Identification of pathogenicity-related genes and the role of a subtilisin-related peptidase S8 (PePRT) in authophagy and virulence of Penicillium expansum on apples

Abstract

Blue mold caused by Penicillium expansum is a major postharvest disease of pome fruit. Several mechanisms possibly involved in P. expansum pathogenicity and virulence. However, factors that mediate pathogenicity and virulence are largely not yet characterized. In this work we analyzed P. expansum predicted secretome to reveal potential genes that have a role in host-pathogen interaction. A prediction pipeline was designed using an approach that combines common effector features, transcriptomic data and homology to proteins reported to be involved in pathogenicity of other pytopathogenic fungi. Among 297 genes predicted in P. expansum secretome, 103 genes (35 %) were found to code for hydrolytic enzymes. The majority of the secreted enzymes are carbohydrate-degrading enzymes among which five coding for pectin-degrading enzymes are highly induced during the infection and decay of apple fruit by P. expansum, indicating that they may represent an important aspect of pathogenicity and virulence. Applying the pipeline we have predicted 17 candidate genes coding for proteins that are most likely involved in pathogenicity and virulence. One of the top candidates is a subtilisin-related peptidase, S8 (PePRT), proteolytic enzyme highly expressed in planta, and potentially involved in authophagy process. Deletion of PePRT-coding gene resulted in reduced virulence of P. expansum on apples. Moreover, ΔPeprt exhibited decreased sporulation as well as affected mycelial morphology and internal mycelial cell structure.

Review of the Impact of Apple Fruit Ripening, Texture and Chemical Contents on Genetically Determined Susceptibility to Storage Rots

“…The host responded by activating pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) one hour after infection, and effector-triggered immunity three hours after infection. In another gene expression study of P. expansum, genes coding for pectin degradation were again shown to be upregulated during infection of apple [ 79 ]. Barad et al [ 32 ] showed that gene expression patterns of P. expansum are, however, extremely versatile; some genes expressed during infection of apple were pH neutral, while others were similar to those obtained when growing the fungus in vitro at pH 4 or at pH 7, respectively.…”

Molecular basis and regulation of pathogenicity and patulin biosynthesis in Penicillium expansum

“…There are >80 proteases in the secretome of P. expansum, and about half of them belong to a superfamily of serine proteases (Li et al, 2015). Levin, Kishore et al (2019) reported that Peprt, a gene encod-ing a protein in the S8 family of serine proteases in P. expansum, was upregulated after 24 hr of inoculation. The deletion of Peprt resulted in reduced P. expansum virulence on apple fruit.…”

“…In recent years, there have been rapid increases in research on the molecular mechanisms of pathogenicity in P. expansum , especially after the sequencing of the genomes of P. expansum and closely related Penicillium species. A large set of genes coding putative virulence factors and regulators have been identified in several omics‐based studies (Ballester et al., 2015; Levin, Kishore et al., 2019; Tannous, Kumar et al., 2018; Wang, Zheng, Zhang et al., 2019; Wu et al., 2019; Zhou et al., 2018), and the functions of some genes have been characterized (Figure 2).…”

“…Levin, Kishore et al. (2019) reported that Peprt , a gene encoding a protein in the S8 family of serine proteases in P. expansum , was upregulated after 24 hr of inoculation. The deletion of Peprt resulted in reduced P. expansum virulence on apple fruit.…”

Identification and Functional Analysis of NLP-Encoding Genes from the Postharvest Pathogen Penicillium expansum

“…In our previous works [11,12], the potential role of PeLysM and subtilisin-related peptidase Peprt genes in the pathogenicity and virulence of P. expansum on apples was investigated. Deletion of Peprt in P. expansum resulted in reduced sporulation and virulence of the fungus on apples [12]. Expression level of four LysM coding genes was induced during the infection of apple fruit and decay development.…”