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

More documents

Recommendations

Info

General Introduction 20 opening of a cAMP dependent channel, suggesting the odour evoked response also activates G proteins. The activation of the OR complex occurs rapidly while the G protein activation is slower and longer lasting (Wicher et al., 2008). No such evidence for a metabotropic signalling mechanism has been observed in any other studies and further experiments have to be conducted to rectify the differences in these three studies. Figure 1.5: The ion channel–GPCR model of odorant signalling in Drosophila. The ion channel formed by OR22a/OR83b complex depicts a rapid, short lived odorant evoked response upon stimulation by the ligand ethyl butyrate (light blue arrow) as suggested by Sato et al. (2008), Smart et al. (2008) and Wicher et al. (2008). The GPCR model suggests a slow and prolonged response upon ligand binding to the OR22a/OR83b complex, leading to an increase in cAMP production that opens up the motif that controls ion permeability in OR83b, thus resulting in membrane depolarisation (green arrow) as suggested by Wicher et al. (2008). This figure has been adapted from Wicher et al. (2008). ORs are a highly divergent group in that there is very little sequence homology both between and within species, for example, D. melanogaster ORs share only 17%–26% amino acid sequence identity (Vosshall et al., 2000); and the moth-specific pheromone receptor clade has an overall amino acid sequence identity of 10% (Jordan et al., 2009). They are broadly tuned as one OR can bind many odorants with different specificities and different ORs can bind the same odorants. For example, B. mori OR45 binds five odorants, three of which are also ligands for BmOR47 (Anderson et al., 2009). Other studies in insects support this broad tuning of ORs (Malnic et al., 1999; Touhara et al., 1999; Malnic et al., 2004; Hallem and Carlson, 2006; Anderson
General Introduction 21 et al., 2009; Jordan et al., 2009). The results in these studies show that the expression levels of ORs and PRs not only vary between the sexes but different ORs are expressed at different levels within a specific tissue. A combinatorial system is used by tens to hundreds of ORs to clearly detect and discriminate hundreds to thousands of different odorants. This combinatorial functioning of ORs can be attributed to the organisation of the olfactory machinery, as different ORNs expressing the same ORs converge to the same glomerulus in the antennal lobe of the brain (Vosshall et al., 2000; Couto et al., 2005; Fishilevich and Vosshall, 2005). 1.6 Insect pest control strategies The problem of insect pests has been ongoing for centuries. They cause damage to food and crops in the field and in storage, and therefore measures need to be taken to bring insect pests under control and minimise the damage and hence loss to the plant- based industries. Current insect pest control strategies include spraying food crops with pesticides, transgenic plants, as well as olfaction-based methods. These methods include lures to monitor pests in fields, mass trapping of insects and killing them (lure and kill approach) and the use of mating disruption and use of biological controls (Jones, 1998; Suckling and Karg, 1999; Suckling et al., 1999). Control strategies using pheromones and plant volatiles have achieved success to some extent. Mating disruption reduces the number of successful matings and hence the number of larvae that cause damage to plants (Jones, 1998). This system employs the release of sex pheromones in the atmosphere that masks the release of pheromone from calling female insects. This pheromone plume in the atmosphere confuses the males which are unable to detect the trail of pheromone towards the female thus reduces the number of successful mating. The success of this strategy is dependent on a number of factors. Knowledge of the time and place of mating will ensure that the pheromones are released at the right time and the number of generations of the target insect in a year will also be indicative of the number of pheromone applications that is needed. The life expectancy of the target insects is an important factor also in that the shorter time the adults have, the better the rates of mating disruptions that can be achieved. The chances of an adult male in locating a female is less if the adult is short
Page 1 and 2: http://researchspace.auckland.ac.nz
Page 3 and 4: Abstract Abstract Olfaction or the
Page 5 and 6: Acknowledgements Acknowledgements I
Page 7 and 8: Contents v Contents Abstract……
Page 9 and 10: Contents 4.2.5 Degenerate PCR .....
Page 11 and 12: List of Figures List of Figures Fig
Page 13 and 14: List of Tables List of Tables Table
Page 15 and 16: List of Abbreviations gDNA Genomic
Page 17 and 18: 1.1 General overview 1 General Intr
Page 19 and 20: General Introduction 3 moth in loca
Page 21 and 22: General Introduction 5 Figure 1.1:
Page 23 and 24: General Introduction 7 1.5 Componen
Page 25 and 26: General Introduction 9 OBPs have al
Page 27 and 28: General Introduction 11 A model has
Page 31 and 32: General Introduction 15 Tanaka et a
Page 33 and 34: General Introduction 17 Table 1.1:
Page 35: General Introduction 19 Figure 1.4:
Page 39 and 40: General Introduction 23 the attract
Page 41 and 42: General Introduction 25 leaves and
Page 45 and 46: General Introduction 29 Expression
Page 47 and 48: General Introduction 31 BmOr2 HvOr2
Page 49 and 50: General Introduction 33 for lepidop
Page 51 and 52: Functional characterisation of Epip
Page 73 and 74: 3.1 Introduction 3 The roles of Epi
Page 75 and 76: The roles of Epiphyas postvittana G
Page 87 and 88:
The roles of Epiphyas postvittana G
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
4.1 Introduction 4 Identification o
Page 97 and 98:
Identification of putative odorant
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Microarray OR 454 Transcriptome OR
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
5.1 Introduction 5 Concluding Discu
Page 143 and 144:
Concluding Discussion 127 VOBA sett
Page 145 and 146:
Concluding Discussion 129 redundant
Page 147 and 148:
Concluding Discussion 131 against t
Page 149 and 150:
Concluding Discussion 133 sequencin
Page 151 and 152:
Appendix B 135 Buffered TB (Sambroo
Page 153 and 154:
Appendix C 137 C. Appendix C - Clus
Page 155 and 156:
Appendix D 139 D. Appendix D - Solu
Page 157 and 158:
Appendix E 141 I II
Page 159 and 160:
Appendix E 143 V
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
Page 187 and 188:
References 171 Turner, C. T., Davy,
Page 189 and 190:
References 173 Vogt, R. G., Riddifo
Page 191 and 192:
References 175 Widmayer, P., Heifet
show all

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

Create successful ePaper yourself

Delete template?

Save as template?