Cross-Species Hybridization withFusarium verticillioidesMicroarrays Reveals New Insights intoFusarium fujikuroiNitrogen Regulation and the Role of AreA and NMR

Abstract

ABSTRACTIn filamentous fungi, the GATA-type transcription factor AreA plays a major role in the transcriptional activation of genes needed to utilize poor nitrogen sources. InFusarium fujikuroi, AreA also controls genes involved in the biosynthesis of gibberellins, a family of diterpenoid plant hormones. To identify more genes responding to nitrogen limitation or sufficiency in an AreA-dependent or -independent manner, we examined changes in gene expression ofF. fujikuroiwild-type and ΔareAstrains by use of aFusarium verticillioidesmicroarray representing ∼9,300 genes. Analysis of the array data revealed sets of genes significantly down- and upregulated in theareAmutant under both N starvation and N-sufficient conditions. Among the downregulated genes are those involved in nitrogen metabolism, e.g., those encoding glutamine synthetase and nitrogen permeases, but also those involved in secondary metabolism. Besides AreA-dependent genes, we found an even larger set of genes responding to N starvation and N-sufficient conditions in an AreA-independent manner. To study the impact of NMR on AreA activity, we examined the expression of several AreA target genes in the wild type and inareAandnmrdeletion and overexpression mutants. We show that NMR interacts with AreA as expected but affects gene expression only in early growth stages. This is the first report on genome-wide expression studies examining the influence of AreA on nitrogen-responsive gene expression in a genome-wide manner in filamentous fungi.