The brlA Gene Deletion Reveals That Patulin Biosynthesis Is Not Related to Conidiation in Penicillium expansum

Abstract

Dissemination and survival of ascomycetes is through asexual spores. The brlA gene encodes a C2H2-type zinc-finger transcription factor, which is essential for asexual development. Penicillium expansum causes blue mold disease and is the main source of patulin, a mycotoxin that contaminates apple-based food. A P. expansum PeΔbrlA deficient strain was generated by homologous recombination. In vivo, suppression of brlA completely blocked the development of conidiophores that takes place after the formation of coremia/synnemata, a required step for the perforation of the apple epicarp. Metabolome analysis displayed that patulin production was enhanced by brlA suppression, explaining a higher in vivo aggressiveness compared to the wild type (WT) strain. No patulin was detected in the synnemata, suggesting that patulin biosynthesis stopped when the fungus exited the apple. In vitro transcriptome analysis of PeΔbrlA unveiled an up-regulated biosynthetic gene cluster (PEXP_073960-PEXP_074060) that shares high similarity with the chaetoglobosin gene cluster of Chaetomium globosum. Metabolome analysis of PeΔbrlA confirmed these observations by unveiling a greater diversity of chaetoglobosin derivatives. We observed that chaetoglobosins A and C were found only in the synnemata, located outside of the apple, whereas other chaetoglobosins were detected in apple flesh, suggesting a spatial-temporal organization of the chaetoglobosin biosynthesis pathway.

Regulation of Secondary Metabolism in the Penicillium Genus

“…A recent study in P. expansum showed that the brlA gene not only affects the stage of conidiation of the fungus but also affects the biosynthesis of secondary metabolites. Zetina-Serrano et al [ 157 ] showed that the suppression of brlA results in a strain devoid of conidia and that the production of communesins and derivatives was drastically decreased, whereas the production of chaetoglobosins and derivatives increased. Neither patulin nor citrinin production was affected by the suppression of brlA .…”

Arginine Methyltransferase PeRmtC Regulates Development and Pathogenicity of Penicillium expansum via Mediating Key Genes in Conidiation and Secondary Metabolism

“…The brlA gene, which encodes the C 2 H 2 zinc-finger transcription factor, modulates conidiation-specific genes and initiates conidiation; abaA activated by BrlA is required for the differentiation and function maintenance of phialides, and wetA activated by AbaA is essential for spore formation and maturation [ 37 ]. A recent study demonstrated the conserved role of BrlA in the conidiophore development of P. expansum [ 38 ]. These findings further support that PeRmtC positively regulates conidiogenesis of P. expansum by mediating the two important regulatory genes PeBrlA and PeAbaA .…”