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

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.

MaNCP1, a C2H2 Zinc Finger Protein, Governs the Conidiation Pattern Shift through Regulating the Reductive Pathway for Nitric Oxide Synthesis in the Filamentous Fungus Metarhizium acridum

“…Subsequently, three core genes of the NCR pathway of M. acridum , MaAreA ( MAC_00939 ) (Fig. S8A and B), MaAreB ( MAC_07065 ) ( 37 ) and MaNmrA ( MAC_00749 ) ( 38 ) were selected for further analyses. A qRT-PCR analysis of the expression of these genes in Δ MaNCP1 versus WT on SYA medium ( Fig.…”

“…S2A), about 1,200-bp up- and downstream fragments of MaNCP1 were amplified from the genomic DNA of WT strain, followed by ligating into pK2-SM-F and pK2-SM-R vectors as described previously ( 55 ). The MaAreB - and MaNmrA -disruption strains were constructed previously ( 37 , 38 ). The constructions of the disruption vectors of MAC_02692 , MAC_03846 , MAC_02196 and MaAreA were made similar to that of MaNCP1 .…”

Host–Pathogen Interactions between Metarhizium spp. and Locusts

“…The expression of Mad1 is increased in the early stages of infection in insects [ 15 , 28 ]. The expression of Mad1 is downregulated by a number of genes, including transcription regulator MaAreB and MaNmrA , Fus3/Kss1-type mitogen-activated protein kinase (MAPK) MaMk1 , the exopolysaccharide galactosaminogalactan (GAG) biosynthetic gene cluster MrGAG , transcription factor MaSom1 , which is located downstream of the cycle adenosine monophosphate (cAMP) -dependent protein kinase A (PKA) pathway [ 29 , 30 , 31 , 32 , 33 ]. Moreover, Mad1 expression is increased by the disruption of MrGprk , which is a class VI fungal G-protein-coupled receptor K (GPRK) [ 34 ].…”

“…Appressorial differentiation was delayed by these impaired genes, including the tetraspanin MaPls1 , the pH-responsive transcription factor MapacC , and the O-mannosyltransferases MaPmt2 and MaPmt4 [ 26 , 54 , 55 , 56 ]. The formation rate of appressorium is reduced by some genes mutants including the negative transcription regulators MaNmrA , MaAreB , and β-tubulin of M. acridum , the actin-regulating kinase MrArk , the sucrose non-fermenting protein kinase MaSnf1, the bifunctional catalase and peroxidase MaKatG1 , MrHex1 , which is related to the formation of the woronin body, and MaPEX33 , which is associated with the peroxisomal import pathway, the polyketide synthase MrPks2 [ 29 , 30 , 40 , 45 , 57 , 58 , 59 , 60 , 61 ]. The appressorial formation ability is lost when the transcription factor MrSkn7 is mutated and the inhibition of Isocitrate lyase ManICL is inhibited [ 62 , 63 ].…”

“…The expression of Pr1C and Try in MaSom1 deficiency was significantly lower than that in WT [ 31 ]. The expression of Pr1 and Chit1 is reduced in cells deficient in MaAreB , MaNmrA , Macwh1 , Macwh43 , MapacC , and MaCrz1 [ 21 , 26 , 29 , 30 , 60 , 79 ]. In contrast, certain genes reduce the expression of those proteases.…”