The angoumois grain moth, Sitotroga cerealella, is one of the most serious stored-grain pests worldwide. Control of this moth may be achieved by interfering with olfactory pathways to disrupt male-female communication with sex pheromones, using plant volatiles like garlic or its active substances. Here, three odorant-binding protein (OBP) genes [namely Si. cerealella general OBP 1 (ScerGOBP1), ScerGOBP2 and Si. cerealella pheromone-binding protein (ScerPBP)] were cloned from Si. cerealella antennae, and quantitative real-time PCR showed that these genes were predominantly expressed in adult antennae. ScerPBP expression was male-biased, but ScerGOBP1 and ScerGOBP2 were similar between sexes. The results of competitive binding assays indicated that a garlic substance, diallyl trisulphide (DATS), had similar or even higher binding affinity to ScerPBP than Si. cerealella sex pheromone, 7Z, 11E-hexadecadien-1-ol acetate (HDA). In olfactometer bioassays, DATS significantly reduced the response of adults to HDA when they were exposed to air filled with HDA and DATS. Surprisingly, ScerGOBP2, which is postulated to be involved in the detection of general odours, displayed higher affinity with HDA than did ScerPBP, indicating that ScerGOBP2 may also have a role in pheromone perception. These data suggest that DATS may interfere with recognition of female-produced sex pheromone, disrupting female and male mating behaviour and resulting in a new idea for controlling stored grain pests.
Ants easily accumulate cadmium (Cd) from the food web
in terrestrial
ecosystems. Cd contamination may cause olfactory dysfunction and consequently
disorders in the social behavior of ants. To explore the molecular
mechanism underlying the effect of Cd exposure on the chemosensory
process of ants, we characterized the Cd-induced variations in the
expression of genes involved in chemoreception and electrophysiological
and behavioral sensitivity to semiochemicals by using the red imported
fire ant, Solenopsis invicta, as a model system.
As a result, Cd exposure increased Cd accumulation and decreased the
survival rate of S. invicta. Cd exposure altered
the expression profiles of odor binding protein genes of S.
invicta (SiOBPs). Specifically, SiOBP15 protein expression
was upregulated upon Cd exposure. Both SiOBP7 and SiOBP15 exhibited
high binding affinities to limonene, nonanal, and 2,4,6-trimethylpyridine. S. invicta exposed to Cd showed less sensitive electrophysiological
and behavioral response to the three chemicals but exhibited sensitive
perception to undecane. Silencing of SiOBP7 and SiOBP15 abolished
the behavioral response of S. invicta to nonanal
and undecane, respectively, suggesting that SiOBP7 and SiOBP15 play
essential roles in the chemoreception of S. invicta. In general, our results suggest that Cd contamination may interfere
with olfactory signal transduction by altering the expression of SiOBPs,
consequently evoking chemosensory dysfunction in fire ants.
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