OsWRKY53-OsGT1 Module Regulates Rice Tiller Development and Is Involved in Fine-Tuning Strigolactone Signaling

Plant architecture, including plant height, tiller number, and leaf angle, is a critical determinant of rice yield. However, few genes have been identified that simultaneously regulate these traits and hold breeding value. We have previously shown that OsWRKY53 regulates the plant height and leaf angle via BR signalling. Here, we establish OsWRKY53 as a novel negative regulator of tillering in rice. The oswrky53 mutant exhibits a semi-dwarf stature coupled with increased tiller number, representing a promising agronomic combination. Genetic and molecular analyses reveal that OsWRKY53 acts as a direct transcriptional activator of OsTB1, thereby suppressing tiller formation. In addition, we found OsWRKY53 physically interacts with OsGT1, and their cooperative action synergistically enhances OsTB1 expression and suppresses tiller number. Intriguingly, the oswrky53 mutant exhibits reduced sensitivity to Strigolactone (SL) and increased SL contents. We further demonstrate that SL promotes degradation of OsWRKY53, and D53 interacts with and stabilises the OsWRKY53. Simultaneously, OsWRKY53 negatively regulates SL biosynthesis, enabling OsWRKY53 to function as a fine-tuning regulator in the SL signalling pathway. Furthermore, OsGT1 exhibits subspecies-specific regulation, with indica accessions carrying the OsGT1^581T allele showing significantly enhanced tillering capacity compared to japonica varieties. These findings collectively reveal the mechanism by which OsWRKY53 regulates the formation of tillers in rice, providing new genetic targets for semi-dwarf and high-tillering rice breeding.