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

Dissemination and survival of ascomycetes is through asexual spores. ThebrlAgene encodes a C2H2-type zinc-finger transcription factor, which is essential for asexual development.Penicillium expansumcauses blue mold disease and is the main source of patulin, a mycotoxin that contaminates apple-based food. AP. expansumPe Delta brlAdeficient strain was generated by homologous recombination. In vivo, suppression ofbrlAcompletely 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 bybrlAsuppression, 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 Pe Delta brlAunveiled an up-regulated biosynthetic gene cluster (PEXP_073960-PEXP_074060) that shares high similarity with the chaetoglobosin gene cluster ofChaetomium globosum. Metabolome analysis of Pe Delta brlAconfirmed 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.