BACKGROUNDParasitic wasps manipulate host development for successful parasitization. When the host Ostrinia furnacalis is parasitized by the parasitoid Macrocentrus cingulum, its larvae fail to pupate and are consumed as nutrition by the wasp larvae. However, the mechanism by which M. cingulum modulates host pupation remains unclear. This study reports on pseudogerm, a newly discovered parasitic factor derived from M. cingulum, which plays a regulatory role in the pupation process of the host.RESULTSOstrinia furnacalis larvae transplanted with pseudogerms failed to pupate, and their prothoracic gland (PG) cells did not enlarge significantly at the prepupal stage compared to the control. Additionally, the nuclei of PG cells fragmented, the number of secretory vesicles in the cytoplasm decreased markedly, and the intracellular channel system on the cell membrane atrophied. Furthermore, the elevation of the 20‐hydroxyecdysone (20E) titer at the prepupal stage was also suppressed, indicating that pseudogerm disrupts the ecdysteroid level by causing PG cell degeneration. Additionally, there was a suppression of Broad Complex (Br‐C) expression in O. furnacalis larvae before the prepupal stage due to pseudogerms transplantation. When OfBr‐C was knocked down by RNA‐interference or knocked out by CRISPR/Cas9, approximately 24% and 48.3% of O. furnacalis larvae failed to pupate, respectively.CONCLUSIONPseudogerm potentially disrupts the 20E titer by destroying the host's PG and further inhibits the expression of OfBr‐C, ultimately preventing host pupation. This study provides new insights into the strategies employed by parasitoids in controlling host development. © 2024 Society of Chemical Industry.

中文翻译：

---

寄生体 Macrocentrus cingulum 的假胚芽通过退化前胸腺和抑制宿主 Ostrinia furnacalis 中 Br-C 的表达来抑制宿主化蛹


背景黄蜂操纵宿主发育以成功寄生。当宿主 Ostrinia furnacalis 被寄生体 Macrocentrus 扣带寄生时，其幼虫无法化蛹并被黄蜂幼虫作为营养消耗。然而，M. cingulum 调节宿主化蛹的机制仍不清楚。本研究报告了假胚芽，这是一种新发现的源自 M. cingulum 的寄生因子，它在宿主的化蛹过程中起调节作用。结果用假细菌移植的糠秃幼虫未能化蛹，与对照相比，它们的前胸腺 （PG） 细胞在蛹前期没有显着增大。此外，PG 细胞的细胞核碎裂，细胞质中分泌囊泡的数量显着减少，细胞膜上的细胞内通道系统萎缩。此外，蛹前期 20-羟基蜕皮激素 （20E） 滴度的升高也受到抑制，表明假胚芽通过引起 PG 细胞变性来破坏蜕皮类固醇水平。此外，由于假细菌移植，O. furnacalis 幼虫在蛹前阶段的 Broad Complex （Br-C） 表达受到抑制。当 OfBr-C 被 RNA 干扰敲低或被 CRISPR/Cas9 敲除时，分别约有 24% 和 48.3% 的 O. furnacalis 幼虫未能化蛹。结论Pseudogerm 可能通过破坏宿主的 PG 来破坏 20E 滴度，并进一步抑制 OfBr-C 的表达，最终阻止宿主化蛹。本研究为类寄生虫在控制宿主发育中采用的策略提供了新的见解。© 2024 化工学会.