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.
Highlights
Penicillium is a well-known genus of filamentous ascomycetous fungi
Our results indicated that some secondary metabolites (SMs) were regulated by the brlA gene in P. expansum and confirmed that patulin production was not linked to the conidiogenesis
Transcriptome analysis showed that the gene network under the positive influence of BrlA was relatively conserved in Penicillium subgenus Penicillium and that many of them were genes involved in conidiation such as wetA, abaA, hydrophobin encoding genes, and melanin-like pigments encoding genes
Summary
Penicillium is a well-known genus of filamentous ascomycetous fungi. Taxonomically, it is a member of the Aspergillaceae family, in nature it is mainly found in the soil it has been detected in decaying organic matter, cereals, seeds, and various food products, and is of great economic importance [1,2,3]. The genus currently contains 483 accepted species [3], fungi that are very common in the environment and are important in different fields including biotechnology, medical and food industries and in phytopathology and food spoilage (pre- and postharvest pathogens) [4,5]. The species of this fungal genus are known to produce biologically active compounds called secondary metabolites (SMs) that can range from potent pharmaceutical drugs to mycotoxins that are harmful to humans and animals [6,7,8,9,10]. A recent study has shown that the deletion of sntB, a gene coding for an epigenetic reader, resulted in a decreased patulin production in vitro and in planta [27]
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