It is not clear whether pheromone-binding
proteins (PBPs) can be readily isolated from antennal extracts of social
insects, since they are expected to have complex chemical communication
systems. We have analyzed urea extracts of antennae of the red imported
fire ant, Solenopsis invicta, using two-dimensional gel electrophoresis.
Worker antennae have many low-abundance proteins with isoelectric points
between 4 and 5 and molecular weights below 20 kDa (the range expected
for PBPs). N-terminal amino acid sequence analysis of the major protein
in this region, W2, shows 62% identity to an RR-1 soft cuticle protein
from Drosophila (gb AAF58518). Consistent with this assignment,
gels of individual antennal segments contain W2 when the dissected segment
includes the non-sclerotized joints, but not when the segment is dissected
to exclude the joints.
Because male fire ants do not forage
or work in the nest, we expect that their olfactory repertoire is more
limited than workers. Two dimensional gel electrophoresis of urea extracts
of male fire ant antennae show only two major acidic low molecular weight
proteins, (18 kDa and 15 kDa). We determined the N-terminal amino acid
sequence of the 18 kDa protein, which did not match any known sequence.
We prepared degenerate 5' PCR primers based on this sequence. After 2-step
PCR amplification and cloning, we obtained one sequence consistent with
the isoelectric point and size of the 18 kDa protein. The derived protein
sequence is 25% identical to apolipophorin-III from Derobrachus geminatus
(Coleoptera, Cerambycidae) (gb AAA64736). Apolipophorin-III has not been
previously identified in insect antennae, and its function in the antenna
is unknown.
Species 1: Hymenoptera Formicidae Solenopsis invicta (red imported fire ant)
Species 2: Coleoptera Cerambycidae Derobrachus geminatus (palo verde root borer)
Species 3: Diptera Drosophilidae Drosophila melanogaster (fruit fly)
Keywords: soft cuticle, apolipophorin-III
Back to Display Presentations, Section B. Physiology, Biochemistry, Toxicology, and Molecular Biology
Back to Posters
Back to The 2002 ESA Annual Meeting and Exhibition