Study On Population Genetics Of Rna-based Gene Duplicates For Caenorhabditis Sp.5

RNA-based gene duplicates (retrocopies) played pivotal roles in many physiological processes. Retroposition is a cellular molecular process in which transcribed and spliced mRNAs are fortuitously reverse-transcribed and inserted into new genomic positions to form a retrogene. Nowadays, functional retrocopies have been systematically identified in several mammals, fruit flies, plants and zebrafish, etc. However, studies about this kind of duplication in Caenorhabditis nematodes have not been reported.C. sp.5is an obligately outbreeding species discovered in China. Like other Caenorhabditis, C.sp.5is a small, transparent nematode amenable to laboratory culture. C.sp.5holds an important position for analyses of molecular evolution and comparative phenotypic analysis based on C. briggsae. However, little is known about the scope of genetic diversity and differentiation within such gonochoristic species, especially those found commonly in eastern Asia.1.In this study, we focused on the study of featured species C.sp.5. Phylogenetic analyses of the concatenated sequences using maximum likelihood (ML) and Bayesian inference (BI), in the nematodes, C. japonica was in the furthest of the genetic relationship. C. elegans was in the base position, C.sp.5and C. briggsae, which were formed as sister group,was located in the top of the tree, and then was close to C. remanei, and was gather with C. brenneri.2. To further understand the selective pressure acting on C.sp.5and to examine possible differences in the evolutionary dynamics among C.sp.5retrocopies, we use branch-site models along with the estimated time-scale of C sp.5phylogeny. Our results showed that:(1) those model reveals that none of retrocopies were under positive selection, further experiments should pay more attention to these sites, in order to find function retrocopies;(2) positive selection has played a dominant role during C.sp.5evolution. This research indicated that cause of the particular structures of such retrogenes lead them may have much more positive sites than another genes in Caenorhabditis genomes. These findings illustrate that molecular population genetic approaches to studying obligately outbreeding species of Caenorhabditis will prove powerful in identifying and characterizing functionally and evolutionarily important features of the genome.3. We amplified the chmeric genes sequences of C.sp.5. The content of (A+T) is56.4%,(G+C) is43.6%, the bases are puite partial abnormal,13haplotypes were defined by using the software DnaSP, haplotype diversity are from0.8701to0.991, nucleotide diversity (Pi) are from0.01085to0.08006, Phylogenetic analyses of the concatenated sequences according to Neighbor-Joining (NJ) and Maximum Parsimony (MP). Among the3geographical populations, which individuals Hubei, Sichuan, Guangzhou, show that the C.sp.5abundant genetic diversity.4. The result of median-joining network and the mismatch distribution did not detect any disjoint groups corresponding to the the chmeric genes, suggesting that genetic differentiation among the different C.sp.5populations do not occur. No obvious geological architecture was detected in the population of C. sp.5.It suggests that the gene flow of this population is very frequent. This may be related to its small size, free-living habit,and conveniented for the phoresy by the invertebrates such as isopods.