| Mosquitoes spread many diseases, and its behavior is largely dependent on the olfactory system, such as seeking hosts, mating, and selecting oviposition site. Mosquito’s olfactory organ are mainly antennae, maxillary palps which usually contain different kinds of olfactory proteins, including chemosensory proteins(CSPs), olfactory receptors(Ors) and odorant binding proteins(OBPs). OBPs are considered one of the most important factors in transmitting the olfactory signals.By the application of bioinformatics, many OBPs have been identified from whole genome, especially the finishing of genome sequencing of mosquitoes such as Anopheles gambiae, Aedes aegypti, Culex pipiens quinquefasciatus, Anopheles stephensi. So far, little is known about the olfactory signal transmission of An. Sinensis. In this study, Anopheles sinensis as the research object, from the genome and transcriptome level of odorant binding proteins were analyzed and studied. The main results presentas follows:1. As a result, a total of 64 OBP genes were identified in An. sinensis. The candidate OBP genes were named as As OBP1-72 based on their homology with An. gambiae OBP genes. 6 genes have 2-6 duplications in An. sinensis genome. One gene in An. sinensis, named as As OBP73, has no homologous sequence in An. gambiae. The molecular weights of these An. sinensis OBP genes are 12.27-52.2 k Da. The isoelectric points of An. sinensis OBP genes range from 4.37 to 8.18, and the signal peptides are 1-32 amino acids. These An. sinensis OBPs were classified into 3 subfamilies, and 37, 15 and 12 genes were grouped into the subfamily Classic, Atypical and Plus-C, respectively.2. The 64 odorant binding protein genes of An. sinensis per gene on average has 1-5 exons and these genes have a total of 85 introns. The intron sizes ranged from 36 to 1, 967 bp(mean 149.6 bp, median 79 bp). The intron phase of An. sinensis odorant binding protein genes mainly in the following three categories: phase 0, phase 1 and phase 2. And most introns are phase 0.3. The genomic organization analysis revealed that 64 OBP genes were distributed across 15 different scaffolds in An. sinensis. Out of them, 43 genes were distributed into 10 clusters of 2-8 genes each. The clusters of most OBP genes of An. sinensis showed similarity and their locations corresponded to that of An. gambiae. Eight genes(OBP23-28, OBP63-64) of cluster 9 are distributed in 3.6 Kb of genomic region on Scaffold5, and correspond to 8 genes with same names and distribution in An. gambiae,Cx. Quinquefasciatus and Ae. Aegypti. These genes have high similarity with each other, which suggest that they might originate from a single gene through a series of historic duplication events at least before divergence of Anopheles, Culex and Aedes.4. From the results of phylogenetic tree, OBPs formed into 3 large clades: subfamily Classic, Atypical and Plus-C, respectively, corresponding to An. gambiae. Interestingly, the OBP70 and OBP71 of An. gambiae were classified to the subfamily Classic through phylogenetic analysis. These 2 genes were subsequently classified to the subfamily Plus-C without including them in the constructed phylogenetic tree, and the group Obp59 a only included a unique gene OBP29. Our research supported the former, and grouped the 2 genes to Obp59 a with 77% of bootstrap support. These two genes have 6 typical conserved cysteines and spaces. Therefore, these genes belong to the group Obp59 a of subfamily Classic. Similarly, the OBP69 was classified in the subfamily Atypical. |
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