Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
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General Introduction 13<br />
Figure 1.3: Model <strong>of</strong> <strong>in</strong>sect pheromone detection demonstrat<strong>in</strong>g a role <strong>of</strong> SNMP <strong>in</strong><br />
cVA mediated response <strong>of</strong> OR67d, as depicted by Benton et al. (2007). The SNMP<br />
may be act<strong>in</strong>g as a prelim<strong>in</strong>ary receptor, destabilis<strong>in</strong>g the OBP/pheromone complex<br />
and convey<strong>in</strong>g the pheromone to the PR for signal transduction to occur.<br />
Odorant receptors are seven transmembrane (7TM) doma<strong>in</strong> prote<strong>in</strong>s localised on the<br />
dendritic membranes <strong>of</strong> ORNs and detect odorants that enter the sensillum lymph<br />
(Benton, 2006). ORs function <strong>in</strong> b<strong>in</strong>d<strong>in</strong>g odorants as they are transported to the<br />
dendritic membrane. This <strong>in</strong>teraction sets <strong>of</strong>f a signall<strong>in</strong>g cascade caus<strong>in</strong>g the ORN to<br />
depolarise and a signal is relayed via the axonal end <strong>of</strong> the ORN to the antennal lobe<br />
<strong>in</strong> the bra<strong>in</strong>. In contrast to the broadly tuned ORs, pheromone receptors <strong>in</strong> <strong>in</strong>sects, like<br />
moths, are thought to be highly tuned to sex pheromones (Nakagawa et al., 2005;<br />
Mitsuno et al., 2008; Forstner et al., 2009; Wang et al., 2010). This represents the<br />
holy grail <strong>of</strong> the <strong>in</strong>sect olfactory system <strong>in</strong> that the identification <strong>of</strong> PRs will give a<br />
better understand<strong>in</strong>g <strong>of</strong> the underly<strong>in</strong>g mechanisms <strong>of</strong> sex pheromone reception and<br />
pheromone controlled behaviours such as mat<strong>in</strong>g.<br />
1.5.2.1 Odorant receptor identification <strong>in</strong> moths<br />
The first putative ORs to be identified <strong>in</strong> moths were from the tobacco budworm H.<br />
virescens us<strong>in</strong>g the basic local alignment search tool (BLAST) <strong>of</strong> Heliothis genomic