Hangzhou Key Laboratory of Animal Adaptation and Evolution, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, Zhejiang 311121, China.
Pestic Biochem Physiol. 2024 Nov;205:106127. doi: 10.1016/j.pestbp.2024.106127. Epub 2024 Sep 12.
Immunity and reproduction are vital functions for the survival and population maintenance of female insects. However, owing to limited resources, these two functions cannot be fulfilled simultaneously, resulting in an energy tradeoff between them. Notably, the mechanisms underlying this immune-reproductive trade-off, in which energy competition likely plays a central role, remain poorly understood. Fatty acid synthase (FAS), a key gene involved in lipid synthesis and insect energy metabolism, was investigated in this study using Locusta migratoria as the research subject. Bacterial infection and RNA interference (RNAi) technology were used to examine changes in the immunity, fecundity, and energy metabolism patterns of locusts under different treatments. The findings of this study demonstrate that infection with Micrococcus luteus triggers an immune response in locusts, significantly upregulates the expression of defensin 3 (DEF3) and Attacin, and enhances pHenoloxidase (PO) activity. Upon FAS2 silencing, bacterial attack upregulated DEF3 and Attacin expression to a lesser extent, leading to increased lysozyme activity instead of PO. Furthermore, bacterial infection results in a decrease in glycogen and glucose content in the fat body, accompanied by a significant increase in triacylglycerol (TAG) content. However, after FAS2 knockdown, both the lipid and carbohydrate contents were significantly reduced in the fat body. Compared with bacterial infection alone, low FAS2 expression further exacerbated fecundity impairment in locusts. The expression levels of vitellogenin A (VgA) and vitellogenin B (VgB) were significantly low, with severe ovarian atrophy observed. Notably, the ovarian weight was only 21 % compared to that of the control group. Moreover, females exhibited minimal egg-laying behavior. In summary, our findings suggest that following FAS2 gene silencing, there is a greater inclination toward immune stimulation energy activation in locusts, whereas reproductive investment is reduced. The outcomes of this study will contribute to the further exploration of the molecular mechanisms underlying the trade-off between immune and reproductive energy in locusts.
免疫和繁殖是雌性昆虫生存和种群维持的重要功能。然而，由于资源有限，这两个功能不能同时满足，导致它们之间存在能量权衡。值得注意的是，这种免疫-繁殖权衡的机制，其中能量竞争可能起着核心作用，目前仍知之甚少。脂肪酸合酶（FAS）是参与脂质合成和昆虫能量代谢的关键基因，本研究以飞蝗为研究对象，对其进行了研究。使用细菌感染和 RNA 干扰（RNAi）技术，研究了不同处理方式下蝗虫的免疫、繁殖力和能量代谢模式的变化。本研究的结果表明，感染微球菌会引发蝗虫的免疫反应，显著上调防御素 3（DEF3）和 Attacin 的表达，并增强酚氧化酶（PO）的活性。沉默 FAS2 后，细菌攻击导致 DEF3 和 Attacin 的表达上调程度较小，反而导致溶菌酶活性增加而不是 PO。此外，细菌感染导致脂肪体中的糖原和葡萄糖含量减少，同时三酰基甘油（TAG）含量显著增加。然而，沉默 FAS2 后，脂肪体中的脂质和碳水化合物含量都明显减少。与单独细菌感染相比，低 FAS2 表达进一步加剧了蝗虫的繁殖力受损。卵黄蛋白原 A（VgA）和卵黄蛋白原 B（VgB）的表达水平明显较低，卵巢严重萎缩。值得注意的是，卵巢重量仅为对照组的 21%。此外，雌性表现出最小的产卵行为。总之，我们的研究结果表明，沉默 FAS2 基因后，飞蝗更倾向于免疫刺激能量激活，而减少生殖投资。本研究的结果将有助于进一步探索飞蝗免疫和生殖能量之间权衡的分子机制。
