GW8-OsMKKK55 module regulates stigma breadth in rice

Stigma breadth in rice is a critical trait influencing pollination efficiency and seed-setting rate, particularly holding significant research value in hybrid rice breeding. This study identified and validated a quantitative trait locus designated qSTB-8 that regulates stigma breadth in rice. Further analysis confirmed GW8, a previously reported grain-width gene, as the candidate gene underlying this trait. Compared to the wild-type ZH11, GW8 knockout mutants exhibited a significant reduction in stigma breadth. Further experiments verified that GW8 directly interacts with OsMKKK55. Moreover, GW8 could bind to the promoter of OsMKKK55 and modulate its transcriptional activity. OsMKKK55 knockout mutants similarly displayed a marked decrease in stigma breadth. Taken together, this study elucidates GW8 as a positive regulator of stigma breadth in rice and proposes that the GW8-OsMKKK55 module plays a crucial role in the regulation of stigma breadth in rice.