Table_5_Juvenile hormone III induction reveals key genes in general metabolism, pheromone biosynthesis, and detoxification in Eurasian spruce bark beetle.XLSX

IntroductionIn recent years, bark beetle Ips typographus, has caused extensive damage to European Norway spruce forests through widespread outbreaks. This pest employs pheromone-assisted aggregation to overcome tree defense, resulting in mass attacks on host spruce. Many morphological and behavioral processes in I. typographus are under the regulation of juvenile hormone III (JH III), including the biosynthesis of aggregation pheromones and associated detoxification monoterpene conjugates.
Objectives and MethodsIn this study, we topically applied juvenile hormone III (JH III) and performed metabolomics, transcriptomics, and proteomics in I. typographus both sexes, with focused aims; 1. Highlight the JH III-regulated metabolic processes; 2. Identify pheromone biosynthesis-linked genes; and 3. Investigate JH III’s impact on detoxification conjugates linked to pheromonal components.
ResultsNumerous gene families were enriched after JH III treatment, including genes associated with catalytic and oxidoreductase activity, esterases, phosphatases, and membrane transporters. Sex-specific enrichments for reproduction-related and detoxification genes in females and metabolic regulation genes in males were observed. On the protein level were enriched metal ion binding and transferase enzymes in male beetles. After JHIII treatment, mevalonate pathway genes, including terminal isoprenyl diphosphate synthase (IPDS), were exclusively 35- folds upregulated in males, providing evidence of de novo biosynthesis of pheromone components 2-methyl-3-buten-2-ol and ipsdienol. In addition, cytochrome P450 genes likely involved in the biosynthesis of cis/trans-verbenol, detoxification, and formation of ipsdienol, were 3-fold upregulated in the male gut. The increase in gene expression correlated with the heightened production of the respective metabolites. Detoxification conjugates, verbenyl oleate in the beetle fat body and verbenyl diglycosides in the gut, were induced by JHIII application, which confirms the hormone regulation of their formation. The JH III induction also increased the gene contigs esterase and glycosyl hydrolase up to proteins from male gut tissue. The esterase was proposed to release pheromone cis-verbenol in adult males by breaking down verbenyl oleate. The correlating analyses confirmed a reduction in the abundance of verbenyl oleate in the induced male beetle.
ConclusionThe data provide evidence of JH III’s regulatory role in the expression of genes and enzymes related to fundamental beetle metabolism, pheromone biosynthesis, and detoxification in Ips typographus.

引言
近年来，云杉八齿小蠹（Ips typographus）通过大规模暴发，对欧洲挪威云杉林造成了严重破坏。该害虫利用信息素辅助聚集以突破树木防御机制，进而对宿主云杉发起大规模攻击。云杉八齿小蠹的诸多形态与行为过程均受保幼激素III（juvenile hormone III, JH III）调控，其中包括聚集信息素的生物合成以及与之相关的解毒单萜结合物的代谢过程。

研究目的与方法
本研究通过体表涂抹保幼激素III（JH III），对云杉八齿小蠹的雌雄个体开展代谢组学、转录组学及蛋白质组学分析，核心研究目标如下：1. 阐明JH III调控的代谢过程；2. 筛选与信息素生物合成相关的基因；3. 探究JH III对与信息素组分相关的解毒结合物的影响。

研究结果
JH III处理后，大量基因家族出现富集现象，其中包括与催化活性、氧化还原酶活性、酯酶、磷酸酶以及膜转运蛋白相关的基因。研究观察到性别特异性富集现象：雌性个体中与繁殖及解毒相关的基因出现富集，雄性个体中则是代谢调控基因富集。在蛋白质组层面，雄性甲虫体内的金属离子结合蛋白与转移酶类出现富集。JH III处理后，甲羟戊酸通路基因（包括末端异戊二烯二磷酸合酶（IPDS））仅在雄性个体中出现35倍上调，这为信息素组分2-甲基-3-丁烯-2-醇与ipsdienol的从头生物合成提供了证据。此外，雄性肠道中参与顺/反-蒎烯醇生物合成、解毒过程以及ipsdienol形成的细胞色素P450基因出现3倍上调。基因表达的上调与相应代谢物的产量提升呈现相关性。JH III处理可诱导解毒结合物的产生：甲虫脂肪体内的油酸蒎烯酯以及肠道中的蒎烯二糖苷，这证实了JH III对其合成的激素调控作用。JH III诱导还上调了雄性肠道组织中基因重叠群（contigs）编码的酯酶与糖苷水解酶的蛋白表达水平。研究推测，酯酶可通过分解油酸蒎烯酯，在雄性成虫体内释放信息素顺-蒎烯醇。相关分析证实，经JH III诱导的雄性甲虫体内油酸蒎烯酯的丰度出现降低。

结论
本研究数据证实，JH III对云杉八齿小蠹体内与基础代谢、信息素生物合成及解毒过程相关的基因与酶的表达具有调控作用。