Antennal Ultrastructure And Transcriptome Analysis Of Endoparasitoid Wasp,Cotesia Chilonis(Munakata)(Hymenoptera:Braconidae)of The Rice Striped Stem Borer,Chilo Suppressalis(Walker)(Lepidoptera:Crambidae)

Rice is one of the most important staple food crops throughout the world.China is the largest producer,consumer and 7th exporter of rice in the world.Rice is susceptible to several pests and pathogens.Among them,the rice striped stem borer,Chilo suppressalis(Walker)(Lepidoptera:Crambidae)is economically the most devastating pest to rice production.C.suppressalis has been a considerable hindrance to rice yields and causes severe losses in the majority of rice growing countries,including China.Usually,chemical control is the main method to protect rice from pest damage.However,the effectiveness of insecticides failed quickly because C.suppressalis developed the resistance to insecticides.Moreover,chemical residues may cause harm to humans,especially farmers.Biological control is one of the safest and most effective methods against rice pests.Cotesia chilonis(Hymenoptera:Braconidae)is an obligate larval endo parasitoid that effectively regulates the density of C.suppressalis(Lepidoptera:Crambidae).Considering the important function of the antennae during parasitoid mating and host finding,the antennal ultra-structure of C.chilonis was observed both with scanning electron microscope(SEM)and transmission electron microscope(TEM).The antennae of C.chilonis were composed of scape,pedicel and 16 flagellomeres.The total length and the diameter of the male antenna were 2.57 mm and 67.77 ?m,respectively.Each sub-segment of the flagellum averages about 153.2?m in length.The length and diameter of the female antenna and length for a sub-segment of the flagellum measured 1.29 mm,59.91 and 84.43?m,respectively,which parameters were significantly smaller than the males.Nine types of sensilla,namely:s.chaetica,s.trichodae type ?,s.trichodea type ?,s.trichodea curvatum,s.cylindrical,s.placodae,s.basiconica,s.campaniformia,and Bohm bristles,were found on the antennae of both female and male.The distribution,morphology and internal structure of C.chilonis antennal sensilla were described,besides the difference between sexes was analyzed.There is pronounced sexual dimorphism in antennal size in C.chilonis.These results provide a theoretical basis for olfactory perception behavior of parasitoids.The antennal transcriptome of C.chilonis female and male adults were sequenced by Illumina Hiseq technology.Approximately 0.332 billion totals raw reads and about 0.316 billion total clean reads were obtained,and then 53,100 unigenes were assembled.The 32,212 unigenes could be annotated in the National Center for Biotechnology Information(NCBI)nr database.Among the annotated unigenes,13,854and 13,023 unigenes could be assigned to gene ontology(GO)and Clusters of orthologous groups of proteins(COG),respectively.Additionally,26,865 unigenes could be annotated in the Swiss-port database,and 25,312 unigenes could be mapped in the Kyoto encyclopedia of genes and genomes(KEGG)pathway database.For protein coding region prediction analysis,the number of coding sequence(CDS)that mapped the protein database is 32,074,and the number of predicted CDS is 1,142.The total number of CDS and simple sequence repeats(SSR)is 33,216 and 34,649,respectively.Totally,6 unigenes related to odorant binding protein(OBPs),734 to odorant receptor(Ors),and 30 to sensory neurron membrane protein(SNMPs)were found to be involved in chemo-detection,while 59 to cytochrome(P450s),48 to esterases,12 to glutathione-s-transferases(GSTs),39 to alcohol oxidase/aldehyde dehydrogenase(ALOXs/ALDHs),and 51 to alcohol oxidase/alcohol dehydrogenase(AOXs/ADHs),were involved in odorant degradation.There were 2 unigenes related to OBPs,21 to ORs,1 to SNMPs,6 to P450s,1 to ALOXs/ALDHs,and 5 to AOXs/ADHs,differently expressed in female and male antennae of C.chilonis.Hierarchical cluster analysis represents gender specific expression of odorant related genes.Further phylogenetic analysis clustered odorant related genes into four groups,which showed that odorant receptor genes were evolved through convergence.This is the first time to observe the ultra-structure and sequence the antennal transcriptome of female and male adults of C.chilonis.Our findings make an important contribution to genetic resources for future studies of C.chilonis and odorant-sensory system in parasitoid wasps.