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PLoS Pathog. 2019 Aug 28;15(8):e1007964. doi: 10.1371/journal.ppat.1007964. eCollection 2019 Aug.

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

Zhang J1,2,3, Jiang H1,2,3, Du Y1,2,3, Keyhani NO1,4, Xia Y1,2,3, Jin K1,2,3.

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School of Life Sciences, Chongqing University, Chongqing, People's Republic of China.
Chongqing Engineering Research Center for Fungal Insecticide, Chongqing, People's Republic of China.
Key Laboratory of Gene Function and Regulation Technologies under Chongqing Municipal Education Commission, Chongqing, PR China.
Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, United States of America.


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 ΔMaChsII and ΔMaChsV 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 ΔMaChsV and ΔMaChsVII mutants showed high sensitivity to Congo red and calcofluor white, suggesting that the three genes are required for cell wall integrity. In addition, ΔMaChsIII and ΔMaChsVII 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, ΔMaChsIII and ΔMaChsV mutants were reduced in virulence by topical inoculation, while the ΔMaChsVII 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.

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