Identification of a Conserved Transcriptional Activator-Repressor Module Controlling the Expression of Genes Involved in Tannic Acid Degradation and Gallic Acid Utilization in Aspergillus niger

Tannic acid, a hydrolysable gallotannin present in plant tissues, consists of central glucose molecule esterified with gallic acid molecules. Some microorganisms, including several Aspergillus species, can metabolize tannic by releasing residues from secreting specific esterases into the medium. The expression these so-called tannases is induced or acid. In this study, we identified conserved transcriptional activator-repressor module involved regulation predicted and other genes metabolism. regulating utilization resembles modules galacturonic quinic utilization. Like modules, Zn(II) 2 Cys 6 activator (TanR) putative repressor (TanX) are located adjacent to each other. Deletion ( ? tanR ) results inability grow on severely reduces growth gene tanX constitutive as well mostly unknown function. Known microbial catabolic pathways for involve ring cleavage enzymes, two enzymes show increased mutant. However, deletion genes, even all 17 encoding potential did not result non-utilizing phenotype. Therefore, A. niger involves hitherto pathway. Transcriptome analysis mutant clusters that were significantly compared parental strain. involvement selection was examined constructing mutants testing their ability Only an FAD-dependent monooxygenase (NRRL3_04659) resulted strain unable Metabolomic studies showed accumulation NRRL3_04659 suggesting first step metabolism likely responsible oxidation aromatic ring.