G-protein-coupled receptor K (GPRK), which is a class VI fungal G-protein-coupled receptor (GPCR), plays a critical role in plant immunity against pathogens by mediating the endocytic pathway, influencing metabolism in response to environmental signals, and regulating asexual reproduction and pathogenic development. However, the function of these proteins in entomopathogenic fungi has rarely been investigated. Accordingly, we characterized MrGPRK, a GPCR in the entomopathogenic fungus Metarhizium robertsii containing a C-terminal seven-transmembrane and a conserved regulator of G protein signaling domain, and found that it localized to endosomes. Mutant phenotype assays showed that a ΔMrGprk strain displayed increased defects in radial growth (~28%) and decreased conidial production (~80%) compared with a wild-type strain. Decreased conidiation rates coincided well with the repression of conidiation-related regulatory genes, including three key conidial transcription factors: brlA, abaA, and wetA. MrGprk deficiency impaired full virulence (both topical and injectable inoculations). Further analysis demonstrated that deleting fungal MrGprk decreased the rates of appressorium formation and suppressed the transcription of several genes contributing to appressorial turgor pressure, cuticle penetration, and pH regulation. Additionally, the ΔMrGprk strain showed higher cyclic (cAMP) levels, suggesting that this GPCR is critical for cAMP signal transduction. In summary, MrGPRK was found to contribute to vegetative growth, conidial production, and full virulence of M. robertsii. These findings are conducive to a better understanding of the roles of GPCRs in the development and pathogenicity of entomopathogenic fungi.

G 蛋白偶联受体 K (GPRK) 是 VI 类真菌 G 蛋白偶联受体 (GPCR)，通过介导内吞途径在植物对病原体的免疫中发挥关键作用，影响代谢以响应环境信号，并调节无性繁殖和病原发育。然而，很少研究这些蛋白质在昆虫病原真菌中的功能。因此，我们表征了 MrGPRK，这是昆虫病原真菌罗伯氏绿僵菌中的一种 GPCR，含有 C 端七跨膜和 G 蛋白信号传导域的保守调节器，并发现它定位于内体。突变表型分析表明，ΔMrGpr与野生型菌株相比，k 菌株的径向生长缺陷增加 (~28%) 和分生孢子产量减少 (~80%)。分生孢子形成率的降低与分生孢子相关调控基因的抑制相吻合，包括三个关键的分生孢子转录因子：brlA、abaA和wetA。MrGprk缺乏会损害完全毒力（局部和注射接种）。进一步的分析表明，删除真菌MrGprk 会降低附着壁的形成率，并抑制几种有助于附着膨压、角质层渗透和 pH 调节的基因的转录。此外，ΔMrGprk 菌株显示出较高的环 (cAMP) 水平，表明该 GPCR 对 cAMP 信号转导至关重要。总之，发现 MrGPRK 有助于M. robertsii 的营养生长、分生孢子生产和完全毒力。这些发现有助于更好地了解 GPCR 在昆虫病原真菌的发育和致病性中的作用。