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

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General Introduction 4 in behavioural assays to decrease the proportion of E. postvittana laying eggs while some compounds have implications in decreasing the number of fertile eggs laid per female moth (Suckling et al., 1996). 1.4 The olfactory system Antennae are the major odorant detection appendages in moths. Hair-like projections on the surface of the antennae called sensilla house chemosensory organs that detect odorants present in the environment (Schneider, 1964). A sensillum has a porous outer wall and the inner layer is filled with an aqueous fluid, the sensillum lymph (Breer, 1997). The bipolar olfactory receptor neuron projects a dendritic membrane into the sensillum lymph, and the other end forms an axon projecting to the antennal lobe (Keil, 1999). The ORN cell is surrounded by three auxiliary cells, the tormogen, trichogen and thechogen (Steinbrecht et al., 1992). These cells function in sensillum structural development and in maintaining the sensillum lymph. Located within the sensillum lymph are soluble odorant binding proteins (OBPs) and odorant degrading enzymes (ODEs) and located within the dendritic membrane are the odorant receptors (ORs) and pheromone receptors (PRs), as depicted in Figure 1.1 (Vogt and Riddiford, 1981; Steinbrecht, 1999; Vogt et al., 2005).
General Introduction 5 Figure 1.1: Structure of a single insect olfactory sensillum (adapted and modified from Vogt (1987)). Odorants enter the sensillum lymph through pores in the cuticular wall and interact with the binding proteins present in the lymph which confer them onto the odorant receptors present on the dendritic membrane of the bipolar olfactory receptor neuron. Degrading enzymes present in the sensillum lymph may help in the clearing of odorants from the lymph. The sensillum types present on moth antennae can be classified into six different groups. These are the sensilla trichodea, sensilla basiconica, sensilla auricillica, sensilla chaetica, sensilla styloconica and sensilla coeloconica. Sensilla trichodea are very long, thin, porous hair-like structures with sharp pointed tips (Schneider, 1964). Unbranched dendrites of up to three neurons innervate this sensilla type (Keil, 1999). They are present in high numbers in male moths, while they occur in low numbers or not at all in female moths and thus were implicated to be involved in recognition of sex pheromone components released by female moths (Seabrook, 1978). The specific tuning of this sensilla type to sex pheromones was confirmed by single sensillum electroantennogram (EAG) recordings (Shields and Hildebrand, 2001). The females of some moth species also carry large numbers of this sensilla type, however, these are shorter and the neurons are responsive to general odorants (Nagy and George, 1981). Sensilla basiconica are shorter with blunt rounded tips and are innervated by the dendrites of up to 50 neurons (Schneider, 1964). This sensilla type has been implicated in the detection of plant volatiles in S. littoralis (Anderson et al., 1995) and
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Page 3 and 4: Abstract Abstract Olfaction or the
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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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4.1 Introduction 4 Identification o
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Identification of putative odorant
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Microarray OR 454 Transcriptome OR
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5.1 Introduction 5 Concluding Discu
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Concluding Discussion 127 VOBA sett
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Concluding Discussion 129 redundant
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Concluding Discussion 131 against t
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Concluding Discussion 133 sequencin
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Appendix B 135 Buffered TB (Sambroo
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Appendix C 137 C. Appendix C - Clus
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Appendix D 139 D. Appendix D - Solu
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Appendix E 141 I II
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Appendix E 143 V
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Appendix E 145 VII continued Figure
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References 147 Ansebo, L., Ignell,
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References 149 Butenandt, A., Beckm
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References 151 Fedurco, M., Romieu,
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References 153 Große-Wilde, E., St
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References 155 Hrdy, I., F. Kuldova
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References 157 Kaissling, K. E. (19
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References 159 Krieger, J., Große-
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References 161 Lopez-Gomez, R. and
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References 163 Miura, N., Nakagawa,
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References 165 Pell, J. K., Macaula
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References 167 Røstelien, T., Stra
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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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