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

Antennal sensilla, electrophysiological responses to an insect and a p lant odorant, and polypeptide profiles were investigated in fifth inst ar nymphs and adults of the tarnished plant bug, Lygus lineolaris. Sen silla with surface pits characteristic of porous olfactory sensilla de velop 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] i ncrease dramatically, Antennal extirpation experiments indicated that sensilla responsive to these odorants are housed principally on the se cond and third antennal segments, A protein with a molecular weight of 17,000 present in the soluble fraction of adult antennae was absent i n nymphs, Localization of this protein to the antenna, the coincidence of its expression with development of olfactory sensilla and its mole cular weight were characteristic of odorant-binding proteins in moths, However, antisera raised against pheromone-binding protein of the gyp sy moth, Lymantria dispar, did not react with the Lygus protein, The N -terminal sequence for our antennal-specific protein was determined, a nd showed no significant homology with other known insect protein sequ ences, This lack of homology with other insect proteins including odor ant binding proteins indicates that if it is an odorant binding protei n as we suspect, it is either widely divergent or independently derive d, This is the first report of an antennal-specific protein in a hemim etabolous insect and the only report of such a protein in an insect ot her than moths or Drosophila melanogaster.