Zeng Baosheng, Huang Yuping, Xu Jun, Shiotsuki Takahiro, Bai Hua, Palli Subba Reddy, Huang Yongping, Tan Anjiang
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
J Biol Chem. 2017 Jul 14;292(28):11659-11669. doi: 10.1074/jbc.M117.777797. Epub 2017 May 10.
Forkhead box O (FOXO) functions as the terminal transcription factor of the insulin signaling pathway and regulates multiple physiological processes in many organisms, including lifespan in insects. However, how FOXO interacts with hormone signaling to modulate insect growth and development is largely unknown. Here, using the transgene-based CRISPR/Cas9 system, we generated and characterized mutants of the silkworm FOXO () to elucidate its physiological functions during development of this lepidopteran insect. The mutant (FOXO-M) exhibited growth delays from the first larval stage and showed precocious metamorphosis, pupating at the end of the fourth instar (trimolter) rather than at the end of the fifth instar as in the wild-type (WT) animals. However, different from previous reports on precocious metamorphosis caused by juvenile hormone (JH) deficiency in silkworm mutants, the total developmental time of the larval period in the FOXO-M was comparable with that of the WT. Exogenous application of 20-hydroxyecdysone (20E) or of the JH analog rescued the trimolter phenotype. RNA-seq and gene expression analyses indicated that genes involved in JH degradation but not in JH biosynthesis were up-regulated in the FOXO-M compared with the WT animals. Moreover, we identified several FOXO-binding sites in the promoter of genes coding for JH-degradation enzymes. These results suggest that FOXO regulates JH degradation rather than its biosynthesis, which further modulates hormone homeostasis to control growth and development in In conclusion, we have uncovered a pivotal role for FOXO in regulating JH signaling to control insect development.
叉头框O（FOXO）作为胰岛素信号通路的终端转录因子，在许多生物体中调节多种生理过程，包括昆虫的寿命。然而，FOXO如何与激素信号相互作用以调节昆虫的生长和发育在很大程度上尚不清楚。在这里，我们使用基于转基因的CRISPR/Cas9系统，生成并鉴定了家蚕FOXO（）的突变体，以阐明其在这种鳞翅目昆虫发育过程中的生理功能。突变体（FOXO-M）从幼虫第一阶段就表现出生长延迟，并出现早熟变态，在四龄末期（三眠蚕）化蛹，而不是像野生型（WT）动物那样在五龄末期化蛹。然而，与之前关于家蚕突变体中因保幼激素（JH）缺乏导致早熟变态的报道不同，FOXO-M幼虫期的总发育时间与WT相当。外源施加20-羟基蜕皮激素（20E）或JH类似物可挽救三眠蚕表型。RNA测序和基因表达分析表明，与WT动物相比，参与JH降解但不参与JH生物合成的基因在FOXO-M中上调。此外，我们在编码JH降解酶的基因启动子中鉴定出了几个FOXO结合位点。这些结果表明，FOXO调节JH降解而非其生物合成，进而进一步调节激素稳态以控制家蚕的生长和发育。总之，我们揭示了FOXO在调节JH信号以控制昆虫发育中的关键作用。
