Smith M W, Aley S B, Sogin M, Gillin F D, Evans G A
Molecular Genetics Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Mol Biochem Parasitol. 1998 Sep 15;95(2):267-80. doi: 10.1016/s0166-6851(98)00113-3.
The parasitic protozoan Giardia lamblia represents one of the earliest diverging lineages in the evolutionary history of eukaryotic organisms as well as an important human pathogen. A representative sampling of gene sequences from this early diverging protozoan could provide insights into genotypic and phenotypic innovations associated with the origin of eukaryotes. Currently, known giardial gene sequences are heavily biased toward a few gene families, including variant surface proteins (VSPs), structural proteins, and ribosomal RNA genes. One-pass sequences of Giardia genomic DNA were obtained using vector flanking priming sequences on the ends of cosmids in two independent libraries. Comparisons of 2304 of these sequences against the GenBank database identified 205 potential giardial genes with BLAST scores P(n) < 10(9). These coding regions encompass a wide range of metabolic, repair, and signaling enzymes, and include some genes not predicted by our current understanding of Giardia biochemistry. The efficiency of identification of putative genes is consistent with earlier findings that coding regions in the Giardia genome are densely packed and do not appear to contain introns. Our current results suggest that direct genome sequencing is an efficient method for identifying giardial genes for evolutionary and biochemical studies.
寄生原生动物蓝氏贾第鞭毛虫是真核生物进化史上最早分化的谱系之一，也是一种重要的人类病原体。对这种早期分化的原生动物的基因序列进行代表性采样，可以深入了解与真核生物起源相关的基因型和表型创新。目前，已知的贾第虫基因序列严重偏向于少数基因家族，包括可变表面蛋白（VSP）、结构蛋白和核糖体RNA基因。利用两个独立文库中粘粒末端的载体侧翼引物序列，获得了贾第虫基因组DNA的单通道序列。将其中2304个序列与GenBank数据库进行比较，通过BLAST评分P(n) < 10(9)鉴定出205个潜在的贾第虫基因。这些编码区域涵盖了广泛的代谢、修复和信号酶，还包括一些根据我们目前对贾第虫生物化学的理解无法预测的基因。推定基因的鉴定效率与早期研究结果一致，即贾第虫基因组中的编码区域紧密排列，似乎不包含内含子。我们目前的结果表明，直接基因组测序是鉴定用于进化和生物化学研究的贾第虫基因的有效方法。
