Expression and immunolocalisation of odorant-binding and chemosensory proteins in locusts

Abstract

We have identified, cloned and expressed a new chemosensory protein (CSP) in the desert locust Schistocerca gregaria belonging to a third sub-class of these polypeptides. Polyclonal antibodies stained a band of 14 kDa, as expected, in the extracts of antennae and palps of the adults, but not in the 4th and 5th instars. In the related species Locusta migratoria, instead, the same antibodies cross-reacted only with a band of apparent molecular mass of 35 kDa in the extract of 1st-5th instars, but not in the adults. The recombinant protein binds the fluorescent probe N-phenyl-1-naphthylamine, but none of the compounds so far reported as pheromones for S. gregaria. The expression of the odorant-binding protein (OBP) and of CSPs of sub-classes I and II was also monitored in antennae, tarsi, palpi, wings and other organs of solitary and gregarious locusts in their nymphal and adult stages. OBP was found to be antenna specific, where it is expressed at least from the 3rd instar in both solitary and gregarious locusts. CSPs, instead, appear to be more ubiquitous, with different expression patterns, according to the sub-class. Immunocytochemistry experiments revealed that OBP is present in the sensillum lymph of sensilla trichodea and basiconica, while CSP-I and CSP-III were found in the outer sensillum lymph of sensilla chaetica and in the sub-cuticular space between epidermis and cuticle of the antenna. Sensilla chaetica on other parts of the body showed the same expression of CSP-I as those on the antenna.

Electrophysiological response patterns of 16 olfactory neurons from the trichoid sensilla to odorant from fecal volatiles in the locust, locusta migratoria manilensis

“…These are classified into four morphologically distinct types: sensilla (s.) basiconica, s. trichoidea, s. ceoloconica, and s. chaetica (Ochieng et al, 1998;Jin et al, 2005). However, until now, a detailed functional classification of neurons from antennal trichoid sensilla of locust was not available.…”

“…Locust (Locusta migratoria) antennae are important chemosensory organs as seen from several studies on its anatomy, electrophysiology, biochemistry, and molecular biology (Altner et al, 1981;Ochieng et al, 1998;Ochieng and Hansson, 1999;Ban et al, 2003;Jin et al, 2005). The basiconic sensilla on desert locust antenna mainly respond to aggregation pheromones produced by both the nymph and adult, while neurons housed in trichoid sensilla are responsive to a putative sex pheromone, the coeloconic sensilla display excitatory responses to green leaf odor, organic acids, and nymphal odors, but their firing is inhibited by aggregation pheromones of mature adult (Ochieng and Hansson, 1999).…”

New isoforms of odorant‐binding proteins and potential semiochemicals of locusts

“…In the locust, a single OBP (LmigOBP) has been reported, specifically expressed in the antennae and in labial palpi, and present in two isoforms differing by a single amino acid substitution (Ban et al, 2003a;Jin et al, 2005). Binding experiments performed with some of the fecal volatiles of the desert locust failed to show any affinity to OBP.…”

Soluble proteins in insect chemical communication

“…The general name of chemosensory proteins (CSPs) was proposed for this class of polypeptides to include roles in both olfaction and taste [54]. CSPs have since been isolated and cloned in several insect species, belonging to different orders, such as Lepidoptera [55][56][57][58][59][60], Hymenoptera [37,[61][62][63][64][65], Blattoidea [50,66,67], Orthoptera [54,[68][69][70] and Hemiptera [71]. CSPs are smaller than OBPs, with 100-120 residues and bear no sequence similarity to OBPs.…”