Genome, Transcriptome, and Functional Analyses of Penicillium expansum Provide New Insights Into Secondary Metabolism and Pathogenicity

Abstract

The relationship between secondary metabolism and infection in pathogenic fungi has remained largely elusive. The genus Penicillium comprises a group of plant pathogens with varying host specificities and with the ability to produce a wide array of secondary metabolites. The genomes of three Penicillium expansum strains, the main postharvest pathogen of pome fruit, and one Pencillium italicum strain, a postharvest pathogen of citrus fruit, were sequenced and compared with 24 other fungal species. A genomic analysis of gene clusters responsible for the production of secondary metabolites was performed. Putative virulence factors in P. expansum were identified by means of a transcriptomic analysis of apple fruits during the course of infection. Despite a major genome contraction, P. expansum is the Penicillium species with the largest potential for the production of secondary metabolites. Results using knockout mutants clearly demonstrated that neither patulin nor citrinin are required by P. expansum to successfully infect apples. Li et al. ( MPMI-12-14-0398-FI ) reported similar results and conclusions in their recently accepted paper.

Effects of carbon, nitrogen and ambient pH on patulin production and related gene expression in Penicillium expansum

“…These results indicated that the relationship between patulin production and sporulation is restricted to certain conditions, and patulin biosynthesis is not essential to sporulation in P. expansum. It has been reported that patulin minus mutants of P. expansum and P. urticae could still sporulate (Ballester et al, 2015;Li et al, 2015;Sekiguchi and Gaucher, 1977). Patulin synthesis and sporulation may only share some common upstream signal transduction or regulating pathways.…”

“…Recently, the gene cluster responsible for patulin biosynthesis in P. expansum has been reported (Ballester et al, 2015;Li et al, 2015;Tannous et al, 2014). The cluster includes 15 genes (PatA ~ PatO), of which PatL encodes a putative pathway specific transcription factor and PatK encodes a 6-methylsalicylic acid synthase, the key enzyme which catalyzes the first step of patulin biosynthesis (Li et al, 2015;Puel et al, 2010).…”

Classic fungal natural products in the genomic age: the molecular legacy of Harold Raistrick

“…For example, in the case of patulin 14 a biosynthetic gene cluster has been reported, 168 and some P450 enzymes have been isolated, 169 but no detailed pathway investigations have yet been made. The pathway should include interesting ring contracting steps.…”

Dominant Selectable Markers for Penicillium spp. Transformation and Gene Function Studies

“…This has stimulated much interest in identifying genes and gene products that mediate pathogen virulence, spore germination and mycotoxin production [19][20][21]. Additionally, an Agrobacterium tumefaciens Mediated Transformation (ATMT) system for P. expansum using hygromycin and the hygromycin phosphotransferase (hph) gene as a single dominant selectable marker (DSM) has allowed researchers to analyze gene function, which has been developed [22].…”

“…Therefore, both functional genetic tools and corresponding genomic platforms have enabled researchers to utilize ATMT coupled with a single DSM to analyze Penicillium spp. gene function [19][20][21]. However, the use of one selectable marker is not optimal or desirable to conduct molecular genetics investigations.…”