Dou Xiaoyi, Chen Kangkang, Brown Mark R, Strand Michael R
Department of Entomology, University of Georgia, Athens, Georgia, 30602, United States.
Department of Plant Protection, College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, Jiangsu Province, China.
Insect Sci. 2023 Apr;30(2):425-442. doi: 10.1111/1744-7917.13110. Epub 2022 Sep 19.
Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs. Each gonadotrophic cycle is subdivided into a sugar-feeding previtellogenic phase that produces primary follicles and a blood meal-activated vitellogenic phase in which large numbers of eggs synchronously mature and are laid. Multiple endocrine factors including juvenile hormone (JH), insulin-like peptides (ILPs), ovary ecdysteroidogenic hormone (OEH), and 20-hydroxyecdysone (20E) coordinate each gonadotrophic cycle. Egg formation also requires nutrients from feeding that are stored in the fat body. Regulation of egg formation is best understood in Aedes aegypti but the role different endocrine factors play in regulating nutrient mobilization and storage remains unclear. In this study, we report that adult female Ae. aegypti maintained triacylglycerol (TAG) stores during the previtellogenic phase of the first gonadotrophic cycle while glycogen stores declined. In contrast, TAG and glycogen stores were rapidly mobilized during the vitellogenic phase and then replenishment. Several genes encoding enzymes with functions in TAG and glycogen metabolism were differentially expressed in the fat body, which suggested regulation was mediated in part at the transcriptional level. Gain of function assays indicated that stored nutrients were primarily mobilized by adipokinetic hormone (AKH) while juvenoids and OEH regulated replenishment. ILP3 further showed evidence of negatively regulating certain lipolytic enzymes. Loss of function assays indicated AKH depends on the AKH receptor (AKHR) for function. Altogether, our results indicate that the opposing activities of different hormones regulate nutrient stores during a gonadotrophic cycle in Ae. aegypti.
非自育性蚊子必须吸食脊椎动物宿主的血液才能产卵。每个促性腺周期可细分为一个产生初级卵泡的吸食糖分的卵黄发生前期阶段，以及一个血液激活的卵黄发生阶段，在此阶段大量卵子同步成熟并排出。包括保幼激素（JH）、胰岛素样肽（ILP）、卵巢蜕皮甾类生成激素（OEH）和20-羟基蜕皮酮（20E）在内的多种内分泌因子协调每个促性腺周期。卵子形成还需要来自取食的营养物质，这些营养物质储存在脂肪体中。埃及伊蚊中对卵子形成的调控了解得最为透彻，但不同内分泌因子在调节营养物质动员和储存中所起的作用仍不清楚。在本研究中，我们报告称，成年雌性埃及伊蚊在第一个促性腺周期的卵黄发生前期维持三酰甘油（TAG）储存，而糖原储存减少。相比之下，TAG和糖原储存在卵黄发生阶段迅速动员，然后再补充。脂肪体中几个编码在TAG和糖原代谢中起作用的酶的基因差异表达，这表明调控部分是在转录水平上介导的。功能获得试验表明，储存的营养物质主要由促脂动激素（AKH）动员，而保幼激素类似物和OEH调节补充。ILP3进一步显示出对某些脂解酶负调控的证据。功能丧失试验表明，AKH的功能依赖于AKH受体（AKHR）。总之，我们的结果表明，不同激素的相反作用调节了埃及伊蚊促性腺周期中的营养储存。
