Types Of Antennal Sensilla And Partial Cloning And Sequence Analysis Of The General Odorant Binding Protein 2 Gene Of The Stripe Stem Borer, Chilo Suppressalis (Walker)

The stripe stem borer, Chilo suppressalis (Walker) is a cosmographical insect pest, attacking many species of monocots (Khan et al. 1991). In Asia, it is one of stem borer species attacking rice, the major stable cereal crop feeding 60% of the world population, and the water bamboo, a common aquatic vegetable in Asian mainland, causing the average yearly yield losses estimated to be 10-15% in average.Host finding behavior of moths was frequently reported as a behavior guided by chemosensors locating in the antennae. In this thesis, we describe the antennal sensory organs and cloning and sequencing of the partial GOBP2 gene of the insect.1) The dimension, external morphology, and distribution of antennal sensilla of Chilo suppressalis (Walker) were determined by light microscopy and scanning electron microscopy. Male C. suppressalis antennae are longer, due to larger flagellum segments, than female antennae, but they have similar number of segments. The antennal flagellum of both sexes has six types of sensilla: trichodea, chaetica, coeloconica, squamiformia, styloconica and basiconic. The sensilla trichodea presents the sexual dimorphism: the long sensilla trichodea (Lst) largely exist in male antenna but are seldom distribute in female antenna, however, the short sensilla trichodea (Sst) mainly occur in female antenna; Sexual dimorphism also can be found in the numbers of sensilla trichodea: male has significantly more sensilla trichodea than female.2) A partial cDNA clone coding for general odorant-binding protein2 (GOBP2) was isolated from the antenna of C. suppressalis by PCR technique. Results of sequencing and structural analyses showed that the partial-length of GOBP2 was 416 bp, possessing 138 amino acid residues. This deduced amino acid sequence shared some common structural features with the general odorant binding proteins from several moth species, including the six conserved cysteine motif, typical of insect's OBPs. Gel electrophoresis analysis of PCR product from antennal cDNA showed that GOBP2 is specifically expressed in the antennae of C. suppressalis at similar levels inboth sexes.