FZP modulates tillering via OsMADS57 in rice.

The number of tillers in rice directly determines the number of panicles, which is crucial for enhancing plant architecture and achieving high yields. Some important genes regulating rice tillering have been identified, but their underlying mechanisms remain unclear. FRIZZY PANICLE (FZP) encodes an AP2/ERF transcription factor. Beyond its well-established role in promoting spikelet formation during the reproductive phase, here we demonstrate that FZP also inhibits axillary buds outgrowth in the vegetative phase by suppressing the expression of a MADS-box gene (OsMADS57) that functions as a growth promoter. Consequently, genome editing of the FZP-bound cis-motif in the promoter of OsMADS57 releases its expression, leading to more tillers. Furthermore, domestication analysis shows that FZP has undergone strong selection in cultivated rice, while the downstream gene OsMADS57 has been differentiated between indica and japonica subspecies. Four functional SNPs in the promoter of OsMADS57 can increase rice tillering in most indica accessions by enhancing its expression. Our findings expose hidden pleiotropy of classic spikelet identity genes that are redeployed to control stem form, potentially enriching the gene resources for rice genetic improvement.