Wu Chen, Crowhurst Ross N, Dennis Alice B, Twort Victoria G, Liu Shanlin, Newcomb Richard D, Ross Howard A, Buckley Thomas R
Landcare Research, Auckland, New Zealand.
School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
PLoS One. 2016 Jun 23;11(6):e0157783. doi: 10.1371/journal.pone.0157783. eCollection 2016.
Phasmatodea, more commonly known as stick insects, have been poorly studied at the molecular level for several key traits, such as components of the sensory system and regulators of reproduction and development, impeding a deeper understanding of their functional biology. Here, we employ de novo transcriptome analysis to identify genes with primary functions related to female odour reception, digestion, and male sexual traits in the New Zealand common stick insect Clitarchus hookeri (White). The female olfactory gene repertoire revealed ten odorant binding proteins with three recently duplicated, 12 chemosensory proteins, 16 odorant receptors, and 17 ionotropic receptors. The majority of these olfactory genes were over-expressed in female antennae and have the inferred function of odorant reception. Others that were predominantly expressed in male terminalia (n = 3) and female midgut (n = 1) suggest they have a role in sexual reproduction and digestion, respectively. Over-represented transcripts in the midgut were enriched with digestive enzyme gene families. Clitarchus hookeri is likely to harbour nine members of an endogenous cellulase family (glycoside hydrolase family 9), two of which appear to be specific to the C. hookeri lineage. All of these cellulase sequences fall into four main phasmid clades and show gene duplication events occurred early in the diversification of Phasmatodea. In addition, C. hookeri genome is likely to express γ-proteobacteria pectinase transcripts that have recently been shown to be the result of horizontal transfer. We also predicted 711 male terminalia-enriched transcripts that are candidate accessory gland proteins, 28 of which were annotated to have molecular functions of peptidase activity and peptidase inhibitor activity, two groups being widely reported to regulate female reproduction through proteolytic cascades. Our study has yielded new insights into the genetic basis of odour detection, nutrient digestion, and male sexual traits in stick insects. The C. hookeri reference transcriptome, together with identified gene families, provides a comprehensive resource for studying the evolution of sensory perception, digestive systems, and reproductive success in phasmids.
竹节虫目，通常被称为竹节虫，在分子水平上对几个关键特征的研究较少，如感觉系统的组成部分以及生殖和发育的调节因子，这阻碍了对其功能生物学的深入理解。在这里，我们采用从头转录组分析来鉴定与新西兰普通竹节虫Clitarchus hookeri（怀特）的雌性气味接收、消化和雄性性特征相关的主要功能基因。雌性嗅觉基因库显示有10种气味结合蛋白，其中3种是最近复制的，12种化学感受蛋白，16种气味受体和17种离子型受体。这些嗅觉基因中的大多数在雌性触角中过度表达，并具有气味接收的推断功能。其他主要在雄性生殖器（n = 3）和雌性中肠（n = 1）中表达的基因分别表明它们在有性生殖和消化中起作用。中肠中过量表达的转录本富含消化酶基因家族。Clitarchus hookeri可能含有一个内源性纤维素酶家族（糖苷水解酶家族9）的9个成员，其中两个似乎是Clitarchus hookeri谱系特有的。所有这些纤维素酶序列都属于四个主要的竹节虫分支，并表明基因复制事件发生在竹节虫目多样化的早期。此外，Clitarchus hookeri基因组可能表达γ-变形菌果胶酶转录本，最近的研究表明这是水平转移的结果。我们还预测了711个富含雄性生殖器的转录本，它们是候选附属腺蛋白，其中28个被注释具有肽酶活性和肽酶抑制剂活性的分子功能，这两组蛋白通过蛋白水解级联反应调节雌性生殖的作用已被广泛报道。我们的研究为竹节虫的气味检测、营养消化和雄性性特征的遗传基础提供了新的见解。Clitarchus hookeri参考转录组以及鉴定出的基因家族，为研究竹节虫的感官感知、消化系统和生殖成功的进化提供了全面的资源。
