ABI4 interacts with ICE1 and JAZ proteins to regulate abscisic acid signaling-mediated cold tolerance in apple.

Abscisic acid (ABA) is involved in the regulation of cold stress response, but its molecular mechanism remains to be elucidated. In this study, we demonstrated that the APETALA2/ethylene responsive factor (AP2/ERF) family protein MdABI4 positively regulates ABA-mediated cold tolerance in apple. We found that MdABI4 interacts with MdICE1, a key regulatory protein involved in the cold stress response, and enhances the transcriptional function of MdICE1 on its downstream target gene MdCBF1, thus improving ABA-mediated cold tolerance. Apple jasmonate-ZIM domain (JAZ) proteins MdJAZ1 and MdJAZ2 negatively modulate MdABI4-improved cold tolerance by interacting with the MdABI4 protein. Further research showed that MdJAZ1 and MdJAZ2 interfere with the interaction between the MdABI4 and MdICE1 proteins. Together, our data revealed that MdABI4 integrates jasmonic acid (JA) and ABA signals to delicately modulate cold tolerance through the JAZ-ABI4-ICE1-CBF regulatory cascade in apple. These findings will provide insights into the crosstalk between JA and ABA signals in the cold stress response.