African rice OgGL8 enhances grain length and yield in Asian rice

Grain length is a critical characteristic of grain shape and significantly impacts grain yield in rice. This study we present African cultivated OgGL8, an allele derived from African-cultivated rice (Oryza glaberrima), as a novel variant of the Grain Width 8 (GW8) gene that regulates both grain length and grain weight. We identified novel polymorphisms in the promoter sequences of OgGL8 and OsGL8. Genetic complementation and overexpression experiments validated that OgGL8 acts as a regulator of grain length and 1000-grain weight. The near-isogenic line (NIL^CG34) carrying OgGL8 displayed significantly enhanced grain length (+12.93 %), grain yield (+13.76 %), and panicle length (+3.98 %) relative to TC65. The findings demonstrate that the OgGL8 allele present in Oryza glaberrima confers a more pronounced enhancement of grain length and yield potential than its counterpart in Oryza sativa. It attributed to enhanced cell proliferation during panicle development. Expression pattern analysis indicated significantly higher GL8 expression levels in young panicles of TC65 than in CG34, consistent with the stronger promoter activity of GL8^TC65 in protoplast assays. Subcellular localization confirmed that OsGL8 protein is nuclear-localized. Yeast transactivation assays further revealed its transcriptional activation activity, with functional domains distributed in both the N-terminal and C-terminal regions. These findings not only elucidate the mechanism by which OgGL8 regulates grain size but also provide new genetic resources for improving rice yield-related traits.