Jasmonic acid signaling inhibits axillary bud development under drought stress via the CmMYC2-CmBRC1b module.

Plant architecture changes to adapt to drought stress. Jasmonic acid (JA) is an endogenous growth regulator that alters plant development in response to changing environments. Teosinte BRANCHED1 (TB1)/BRANCHED 1 (BRC1) can integrate multiple signalling pathways. However, the molecular mechanism by which and how drought stress regulates the development of axillary buds and the relationship between JA and BRC1 remain elusive. In this study, we found that the development of axillary buds in chrysanthemum (Chrysanthemum morifolium) is inhibited under drought stress and after exogenous spraying of methyl jasmonate (MeJA). RNA-seq analysis revealed the response of CmBRC1b to this process. Molecular validation confirmed that CmMYC2 directly binds to the promoter of CmBRC1b and promotes its expression in vitro and in vivo, but CmMYC2 cannot bind to the CmBRC1a promoter. Genetic transformation confirmed that both CmMYC2 and CmBRC1b inhibit lateral bud outgrowth. We conclude that JA signalling inhibits the development of axillary buds through the CmMYC2-CmBRC1b module under drought stress. These findings reveal the molecular mechanisms by which plants respond to drought and alter axillary shoot development, which provide a strategy for developing cultivars with high resistance to drought stress and high yield.