Xu Kang-Kang, Yang Wen-Jia, Tian Yi, Wu Yi-Bei, Wang Jin-Jun
Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
Gen Comp Endocrinol. 2015 May 15;216:125-33. doi: 10.1016/j.ygcen.2014.11.022. Epub 2014 Dec 9.
Insulin signaling pathways have integral roles in regulating organ growth and body size of insects. Here, we identified and characterized six insulin signaling pathway components-InR, IRS, PI3K92E, PI3K21B, Akt, and PDK-from Bactrocera dorsalis. Quantitative real-time polymerase chain reaction was used to establish gene expression profiles for the insulin signaling pathway components for different developmental stages and tissues, and in response to 20-hydroxyecdysone (20E) and starvation. IRS, PI3K92E, and PI3K21B were highly expressed in the head, while InR, Akt, and PDK were most abundant in Malpighian tubules. Both IRS and PI3K92E were highly expressed during the larval-pupal and pupal-adult transition, while the remaining four genes were highly expressed only during the pupal-adult transition. Following initial exposure to 20E, the expression levels of most genes were significantly decreased. However, the expression levels of IRS, PI3K92E, and PI3K21B were significantly increased at 8 and 12h post-treatment compared with the control. Moreover, we found that most insulin signaling pathway genes in B. dorsalis were up-regulated in response to starvation, but decreased when re-fed. On the contrary, transcript levels of PI3K21B decreased significantly during starvation. Furthermore, injection of IRS dsRNA into adult females significantly reduced IRS transcript levels. Suppression of IRS expression inhibited ovarian development, and the average ovary size was reduced by 33% compared with the control. This study provides new insight into the roles of insulin signaling pathway components in B. dorsalis, and demonstrates an important role for IRS in ovarian development.
胰岛素信号通路在调节昆虫器官生长和体型方面发挥着不可或缺的作用。在此，我们从桔小实蝇中鉴定并表征了六个胰岛素信号通路组分——胰岛素受体（InR）、胰岛素受体底物（IRS）、磷脂酰肌醇-3激酶92E（PI3K92E）、磷脂酰肌醇-3激酶21B（PI3K21B）、蛋白激酶B（Akt）和磷酸肌醇依赖性蛋白激酶（PDK）。采用定量实时聚合酶链反应来建立胰岛素信号通路组分在不同发育阶段和组织中的基因表达谱，并研究其对20-羟基蜕皮酮（20E）和饥饿的响应。IRS、PI3K92E和PI3K21B在头部高表达，而InR、Akt和PDK在马氏管中含量最高。IRS和PI3K92E在幼虫-蛹期和蛹-成虫期转变过程中均高表达，而其余四个基因仅在蛹-成虫期转变过程中高表达。初次暴露于20E后，大多数基因的表达水平显著下降。然而，与对照相比，处理后8小时和12小时时，IRS、PI3K92E和PI3K21B的表达水平显著升高。此外，我们发现桔小实蝇中大多数胰岛素信号通路基因在饥饿时上调，但再喂食时下降。相反，饥饿期间PI3K21B的转录水平显著下降。此外，向成年雌性注射IRS双链RNA可显著降低IRS转录水平。抑制IRS表达会抑制卵巢发育，与对照相比，平均卵巢大小减小了33%。本研究为桔小实蝇中胰岛素信号通路组分的作用提供了新的见解，并证明了IRS在卵巢发育中的重要作用。
