Expression in Antennae and Reproductive Organs Suggests a Dual Role of an Odorant-Binding Protein in Two Sibling Helicoverpa Species

Abstract

Odorant-binding proteins (OBPs) mediate both perception and release of semiochemicals in insects. These proteins are the ideal targets for understanding the olfactory code of insects as well as for interfering with their communication system in order to control pest species. The two sibling Lepidopteran species Helicoverpa armigera and H. assulta are two major agricultural pests. As part of our aim to characterize the OBP repertoire of these two species, here we focus our attention on a member of this family, OBP10, particularly interesting for its expression pattern. The protein is specifically expressed in the antennae of both sexes, being absent from other sensory organs. However, it is highly abundant in seminal fluid, is transferred to females during mating and is eventually found on the surface of fertilised eggs. Among the several different volatile compounds present in reproductive organs, OBP10 binds 1-dodecene, a compound reported as an insect repellent. These results have been verified in both H. armigera and H. assulta with no apparent differences between the two species. The recombinant OBP10 binds, besides 1-dodecene, some linear alcohols and several aromatic compounds. The structural similarity of OBP10 with OBP1 of the mosquito Culex quinquefasciatus, a protein reported to bind an oviposition pheromone, and its affinity with 1-dodecene suggest that OBP10 could be a carrier for oviposition deterrents, favouring spreading of the eggs in these species where cannibalism is active among larvae.

Identification of candidate chemosensory genes in the antennal transcriptome of Tenebrio molitor (Coleoptera: Tenebrionidae)

“…OBPs distributed in the abdomen and legs are unlikely to play a direct role in olfaction but may be involved in other physiological processes. For instance, in Helicoverpa armigera, an OBP which is abundant in male seminal fluid and transferred to females is able to carry oviposition deterrents to label fertilized eggs, thus prompting the female moth away from the location where the first egg was laid (Sun et al, 2012). Similarly in D. melanogaster, two OBPs have been found exclusively on the taste bristles located on the tarsi and function in taste perception (Matsuo et al, 2007).…”

Antibody-based detection of alkaline phosphatase in lepidopteran insects (Lepidoptera: Noctuidae)

“…Polyclonal antibody was also used to detect the odorant-binding protein of H. armigera (Sun et al, 2012). In another report, polyclonal antibody was used to study the function of nuclear transport factor 2 and Ran in the 20E signal transduction pathway in H. armigera (He et al, 2010).…”

Unique function of a chemosensory protein in the proboscis of two Helicoverpa species

“…Helicoverpa armigera and H. assulta were collected as larvae from Zhengzhou, Henan province of China and maintained in the laboratory on artificial diet, as previously described (Sun et al, 2012).…”

“…Apart from those expressed in chemosensilla, the family of CSPs includes members present in pheromone glands or reproductive organs, where they could act as carriers for semiochemicals, assisting their release into the environment (Dyanov and Dzitoeva, 1995;Jacquin-Joly et al, 2001;Dani et al, 2011;Iovinella et al, 2011;Iovinella et al, 2013;Sun et al, 2012;Zhou et al, 2013). Most interestingly, other functions, completely unrelated to chemical communication, have been reported to be associated with some CSPs.…”