Department of Plant Medicals, College of Life Sciences, Andong National University, Andong, Korea.
PLoS Pathog. 2021 Mar 25;17(3):e1009467. doi: 10.1371/journal.ppat.1009467. eCollection 2021 Mar.
Xenorhabdus hominickii, an entomopathogenic bacterium, inhibits eicosanoid biosynthesis of target insects to suppress their immune responses by inhibiting phospholipase A2 (PLA2) through binding to a damage-associated molecular pattern (DAMP) molecule called dorsal switch protein 1 (DSP1) from Spodoptera exigua, a lepidopteran insect. However, the signalling pathway between DSP1 and PLA2 remains unknown. The objective of this study was to determine whether DSP1 could activate Toll immune signalling pathway to activate PLA2 activation and whether X. hominickii metabolites could inhibit DSP1 to shutdown eicosanoid biosynthesis. Toll-Spätzle (Spz) signalling pathway includes two Spz (SeSpz1 and SeSpz2) and 10 Toll receptors (SeToll1-10) in S. exigua. Loss-of-function approach using RNA interference showed that SeSpz1 and SeToll9 played crucial roles in connecting DSP1 mediation to activate PLA2. Furthermore, a deletion mutant against SeToll9 using CRISPR/Cas9 abolished DSP1 mediation and induced significant immunosuppression. Organic extracts of X. hominickii culture broth could bind to DSP1 at a low micromolar range. Subsequent sequential fractionations along with binding assays led to the identification of seven potent compounds including 3-ethoxy-4-methoxyphenol (EMP). EMP could bind to DSP1 and prevent its translocation to plasma in response to bacterial challenge and suppress the up-regulation of PLA2 activity. These results suggest that X. hominickii inhibits DSP1 and prevents its DAMP role in activating Toll immune signalling pathway including PLA2 activation, leading to significant immunosuppression of target insects.
黄野单胞菌，一种昆虫病原细菌，通过与鳞翅目昆虫甜菜夜蛾的损伤相关分子模式（DAMP）分子背侧开关蛋白 1（DSP1）结合，抑制磷脂酶 A2（PLA2），从而抑制靶昆虫的类二十烷酸生物合成，抑制其免疫反应。然而，DSP1 和 PLA2 之间的信号通路尚不清楚。本研究旨在确定 DSP1 是否可以激活 Toll 免疫信号通路以激活 PLA2 激活，以及黄野单胞菌代谢物是否可以抑制 DSP1 以关闭类二十烷酸生物合成。Toll-Spätzle（Spz）信号通路包括甜菜夜蛾中的 2 个 Spz（SeSpz1 和 SeSpz2）和 10 个 Toll 受体（SeToll1-10）。使用 RNA 干扰的功能丧失方法表明，SeSpz1 和 SeToll9 在连接 DSP1 介导以激活 PLA2 方面发挥着关键作用。此外，使用 CRISPR/Cas9 针对 SeToll9 的缺失突变消除了 DSP1 介导作用并诱导了显著的免疫抑制。黄野单胞菌培养物的有机提取物可以在低微摩尔范围内与 DSP1 结合。随后的顺序分级和结合测定导致鉴定出 7 种有效化合物，包括 3-乙氧基-4-甲氧基苯酚（EMP）。EMP 可以与 DSP1 结合并防止其在细菌攻击时向血浆易位，并抑制 PLA2 活性的上调。这些结果表明，黄野单胞菌抑制 DSP1 并防止其在激活 Toll 免疫信号通路（包括 PLA2 激活）中的 DAMP 作用，从而导致靶昆虫的显著免疫抑制。
Zotero 插件
