Transmembrane proteins as sensors encoded by fungal genes activate specific intracellular signal pathways in response to stress cues to help the fungus survive in a changing environment. To better understand the role of the cell wall integrity (CWI) pathway in the entomopathogenic fungus Metarhizium rileyi, an ortholog encoding the transmembrane protein Mid2, MrMid2, was identified and characterized functionally. Transcriptional analysis indicated that MrMid2 was involved in dimorphic transition, conidiation, and microsclerotium formation. After a targeted deletion of MrMid2, all three traits were impaired. Compared with the wild-type strain, the △MrMid2 mutants were hypersensitive to thermal stress, and cell wall and oxidative stress. Insect bioassays revealed that △MrMid2 mutants had decreased virulence levels following topical (22.5%) and injection bioassays (38.7%). Furthermore, transcription analysis showed that other genes of the CWI pathway, with the exception of another major sensor protein encoding gene, MrWsc1, were down-regulated in △MrMid2 mutants. These results suggest that MrMid2 plays important roles in dimorphic transition, conidiation, the stress response, virulence, and microsclerotium development in M. rileyi.

中文翻译：

---

MrMid2，编码细胞壁应力传感器蛋白，是昆虫病原真菌莱氏霉菌中分生孢子的产生，胁迫耐受性，微菌核形成和毒力所必需的。

跨膜蛋白作为由真菌基因编码的传感器，响应应激信号而激活特定的细胞内信号通路，从而帮助真菌在不断变化的环境中生存。为了更好地了解细胞壁完整性（CWI）途径在昆虫病原性真菌Metarhizium rileyi中的作用，已鉴定和编码了跨膜蛋白Mid2 MrMid2的直向同源物，并对其功能进行了表征。转录分析表明，MrMid2参与了双态转变，分生和微菌核的形成。在有针对性地删除MrMid2之后，所有这三个特征均受损。与野生株相比，△MrMid2突变体对热应激，细胞壁和氧化应激均敏感。昆虫生物测定结果显示，△MrMid2突变体局部用药后毒力水平降低（22。5％）和注射生物测定（38.7％）。此外，转录分析表明，除了另一个主要的传感器蛋白编码基因MrWsc1，CWI途径的其他基因在△MrMid2突变体中也被下调。这些结果表明，MrMid2在rileyi菌的双态转化，分生，应力反应，毒力和小菌核发育中起着重要作用。