The F-box protein RCN127 enhances rice tillering and grain yield by mediating the degradation of OsTB1 and OsTCP19.

Tillering ability is a crucial agronomic trait that determines rice yield potential. OsTB1 (the rice ortholog of TEOSINTE BRANCHED 1) and OsTCP19 of the TCP protein family are two key repressors of rice tillering. Until now, their post-translational regulatory mechanisms have remained elusive. In this study, we identified the F-box protein RCN127 as a novel post-translational regulator that promotes rice tillering by targeting them for degradation. The rcn127 mutant exhibits reduced tillering. The target gene RCN127 encodes an F-box protein that localizes in both the nucleus and cytoplasm, with higher expression levels in roots, stem bases, and young panicles. We demonstrate that RCN127 physically interacts with both OsTB1 and OsTCP19, mediating their ubiquitination and subsequent degradation via the 26S proteasome pathway. This reduction in OsTB1 and OsTCP19 protein levels weakens their suppression on tillering, leading to significantly increased tiller numbers. Importantly, RCN127-mediated regulation enhances grain yield in both the model variety Nipponbare and the dominant cultivated variety LJ31, providing a promising strategy for yield improvement. Therefore, our study unveils a novel post-translational regulatory mechanism of TCP protein family, providing a new strategy to increase grain yield by enhancing rice tillering capacity.