ZmMYB127 controls maize endosperm filling via dual-transcriptional regulation to improve grain yield and quality.

As the main nutrient reservoir in cereal grains, the endosperm largely determines grain yield, performance and nutrition. However, knowledge of genes that coordinate endosperm filling and nutrient deposition, which could offer potential for genetic improvement of grain traits, remain limited. Here we identified ZmMYB127, a filling-endosperm-specific MYB transcription factor. Its knockout disrupted filling-stage aleurone layer morphology and nutrient accumulation, leading to reduced kernel weight, quality and nutrition. ZmMYB127 exerts dual transcriptional control over core endosperm-filling genes, including naked endosperm-1/2 (NKD1/2), crinkly4 (CR4) and opaque2 (O2). ZmMYB127 forms an activation complex with O2 to synergistically induce NKD1/2 expression by binding to two distinct cis-regulatory elements (CREs). Conversely, the co-repressor ZmLUG3 bridges ZmMYB127 and ZmABI4, a B3-domain transcription factor, to form a repressive complex that suppresses O2 and CR4 via another CRE pair. Filling-endosperm-specific overexpression of ZmMYB127 enhanced kernel weight, quality and nutrition. Introducing this overexpression into the elite cultivar Zhengdan958 confirmed its breeding potential. Furthermore, its rice homologue OsMYB20 also plays a conserved role in endosperm filling. Our findings establish ZmMYB127 as a promising target for grain improvement without trade-offs for precision breeding.