Providing fast and effective detection of pest insect infestation in food storage facilities is the foreseen outcome of an insect-based olfactory biosensor. Current visual methods for the detection of an infestation are not sensitive or reliable, so unless the produce has recently been fumigated with phosphine, pests are assumed to be present and the grain is re-treated. This leads to continued selection pressure for phosphine resistance and increases the costs of pest management in the grains industry. In the development of the detection technology, we are focussed on providing the biological recognition element for a biosensor platform capable of in situ measurement of insect produced volatiles.

We are taking two approaches to identify which of the many odorant receptors (ORs) annotated in the T. castaneum genome, can detect infestation odours. Here I will concentrate on an approach that focuses on sex pheromones; the other approach is outlined by Bradley Stevenson. Sequencing of the T. castaneum genome has recently been completed and revealed a large family of putative OR genes. It is within these genes that we are searching for one that encodes a target receptor. Determining which receptor gene sequences are potentially involved in pheromone communication involves quantification of gene transcript levels in the beetles.

We hypothesise sex pheromone receptors will show sex-biased expression and are therefore examining OR expression in the heads of male or female beetles. Some differences in expression levels have been observed using real-time quantitative PCR and our search for a receptor solely expressed in one sex continues. Receptor function in the beetle will be confirmed using behavioural studies and RNA interference. RNA interference eliminates expression of a targeted gene, and if that gene is involved in a measurable behavioural response (such as attraction to the opposite sex), we can measure this in a test arena called an olfactometer.

It is envisioned that research into insect pheromone receptor systems will not only demonstrate the feasibility of using them as a potential bio-recognition element in a biosensor device, but would additionally aid in our overall understanding of the mechanisms involved in invertebrate olfaction.