title: De Novo Transcriptome Analysis of the Common New Zealand Stick Insect Clitarchus hookeri (Phasmatodea) Reveals Genes Involved in Olfaction, Digestion and Sexual Reproduction.
abstract: 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.
authors.affiliation: Landcare Research, Auckland, New Zealand.|School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: Chen
authors.initials: C
authors.lastname: Wu
authors.affiliation: New Zealand Institute for Plant & Food Research Ltd, Auckland, New Zealand.
authors.forename: Ross N
authors.initials: RN
authors.lastname: Crowhurst
authors.affiliation: Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland.|EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
authors.forename: Alice B
authors.initials: AB
authors.lastname: Dennis
authors.affiliation: Landcare Research, Auckland, New Zealand.|School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: Victoria G
authors.initials: VG
authors.lastname: Twort
authors.affiliation: China National GeneBank, BGI-Shenzhen, Shen Zhen, China.
authors.forename: Shanlin
authors.initials: S
authors.lastname: Liu
authors.affiliation: School of Biological Sciences, The University of Auckland, Auckland, New Zealand.|New Zealand Institute for Plant & Food Research Ltd, Auckland, New Zealand.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Newcomb
authors.affiliation: School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: Howard A
authors.initials: HA
authors.lastname: Ross
authors.affiliation: Landcare Research, Auckland, New Zealand.|School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Buckley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019295:Computational Biology / Q000379:methods; D004063:Digestion / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D059014:High-Throughput Nucleotide Sequencing; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics; D007313:Insecta / Q000145:classification / Q000235:genetics*; D008297:Male; D058977:Molecular Sequence Annotation; D055696:Olfactory Perception / Q000235:genetics*; D010802:Phylogeny; D012098:Reproduction / Q000235:genetics*; D059467:Transcriptome
chemical_list: D019476:Insect Proteins