Insect Biochemistry and Molecular Biology 30 (2000) 233–241 www.elsevier.com/locate/ibmb Chemosensory proteins of Locusta migratoria (Orthoptera: Acrididae) Jean-Franc ¸ois Picimbon * , Karen Dietrich, Heinz Breer, Ju ¨rgen Krieger Institute of Physiology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany Received 28 June 1999; received in revised form 1 November 1999; accepted 5 November 1999 Abstract We describe a family of proteins abundantly expressed in the chemoreception sensory organs, the antennae and legs, of the desert locust, Locusta migratoria (Orthoptera, Acrididae). Using polymerase chain reaction-based approaches and homology screenings, “OS-D”-like proteins were identified in L. migratoria. The different sub-types (LmigOS-Ds) are very similar to each other and share about 50–70% identity with OS-Ds from Drosophila melanogaster and Periplaneta americana. A similar degree of identity was also observed with moth OS-Ds. Northern blot analysis revealed a strong expression of the LmigOS-Ds in the antennae and legs, suggesting their involvement in chemosensory processes. Despite the lack of direct evidence for their role in chemosensation, LmigOS-Ds and their homologs seem to constitute a large protein family, characterized by a striking abundance and diversity among insect chemosensory organs.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Insect; Olfaction; Chemosensation; Odorant binding protein; OS-D; Antennae; Legs 1. Introduction Locusts have not only developed remarkable visual and acoustic systems to find food and mating partners, a role of olfactory cues (sex pheromones) has also been reported for mate finding in different acridid species, like Hieroglyphus nigrorepletus (Siddiqui and Khan, 1981), Taeniopoda eques (Whitman, 1982) and Schistocerca gregaria (Inayatullah et al., 1994). Furthermore, olfac- tion plays a key role in controlling different develop- mental stages of the insect life, in maturation processes (Loher, 1960), gregarization (Obeng-ofori et al., 1993) and oviposition (Norris, 1970) behaviours, as well as locating food from a distance. In particular, cuticular hydrocarbons, important effectors in insect chemical communication, have been demonstrated to control the nymphal behavioural phase transition (Heifetz et al., 1998) and activate the antennal sensory system (Heifetz et al., 1997). This antennal sensory system also bears elements involved in food finding, more specific to the * Corresponding author. Tel.: + 49-711-459-2266; fax: + 49-711- 459-3726. E-mail address: jfp@uni-hohenheim.de (J.-F. Picimbon) 0965-1748/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII:S0965-1748(99)00121-6 perception of food odours released by plants (Kafka, 1970), especially hexenal or hexenoic acid from green leaves (Greenwood and Chapman, 1984). The antennal sensory system in insects involves speci- alized micro-units, the sensillae; hollow cuticular hair structures in which the dendrites from the sensory neu- rons extend to the lumen bathing in an aqueous lym- phatic medium. Cuticular hydrocarbons, plant volatiles and their derivatives are highly hydrophobic compounds and therefore cannot diffuse through the hydrophilic lymph to reach the dendritic membrane. A class of small (14–20 Kd) water-soluble proteins, called odorant bind- ing proteins (OBPs), first discovered in the insect sensil- lar lymph (Vogt and Riddiford, 1981) but also in the mucus of vertebrates (Pelosi et al., 1982), is postulated to mediate the solubilization of hydrophobic odorant molecules, and thereby to facilitate their transport to the receptor neurons (Pelosi, 1994; Du and Prestwich, 1995). OBPs have been extensively studied in moths where so far three different types of OBP have been described: the Pheromone Binding Proteins (PBP) and two classes of General Odorant Binding Proteins (GOBPs), so-called for their respective expression in cells located in phero- mone or general-odorant sensitive sensillae (Steinbrecht et al., 1995; Laue et al., 1994). A fourth class of antennal