Interaction of olfactory receptor (OR) genes with environmental odors is regarded as the first step of olfaction.In this study,OR genes of two fish,medaka (Oryzias latipes) and stickleback (Gasterosteus aculeatus),were identified and an evolutional analysis was conducted.The selection pressure of different TM regions and complete coding region were compared.Three TM regions (TM4,TM5 and TM6) were found to have higher average Ka/Ks values,which might be partly caused by positive selection as suggested by subsequent positive selection analysis.Further analysis showed that many PTSs overlap,or are adjacent to previously deduced binding sites in mammals.These results support the hypothesis that binding sites of fish OR genes may evolved under positive selection.
CHEN Ming1,2,PENG ZuoGang1 & HE ShunPing1 1 Laboratory of Fish Phylogenetics and Biogeography,Institute of Hydrobiology,Chinese Academy of Sciences,Wuhan 430072,China
鲤科鱼类在东亚分布广泛且数量丰富,在物种演化上具有重要的系统发育地位.本研究基于S6K1基因5′端功能调控序列,通过PCR扩增、克隆和测序,共获得30种鱼类S6K1前端部分DNA序列(外显子1,外显子2及内含子1),对序列变异进行分析,并采用邻接法(NJ)、最大简约法(MP)、最大似然法(ML)和贝叶斯法(Bayesian)重建鲤科鱼类系统发育关系.亚口鱼科的胭脂鱼(Myxocyprinus asiaticus)作为外类群,通过4种方法所得系统发育分支图大致相同,均以较高的节点支持率支持雅罗鱼系和鲃系的划分,雅罗鱼系包括雅罗鱼亚科东亚类群(East Asian group in Leuciscinae)、鲢亚科(Hypophthalmichthyinae)、鲴亚科(Xenocyprinae)、鲌亚科(Cultrinae)、亚科(Gobioninae)、鳑鲏亚科(Acheilognathinae)和亚科(Danioninae)部分种类;系统分支图也以较高的节点支持率支持鲤科鱼类东亚类群形成单系群.鲃系包括裂腹鱼亚科(Schizothoracinae)、鲃亚科(Barbinae)、鲤亚科(Cyprininae)和野鲮亚科(Labeoninae);另外,亚科中的斑马鱼(Danio rerio),麦氏(Danio myersi)和三线波鱼(Rasbora trilineata)形成一个单系群,位于系统树基部.以内含子1中大片段的插入或缺失(Indel)对物种分化及亲缘关系进行分析,以帮助理解鲤科鱼类系统发育关系或争议物种之间的亲缘关系.结果显示,内含子1中大片段的插入或缺失与物种分化具有一定的相关性,对于理解系统发育关系具有补充作用;内含子1中有许多区域较为保守,可能与功能调控有关,但本研究中并未发现S6K1序列变异与鱼类物种特征尺寸之间具有对应关系.
金线鲃属分布于中国云贵高原及周边地区,包括10多种适应于洞穴生活、具有不同程度眼睛和色素退化的典型洞穴鱼类.迄今为止,金线鲃属的系统发育关系还存在很大争议.我们获得了34种金线鲃属鱼类及外类群的细胞色素b和ND4基因序列,用贝叶斯联合模型分析数据,重建了金线鲃属的系统发育关系;并用松散分子钟估算了本属及内部分支的起源时间.金线鲃属的单系性得到强烈的支持,本属可分为6个分支.此外,本研究结果还支持洞穴物种的多系起源假说以及季氏金线鲃(Sinocyclocheilus jii)的基部位置.松散分子钟估算表明,金线鲃属起源于晚中新世,在11百万年前(million years ago,Ma)左右,比以前设想的要古老.
The insulin receptor (IR) gene plays an important role in regulating cell growth,differentiation and development.In the present study,DNA sequences of insulin receptor genes,IRa and IRb,were amplified and sequenced from 37 representative species of the Cyprinidae and from five outgroup species from non-cyprinid Cypriniformes.Based on coding sequences (CDS) of tyrosine kinase regions of IRa and IRb,molecular evolution and phylogenetic relationships were analyzed to better understand the characteristics of IR gene divergence in the family Cyprinidae.IRa and IRb were clustered into one lineage in the gene tree of the IR gene family,reconstructed using the unweighted pair group method with arithmetic mean (UPGMA).IRa and IRb have evolved into distinct genes after IR gene duplication in Cyprinidae.For each gene,molecular evolution analyses showed that there was no significant difference among different groups in the reconstructed maximum parsimony (MP) tree of Cyprinidae;IRa and IRb have been subjected to similar evolutionary pressure among different lineages.Although the amino acid sequences of IRa and IRb tyrosine kinase regions were highly conserved,our analyses showed that there were clear sequence variations between the tyrosine kinase regions of IRa and IRb proteins.This indicates that IRa and IRb proteins might play different roles in the insulin signaling pathway.
The family Cyprinidae is widely distributed in East Asia, and has the important phylogenetic signifi- cance in the fish evolution. In this study, the 5′ end partial sequences (containing exon 1, exon 2 and indel 1) of S6K1 gene were obtained from 30 representative species in Cyprinidae and outgroup using PCR amplification and sequencing. The phylogenetic relationships of Cyprinidae were reconstructed with neighbor joining (NJ), maximum parsimony (MP), maximum likelihood (ML), and Bayesian meth- ods. Myxocyprinus asiaticus (Catostomidae) was assigned to the outgroup taxon. Similar phylogenetic relationships within the family Cyprinidae were achieved with the four analyses. Leuciscini and Barbini were monophyletic lineages respectively with the high nodal supports. Leuciscini comprises Hy- pophthalmichthyinae, Xenocyprinae, Cultrinae, Gobioninae, Acheilognathinae and East Asian species of Leuciscinae and Danioninae. Monophyly of East Asian clade was supported with high nodal support. Barbini comprises Schizothoracinae, Barbinae, Cyprininae and Labeoninae. The monophyletic lineage consisting of Danio rerio, D. myersi, and Rasbora trilineata was basal in the tree. In addition, the large fragment indels in intron 1 were analyzed to improve the understanding of Cyprinidae relationships. The results showed that the large fragment indels were correlated with the relations among species. Some conserved regions in intron 1 were thought to be involved in the functional regulation. However, no correlation was found between sequence variations and species characteristic size.
KONG XiangHui1,2, WANG XuZhen1, GAN XiaoNi1, LI JunBing1 & HE ShunPing1 1 Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
A PCR survey for Sox genes in a young tetraploid fish Tor douronensis (Teleostei:Cyprinidae) was per-formed to access the evolutionary fates of important functional genes after genome duplication caused by polyploidization event. Totally 13 Sox genes were obtained in Tor douronensis,which represent SoxB,SoxC and SoxE groups. Phylogenetic analysis of Sox genes in Tor douronensis provided evidence for fish-specific genome duplication,and suggested that Sox19 might be a teleost specific Sox gene member. Sequence analysis revealed most of the nucleotide substitutions between duplicated copies of Sox genes caused by tetraploidization event or their orthologues in other species are silent substitutions. It would appear that the sequences are under purifying selective pressure,strongly suggesting that they repre-sent functional genes and supporting selection against all null allele at either of two duplicated loci of Sox4a,Sox9a and Sox9b. Surprising variations of the intron length and similarities of two duplicated copies of Sox9a and Sox9b,suggest that Tor douronensis might be an allotetraploidy.
