat ASPARTIC PROTEASE 1 promotes the homeostasis of PsbO, stabilizes the photosystem complex and elongates the duration of active photosynthesis, leading to increases in the CO 2 assimilation rate, kernel weight and yield.