Ber not for citation purposes)BMC Evolutionary Biology 2007, 7:http://www.biomedcentral.
Ber not for citation purposes)BMC Evolutionary Biology 2007, 7:http://www.biomedcentral.com/1471-2148/7/activity in Culex quinquefasciatus and Aedes aegypti, but not in A. gambiae [17]. However, Syt I is also edited in mosquitoes, sharing two editing sites with Drosophila species, and one mosquito-specific site [25]. This suggests that adenosine deaminase functions in the Anopheles lineage, as in Drosophila. A comparative sequence analysis of these species showed that the exon 5 was highly conserved at both the nucleotide and amino acid level among these species (Figure 5), but the flanking intronic sequences were highly divergent. The downstream intron 5 was extraordinarily short in length, 97 bp, in A. gambiae, while it was > 1 kb in Drosophila, > 4 kb in B. mori, > 2 kb T. castaneum, and > 30 kb in A. mellifera, respectively (Figure 7A). Likewise, the upstream intron 4 was also extraordinarily short, 94 bp, in A. gambiae, while it was much more than 1 kb in the other insect species (Figure 7A). The absence of editing in Anopheles correlated with the lack of downstream intronic sequences, which were necessary to direct editing by forming duplex RNA substrates for ADARs within larger, energetically stable RNA secondary structures. Similarly, sequential decrease and loss of editing in A. gambiae, through weakening of the ECS-editing site interaction to form poorer duplex RNA substrates for ADARs, could PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/27486068 titrate in the edited form of the protein to the least advantageous level, or even an undetectable level. RNA editing conserved between the orders Diptera and Lepidoptera for one nAChR gene was previously considered an example of convergent evolution [17]. However, our phylogenetic analysis of RNA editing in orthologous nAChR SKF-96365 (hydrochloride) site alpha6 genes from different species revealed a divergent evolution from a common ancestor. Moreover, this implies that divergent evolution from a common ancestor would have been accompanied by editing loss or gain in paralogous genes. We suggest that the data presented here comprise a credible phylogeny of RNA editing for a gene, graphically illustrating descent with modification (Figure 7A). RNA editing in insect nAChR subunit alpha6 genes predates at least the radiation of the Coleopteranand Hymenopteran orders, beginning with sites 5 and 10. New editing sites were probably generated and ancestral editing sites were lost in subsequent evolution through global intronic variation (Figure 7A). Our evidence suggests that Anopheles lost editing in the nAChR alpha6 gene during the evolution of the Diptera; such a loss might be consistent with the phylogenic evolution of the introns. The nAChR alpha6 genes possess tandem duplication of coding exons in their genomic sequences in insect species, which represents alternative spliced exons. Dating exon duplications through a combination of the available experimental data on alternative splicing in orthologous genes from different species and computational analysis indicated that the exon 3 and 8 duplications predated at least the radiation of insect ordersspanning 300 million years of evolution. Our results disproved the previous hypothesis that a duplication event gave rise to exon 8b and 8c before the divergence of an ancestor of Drosophila and Anopheles, whereas after the divergence PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28212752 a further duplication gave rise to an extra exon (exon 8a) in the Drosophila lineage [17]. However, our evidence suggests the possibility that divergent evolution from a common ancestor was ac.
