Olfactory Mechanism Of Host Location By Aenasius Bambawalei (Hayat)

Olfactory plays a very important role in host searching and locating by parasitic wasps.The olfactory sensillum on the antennas of parasitic wasps can receive chemical messages from plant volatiles or hosts as cues of host locating of parasitic wasps.So make research on olfactory system of parasitoid and clarify the olfactory mechanism of the host locating,will provide new ideas for the biological control of pests.Phenacoccus solenopsis Tinsley is a seriously invasive mealybug in China.Aenasius bambawalei Hayat is a solitary endoparasitoid and has high field parasitic rate of P.solenopsis.Chemical information plays an important role in host location of parasitoid wasps.It will may provide a theoretical basis for the biological control of P.solenopsis if it can be made clear the olfactory mechanism of host location of A.bambawalei.In this study,we find the chemosensory genes and explore the espression profile of Abam OBPs based on the construction of the antennal transcriptome of A.bambawalei.By the testing of the binding characteritics of recombinant Abam OBPs with the cotton volatiles,we discovered the chemical compounds with good combination,and checked the reaction of A.bambawalei to these compounds by behavior choice experiments.The main results are as follows:1 construction and analysis of the antennal transcriptome of A.bambawaleiBy Illumina Hi Seq2000 technology and de novo assembly,the antennal transcriptome of A.bambawalei total output 7154582040 nt.The assembly generated 89,469 contigs and 60,198 unigenes.Among all the unigenes 30959 were aligned to the non-redundant protein(NR)database.The result of NR annotation shows that 61.5% of A.bambawalei unigenes were orthologs of the proteins in Nasonia vitripennis.Through screening and alignment in the NCBI,we identified 54 transcripts encoding odorant-binding proteins(OBPs)including 4 pieces,226 transcripts encoding olfactory receptors(ORs)including 63 pieces,41 transcripts encoding gustatory receptors(GRs)including 13 pieces,3 transcripts encoding full-length sensory neuron membrane proteins(SNMPs).2 The expression profiles of Abam OBPs genes in A.bambawaleiWe tests 10 Abam OBP genes in different parts of A.bambawalei between male and female by q-PCR,the expression results show that: Abam OBP31 was specifically expressed in female antennae;Abam OBP1,Abam OBP23,Abam OBP24,and Abam OBP30 were male antenna-specific expressed;Abam OBP26,Abam OB34 and Abam OBP43 had high expression in the female foot;The gene Abam OBP2 and Abam OBP50 were specifically expressed in female and male head of A.bambawalei.3 The binding property of Abam OBP1 to the odorsAbam OBP1 gene was cloned and recombinant plasmid(p ET17b-Abam OBP1)was constructed successfully.Then we got the pure Abam OBP1 protein by prokaryotic expression assay.Through the fluorescence competitive binding assay,we test the binding property of Abam OBP1 with the 22 kinds of cotton volatiles in neutral(p H = 7.4)and acidic conditions(p H = 5.0)environment.The results showed that the binding affinity of Abam OBP1 with the volatiles in acidic environment were generally better than in neutral environment,except for with the Nonanal and Diethyl Suberate.In neutral environment,the binding affinity of Abam OBP1 with 1-Octen-3-one,2,4,4–Tri Methyl–2-pentene,methyl benzoate,(E)–2-Hexenal,dodecane,nerolidol,(S)-(-)-limonene,(R)-(-)-limomene and linalool were strong(Ki ? 20?M).4 Behavioral responses to the odors of the parasitoid wasp A.bambawaleiUsing Y-tube olfactometer,we test the behavior choice of A.bambawalei to the three cotton volatiles(1-Octen-3-one,2,4,4-Tri Methyl-2-pentene and S-(-)-limonene)that had good binding affinity with Abam OBP1.The results showed that both females and males of A.bambawalei showed significant selectivity to 1-Octen-3-one and 2,4,4-Tri Methyl-2-pentene.The male adults of A.bambawalei showed highly significant selectivity to 2,4,4-Tri Methyl-2-pentene.While,the males and females of A.bambawalei showed no selectivity to S-(-)-limonene compared with control.