Table_2_Disruption of the Serine/Threonine Kinase Akt Gene Affects Ovarian Development and Fecundity in the Cigarette Beetle, Lasioderma serricorne.DOC

Serine/threonine kinase Akt, an important component of the insulin signaling pathway, plays an essential role in many physiological processes. In this study, we identified and characterized an Akt gene (designated LsAkt) from the cigarette beetle, Lasioderma serricorne. LsAkt contains a 1614 bp open reading frame encoding a 537 amino acid protein that possesses a conserved pleckstrin homology domain and a serine/threonine kinase domain. The expression of LsAkt was high in pupal stages and peaked in day-4 female pupae. In adult tissues, LsAkt was highly expressed in the thorax, ovary, and midgut. The expression of LsAkt was induced by methoprene or bovine insulin in vivo, but significantly decreased by 20-hydroxyecdysone. RNA interference-mediated knockdown of LsAkt resulted in severely blocked ovarian development and reduced fecundity and hatchability. The vitellogenin (Vg) content and juvenile hormone (JH) titers of LsAkt-depletion beetles were decreased, and expressions of Vg and four JH signaling and biosynthetic genes were significantly decreased. Silencing of LsAkt reduced the amounts of glucose, glycogen, and trehalose in female adults and affected the expressions of seven key carbohydrate metabolic genes. Taken together, it is inferred that Akt implicates in L. serricorne reproduction by modification of Vg synthesis, juvenile hormone production and carbohydrate metabolism.

丝氨酸/苏氨酸激酶Akt（Serine/threonine kinase Akt）是胰岛素信号通路的核心组分，在众多生理过程中发挥不可或缺的作用。本研究从烟草甲（Lasioderma serricorne）中鉴定并表征了一个Akt基因，将其命名为LsAkt。LsAkt包含一段长1614 bp的开放阅读框，编码一个由537个氨基酸残基组成的蛋白质，该蛋白拥有保守的普列克底物蛋白同源结构域（pleckstrin homology domain，PH结构域）与丝氨酸/苏氨酸激酶结构域。LsAkt在蛹期整体表达量较高，且在4日龄雌蛹中达到表达峰值。在成虫组织中，LsAkt在胸部、卵巢及中肠中呈高表达状态。体内实验显示，甲氧普烯与牛胰岛素可诱导LsAkt的表达，而20-羟基蜕皮酮则会显著下调其转录水平。通过RNA干扰（RNA interference，RNAi）介导的LsAkt基因沉默，可导致烟草甲卵巢发育严重受阻，产卵量与卵孵化率均显著降低。LsAkt沉默后的烟草甲个体，其体内卵黄原蛋白（vitellogenin，Vg）含量与保幼激素（juvenile hormone，JH）滴度均有所下降，同时Vg以及4个JH信号通路与生物合成相关基因的表达量均显著下调。沉默LsAkt还会降低雌成虫体内葡萄糖、糖原及海藻糖的含量，并影响7个关键碳水化合物代谢相关基因的转录水平。综上，本研究推测Akt通过调控卵黄原蛋白合成、保幼激素生成与碳水化合物代谢，参与烟草甲的生殖过程。