Progress in Research on Insect Olfactory Perception of Habitat Odor Molecules

A highly sensitive olfactory system allows insects to precisely identify and position volatile compounds from different sources in their habitats,and plays a crucial role in their foraging,mating,and oviposition activities.During evolution,insects have successfully developed a large and complex olfactory system to adapt to heterogeneous environments,enabling the maintenance of inset population.A comprehensive examination of the olfactory system of insects may therefore yield novel insights into the development of innovative pest control and prevention strategies,as well as the study of olfactory mechanisms in vertebrates and even humans.This paper outlines the current state of research into the signal transduction mechanism by which insects perceive the olfactory molecules of their habitats.The aim of this review is to provide a reference point for future studies into the olfactory perception mechanism and its potential applications in pest management.

The olfactory system of Pieris brassicae caterpllars:from receptors to glomeruli

Tolfactory system of adult lepidopterans is among the best described neuronal circuits.However,comparatively little is known about the organization of the olfactory system in the larval stage of these insects.Here,we explore the expression of olfactory receptors and the organization of olfactory sensory neurons in caterpillars of Pieris brassicae,a significant pest species in Europe and a well-studied species for its chemical ecology.To describe the larval olfactory system in this species,we first analyzed the head transcriptome of third-instar larvae(L3)and identified 16 odorant receptors(ORs)including the OR coreceptor(Orco),13 ionotropic receptors(IRs),and 8 gustatory receptors(GRs).We then quantified the expression of these 16 ORs in different life stages,using qPCR,and found that the majority of ORs had significantly higher expression in the L4 stage than in the L3 and L5 stages,indicating that the larval olfactory system is not static throughout caterpillar development.Using an Orco-specific antibody,we identified all olfactory receptor neurons(ORNs)expressing the Orco protein in L3,L4,and L5 caterpillars and found a total of 34 Orco-positive ORNs,distributed among three sensilla on the antenna.The number of Orco-positive ORNs did not differ among the three larval instars.Finally,we used retrograde axon tracing of the antennal nerve and identified a mean of 15 glomeruli in the larval antennal center(LAC),suggesting that the caterpillar olfactory system follows a similar design as the adult olfactory system,although with a lower numerical redundancy.Taken together,our results provide a detailed analysis of the larval olfactory neurons in P brassicae,highlighting both the differences as well as the commonalities with the adult olfactory system.These findings contribute to a better understanding of the development of the olfactory system in insects and its life-stage-specific adaptations.