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| Background: The efficacy of entomopathogenic fungi in pest control is mainly affected by various adverse environmental factors, such as heat shock and UV-B radiation, and by responses of the host insect, such as oxidative stress, osmotic stress and fever. In this study, an adenylate cyclase gene (MaAC) was cloned from the locust-specific entomopathogenic fungus Metarhizium acridum, which is homologous to various fungal adenylate cyclase genes. RNA silencing was adapted to analyze the role of MaAC in virulence and tolerance to adverse factors from environment and host insect. Results: Compared with the wild type, the vegetative growth of the RNAi mutant was decreased in PD (potato dextrose medium), Czapek-dox and PDA plates, respectively, the cAMP levels was also reduced in PD liquid culture. Knockdown of MaAC by RNAi led to a great reduction in fungal growth in the hemolymph of locusts after injection and topical inoculation, thus demonstrating that MaAC encodes an adenylate cyclase and is required for virulence of M. acridum. Virulence assay indicated that the effect of MaAC on the virulence was mainly inside the host locust. A plate assay indicated that the tolerances of the MaAC RNAi mutant under oxidative stress, osmotic stress, heat shock and UV-B radiation was decreased compared with the wild type. Conclusion: MaAC affects virulence, primarily by fungal growth inside the insect, and is required for tolerance to oxidative stress, osmotic stress, heat shock and UV-B radiation. MaAC affects the fungal virulence via vegetative growth and tolerance against oxidative stress, osmotic stress and locust fever. |
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| Keywords:Biocontrol agents; entomopathogenic fungi; conidia; virulence; environmental stress |
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