A gene regulating ergot alkaloid biosynthesis in .

UNLABELLED

Ergot alkaloid synthesis () gene clusters found in several fungi encode biosynthesis of agriculturally and pharmaceutically important ergot alkaloids. Although the biosynthetic genes of the ergot alkaloid pathway have been well characterized, regulation of those genes is unknown. We characterized a gene with sequence similarity to a putative transcription factor and that was found adjacent to the cluster of , a plant symbiont and insect pathogen. Function of the novel gene, was explored by CRISPR-Cas9-derived gene knockouts. To maximize potential for ergot alkaloid accumulation, strains of were injected into larvae of the insect . Larvae infected with the wild type contained abundant ergot alkaloids, but those infected with knockouts lacked detectable ergot alkaloids. The knockout strains had significantly reduced or no detectable mRNA from cluster genes in RNAseq and qualitative RT-PCR analyses, whereas the wild-type strain contained abundant mRNA from all genes. These data demonstrate that the product of is required for ergot alkaloid accumulation and provide evidence that it has a role in the expression of ergot alkaloid biosynthesis genes. Larvae infected with an knockout survived significantly longer than those infected with the wild type ( < 0.0001), indicating a role for EasR, and indirectly confirming a role for ergot alkaloids, in the virulence of to insects. Homologs of were found associated with clusters of at least 15 other ergot alkaloid-producing fungi, indicating that EasR homologs may contribute to regulation of ergot alkaloid synthesis in additional fungi.

IMPORTANCE

Ergot alkaloids produced by several species of fungi are important as contaminants of food and feed in agriculture and also as the foundation of numerous pharmaceuticals prescribed for dementia, migraines, hyperprolactinemia, and several other disorders. Information on control of the ergot alkaloid pathway may contribute to strategies to limit their production in agricultural settings or increase their yield for pharmaceutical production. Our results demonstrate that a previously uncharacterized gene clustered with the ergot alkaloid synthesis genes is required for the sufficient transcription of the ergot alkaloid biosynthesis genes. This observation suggests the gene encodes a factor regulating transcription of those biosynthetic genes.