The epigenetic reader SntB regulates secondary metabolism, development and global histone modifications in Aspergillus flavus

Due to the role, both beneficial and harmful, that fungal secondary metabolites play in society, the study of their regulation is of great importance. Genes for any one secondary metabolite are contiguously arranged in a biosynthetic gene cluster (BGC) and subject to regulation through the remodeling of chromatin. Histone modifying enzymes can place or remove post translational modifications (PTM) on histone tails which influences how tight or relaxed the chromatin is, impacting transcription of BGCs. In a recent forward genetic screen, the epigenetic reader SntB was identified as a transcriptional regulator of the sterigmatocystin BGC in A. nidulans, and regulated the related metabolite aflatoxin in A. flavus. In this study we investigate the role of SntB in the plant pathogen A. flavus by analyzing both Delta sntB and overexpression sntB genetic mutants. Deletion of sntB increased global levels of H3K9K14 acetylation and impaired several developmental processes including sclerotia formation, heterokaryon compatibility, secondary metabolite synthesis, and ability to colonize host seeds; in contrast the overexpression strain displayed fewer phenotypes. Delta sntB developmental phenotypes were linked with SntB regulation of NosA, a transcription factor regulating the A. fiavus cell fusion cascade.