尖毛虫属Actin Ⅰ、α-TBP和DNA pol α乱序基因的模式研究

EVOLUTION OF THE SCRAMBLED PATTERN OF THE ACTIN Ⅰ, Α-TBP AND DNA POL Α GENE WITHIN THE GENUS OXYTRICHA (PROTOZOA, CILIATES)

  • 摘要: 研究旨在对尖毛虫属内现有物种的3种乱序小核基因结构进行比较,探讨其乱序模式。于湛江湖光红树林水域中采集到一个尖毛虫属物种Oxytricha sp.(ZJ),成功扩增了其肌动蛋白Ⅰ(ActinⅠ)、端粒结合蛋白(α-TBP)、DNA聚合酶α(DNA pol α)3个乱序基因的完整大核基因序列和完整/部分小核基因序列,并结合已有资料对比研究了尖毛虫属这3个乱序基因的进化。结果表明:(1)Oxytricha sp.(ZJ)与O.nova的小核Actin Ⅰ基因具有相同的乱序模式,区别于其余的尖毛虫属物种;在增加尖毛虫属物种的基础上,对前人推测提出了质疑,我们认为MDS-IES接合处移动现象在乱序MDSs之间并非比非乱序MDSs之间更保守。(2)Oxytricha sp.(ZJ)与O.nova的小核α-TBP基因具有相同乱序模式和相似长度的IESs。(3)Oxytricha sp.(ZJ)的小核DNA pol α基因乱序模式,区别于任一已报道物种,与属内O. trifallax最为相近。基于序列分析,在DNA pol α基因中发现了一例IES转换为MDS的痕迹,以及由此导致原先MDS的丢失。研究发现在编码区内IES向MDS的转变,使得本应删除的序列成为基因组永久保留的一部分。

     

    Abstract: Genes in the germline (micronuclear) genome of protozoan ciliates are interrupted by multiple, non-coding sequences called internal eliminated segments (IESs) and macronuclear destined segments (MDSs). In the micronucleus, the MDSs are not arranged sequentially but scrambled for some genes. Studying scrambled gene structures will provide a better understanding of the molecular mechanisms of its evolution. In this study, we compared the complete macronuclear gene sequences and complete/incomplete micronuclear gene sequences of Actin I, α-telomere-binding protein (α-TBP), and DNA polymerase α (DNA pol α) of Oxytricha species (Oxytricha sp. (ZJ)) collected from water samples of Huguang mangrove in Zhanjiang with those of other Oxytricha species, and had 3 major findings. The scrambled patterns of the micronuclear Actin I gene in O. sp. (ZJ) were similar with those of O. nova, but shown significant differences with other species in genus Oxytricha. We revealed that the shifts of MDS-IES junctions between scrambled MDSs are not more conservative than those between non-scrambled MDSs, which is inconsistent with a previous study. The scrambled pattern of micronuclear α-TBP gene in O. sp. (ZJ) is same with that of O. nova, and the lengths of their IESs of these two species are also similar. The scrambled pattern of micronuclear DNA pol α gene in O. sp. (ZJ) is different from any of the previously reported species, and it is only somewhat similar to O. trifallax. Moreover, an IES transited to MDS was observed in DNA pol α gene, which caused the missing of its original MDS.

     

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