1. 中国农业科学院棉花研究所/棉花生物学国家重点实验室；2. 棉花生物学国家重点实验室郑州大学科研中心；3. 棉花生物学国家重点实验室安阳工学院基地

背景：棉蚜为世界性害虫，其通过刺吸植物汁液的方式危害多种寄主，并可传播50多种植物病毒。棉蚜可因种群密度不同而选择性的产生有翅蚜或无翅蚜，这种现象被称为翅非遗传多型性，也是其适应多种环境的重要原因。但是，与之相关的分子机制仍不明了。在本研究中，我们评估了初孵若虫期的拥挤效应对棉蚜成虫翅型分化的影响，而后分析了由此所产生的有翅蚜和无翅蚜在转录水平的基因表达差异，以期揭示棉蚜翅非遗传多型性的分子机制。
结果：本研究首先评估了初孵若虫期的拥挤效应对棉蚜翅型分化的影响。当初孵若虫种群密度低于5头·cm^-2时，成虫全部发育为无翅蚜；当初孵若虫种群密度介于5～20头·cm^-2时，成虫发育为有翅蚜的比例逐渐升高，最高达56.1%；而后随着初孵若虫种群密度的增加，成虫发育为有翅蚜的比例却出现了不同程度地下降。在此基础上，我们对有翅蚜和无翅蚜成虫分别进行了转录组测序、组装、注释，并进行了对比分析，以期鉴定棉蚜两种翅型间的差异表达基因和特异表达基因。经非冗余蛋白序列（Non-redundant protein sequence, Nr）数据库注释，我们发现分别有3 126、3 392个转录本只在无翅蚜、有翅蚜中表达；此外，相对于无翅蚜，有3 187个转录本在有翅蚜中表达上调，1 880个表达下调。信号通路分析显示，参与棉蚜翅型分化的差异表达基因富集在多个细胞信号通路，如脂质分解代谢、胰岛素、蜕皮激素和保幼激素生物合成。最后，本研究采用实时荧光定量聚合酶链式反应（Real time polymerase chain reaction, RT-qPCR）方法，对参与棉蚜翅型分化调控的候选基因进行了表达量验证。
结论：本研究鉴定了若虫期拥挤效应对棉蚜成虫翅型分化的影响，确定棉蚜有翅蚜翅分化的临界种群密度为20头·cm^-2；并采用比较转录组分析策略鉴定了棉蚜有翅蚜与无翅蚜间潜在的特异表达转录本、差异表达转录本、以及与之相关的翅型分化调控信号通路。
意义：本研究评估了若虫期拥挤对棉蚜翅型分化的影响，并运用单独组装、对比分析的比较转录组学方法，鉴定了与棉蚜翅型分化相关的特异表达、差异表达转录本、及相关信号通路，为生物界普遍存在的表型可塑性现象研究提供了新的研究思路。



Abstract
Background
Aphis gossypii is a worldwide sap-sucking pest with a variety of hosts and a vector of more than 50 plant viruses. The strategy of wing polyphenism, mostly resulting from population density increasing, contributes to the evolutionary success of this pest. However, the related molecular basis remains unclear. Here, we identified the effects of postnatal crowding on wing morph determination in cotton aphid, and examined the transcriptomic differences between wingless and wing morphs.
Results
Effect of postnatal crowding on wing determination in A. gossypii was evaluated firstly. Under the density of 5 nymphs·cm^??2, no wing aphids appeared. Proportion of wing morphs rised with the increase of density in a certain extent, and peaked to 56.1% at the density of 20 nymphs·cm^??2, and reduced afterwards. Then, transcriptomes of wingless and wing morphs were assembled and annotated separately to identify potentially exclusively or differentially expressed transcripts between these two morphs, in which 3 126 and 3 392 unigenes annotated in Nr (Non-redundant protein sequence) database were found in wingless or wing morphs exclusively. Moreover, 3 187 up- and 1 880 down-regulated genes were identified in wing versus wingless aphid. Pathways analysis suggested the involvement of differentially expressed genes in multiple cellular signaling pathways involved in wing morphs determination, including lipid catabolic and metabolism, insulin, ecdysone and juvenile hormone biosynthesis. The expression levels of related genes were validated by the reverse transcription quantitative real time polymerase chain reaction (RT-qPCR) soon afterwards.
Conclusions
The present study identified the effects of postnatal crowding on wing morphs induction and demonstrated that the critical population density for wing morphs formation in A. gossypii was 20 nymphs·cm^??2. Comparative transcriptome analysis provides transcripts potentially expressed exclusively in wingless or wing morph, respectively. Differentially expressed genes between wingless and wing morphs were identified and several signaling pathways potentially involved in cotton aphid wing differentiation were obtained.
Title: Comparative transcriptional analysis provides insights of possible molecular mechanisms of wing polyphenism induced by postnatal crowding in Aphis gossypii
Authors: JI Jichao, ZHANG Shuai, LUO Junyu, WANG Li, ZHU Xiangzhen, ZHANG Kaixin, ZHANG Lijuan & CUI Jinjie  
Journal of Cotton Research. 2019; 2:17
https://doi.org/10.1186/s42397-019-0036-z
https://jcottonres.biomedcentral.com/articles/10.1186/s42397-019-0036-z