The MsZFP1-MsWRKY40-MsWRKY41 module efficiently regulates LHCII biogenesis via ABA-dependent manner in alfalfa

The light-harvesting complex (LHC) is the antenna system of photosystem that affects the photosynthetic efficiency of plants. In this study, MsWRKY41 was demonstrated to directly activate the expression of MsAlb3 and MsDVR1, which involved in LHC protein insertion into thylakoid membrane and chlorophyll biosynthesis, respectively. Knockdown of MsWRKY41 in alfalfa led to yellow-green leaves and abnormal thylakoid structure. MsWRKY41 was the downstream target gene of MsWRKY40, which also directly and positively regulated the expression of four LHC protein genes MsLHCB1/4.3/5/7. Overexpression of MsWRKY40 increased the accumulation of PSII-LHCII supercomplexes. MsWRKY40 physically interacted with zinc finger protein MsZFP1, which partly inhibited the expression of MsWRKY40-targeted genes. This interaction was weakened by physiologically high levels of ABA, leading to up-regulated expression of MsWRKY40-targeted genes. These results revealed a regulatory module centered on MsWRKY40-MsWRKY41, which integrates the biosynthetic processes of LHCB subunits and chlorophyll into a gene regulatory network, efficiently regulating LHCII biogenesis.