Metarhizium rileyi, a well-known filamentous biocontrol fungus, is the main pathogen of numerous field pests, especially noctuid pests. To explore the potential factors involved in the fungal pathogenicity, MrSte12, an important and conserved functional transcription factor in mitogen-activated protein kinase pathway was carried out by functional analysis. Homologous recombination was used to disrupt the MrSte12 gene in M. rileyi. The deletant fungal strain exhibited malformed hyphae and impaired conidiogenesis, and conidia could not be collected from △MrSte12 in vitro towards SMAY medium. Although conidia could be collected again supplemented with KCl within SMAY medium, the conidial germination, growth and stress tolerance were much weaker compared with that in WT. Additionally, △MrSte12 showed a dramatic reduction in virulence in intra-hemolymph injections and no pathogenicity in topical inoculations against noctuid pests, which is due to the failure of appressorium formation. Moreover, the content of chitin and β-1, 3-glucan in cell wall significantly reduced in mutant conidia. These results indicate that the MrSte12 gene markedly contributes to invasive growth and conidiation, as well as the major pathogenicity in M. rileyi.

绿僵菌是著名的丝状生防真菌，是众多田间害虫，尤其是夜蛾类害虫的主要病原菌。为了探索真菌致病性的潜在因素，通过功能分析对丝裂原活化蛋白激酶途径中重要且保守的功能转录因子MrSte12进行了功能分析。同源重组被用来破坏M. rileyi中的MrSte12基因。删除的真菌菌丝畸形，分生孢子发生受损，不能从△MrSte12体外采集分生孢子朝向 SMAY 介质。虽然在 SMAY 培养基中补充 KCl 可以再次收集分生孢子，但与 WT 相比，分生孢子的萌发、生长和胁迫耐受性要弱得多。此外，△MrSte12在血淋巴内注射中的毒力显着降低，而在针对夜蛾害虫的局部接种中则没有致病性，这是由于附着胞形成失败所致。此外，突变型分生孢子细胞壁中几丁质和β-1, 3-葡聚糖的含量显着降低。这些结果表明，MrSte12基因显着有助于侵入性生长和分生孢子，以及M. rileyi的主要致病性。