ABSTRACTMost of the biosynthetic gene clusters (BGCs) found in filamentous fungi are silent under standard laboratory cultivation conditions due to the lack of expression triggering stimuli, representing a considerable drawback in drug discovery. To access the full biosynthetic potential of these microbes, studies towards the activation of cryptic BGCs are essential. Histone acetylation status is an important regulator of chromatin structure which impacts in cell physiology and, therefore, expression of biosynthetic gene clusters in filamentous fungi. Histone deacetylases (HDACs) and histone acetyl-transferases (HATs) are responsible for maintaining and controlling this process under different cell conditions. In this study, clr3, a gene encoding a histone deacetylase in Penicillium brasilianum was deleted and associated phenotypic and metabolic changes evaluated. Results indicate reduced growth under oxidative stress conditions in the Δclr3 knockout strain. Also, the production of several secondary metabolites including austin-related meroterpenoids, brasiliamides, mycotoxins such as verruculogen and penicillic acid, as well as cyclodepsipeptides was reduced in the Δclr3 strain when compared to wild-type strain. Accordingly, addition of epigenetic modulators responsible for HDAC inhibition such as suberoylanilide hydroxamic acid (SAHA) and nicotinamide (NAA) to P. brasilianum growth media also culminated in reduction of secondary metabolite production. Mass Spectrometry Imaging (MSI) was applied to compare metabolite production and spatial distribution on the colony. Results suggest that Clr3 plays an important role in secondary metabolite biosynthesis in P. brasilianum, thus offering new strategies for regulation of natural product synthesis by assessing chromatin modification in P. brasilianum.
Molecular Genetics of Filamentous Fungi. Edited by W. E. Timberlake, UCLA Symposium on Molecular and Cellular Biology, vol. 34465 pages, N.Y.: A. R. Liss Inc. £57·00. ISBN 0 8451 2633 4.