MdMAPKKK1 Regulates Apple Resistance to by Interacting with MdBSK1.

Plant MAPK cascade performs a critical role in the regulation of plant immunity and disease resistance. Although the function of MAPK cascade in immunity regulation is partially conserved between different species, the mechanism varies in different host and pathogen combinations. To date, the MAPK cascade function of woody plants in the regulation of disease resistance has seldom been reported. Here, we present evidence to show that apple performed an important role in the regulation of apple resistance to , the causal agent of apple ring rot. infection leads to enhanced expression and MAPK cascade activation, indicating that the MAPK cascade is involved in the defense against . overexpression-induced pathogen-independent cell death. silencing decreases the resistance of apple calli and fruits to . Further analysis indicates that MdMAPKKK1 can bind MdBSK1 and is likely phosphorylated by it. The MdBSK1-mediated phosphorylation of is important for resistance to . These results collectively indicate that apple resistance to is regulated by the interaction between MAPKKK1 and MdBSK1.