Identification of phosphorylation sites of transcription factor after reaction with protein kinase

In previous study, we reported that MdERF17 contributes to Chl degradation in apple fruit peels. Here, we demonstrated that MdERF17 and MdMPK4 interact with each other in vitro and in vivo and raised the possibility that MdMPK4 may contribute to fruit degreening via post-transcriptional regulation of MdERF17. So an in vitro kinase assay was conducted and LC-MS/MS was used to examine the phosphorylation sites.