College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Appl Microbiol Biotechnol. 2019 Sep;103(17):7111-7128. doi: 10.1007/s00253-019-09997-4. Epub 2019 Jul 4.
The fungus Isaria javanica is an important entomopathogen that parasitizes various insects and is effective for pest control. In this study, we sequenced and assembled the genomes (IJ1G and IJ2G) of two I. javanica strains isolated from different insects. The genomes were approximately 35 Mb in size with 11,441 and 11,143 protein-coding genes, respectively. Using a phylogenomic approach, we evaluated genome evolution across five entomopathogenic fungi in Cordycipitaceae. By comparative genome analysis, it was found that family S53 serine peptidases were expanded in Cordycipitaceae entomopathogens, particularly in I. javanica. Gene duplication events were identified based on phylogenetic relationships inferred from 82 S53 peptidases within six entomopathogenic fungal genomes. Moreover, we found that carbohydrate-active enzymes and proteinases were the largest secretory protein groups encoded in the I. javanica genome, especially chitinases (GH18), serine and aspartic peptidases (S53, S08, S10, A01). Pathogenesis-related genes and genes for bacterial-like toxins and secondary metabolites were also identified. By comparative transcriptome analysis, differentially expressed genes in response to insect nutrients (in vitro) were identified. Moreover, most S53 peptidases were detected to be significantly upregulated during the initial fungal infection process in insects (in vivo) by RT-qPCR. Our results provide new clues about understanding evolution of pathogenic proteases and may suggest that abundant S53 peptidases in the I. javanica genome may contribute to its effective parasitism on various insects.
被毛孢属真菌是一种重要的昆虫病原真菌，可寄生多种昆虫，对害虫防治具有良好的效果。本研究对 2 株来源于不同昆虫的被毛孢属真菌（IJ1G 和 IJ2G）进行了基因组测序和组装。两株真菌的基因组大小约为 35 Mb，分别包含 11441 个和 11143 个蛋白质编码基因。采用系统发育基因组学方法，对 5 种虫草菌的基因组进化进行了评估。通过比较基因组分析，发现在虫草菌科中 S53 丝氨酸肽酶家族发生了扩张，特别是在被毛孢属真菌中。基于 6 种昆虫病原真菌基因组中 82 个 S53 肽酶的系统发育关系推断，发现了基因重复事件。此外，我们发现，碳水化合物活性酶和蛋白酶是被毛孢属真菌基因组中编码的最大的分泌蛋白组，尤其是几丁质酶（GH18）、丝氨酸和天冬氨酸肽酶（S53、S08、S10、A01）。还鉴定了与发病相关的基因以及细菌样毒素和次生代谢物的基因。通过比较转录组分析，鉴定了对昆虫营养物质（体外）响应的差异表达基因。此外，通过 RT-qPCR 检测到大多数 S53 肽酶在昆虫体内真菌初始感染过程中显著上调。我们的研究结果为了解致病蛋白酶的进化提供了新线索，并且可能表明被毛孢属真菌基因组中丰富的 S53 肽酶可能有助于其对各种昆虫的有效寄生。
