Members of chitin synthase family in Metarhizium acridum differentially affect fungal growth, stress tolerances, cell wall integrity and virulence

Abstract

Chitin is an important component of the fungal cell wall with a family of chitin synthases mediating its synthesis. Here, we report on the genetic characterization of the full suite of seven chitin synthases ( MaChsI-VII ) identified in the insect pathogenic fungus, Metarhizium acridum . Aberrant distribution of chitin was most evident in targeted gene knockouts of MaChsV and MaChsVII . Mutants of MaChsI , MaChsIII , MaChsIV showed delayed conidial germination, whereas Δ MaChsII and Δ MaChsV mutants germinated more rapidly when compared to the wild-type parent. All MaChs genes impacted conidial yield, but differentially affected stress tolerances. Inactivation of MaChsIII , MaChsV , MaChsVII resulted in cell wall fragility, and Δ MaChsV and Δ MaChsVII mutants showed high sensitivity to Congo red and calcofluor white, suggesting that the three genes are required for cell wall integrity. In addition, Δ MaChsIII and Δ MaChsVII mutants showed the highest sensitivities to heat and UV-B stress. Three of seven chitin synthase genes, MaChsIII , MaChsV , MaChsVII , were found to contribute to fungal virulence. Compared with the wild-type strain, Δ MaChsIII and Δ MaChsV mutants were reduced in virulence by topical inoculation, while the Δ MaChsVII mutant showed more severe virulence defects. Inactivation of MaChsIII , MaChsV , or MaChsVII impaired appressorium formation, affected growth of in insecta produced hyphal bodies, and altered the surface properties of conidia and hyphal bodies, resulting in defects in the ability of the mutant strains to evade insect immune responses. These data provide important links between the physiology of the cell wall and the ability of the fungus to parasitize insects and reveal differential functional consequences of the chitin synthase family in M . acridum growth, stress tolerances, cell wall integrity and virulence.

Transcriptional profile of oil palm pathogen, Ganoderma boninense, reveals activation of lignin degradation machinery and possible evasion of host immune response

“…During normal growth, chitin biosynthesis genes like chitin synthases (CHS) and endochitinases [ 37 ] are needed for hyphal development and maintenance of cell wall integrity in fungi [ 38 ]. The observed up-regulation of CHS and endochitinases suggests that the fungus is growing and increasing in biomass during the interaction.…”

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

“…Chitin is synthesized by chitin synthases and is crucial to the fungal cell wall integrity [ 63 ]. Studies have shown that ChsIII , ChsV , ChsVI and ChsVII affect the synthesis of polysaccharide in the cell wall, and ChsIII , ChsV and ChsVII are necessary for the cell wall integrity in M. acridum [ 36 ]. In addition, chitin syn synthases in A. fumigatus [ 64 ] and Botrytis cinerea [ 65 ] also affect the cell wall integrity.…”

“…The cell wall contents, chitin, β-1,3-glucan and mannoproteins, of M. acridum were determined according to the previous study [ 36 ]. Briefly, hyphae of the WT, Δ MaAreB and CP strains were respectively inoculated in a 40 mL 1/4SDY liquid medium (1/4 SDAY without agar) and cultured at 28 °C with 220 rpm for 3 days.…”

CgEnd3 Regulates Endocytosis, Appressorium Formation, and Virulence in the Poplar Anthracnose Fungus Colletotrichum gloeosporioides

“…In filamentous fungi, the chitin synthase was reported to be responsible for the synthesis of chitin [64]. In S. cerevisiae [65], Metarhizium acridum [66], Fusarium graminearum [67], and B. cinerea [68] chitin synthase are required for cell-wall integrity. In this study, we identified seven chitin synthases CgChs1-CgChs7 (Protein IDs: 1900258, 361644, 1836492, 1744167, 1830816, 1462050, and 30251, respectively) in C. gloeosporioides, and qRT-PCR was applied to determine the relative expression levels of these genes in WT and ∆CgEnd3.…”