The Nhd1-MYB110-MADS15 transcription factor module regulates flowering time in rice

The precise regulation of flowering time, known as heading date in rice (Oryza sativa L.), is critical for regional adaptation, agricultural productivity, and crop rotation practices. In rice, the florigen activation complex and its downstream effectors are well-characterized mediators of the floral transition in the shoot apical meristem (SAM). Here, we characterized OsMYB110 as a SAM-localized transcription factor that promotes flowering, exhibiting functional similarity to the established flowering regulator Nhd1 (N-mediated heading date-1). Through integrated molecular and genetic analyses, we demonstrate that: (i) Nhd1 directly binds to the OsMYB110 promoter to activate its expression, while OsMYB110 in turn binds to and activates the OsMADS15 promoter to control flowering progression, and (ii) genetic epistasis places OsMYB110 downstream of Nhd1 but upstream of OsMADS15 in the flowering regulation hierarchy. Furthermore, while elevated phosphate accelerates flowering, this response is abolished in myb110 and mads15 mutants but maintained in nhd1 mutants. These results define a previously unrecognized Nhd1-OsMYB110-OsMADS15 regulatory module that integrates developmental and nutrient signaling pathways to control rice flowering time.