Barbrook Adrian C, Visram Shakil, Douglas Angela E, Howe Christopher J
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
Protist. 2006 Jun;157(2):159-71. doi: 10.1016/j.protis.2005.12.002. Epub 2006 Apr 17.
Dinoflagellate algae of the genus Symbiodinium are important symbionts within corals and other benthic marine animals. The molecular diversity of Symbiodinium has been described mainly by use of ribosomal DNA sequence data. We tested whether minicircle sequences, which appear to form the chloroplast genome in many dinoflagellates, could be used as a marker for molecular diversity among symbionts found in corals and sea anemones. Partial and full-length sequences for psbA were obtained from environmental samples of coral and sea anemones of wide-ranging geographical distribution. Phylogenetic trees constructed with partial psbA sequences were consistent with the known phylotypes of the isolates. Further sequencing suggested that the psbA gene is present on a minicircle in all Symbiodinium phylotypes. The length and DNA sequence of the non-coding portion of the minicircles varied considerably among Symbiodinium phylotypes. In two Symbiodinium isolates from different phylotypes an elaborate pattern of repeat sequences of unknown function was found in the non-coding region. Phylogenetic analysis of the non-coding region of the psbA minicircle indicates that minicircle sequences could be a useful chloroplast-derived marker for differentiating both closely related and distantly related Symbiodinium isolates.
共生藻属的甲藻是珊瑚和其他底栖海洋动物体内重要的共生体。共生藻的分子多样性主要通过核糖体DNA序列数据来描述。我们测试了在许多甲藻中似乎构成叶绿体基因组的微环序列，是否可作为珊瑚和海葵中共生体分子多样性的标记。从地理分布广泛的珊瑚和海葵环境样本中获得了psbA的部分和全长序列。用部分psbA序列构建的系统发育树与已知分离株的系统型一致。进一步测序表明，psbA基因存在于所有共生藻系统型的微环上。微环非编码部分的长度和DNA序列在共生藻系统型之间差异很大。在来自不同系统型的两个共生藻分离株中，在非编码区发现了一种功能未知的复杂重复序列模式。对psbA微环非编码区的系统发育分析表明，微环序列可能是一种有用的源自叶绿体的标记，可用于区分亲缘关系近和远的共生藻分离株。
