Overexpression of Vvmapk affects growth, stress responses, and virulence of Beauveria bassiana

Abstract:

[Background] Mitogen-activated protein kinase (MAPK) plays pivotal roles in cell proliferation, differentiation, apoptosis, and stress responses in eukaryotes. [Objective] To identify the roles of Vvmapk in Volvariella volvacea for applications. [Methods] Vvmapk was overexpressed under the control of Vvpgd promoter in Beauveria bassiana, and the roles of Vvmapk in the growth, development, stress responses, and virulence were examined. Compared with the wild type, the overexpression of Vvmapk in B. bassiana increased the pigment level and conidial yield but did not affect the growth. The strains overexpressing this gene displayed higher conidial germination rates under heat shock, salt, and UV-irradiation stress conditions than the control. Furthermore, Vvmapk overexpression endowed the fungi with stronger virulence against Galleria mellonella but weaker antagonistic effects against Fusarium solani and Fusarium oxysporum than the wild type. The relative transcription levels of BbBrlA, BbabaA, and BbwetA associated with the conidial development were significantly up-regulated in the recombinant strain. [Conclusion] VvMAPK positively regulated the conidial development, pigmentation level, and virulence of B. bassiana. The findings laid a theoretical foundation for the functional identification and applications of V. volvacea genes.