Engineering a transport-facilitating molecular module to improve seed-setting rate and yield in rice

Rice yield is fundamentally governed by source-sink dynamics, in which the efficient translocation of non-structural carbohydrates (NSC) plays a pivotal role. Our previously developed GCGT photorespiratory bypass rice, while possessing high photosynthetic capacity, exhibits disordered sugar metabolism that impedes photoassimilate translocation and leads to a reduced seed-setting rate. To tackle this bottleneck, we construct a transport-facilitating molecular module, RSS, by integrating α-amylase (OsRAmy2A), sucrose phosphate synthase (OsSPS8), and sucrose transporter (OsSUT1) genes. In field trials, RSS rice plants (in both ZH11 and GCGT backgrounds) display significant increases in seed-setting rate, harvest index (HI), and grain yield. Crucially, the RSS module redirects photoassimilate partitioning, reducing NSC accumulation in vegetative tissues while enhancing allocation to panicles. This strategy not only improves yield in wild-type plants but also effectively ameliorates the sugar metabolism defects and photoassimilate stagnation in high-photosynthetic-efficient GCGT rice, substantially restoring the seed-setting rate. Taken together, our results demonstrate that the transport-facilitating molecular module RSS can significantly improve seed-setting rate and yield in rice, offering an effective strategy to unlock yield potential for rice.