Research On The Mechanism Of WSC1 In The Infection Of Pear Fruit By Penicillium Expansum

Pear is one of the most important traditional fruits with rich nutrition and high global demand.However,pear is vulnerable to various pathogenic fungi during harvesting,packaging,storage and transportation,resulting in significant economic losses.Postharvest blue mold decay of pear fruit caused by Penicillium expansum is one of the main diseases of pear fruit decay.At present,the infection mechanism of P.expansum on pear fruit is still at the primary stage,so it is particularly important to study the infection mechanism of P.expansum on postharvest pear fruit.WSC1 mainly encodes WSC protein,which is a component of cell wall integrity and stress response.As a signal receiver in MAPK signaling pathway,WSC1 plays an important role in fungal cell response to external environmental stress.This study intended to knock out and complement WSC1 gene through Agrobacterium-mediated homologous recombination technology,and then analyzed the phenotypic changes of the knockout and complement mutants in the aspects of growth,development and pathogenic process.Then,the infection mechanism of WSC1 knockout mutant and the defense mechanism of pear against WSC1 knockout strain infection were analyzed by transcriptomics and bioinformatics technology.The main research results are as follows:(1)Bioinformatics analysis found that the relative molecular weight of WSC protein was 32 k Da,with a total of 318 amino acids.The theoretical isoelectric point was 8.09,the instability coefficient was 48.16,the fat coefficient was 63.27,and the hydrophilicity evaluation was-0.116,indicating that WSC was a hydrophilic protein.Through signal peptide prediction,it was found that the protein had a signal peptide sequence at the 1-20 th amino acid residue.Subcellular localization is located on the plasma membrane and the protein forms a typical transmembrane helical region between 205-225 amino acids.(2)The knockout mutant of WSC1 was constructed by agrobacterium-mediated homologous recombination technology ΔWSC1 and complementary mutants ΔWSC1-C.Functional verification tests showed that the deletion of WSC1 slowed down the growth rate of WSC1 knockout strains and reduced the mycelial yield and spore yield of P.expansum;It reduced the pathogenicity of P.expansum infecting pear fruit and the ability of P.expansum to produce PAT in vitro and in vivo and its toxigenic activity.At the same time,the deletion of WSC1 reduced the tolerance of knockout strains to cell wall stress factors,enhanced antioxidant capacity,decreased hypertonic sensitivity,decreased salt stress resistance,and more sensitive to most metal ions.(3)The mechanism of WSC1 knockout strain infecting pear fruit was analyzed and studied by transcriptomics and bioinformatics technology.It was found that the expression levels of some genes related to cell wall integrity and signal transduction,oxidative stress and toxin production were changed.The changes in the expression levels of genes related to cell wall integrity and signal transduction make the pathogenic bacteria more sensitive to stress response.The down-regulation of oxidative stressrelated genes reduced the pathogenic ability of pathogenic bacteria.The downregulation of toxin production-related genes led to a decrease in its ability to produce toxins and infect.(4)The response and regulation mechanism of pear fruit to WSC1 knockout strain infection was analyzed by using transcriptomics and bioinformatics technology.It was found that the expression level of some genes related to response to stress signal transduction,defense resistance and oxidative stress were changed.The changes in the expression levels of genes related to stress signal transduction make pear fruit respond to stress and produce a series of reactions.The up-regulation of defense resistancerelated genes enhanced the defense ability of pear fruit.The up-regulation of oxidative stress-related genes enhanced the antioxidant capacity of pear fruit.