Identification of the oosporein biosynthesis gene cluster in an entomopathogenic fungus .

(≡ ) is an entomopathogenic fungus that hosts lepidopteran insect larvae. Oosporein, produced by , is a red secondary metabolite that is also produced by other entomopathogens and is known to contribute to entomopathogenic activity. In this study, a homologous region of the oosporein biosynthesis gene cluster ( cluster) was found from the genome sequence of strain NBRC 103832. Within the cluster, a putative transcription factor gene was deleted by homologous recombination. The deletion strain () did not produce oosporein. Real-time qPCR analysis showed that the expression of all genes was either lost or greatly reduced compared to the wild type strain (WT). Infection assay using silkworms showed that the virulence of the strain was not different from that of the WT strain. We compared the expression levels of antimicrobial peptide genes in silkworm infected with these strains, and found that the increased expression of the gene in WT was not observed in the strain, suggesting that the immune response of the silkworm was altered.