以粒線體DNA及乳酸去氫 酉每 基因研究盲鰻的親緣關係與演化

Molecular phylogeny and evolution of hagfish based on mtDNA and lactate dehydrogenase genes

郭建賢(Chien-Hsien Kuo)

指導教授 ： 李信徹 ； 黃生 ； 施河

國立臺灣師範大學/理學院/生物學系/博士(2000年)

摘要

無資料

關鍵字

盲鰻 ； 乳酸去氫 酉每 ； 親緣關係 ； 演化 ； 脊椎動物

並列摘要

Abstracts
The study included molecular phylogeny of hagfish and evolution of lactate dehydrogenase. The mitochondrial DNA sequences from the large ribosomal RNA gene may be of great value for systematic and phylogenetic studies within families. Partial sequences of the 16S rRNA gene were obtained for comparisons among the following hagfish species, Paramyxine nelsoni, P. sheni, P. taiwanae, P. yangi, P. cheni, Eptatretus burgeri, E. stouii, E. cirrhatus, Myxine glutinosa, M. formosana, M. circifrons, M. sp1 and M. sp2. The boundary of first four Paramyxine species from 16S rRNA sequences is ambiguous; however, they are valid based on our further unpublished isozyme data as well as the gill aperture arrangement pattern. The present molecular data show that the genus Paramyxine is polyphyletic. Eptatretus and Paramyxine form a clade, but their included species can be grouped separately into two different subfamilies, the Myxininae and Eptatretinae. The phylogenetic pattern is not congruent with the number of branchial pouches or branchial apertures proposed by Nelson (1994) and Fernholm (1998), who addressed the evolutionary trend of hagfish as being from polybranchiates to monobranchiates and with all hagfish belonging to a monophyletic group. Furthermore, the larger genetic distance between P. cheni and the other Eptatretinae species suggest that P. cheni could be as a basal taxa in Eptatretinae. A new genus and species of Rubicundus oligoporos collected from the northeastern coast of Taiwan is described here. Rubicundus is distinguished by pink body coloration. Rubicundus oligoporos is a five-gilled species with a three-cusp multicusp on the anterior rows and a two-cusp one on the posterior rows. The putative taxonomic position of Rubicundus is discussed based on mitochondrial 16S rRNA gene fragment sequences.
In order to understand the expression of the multiple LDH isozymes in aves, the brain, eye, heart, liver, muscle, and testis were analyzed. Horizontal starch gel electrophoresis was used to examine isozymes of L-lactate dehydrogenase in 4 families and 7 genera of lizards and 33 aves species assigned to 6 orders. Like all other vertebrates, bords possess 2 fundamental LDH loci (LDH-A and LDH-B). A LDH-C product of the third locus was detected in only 8 species of birds and 4 lizards and, for the first time, was reported from the Passeriformes and lizards. The results of this study and those of other previous research suggest that avian LDH-C, reptile LDH-C, and mammalian LDH-C may be orthologous, and may have been derived from ancestor amniote LDH-A.
The present study has determined a cDNA sequence of LDH-A from the muscle of hagfish, it contains 1428 nucleotides including a protein-encoding sequences of 1026 nucleotides, the 5’(54 nucleotides) and 3’ (342 nucleotides) untranslated region.
The hagfish LDH-A protein that we deduced from the nucleotide sequence is 341 amino acids long. Compared to the other vertebrate LDH, the sequence added 8 amino acids in the low hydrophobicity region at position 220-227. Hagfish LDH unique 9 positions exhibit alternative amino acid those conserved in all vertebrates. None of the alternative amino acids positions makes up the active center. Of the 10 positions that are diagnostic for LDH-A versus LDH-B in the gnathostome vertebrate examined, the hagfish LDH-A sequence resemble LDH-A at four, LDH-B at two, and neither at four. Hagfish LDH, like that of the all vertebrate LDH-As is also missing an amino acid at the penultimate position. The hagfish sequence, with its greater similarity to chordate LDH-A sequence in this region, provides additional evidence that the amino acid was added in the common ancestor of LDH-Bs. Our phylogenetic conclusions that LDH of hagfish muscle is a ancestral LDH-A and the lamprey single locus condition is due to gene loss. Both distance and maximum parsimony analysis strongly reject a relationship of hagfish LDH-A with lamprey LDH.

並列關鍵字

hagfish ； lactate dehydrogenase ； phylogeny ； evolution ； vertebrate

參考文獻

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