Functional Analysis of the Nitrogen Metabolite Repression Regulator Gene nmrA in Aspergillus flavus

Abstract

In <i>Aspergillus nidulans</i>, the nitrogen metabolite repression (NMR) regulator NmrA plays a major role in regulating the activity of the GATA transcription factor AreA during nitrogen metabolism. However, the function of <i>nmrA</i> in <i>A. flavus</i> has not been previously studied. Here, we report the identification and functional analysis of <i>nmrA</i> in <i>A. flavus</i>. Our work showed that the amino acid sequences of NmrA are highly conserved among <i>Aspergillus</i> species and that <i>A. flavus</i> NmrA protein contains a canonical Rossmann fold motif. Deletion of <i>nmrA</i> slowed the growth of <i>A. flavus</i> but significantly increased conidiation and sclerotia production. Moreover, seed infection experiments indicated that <i>nmrA</i> is required for the invasive virulence of <i>A. flavus</i>. In addition, the Δ<i>nmrA</i> mutant showed increased sensitivity to rapamycin and methyl methanesulfonate, suggesting that <i>nmrA</i> could be responsive to target of rapamycin signaling and DNA damage. Furthermore, quantitative real-time reverse transcription polymerase chain reaction analysis suggested that <i>nmrA</i> might interact with other nitrogen regulatory and catabolic genes. Our study provides a better understanding of NMR and the nitrogen metabolism network in fungi.