Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...

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Identification of putative odorant receptors from Epiphyas postvittana 120 mori (Wanner et al., 2007; Tanaka et al., 2009) and the 52 ORs identified in Jordan et al. (2009) and in this study from E. postvittana will be looked at. From pairwise sequence alignment of E. postvittana ORs with B. mori ORs (Table 4.6), 24 one-to- one orthologs of E. postvittana and B. mori ORs were identified, with pairwise amino acid identity ranging from 15% to 88%. The lowest pairwise amino acid identity is shared between EpOR9 and BmOR4 while the highest homology is shared by EpOR2 and BmOR2. Eleven EpORs share more than 50% amino acid identity with their B. mori homologues suggesting conservation of some ORs to a certain extend within this highly divergent group of proteins. Members of the highly conserved OR2 clade have been shown to be co-expressed with other ORs in nearly all ORNs and may function in transport of the ORs to the dendritic membrane (Larsson et al., 2004; Neuhaus et al., 2004; Nakagawa et al., 2005). A similar function of EpOR2 is predicted based on its high homology to other members of this clade. EpOR3 has previously been shown to be highly conserved in some moth species and share 65% amino acid identity with its B. mori homologue, BmOR49J (Jordan et al., 2009). Based on the high levels of shared amino acid identity and functional conservation of EpOR2 and EpOR3 with their B. mori counterparts, it was hypothesised that more EpORs will share these high conservation levels with the B. mori ORs. Indeed nine more ORs have been identified in the E. postvittana genome (namely EpOR4, 8, 13, 17, 27, 29, 38, 39 and 47) that share medium to high levels of amino acid identity (between 52% to 71%) with their B. mori counterparts, suggesting evolution of these ORs occurred before divergence of the Tortricidae from the Bombycidae. EpOR8 shares 71% amino acid identity with BmOR8, which is a larval-specific OR in B. mori. Based on this high level of amino acid identity, it can be postulated that EpOR8 is a larval-specific OR in E. postvittana. Interestingly, EpOR3 and BmOR49J (65% shared amino acid identity) bind citral, an oviposition deterrent of E. postvittana (Jordan et al., 2009). If shared amino acid identity conferred functional conservation on ORs, then EpOR4 (shares 60% amino acid identity with BmOR56) would bind cis-jasmone, the ligand of BmOR56 and EpOR29 (shares 57% amino acid identity with BmOR29) would bind linalool, citral and linalyl acetate, the ligands of BmOR29 (Tanaka et al., 2009). However, this is only a postulation and functional analysis of these E. postvittana ORs would confirm their ligands. Expansions can also be seen to have occurred in the E. postvittana OR repertoire, with 13 B. mori ORs having 28 homologues in E. postvittana. BmORs1, 4, 13, 14, 15, 16,
Identification of putative odorant receptors from Epiphyas postvittana 121 27, 28, 29, 49 and 68 have two homologues, while BmORs 26 and 30 have three homologues in E. postvittana OR repertoire, suggesting the E. postvittana ORs within these clades duplicated after diverging from their B. mori homologues. Sexually dimorphic expression of ORs have been documented in some Lepidoptera species and is one of the criteria used for identifying species-specific sex pheromone receptors. To date sex-specific pheromone receptors have been identified from B. mori, H. virescens, H. armigera, H. assulta, M. sexta, M. separate, D. indica and P. xylostella; some based on tissue expression analysis (qRT-PCR and in situ hybridisation experiments) and some based on their phylogenetic relatedness to PRs in other moths that bind pheromone components in functional characterisation assays (Krieger et al., 2004; Sakurai et al., 2004; Krieger et al., 2005; Mitsuno et al., 2008; Patch et al., 2009; Große-Wilde et al., 2010; Zhang et al., 2010). Most male-specific moth PRs cluster together on the same phylogenetic lineage based on amino acid identity. BmOR1, BmOR3, DiOR1, MsOR1, PxOR1 and HvOR13 have been shown to be expressed highly in male moth antennae and bind female released sex pheromone components. Two EpORs, EpOR1 and EpOR6 also belong to this PR clade, with both sharing 17-38% amino acid identity with BmOR1. EpOR1 is expressed at similar levels in both male and female antennae and has been shown to be the receptor for plant volatiles in Chapter 2, suggesting that even though it shares the highest amino acid identity with PRs from other moths, it is not the PR of E. postvittana. This is supported by other non-pheromone receptor members of this clade such as BmOR9 being expressed in similar levels in both male and female antennae (Krieger et al., 2002; Wanner et al., 2007) and BmOR4, BmOR5, and BmOR7 are expressed in both male and female antennae albeit at higher levels in male antennae (Wanner et al., 2007). Functional characterisation of BmOR4 and BmOR5 against the sex pheromones of B. mori have not yielded any ligands for these two ORs yet (Nakagawa et al., 2005), indicating that perhaps these are receptors for plant volatiles or for unidentified pheromone components, providing support for EpOR1 being an OR for plant volatiles and rendering EpOR6 as a possible PR of E. postvittana. If the E. postvittana PR is a member of the PR clade, then based on amino acid identity, EpOR6 can be postulated to be a PR candidate in E. postvittana. However, tissue expression analysis and functional characterisation of EpOR6 is required to resolve its role in E. postvittana olfaction.
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Abstract Abstract Olfaction or the
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Acknowledgements Acknowledgements I
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Contents v Contents Abstract……
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Contents 4.2.5 Degenerate PCR .....
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List of Figures List of Figures Fig
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List of Tables List of Tables Table
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List of Abbreviations gDNA Genomic
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1.1 General overview 1 General Intr
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General Introduction 3 moth in loca
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General Introduction 5 Figure 1.1:
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General Introduction 7 1.5 Componen
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General Introduction 9 OBPs have al
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General Introduction 11 A model has
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General Introduction 15 Tanaka et a
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General Introduction 17 Table 1.1:
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General Introduction 21 et al., 200
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General Introduction 23 the attract
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General Introduction 25 leaves and
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General Introduction 29 Expression
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General Introduction 31 BmOr2 HvOr2
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General Introduction 33 for lepidop
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Functional characterisation of Epip
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3.1 Introduction 3 The roles of Epi
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The roles of Epiphyas postvittana G
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Page 149 and 150: Concluding Discussion 133 sequencin
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Page 161 and 162: Appendix E 145 VII continued Figure
Page 163 and 164: References 147 Ansebo, L., Ignell,
Page 165 and 166: References 149 Butenandt, A., Beckm
Page 167 and 168: References 151 Fedurco, M., Romieu,
Page 169 and 170: References 153 Große-Wilde, E., St
Page 171 and 172: References 155 Hrdy, I., F. Kuldova
Page 173 and 174: References 157 Kaissling, K. E. (19
Page 175 and 176: References 159 Krieger, J., Große-
Page 177 and 178: References 161 Lopez-Gomez, R. and
Page 179 and 180: References 163 Miura, N., Nakagawa,
Page 181 and 182: References 165 Pell, J. K., Macaula
Page 183 and 184: References 167 Røstelien, T., Stra
Page 185 and 186: References 169 Stowers, L. and Loga
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References 171 Turner, C. T., Davy,
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References 173 Vogt, R. G., Riddifo
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References 175 Widmayer, P., Heifet
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