The Function And Applied Potential Of Cellobiose Hydrolase PsGH7a Of Phytophthora Sojae

Phytophthora sojae belongs to the Chromista genus Oomycota,although similar in form to filamentous fungi,it is close to diatoms and Cyanobacteria in a phylogenetic and evolutionary background.In the field,Phytophthora sojae has evolved rapidly and its virulence structure has changed frequently.At present,Phytophthora sojae has basically captured all the known soybean disease resistance genes,and urgently needs to develop new resistance resources.Therefore,in-depth study of the pathogenic mechanism of Phytophthora sojae is of great value for the discovery of new molecular breeding resources and the design of control strategies.The cell wall is a powerful protective structure for plants against infection by pathogenic bacteria.Pathogens in the early stages of infection usually secrete many cell-wall degrading enzymes(CWDEs)that damage host cells.Cellulose is the main component of plant cell walls(about 40%-60%).Cellulase secreted by pathogenic bacteria plays a key role in cell wall degradation.In this study,a new GH7 family cellobiose hydrolase gene,PsGH7 a,was screened from Phytophthora sojae,and its expression was significantly up-regulated at the initial stage of the soybean-Phytophthora interaction,and the enzyme protein was highly conserved in Phytophthora.It has been discovered that cellulases secreted by pathogenic bacteria can be used as pathogen-associated molecular patterns(PAMPs)that trigger plant immune responses.PAMPs specific conserved peptides or amino acid sites can be recognized by plant cell surface transmembrane receptors(PRRs),and pattern recognition receptors(PRR)can trigger immunity(PTI)and inhibit pathogenic microorganism infection.Studies have found that PsGH7 a can induce cell death in soybean,tobacco,and tomato,which indicates that PsGH7 a is a new PAMP and has extensive excitability on different plants.PsGH7a can promote the infection of Phytophthora.Site-directed mutagenesis was used to lose the hydrolytic activity of PsGH7 a.It was found that the mutant lost its virulence function,indicating that the hydrolytic activity is necessary for PsGH7 a to promote infection;use CRISPR / Cas9 gene editing technology to knock out PsGH7 a.Compared to wild-type strains,the knockout mutants lost virulence in soybean.It is shown that PsGH7 a is necessary for the toxicity of Phytophthora sojae.This study found that the conservative Phytophthora sojae PsGH7 a is a key virulence factor and is very important for the pathogenicity of P.sojae.In-depth study of the pathogenic function and mechanism of cell wall degrading enzymes of this family has important guiding significance for enhancing our understanding of plant cell wall resistance and the targeted development of soybean molecular breeding targets and new pesticides for plant diseases.