Wang Yulong, Liu Zhen, Yin Xuebing, Liu Shihong, Wang Kai, Wan Rongjie, Chen Haoran, Li Xinyang, Huang Bo
Anhui Provincial Key Laboratory of Microbial Pest Control, Anhui Agricultural University, Hefei, China.
Insect Sci. 2024 Feb;31(1):211-224. doi: 10.1111/1744-7917.13209. Epub 2023 Jun 23.
Entomopathogenic fungi are protected by a cell wall with dynamic structure for adapting to various environmental conditions. β-1,3-Glucan recognition proteins activate the innate immune system of insects by recognizing surface molecules of fungi. However, the associations between pathogenicity and the different components of entomopathogenic fungal cell walls remain unclear. Three Beauveria bassiana strains were selected that have significantly differing virulence against Bombyx mori. The molecular mechanisms underlying the immune response in B. mori were investigated using RNA sequencing, which revealed differences in the immune response to different B. bassiana strains at 12 h post-infection. Immunofluorescence assays revealed that β-1,3-glucan content had an opposite trend to that of fungal virulence. β-1,3-Glucan injection upregulated BmβGRP4 expression and significantly reduced the virulence of the high-virulence strain but not that of the medium-virulence or low-virulence strains. BmβGRP4 silencing in B. mori with RNA interference resulted in the opposite virulence pattern, indicating that the virulence of B. bassiana was affected by the cell walls' content of β-1,3-glucan, which could be recognized by BmβGRP4. Furthermore, interference with the gene CnA (calcineurin catalytic A subunit) involved in β-1,3-glucan synthesis eliminated differences in virulence between B. bassiana strains. These results indicate that strains of a single species of pathogenic fungi that have differing cell wall components are recognized differently by the innate immune system of B. mori.
昆虫病原真菌受到具有动态结构的细胞壁保护，以适应各种环境条件。β-1,3-葡聚糖识别蛋白通过识别真菌表面分子激活昆虫的先天免疫系统。然而，昆虫病原真菌细胞壁的不同成分与致病性之间的关联仍不清楚。选择了对家蚕毒力差异显著的三株球孢白僵菌菌株。利用RNA测序研究了家蚕免疫反应的分子机制，结果显示感染后12小时对不同球孢白僵菌菌株的免疫反应存在差异。免疫荧光分析表明，β-1,3-葡聚糖含量与真菌毒力呈相反趋势。注射β-1,3-葡聚糖上调了BmβGRP4的表达，并显著降低了高毒力菌株的毒力，但对中、低毒力菌株的毒力没有影响。通过RNA干扰在家蚕中沉默BmβGRP4导致了相反的毒力模式，表明球孢白僵菌的毒力受细胞壁β-1,3-葡聚糖含量的影响，而BmβGRP4可以识别该成分。此外，干扰参与β-1,3-葡聚糖合成的基因CnA（钙调神经磷酸酶催化A亚基）消除了球孢白僵菌菌株之间的毒力差异。这些结果表明，具有不同细胞壁成分的单一病原真菌物种的菌株被家蚕的先天免疫系统以不同方式识别。
