| Adelphocoris suturalis Jakovlev(Hemiptera: Miridae) is an insect pest on cotton, which has a wide host range. In recent years, with the large-scale cultivation of Bt cotton, the lepidopteran pests have been controlled effectively. However, due to a substantial reduction in the use of broad-spectrum insecticides, minor pests such as A.suturalis emerged as major pests in cotton field and caused severe economic damages to many other crops such as beans, alfalfa and wheat.Olfaction is very important in the survival and reproduction of insects. They use their specific chemosensory system to detect the chemical signals in the environment. Through a complex process of smell identification, insects would have some behavioral responses such as forgaging, mating and oviposition. There are many types of proteins participate in the process of smell identification, including odorant bingding proteins(OBPs), odorant degrading esterases(ODEs) and odorant receptors(ORs).In this study, we sequenced and analyzed the A. suturalis antennal transcriptome using Ion Proton? sequencing and identified 16 novel OBP genes, 8 CSP genes, 24 OR genes, 19 IR genes and 3 co-receptors(ORco, IR25 a and IR8a). For the identified 16 OBPs, 12 belong to classical OBP and four are Plus-C OBP. Through the research of expression features, we found that 13 of the 16 OBP transcripts were highly expressed in the antennae of both sexes, and 4 OBPs were expressed higher in the male antennae compared to the female antennae. Five CSPs were expressed specifically in antennae. These OBPs and CSPs genes expressd specifically in the antennae may play an important role in the sense of smell, and the male antennae specific OBPs may be closely related to the detection of pheromone.Using PCR technology, the gene structure of ORco, which inluding six introns in A. suturalis, A. lineolatus, A. fasciticollis, A. lucorum and L. pratensis are acquired. Although the sequences of introns are variable, the location and length are conserved. A. suturalis, A. lineolatus, A. fasciticollis belong to Adelphocoris. The position and length in them are very similar, particularly in A.lineolatus and A. fasciticollis. However, the introns in A. lucorum and L. pratensis are somewhat different from the other three insects. This result is corresponded to the result of neighbour joining tree. It reveals that, the analysis of gene structure can help us to conduct the evolutionary research among different insects, and that the ORco gene is very conservative among insects in the same genus.The sequence characteristics and expression patterns of three co-receptors(ORco, IR25 a and IR8a) were studied. Multiple alignments of amino acid sequences revealed that the three co-receptors of A. suturalis were very conserved among different insects but there are still some difference. The results of qRT-PCR revealed that the three co-receptors expressed mainly in the antennae of A. suturalis. We knocked down the three co-receptor genes by RNAi, and the qRT-PCR results indicated that 24 h after siRNA injection, the expression levels of AsutORco, AsutIR25 a and AsutIR8 a reduced 45.5%, 43.5% and 36.9% respectively. The verification experiments of electrophysiology and behavior are in progress.In this study, we conducted a preliminary research on gene structure and expression profiles of three co-receptors(ORco, IR25 a and IR8a) in A. suturalis, which provides foundations for the deep understanding of insect olfactory recognition and technical support for the research of insect behavior regulators. |
PDF Full Text Request