Odorant binding proteins from Hermetia illucens: potential sensing elements for detecting volatile aldehydes involved in early stages of organic decomposition

Abstract

Organic decomposition processes, involving the breakdown of complex molecules such as carbohydrates, proteins and fats, release small chemicals known as volatile organic compounds (VOCs), smelly even at very low concentrations, but not all readily detectable by vertebrates. Many of these compounds are instead detected by insects, mostly by saprophytic species, for which long-range orientation towards organic decomposition matter is crucial. In the present work the detection of aldehydes, as an important measure of lipid oxidation, has been possible exploiting the molecular machinery underlying odour recognition in Hermetia illucens (Diptera: Stratiomyidae). This voracious scavenger insect is of interest due to its outstanding capacity in bioconversion of organic waste, colonizing very diverse environments due to the ability of sensing a wide range of chemical compounds that influence the choice of substrates for ovideposition. A variety of soluble odorant binding proteins (OBPs) that may function as carriers of hydrophobic molecules from the air-water interface in the antenna of the insect to the receptors were identified, characterised and expressed. An OBP-based nanobiosensor prototype was realized using selected OBPs as sensing layers for the development of an array of quartz crystal microbalances (QCMs) for vapour phase detection of selected compounds at room temperature. QCMs coated with four recombinant H. illucens OBPs (HillOBPs) were exposed to a wide range of VOCs indicative of organic decomposition, showing a high sensitivity for the detection of three chemical compounds belonging to the class of aldehydes and one short-chain fatty acid. The possibility of using biomolecules capable of binding small ligands as reversible gas sensors has been confirmed, greatly expanding the state-of the-art in gas sensing technology.

An odorant binding protein is involved in counteracting detection-avoidance and Toll-pathway innate immunity

“…Chemosensory proteins (CSPs) and odorant-binding proteins (OBPs) are small molecular weight ligand carrier proteins originally considered to act to transport odorants to receptors within sensory cells and modulate the insect behavioral response [20] , [21] , [22] . The function of CSPs and OBPs in VOCs recognition has been widely confirmed [23] , [24] , [25] , [26] . However, increasing evidence shows that some CSPs and OBPs function in alternate ways to regulate other physiological processes beyond olfaction by binding to exogenous or endogenous metabolites [27] , [28] .…”

Selection Behavior and OBP-Transcription Response of Western Flower Thrips, Frankliniella occidentalis, to Six Plant VOCs from Kidney Beans

“…Odorant-binding proteins play critical roles in the insect olfactory system, and are responsible for capturing and transporting outside odorants through hydrophilic lymph to olfactory receptors [ 53 , 54 ]. The function of OBPs in VOCs’ recognition has been widely confirmed [ 55 , 56 , 57 ]. Nine differential OBP genes from transcriptome analysis results of F. occidentalis under different treatments [ 30 ] were selected to measure their relative expression levels for the purpose of exploring the reasons for the above phenomenon.…”

Artificial Olfactory Biohybrid System: An Evolving Sense of Smell

“…[50a,c,64] QCMs are more sensitive than SAWs and are capable of detecting concentrations up to the parts per million (ppm) level. [65] To improve the sensitivity of SAW, a thin layer of diamond nanoparticles can also be coated on the surface of the sensor, detecting odors up to the parts per billion (ppb) level. [66] After the concept of B-EN was proposed by Goepl et al in 1998, the development of B-EN based on the QCM system using OR was attempted in 1999.…”