Multiple transcriptomic analyses and characterization of pathogen-related core effectors and LysM family members reveal their differential roles in fungal growth and pathogenicity inPenicillium expansum

摘要

Penicillium expansumis a destructive phytopathogen causing postharvest decay on many stored fruits. To develop effective and safe management strategies, it is important to investigate its pathogenicity-related mechanisms. In this study, a bioinformatic pipeline was constructed and 50 core effector genes were identified inP. expansumusing multiple RNA-seq data sets and their putative functions were implicated by comparatively homologous analyses using pathogen-host interaction database. To functionally characterizeP. expansumLysM domain proteins during infection, null mutants for the 15 uncharacterized putative LysM effectors were constructed and the fungal growth rate on either PDA or Cazpek medium or lesion expansion rate on the infected apple fruits was evaluated. The results showed the growth rate of knockout mutants fromPeLysM5,PeLysM12andPeLysM15was retarded on PDA medium. No significant difference in growth rate was observed between wild type and all mutants on solid Cazpek medium. Nevertheless, the hypha of wild type displayed deeper yellow on the back of Cazpek medium than those of knockout mutants. On the infecting apples fruits, the knockout mutants fromPeLysM5,PeLysM7,PeLysM8,PeLysM9,PeLysM10,PeLysM11,PeLysM14,PeLysM15,PeLysM16,PeLysM18andPeLysM19showed enhanced fungal virulence, with faster decaying on infected fruits than those from wild type. By contrast, the knockout mutation atPeLysM12locus led to reduced lesion expansion rate on the infected apple fruits. In addition,P.expansum-apple interaction RNA-seq experiment was performed using apple fruit tissues infected by the wild type and knockout mutant Delta PeLysM15, respectively.Transcriptome analyses indicated that deletion ofPeLysM15could activate expression of several core effector genes, such asPEX2_055830,PEX2_036960andPEX2_108150, and a chitin-binding protein,PEX2_064520. These results suggest PeLysM15 may play pivotal roles in fungal growth and development and involve pathogen-host interaction by modulating other effector genes' expression. Our results could provide solid data reference and good candidates for further pathogen-related studies inP. expansum.