Coordination of secondarymetabolism and development in fungi: the velvet familyof regulatory proteins

Abstract

Filamentous fungi produce a number of small bioactive molecules as part of their secondary metabolism ranging from benign antibiotics such as penicillin to threatening mycotoxins such as aflatoxin. Secondary metabolism can be linked to fungal developmental programs in response to various abiotic or biotic external triggers. The velvet family of regulatory proteins plays a key role in coordinating secondary metabolism and differentiation processes such as asexual or sexual sporulation and sclerotia or fruiting body formation. The velvet family shares a protein domain that is present in most parts of the fungal kingdom from chytrids to basidiomycetes. Most of the current knowledge derives from the model Aspergillus nidulans where VeA, the founding member of the protein family, was discovered almost half a century ago. Different members of the velvet protein family interact with each other and the nonvelvet protein LaeA, primarily in the nucleus. LaeA is a methyltransferase-domain protein that functions as a regulator of secondary metabolism and development. A comprehensive picture of the molecular interplay between the velvet domain protein family, LaeA and other nuclear regulatory proteins in response to various signal transduction pathway starts to emerge from a jigsaw puzzle of several recent studies.

Fungal S-adenosylmethionine synthetase and the control of development and secondary metabolism in Aspergillus nidulans

“…Light is sensed by photoreceptors that transmit the signal to recipients like the velvet regulators. In the dark, the velvet protein VeA is transported together with the second velvet-like protein VelB into the nucleus, where they can form together with the putative methyltransferase LaeA the trimeric VelB-VeA-LaeA complex which coordinates sexual development and secondary metabolism (Bayram and Braus, 2011;Bayram et al, 2008). A. nidulans LaeA is required for secondary metabolite expression of the sterigmatocystin (ST) or penicillin clusters (Bok and Keller, 2004;Bok et al, 2006).…”

bZIP transcription factors affecting secondary metabolism, sexual development and stress responses in Aspergillus nidulans

“…We found that both RsmA and NapA, previously identified as having a major role in the fungal stress response, have significant and distinct effects on SM and sexual development, a linkage previously characterized by the Velvet Complex (Bayram & Braus, 2012).…”

FgVelB globally regulates sexual reproduction, mycotoxin production and pathogenicity in the cereal pathogen Fusarium graminearum

“…In addition to the specific TFs, putative global regulators that are involved in the regulation of more diverse functions have also received attention. Recently, the velvet family proteins, which are global regulators conserved in filamentous fungi (Bayram & Braus, 2012;Jiang et al, 2011;Kato et al, 2003;Kim et al, 2002;Merhej et al, 2012;Wiemann et al, 2010), have been identified in F. graminearum. In Aspergillus nidulans, the velvet protein complex forms a heterotrimeric complex consisting of VelB-VeA-LaeA proteins, and regulates diverse cellular functions such as sexual development and secondary metabolism by participating in chromatin remodelling.…”