AUTHOR=Niehaus Eva-Maria , Schumacher Julia , Burkhardt Immo , Rabe Patrick , Münsterkötter Martin , Güldener Ulrich , Sieber Christian M. K. , Dickschat Jeroen S. , Tudzynski Bettina 

TITLE=The GATA-Type Transcription Factor Csm1 Regulates Conidiation and Secondary Metabolism in Fusarium fujikuroi

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01175

DOI=10.3389/fmicb.2017.01175

ISSN=1664-302X

ABSTRACT=<p>GATA-type transcription factors (TFs) such as the nitrogen regulators AreA and AreB, or the light-responsive TFs WC-1 and WC-2, play global roles in fungal growth and development. The conserved GATA TF NsdD is known as an activator of sexual development and key repressor of conidiation in <italic>Aspergillus nidulans</italic>, and as light-regulated repressor of macroconidia formation in <italic>Botrytis cinerea.</italic> In the present study, we functionally characterized the NsdD ortholog in <italic>Fusarium fujikuroi</italic>, named Csm1. Deletion of this gene resulted in elevated microconidia formation in the wild-type (WT) and restoration of conidiation in the non-sporulating velvet mutant Δ<italic>vel1</italic> demonstrating that Csm1 also plays a role as repressor of conidiation in <italic>F. fujikuroi</italic>. Furthermore, biosynthesis of the PKS-derived red pigments, bikaverin and fusarubins, is de-regulated under otherwise repressing conditions. Cross-species complementation of the Δ<italic>csm1</italic> mutant with the <italic>B. cinerea</italic> ortholog <italic>LTF1</italic> led to full restoration of WT-like growth, conidiation and pigment formation. In contrast, the <italic>F. fujikuroi CSM1</italic> rescued only the defects in growth, the tolerance to H<sub>2</sub>O<sub>2</sub> and virulence, but did not restore the light-dependent differentiation when expressed in the <italic>B. cinerea</italic> Δ<italic>ltf1</italic> mutant. Microarray analysis comparing the expression profiles of the <italic>F. fujikuroi</italic> WT and the Δ<italic>csm1</italic> mutant under different nitrogen conditions revealed a strong impact of this GATA TF on 19 of the 47 gene clusters in the genome of <italic>F. fujikuroi</italic>. One of the up-regulated silent gene clusters is the one containing the sesquiterpene cyclase-encoding key gene <italic>STC1.</italic> Heterologous expression of <italic>STC1</italic> in <italic>Escherichia coli</italic> enabled us to identify the product as the volatile bioactive compound (–)-germacrene D.</p>