Expression Pattern And Rnai Of Odorant Receptor Sexi\Orco Gene In Spodoptera Exigua ( Húbner)

The insect olfactory system has evolved the capacity to recognize and discriminate an inordinate number of chemically distinct odors that signal the presence of food sources, oviposition sites, predators, or mating partners. The detection and transduction of olfactory signals requires olfactory receptors (ORs) expressed in olfactory receptor neurons (ORNs) and housed in olfactory sensilla. Insect ORs have seven putative transmembrane domains, which is the typical characteristic of G protein-coupled receptors.Unlike most other insect ORs that share low homology, the OR83b family is one insect-specific receptor family whose molecular structure and function are conserved across diverse insect species. OR83b is coexpressed with conventional ORs in all ORNs. The olfactory-based control strategies have developed an important means for pest control.The beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), are severe pests of various agricultural crops. This lack of knowledge hinders the development of compounds that may modulate OR function and potentially control insects involved in disease propagation and agricultural damage.With the insights on the molecular machemism, it will be facilitated for molecular designing of specific regulator to these key olfactory proteins, and for further development of more effective pest behaviorally interfereing techniques.Based on our previous molecular charaeterization of the Sexi\Orco gene in S. exigua, we make further reaseareh for the Sexi\Orco from S. exigua. The main results were as follows:1. Molecular identification of Sexi\Orco gene structure from S. exiguaBasesd on the beet armyworm Sexi\Orco cDNA full sequence (Genbank accession number: AY862142) and compared with the gene structure published of other insect antypical olfactory receptor, we designed some pairs of primers to molecular identification of Sexi\Orco gene structure using the polymerase chain reaction (PCR). Finally we found that Sexi\Orco gene contains 10 extrons and 9 introns. The ends of the introns have a typical GT-AG structure.2. Tissue-specific,temporal and spatial expression of Sexi\OrcoIn this study, the tissue expression pattern and level of Sexi\Orco was inferred at different developmental stages. To study the tissue-specific expression and quantitative analysis of atypical ofactory receptor gene Sexi\Orco in S. exigua, we performed researchs on mRNA expression level and specific of Sexi\Orco at different developmental stages in S. exigua by reverse transcription polymerase chain reaction (RT-PCR) and real-time quantitative polymerase chain reaction (Real-time quantitative PCR). We found that Sexi\Orco was expressed in egg, larva, pupae and adult. During the adult stage, Sexi\Orco was expressed in antennae and proboscis of male and female moths. The expression level of Sexi\Orco was very low in proboscis, and was no significant diffenrence among the eggs, larvae and pupae. The expression level of Sexi\Orco in moths antennae was 104~105-fold higher than the other stages; The expression level was the highest in male antennae 36 h after emergence, and was 5.5-fold higher than female antennae.3. RNAi of Sexi\Orco in S. exiguaAbodomen injection approach has been applied to introduce dsRNA molecules for Sexi\Orco into the moth abdomen cavity. RT-PCR and qRT-PCR detections at 24 hours after injecting of dsRNA molecules revealed that the mRNA expression level of Sexi\Orco in male and female antenna was significantly reduced by about 90%,and that the moth survivalrates were not significantly different between treatments of dsRNA injected, dsEGFP and DEPC-water injeeted. Therefore, the abodomen injection method was effective to be used for Sexi\Orco RNAi study.