Submitted to: Eukaryotic Cell
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/4/2008
Publication Date: 11/1/2008
Citation: Schonig, B., Brown, D.W., Oeser, B., Tudzynski, B. 2008. Cross-Species Hybridization with Fusarium verticillioides Microarrays Reveals New Insights into Fusarium fujikuroi Nitrogen Regulation and the Role of AreA and NMR. Eukaryotic Cell. 7(10):1831-1846. Interpretive Summary: Nitrogen plays a central role in the ability of fungi to grow and colonize plants, cause disease, and make toxins. During the life cycle of corn, the amount of nitrogen available for growth changes significantly. These changes may affect the ability of infecting fungi to grow, as well as its ability to synthesis toxins. The fungus Fusarium fujikuroi and F. verticillioides are closely related and both have some unique genetic tools. We used some of these tools from both fungi to find genes from F. verticillioides that are involved in using nitrogen. Studies of some of these genes indicate that genetic regulation of nitrogen use is complicated, but we are making progress. Understanding how Fusarium responds to its nitrogen needs, and the role of this central molecule in toxin synthesis, will allow us to develop novel strategies to limit disease and contamination of food and/or feed with toxins.
Technical Abstract: In filamentous fungi, the GATA-type transcription factor AreA plays a major role in transcriptional activation of genes needed to utilize poor nitrogen sources. Previously we have shown that in Fusarium fujikuroi AreA also controls genes involved in biosynthesis of nitrogen-free secondary metabolites, such as gibberellins (GAs), a family of plant hormones. To identify more genes responding to nitrogen limitation or sufficiency in an AreA-dependent or AreA-independent manner, we examined changes in gene expression of F. fujikuroi wild-type and a delta areA mutant using an oligonucleotide microarray representing ~11,000 F. verticillioides genes. Analysis of the array data revealed sets of genes significantly down-regulated and up-regulated in the areA mutant under both nitrogen (N)-starvation and N-sufficient conditions. Among the former set are genes involved in nitrogen metabolism, e.g., those encoding the glutamine synthase and nitrogen permeases, but also genes involved in secondary metabolism. Beside AreA-dependent genes, we found an even larger set of genes responding to nitrogen starvation or glutamine excess in an AreA-independent manner. Interestingly, among the glutamine-induced AreA-independent genes are those involved in ribosome biogenesis and translation control that were previously shown to be under TOR control. To study the impact of Nmr, the negative regulator of AreA in A. nidulans, we compared the expression of nitrogen-regulated genes in the wild-type, in areA or nmr overexpressing mutants, and in areA and nmr deletion strains. Furthermore, we show for the first time that Nmr interacts with the C-terminus of AreA in F. fujikuroi.