利用rDNA和ITS序列对1株裸甲藻的初步鉴定

测定了 1株分离自青岛胶州湾海水样品、从形态上初步确定为裸甲藻属 (Gymnodiniumsp,编号为 GYN- 1 5)的核糖体基因 (r DNA)和转录单元内间隔区 (Internal Transcribed Spacer,ITS)序列 ,并利用该序列对该藻进行了初步鉴定。测定的序列长 2 658bp,涵盖了小亚基 (smallsubunit,SSU) r DNA基因 3'端 1 747bp,ITS1 - 5.8S r DNA- ITS2全长和大亚基 (large subunit,LSU) r DNA基因 5'端 337bp。同源性分析该序列发现 GYN- 1 5与共生甲藻属 (Symbiodinium)中的 2个种 (Symbiodinium californium和 Gymnodinium varians)的对应序列具有很高的相似性 ;3株藻的各段 r DNA和 ITS序列的相似性均为 99%以上 ;以 SSU r DNA序列中的 3个可变区 (V1 V2 V3)和邻接法构建的系统树表明 ,GYN- 1 5与 S.californium和 G.varians构成 1个独立的新的子类群 ,该子类群属于共生甲藻属 ,而与各种裸甲藻的亲缘关系较远。根据这些结果可将GYN- 1 5初步鉴定为属于共生甲藻属。鉴于 GYN- 1 5和其它 2个种所构成的分支明显与 5个已知的子类群 (A,B,C,D,E)不同 ,因此将该分支命名为子类群 F。

The Preliminary Identification of an Isolation of Gymnodinium sp.Using the rDNA and ITS Sequences

Sequence of the rDNA and ITS regions from Gymnodinium sp. (GYN-15), which was isolated from the sea water collected at Jiaozhou Bay, Qingdao, and was preliminarily identified as Gymnodinium sp. based on its morphological features, was sequenced, and was used to identify further GYN-15. The total DNA and ITS sequence from GYN-15 was 2 658 bp in length, spanning 1 748 bp of the 3' end of the SSU rDNA, the complete sequence of the ITS1-5.8S rDNA-ITS2 region, and 336 bp of the 5'end of the LSU rDNA. The BLASTn results showed that GYN-15 was closely related to two strains within Symbiodinium (S. californium and Gymnodinium varians).Sequence comparison showed that the similarities among each part of the sequences from these three strains were all above 99%. Phylogenetic reconstruction with the Neighbor-joining (NJ) method using sequences of variable regions (V1 V2 V3) of SSU rDNA indicated that GYN-15, S. californium and G. varians formed a new clade in Symbiodinium, which was apartly related to the included Gymnodinium species. Based on these results, it was suggested that GYN-15 might be clustered into the genus Symbiodinium. In addition, the branch formed by GYN-15 and other two Symbiodinium strains was named as the novel Clade F because it was evidently different from the other known five clades (A, B, C, D, E).