Open AccessActivation of the Ustilagic Acid Biosynthesis Gene Cluster in Ustilago maydis by the C 2 H 2 Zinc Finger Transcription Factor Rua1
Author(s) -
Beate Teichmann,
Lidan Liu,
Kay Oliver Schink,
Michael Bölker
Publication year - 2010
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.02211-09
Subject(s) - ustilago , biology , gene cluster , promoter , gene , zinc finger , consensus sequence , genetics , biochemistry , aspergillus nidulans , transcription factor , peptide sequence , gene expression , mutant
The phytopathogenic basidiomycetous fungusUstilago maydis secretes, under conditions of nitrogen starvation, large amounts of the biosurfactant ustilagic acid (UA). This secreted cellobiose glycolipid is toxic for many microorganisms and confers biocontrol activity toU. maydis . Recently, a large gene cluster that is responsible for UA biosynthesis was identified. Here, we show that expression of all cluster genes depends on Rua1, a nuclear protein of the C2 H2 zinc finger family, whose gene is located within the gene cluster. While deletion ofrua1 results in complete loss of UA production, overexpression ofrua1 promotes increased UA synthesis even in the presence of a good nitrogen source. Bioinformatic analysis allowed us to identify a conserved sequence element that is present in the promoters of all structural genes involved in UA biosynthesis. Deletion analysis of several promoters within the cluster revealed that this DNA element serves as an upstream activating sequence (UAS) and mediates Rua1-dependent expression. We used the yeast one-hybrid system to demonstrate specific recognition of this DNA element by Rua1. Introduction of nucleotide exchanges into the consensus sequence interfered with Rua1-dependent activation, suggesting that this sequence element acts as a direct binding site for Rua1.