Pecher Wolf T, Robledo José A F, Vasta Gerardo R
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, University of Maryland, Baltimore, Maryland 21202, USA.
J Eukaryot Microbiol. 2004 Mar-Apr;51(2):234-45. doi: 10.1111/j.1550-7408.2004.tb00553.x.
Perkinsus species are parasitic protozoa of mollusks, currently classified within the Perkinsozoa, a recently established phylum that is basal to the Apicomplexa and Dinozoa. Ribosomal RNA (rRNA) genes and their intergenic spacers have been used to support the taxonomy of Perkinsus species, the description of new species, and to develop molecular probes for their detection and identification. We previously described ultrastructure, behavior in culture, and partial sequence of the rRNA locus of a Perkinsus species isolated from the baltic clam Macoma balthica. The rRNA genes and intergenic spacers of this Perkinsus isolate differed from those described in the currently accepted species to a degree that led to its designation as a new species, Perkinsus andrewsi. In this study, we identify an additional rRNA gene unit (rRNA-B) in the P. andrewsi holotype, and report the complete sequences of both rRNA gene units. Except for the 5.8S, all regions of the rRNA-B gene unit exhibited sequence differences from that initially described (rRNA-A). Each rRNA gene unit is arranged in a "head-to-tail" tandem repeat. This is the first report demonstrating two distinct rRNA units in a Perkinsus species.
派金虫属物种是软体动物的寄生原生动物，目前归类于派金虫门，这是一个最近建立的门，位于顶复门和恐龙虫门的基部。核糖体RNA（rRNA）基因及其基因间隔区已被用于支持派金虫属物种的分类学、新物种的描述，并开发用于其检测和鉴定的分子探针。我们之前描述了从波罗的海蛤仔Macoma balthica分离出的一种派金虫属物种的超微结构、培养行为以及rRNA基因座的部分序列。这种派金虫分离株的rRNA基因和基因间隔区与目前公认物种中描述的有所不同，程度足以使其被指定为一个新物种，即安德鲁派金虫（Perkinsus andrewsi）。在本研究中，我们在安德鲁派金虫模式标本中鉴定出一个额外的rRNA基因单元（rRNA-B），并报告了两个rRNA基因单元的完整序列。除了5.8S外，rRNA-B基因单元的所有区域与最初描述的（rRNA-A）都存在序列差异。每个rRNA基因单元以“头对尾”的串联重复形式排列。这是首次报道在派金虫属物种中存在两个不同的rRNA单元。
