Functional analysis of apple defense protein MdPL and screening of proteins interaction with Penicillium expansum

Blue mold disease, caused by Penicillium expansum, is the most devastating post-harvest fungal disease affecting apples. During the fungal infection, there is a significant interaction between the pathogen and the apple, leading to the production of important metabolites and the activation of related metabolic processes. As one of the metabolites, pectin lyase is an important pectin-modifying enzyme that regulates the elasticity and permeability of cell wall and plays a key role in plant disease resistance and fruit softening. In this study, a pectin lyase protein MdPL was identified, which has the function of regulating cell wall permeability. It is up-regulated in the process of apple defense against P. expansum infection, and may have a key defense function. Protein bioinformatics analysis showed that MdPL belonged to the PL1 family, and subcellular localization was predicted to be located in the nucleus. The protein expression of P. expansum at different stages of infection was analyzed by RT-qPCR. The results of subcellular localization of Agrobacterium transformation showed that MdPL was localized in the nucleus, which was consistent with the results of bioinformatics analysis. The Y2H system explored the proteins interacting with apple proteins during P. expansum infection. The results showed that apple bait protein had no self-activation and no toxic effect on Y2H cells. The interacting protein MdPL-PeXR was screened from 10 pairs of candidates interacting protein pairs. HDOCK was used to analyze the interaction protein of MdPL, the results showed that the docking score was −225.61 and the confidence score was 0.8194, which verified the results of the Y2H test. This study provides ideas and references for further exploring the interaction mechanism between apple and P. expansum, and is of great significance for the study of plant-pathogen interaction.