Interaction between MAPKs and MKPs in hexaploid chrysanthemum illuminates functional paralogue diversification in polyploids

Mitogen-activated protein kinases (MAPKs, also known as MPKs) regulate diverse cellular and physiological functions, and dual-specificity MAPK phosphatases (MKPs) modulate MAPK signalling through MAPK dephosphorylation and inactivation. Due to lacking of overall understanding for the regulatory networks between Chrysanthemum morifolium MKPs (CmMKPs) and C. morifolium MAPKs (CmMPKs), we systematically studied the interactions between four groups of CmMPKs and eight identified CmMKPs in chrysanthemum and found that the interaction between the specific CmMKP and the specific CmMPK differed from those in other plants. Furthermore, the expression of CmMKP1 and CmMKP1-LIKE1 showed opposite trends during the development of chrysanthemum flower buds under salt treatment and Alternaria alternata inoculation, but these genes could interact with the same CmMPKs, providing insight into the subfunctionalization of paralogues. Amino acid variations (M87V, T277P and V6L) in dual-specificity protein phosphatases (DsPTP1)-LIKE1/2/3 changed the interactions of these proteins with the four CmMPK groups in chrysanthemum, providing evidence for the de/neofunctionalization of paralogues in polyploids, suggesting that we can identify the key functional sites of proteins by studying polyploid paralogues.