Y.-L. Sun,J.-F. Dong,C. Ning,P.-P. Ding,L.-Q. Huang,J.-G. Sun,C.-Z. Wang
Parasitic wasps rely on olfaction to locate their hosts in complex chemical environments. Odorant receptors (ORs) function together with well-conserved odorant coreceptors (ORcos) to determine the sensitivity and specificity of olfactory reception. Campoletis chlorideae (Hymenoptera: Ichneunmonidae) is a solitary larval endoparasitoid of the cotton bollworm, Helicoverpa armigera , and some other noctuid species . To understand the molecular basis of C. chlorideae ’s olfactory reception, we sequenced the transcriptome of adult male and female heads (including antennae) and identified 211 OR transcripts, with 95 being putatively full length. The tissue expression profiles, as assessed by reverse-transcription PCR, showed that seven OR s were expressed only or more highly in female antennae. Their functions were analysed using the Xenopu slaevis oocyte expression system and two-electrode voltage-clamp recordings. CchlOR62 was tuned to cis -jasmone, which was attractive to female C. chlorideae adults and H. armigera larvae in the subsequent behavioural assays. Further bioassays using caged plants showed that the parasitism rate of H. armigera larvae by C. chlorideae on cis -jasmone-treated tobacco plants was higher than on the control plants. Thus, cis -jasmone appears to be an important infochemical involved in the interactions of plants, H. armigera and C. chlorideae , and CchlOR62 mediates the attractiveness of cis -jasmone to C. chlorideae .
Sun Ya-Lan,Dong Jun-Feng,Huang Ling-Qiao,Wang Chen-Zhu
Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) is an important larval endoparasitoid of the cotton bollworm Helicoverpa armigera (Hübner). A better understanding of herbivore-induced plant volatiles (HIPVs) employed by C. chlorideae to locate hosts will contribute towards the biological control of this notorious crop pest. In this study, we first investigated the electrophysiological and behavioral responses of C. chlorideae to 19 volatile compounds emitted by herbivore-infested plants. Eleven odorants induced EAG responses of C. chlorideae , while only two compounds, cis -jasmone and cis -3-hexenyl acetate, were attractive to the parasitoid in Y-tube olfactometer assays. Next, we used two- and four-choice tests in cage settings to investigate the parasitism rate of H. armigera larvae by C. chlorideae on tobacco plants treated with different doses of cis -jasmone, cis -3-hexenyl acetate, and their mixtures. Results showed that the parasitism rate of H. armigera was significantly higher on the plants treated with cis -jasmone or cis -3-hexenyl acetate, and their optimal dose for both compounds was 1 mg. However, the mixtures of cis -jasmone and cis -3-hexenyl acetate did not increase H. armigera parasitism rate by C. chlorideae when compared with control groups. Our results indicate that the single compounds cis -jasmone and cis -3-hexenyl acetate, at certain doses, enhance parasitic efficiency of C. chlorideae , but their mixtures negate this effect. These results will help us in the exploitation of C. chlorideae as biological control agent to reduce the populations of H. armigera .
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