MaAreB, a GATA Transcription Factor, Is Involved in Nitrogen Source Utilization, Stress Tolerances and Virulence in Metarhizium acridum.

Chaochuang Li,Qipei Zhang,Yuxian Xia,Kai Jin

doi:10.3390/jof7070512

Abstract

The nitrogen catabolite repression (NCR) pathway is involved in nitrogen utilization, in which the global GATA transcription factor AreA plays an indispensable role and has been reported in many fungi. However, relatively few studies are focused on AreB, another GATA transcription factor in the NCR pathway and the functions of AreB are largely unknown in entomopathogenic fungi. Here, we characterized MaAreB in the model entomopathogenic fungus Metarhizium acridum. Sequence arrangement found that MaAreB had a conserved GATA zinc finger DNA binding domain and a leucine zipper domain. Disruption of MaAreB affected the nitrogen utilization and led to decelerated conidial germination and hyphal growth, decreased conidial yield, and lower tolerances to UV-B irradiation and heat-shock. Furthermore, the MaAreB mutant (ΔMaAreB) exhibited increased sensitivity to CFW (Calcofluor white), decreased cell wall contents (chitin and β-1,3-glucan) and reduced expression levels of some genes related to cell wall integrity, indicating that disruption of MaAreB affected the cell wall integrity. Bioassays showed that the virulence of the ΔMaAreB strain was decreased in topical inoculation but not in intra-hemocoel injection. Consistently, deletion of MaAreB severely impaired the appressorium formation and reduced the turgor pressure of appressorium. These results revealed that MaAreB regulated fungal nitrogen utilization, cell wall integrity and biological control potential, which would contribute to the functional characterization of AreB homologous proteins in other insect fungal pathogens, and even filamentous fungi.

Highlights

There are many fungi in the natural environment; some are pathogenic and are a threat to human health, agriculture and forestry, such as Aspergillus fumigatus, Candida albicans, A. flavus, Fusarium graminearum, and Magnaporthe oryzae [1,2]
These results revealed that MaAreB regulated fungal nitrogen utilization, cell wall integrity and biological control potential, which would contribute to the functional characterization of AreB
This phenomenon of nitrogen utilization is well known as nitrogen metabolite repression (NMR), called nitrogen catabolite repression (NCR) in Saccharomyces cerevisiae, which mainly regulates genes related to nitrogen utilization at the transcription level [12]

Summary

Introduction

There are many fungi in the natural environment; some are pathogenic and are a threat to human health, agriculture and forestry, such as Aspergillus fumigatus, Candida albicans, A. flavus, Fusarium graminearum, and Magnaporthe oryzae [1,2]. Fungi can uptake some kinds of compound as nitrogen sources, but other nitrogen sources will not be assimilated in the presence of preferentially used ammonium or glutamine; if not, they can assimilate other nitrogen sources, such as nitrate and urea [12,13]. This phenomenon of nitrogen utilization is well known as nitrogen metabolite repression (NMR), called nitrogen catabolite repression (NCR) in Saccharomyces cerevisiae, which mainly regulates genes related to nitrogen utilization at the transcription level [12]. NCR is mediated by GATA transcription factors, and four GATA transcription factors are characterized in

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