原始腹足目四物種之粒線體基因組

Abstract

本研究利用長片段聚合酶連鎖反應及引子延伸定序技術，建立四種原始腹足目物種之粒線體基因組，分別為瘤珠螺 (Lunella granulata (Gmelin, 1791))、白星螺 (Astralium haematragum (Menke, 1829))、黑鐘螺 (Chlorostoma argyrostoma (Gmelin, 1791)) 及臍孔黑鐘螺 (Omphalius nigerrima (Gmelin, 1791))。此四物種之粒線體基因組大小介於 16,310 - 17,780 個鹼基對之間，各基因組中包含13個蛋白質轉譯基因 (protein-coding gene)、2個核醣體RNA (ribosomal RNA)，以及21個轉移RNA (transfer RNA)。相較於大部分動物界物種，此四種物種之粒線體基因組缺乏tRNAGlu基因，在所知之腹足綱粒線體基因組中，此為第一個被發現基因缺失 (gene lack) 之狀況。此四種新粒線體基因組之基因間隔區 (intergenic spacer) 較其他腹足綱物種粒線體基因組為大。相似於新進腹足目之物種，其調控區 (control region) 辨識困難。比較其與其他腹足綱物種粒線體基因組之基因排列差異，發現其基因排列位置除了少數tRNA外，皆相似於同為原始腹足目之物種黑鮑 (black lip abalone, Haliotis rubra)、頭足綱之真蛸 (common octopus, Octopus vulgaris) ，及多板綱之黑肉石鱉 (black katy chiton, Katharina tunicata)。同為鐘螺超科 (Trochoidea) 之鐘螺科 (Trochidae) 與蠑螺科 (Turbinidae) 物種，其tRNAThr之相對位置不同。最後，以現有粒線體基因組建立腹足綱之親緣關係樹，發現原始腹足目為一單系群，並與新進腹足目為姊妹群。然而，原始腹足目之粒線體基因組研究仍十分不足，未來需要更多的探究與討論。

Long PCR and primer walking method were used to acquire the whole mt genomes of 4 vetigastropod species, Lunella granulata (Gmelin, 1791), Astralium haematragum (Menke, 1829), Chlorostoma argyrostoma (Gmelin, 1791), and Omphalius nigerrima (Gmelin, 1791). The gene order of four mt genomes were compared with other mt genomes of gastropods. The phylogenetic analyses with other gastropods were also taken. The size of these mt genomes is approximately 16,310-17,780 bp and they contain 13 protein-coding genes, 2 ribosomal RNAs and 21 transfer RNAs, respectively. Compared with most animal mt genomes, the tRNAGlu gene is missing in these four species of. This result is the first report of gene lack in gastropods. The intergenic spacers of these four mt genomes are larger than those of other gastropods, while, the recognition of control regions in these four mt genomes was difficult. Their gene arrangements are similar to that of black lip abalone (Haliotis rubra), common octopus (Octopus vulgaris) and black katy chiton (Katharina tunicata) with a few differences in transfer RNAs. In Trochoidea, the tRNAThr gene is located in different places in the mt genome of the species from Trochidae and Turbinidae. Phylogenetic analyses based on four mt genomes derived in this study and that of H. rubra showed that the Vetigastropoda forms a monophyletic group and is a sister group to Caenogastropoda. Since studies on mt genomes of Vetigastropoda are still very limited, more genomic data are needed to reveal their phylogenetic relationships in the future.