CUL3(BPM) E3 ubiquitin ligases regulate MYC2, MYC3 and MYC4 stability and JA responses

The Jasmonate pathway regulators MYC2, MYC3 and MYC4 are central nodes in plant signaling networks integrating environmental and developmental signals to fine-tune jasmonate defenses and plant growth. Hence, their activity needs to be tightly regulated in order to optimize plant fitness. Among the increasing number of mechanisms regulating MYCs, protein stability is arising as a major player. However, how the levels of MYCs proteins are modulated is still poorly understood. Here, we report that MYC2, MYC3 and MYC4 are targets of BPM proteins, which act as substrate adaptors of CUL3-based E3 ubiquitin ligases. Reduction-of-function of CUL3(BPM) in amiR-bpm lines, bpm235 triple mutants and cul3ab double mutants enhance MYC2 and MYC3 stability and accumulation, and potentiates plant responses to JA such a root-growth inhibition, and MYC-regulated gene expression. BPM3 protein is stabilized by JA, suggesting a new negative feedback regulatory mechanism to control MYCs activity. Our results uncover a new layer for JA-pathway regulation by CUL3(BPM)-mediated degradation of MYC TFs.