An apple MYB transcription factor regulates cold tolerance and anthocyanin accumulation and undergoes MIEL1‐mediated degradation

Summary MYB transcription factors ( TF s) have been demonstrated to play diverse roles in plant growth and development through interaction with basic helix‐loop‐helix ( bHLH ) TF s. Mdb HLH 33, an apple bHLH TF , has been identified as a positive regulator in cold tolerance and anthocyanin accumulation by activating the expressions of Md CBF 2 and Md DFR . In the present study, a MYB TF Md MYB 308L was found to also positively regulate cold tolerance and anthocyanin accumulation in apple. We found that Md MYB 308L interacted with Mdb HLH 33 and enhanced its binding to the promoters of Md CBF 2 and Md DFR . In addition, an apple RING E3 ubiquitin ligase MYB 30‐ INTERACTING E3 LIGASE 1 (Md MIEL 1) was identified to be an Md MYB 308L‐interacting protein and promoted the ubiquitination degradation of Md MYB 308L, thus negatively regulated cold tolerance and anthocyanin accumulation in apple. These results suggest that Md MYB 308L acts as a positive regulator in cold tolerance and anthocyanin accumulation in apple by interacting with Mdb HLH 33 and undergoes Md MIEL 1‐mediated protein degradation. The dynamic change in MYB ‐ bHLH protein complex seems to play a key role in the regulation of plant growth and development.