OLFACTION IN A HEMIMETABOLOUS INSECT - ANTENNAL-SPECIFIC PROTEIN IN ADULT LYGUS-LINEOLARIS (HETEROPTERA, MIRIDAE)

Antennal sensilla, electrophysiological responses to an insect and a plant odorant, and polypeptide profiles were investigated in fifth instar nymphs and adults of the tarnished plant bug, Lygus lineolaris. Sensilla with surface pits characteristic of porous olfactory sensilla develop on the second and third antennal segments during the final molt from fifth instar nymph to adult, Concurrent with development of these sensilla in the adult, neural responses to a component of green odor (1-hexanol) and an insect-produced volatile [(E)-2-hexenyl butyrate] increase dramatically, Antennal extirpation experiments indicated that sensilla responsive to these odorants are housed principally on the second and third antennal segments, A protein with a molecular weight of 17,000 present in the soluble fraction of adult antennae was absent in nymphs, Localization of this protein to the antenna, the coincidence of its expression with development of olfactory sensilla and its molecular weight were characteristic of odorant-binding proteins in moths, However, antisera raised against pheromone-binding protein of the gypsy moth, Lymantria dispar, did not react with the Lygus protein, The N-terminal sequence for our antennal-specific protein was determined, and showed no significant homology with other known insect protein sequences, This lack of homology with other insect proteins including odorant binding proteins indicates that if it is an odorant binding protein as we suspect, it is either widely divergent or independently derived, This is the first report of an antennal-specific protein in a hemimetabolous insect and the only report of such a protein in an insect other than moths or Drosophila melanogaster.