Lefoulon Emilie, McMullen John G, Stock S Patricia
School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, United States.
Department of Biology, Indiana University, Bloomington, IN, United States.
Front Physiol. 2022 Feb 25;13:821845. doi: 10.3389/fphys.2022.821845. eCollection 2022.
Entomopathogenic nematodes of the genus have a mutualistic relationship with bacteria of the genus and together they form an antagonist partnership against their insect hosts. The nematodes (third-stage infective juveniles, or IJs) protect the bacteria from the external environmental stressors and vector them from one insect host to another. produce secondary metabolites and antimicrobial compounds inside the insect that protect the cadaver from soil saprobes and scavengers. The bacteria also become the nematodes' food, allowing them to grow and reproduce. Despite these benefits, it is yet unclear what the potential metabolic costs for IJs are relative to the maintenance and vectoring of . In this study, we performed a comparative dual RNA-seq analysis of IJs of two nematode-bacteria partnerships: - and -. For each association, three conditions were studied: (1) IJs reared in the insect ( colonized), (2) colonized IJs reared on liver-kidney agar ( colonized), and (3) IJs depleted by the bacteria reared on liver-kidney agar ( aposymbiotic). Our study revealed the downregulation of numerous genes involved in metabolism pathways, such as carbohydrate, amino acid, and lipid metabolism when IJs were reared , both colonized and without the symbiont. This downregulation appears to impact the longevity pathway, with the involvement of glycogen and trehalose metabolism, as well as arginine metabolism. Additionally, a differential expression of the venom protein known to be secreted by the nematodes was observed when both species were depleted of their symbiotic partners. These results suggest IJs may have a mechanism to adapt their virulence in absence of their symbionts.
属的昆虫病原线虫与属的细菌具有共生关系，它们共同形成了针对昆虫宿主的拮抗伙伴关系。线虫（第三阶段感染性幼虫，即IJs）保护细菌免受外部环境压力，并将其从一个昆虫宿主传播到另一个昆虫宿主。在昆虫体内产生次生代谢产物和抗菌化合物，保护尸体免受土壤腐生菌和食腐动物的侵害。细菌也成为线虫的食物，使其能够生长和繁殖。尽管有这些益处，但尚不清楚IJs相对于的维持和传播的潜在代谢成本是什么。在本研究中，我们对两种线虫-细菌伙伴关系的IJs进行了比较性双RNA测序分析：-和-。对于每种组合，研究了三种条件：（1）在昆虫体内饲养的IJs（定殖），（2）在肝肾琼脂上饲养的定殖IJs（定殖），以及（3）在肝肾琼脂上由细菌耗尽共生菌的IJs（共生菌缺失）。我们的研究表明，当IJs在有共生菌和无共生菌的情况下饲养时，参与代谢途径（如碳水化合物、氨基酸和脂质代谢）的许多基因表达下调。这种下调似乎影响了长寿途径，涉及糖原和海藻糖代谢以及精氨酸代谢。此外，当两种线虫物种的共生伙伴都缺失时，观察到已知由线虫分泌的毒液蛋白的差异表达。这些结果表明，IJs在没有共生菌的情况下可能有一种机制来调节其毒力。
