Field D, Wills C
Department of Biology-0116, University of California at San Diego, La Jolla 92093-0116, USA.
Proc Biol Sci. 1996 Feb 22;263(1367):209-15. doi: 10.1098/rspb.1996.0033.
We have examined the phylogenetic distribution of the longest, perfect microsatellites in GenBank. Despite the large contributions of model higher-eukaryotic organisms to GenBank, the selective cloning of long microsatellites from these organisms as genetic markers, and the relative lack of concentration on the microsatellites in lower eukaryotes and prokaryotes, we found that simple organisms, defined here as slime molds, fungi, protists, prokaryotes, viruses, organelles and plasmids, contributed 78 of the 375 examined sequences. These 78 simple-organism microsatellites are characterized predominantly by trinucleotide repeats, nearly half of which lie in exons, and in general show a bias towards A+T rich motifs. Simple-organism microsatellites represented more than once in GenBank displayed length polymorphisms when independent clones were compared. These facts collectively raise speculation as to the role of these 'junk' sequences in such highly economical genomes, especially when precise changes in long microsatellites are known to regulate critical virulence factors in several prokaryotes. Regardless of their biological significance, simple-organism microsatellites may provide a general source of molecular markers to track disease outbreaks and the evolution of microorganisms in unprecedented detail.
我们研究了GenBank中最长的完美微卫星的系统发育分布。尽管模式高等真核生物对GenBank贡献巨大，从这些生物中选择性克隆长微卫星作为遗传标记，且相对较少关注低等真核生物和原核生物中的微卫星，但我们发现，这里定义为黏菌、真菌、原生生物、原核生物、病毒、细胞器和质粒的简单生物，在所检测的375个序列中贡献了78个。这78个简单生物微卫星主要以三核苷酸重复为特征，其中近一半位于外显子中，并且总体上表现出对富含A+T基序的偏好。当比较独立克隆时，在GenBank中多次出现的简单生物微卫星显示出长度多态性。这些事实共同引发了对于这些“垃圾”序列在如此高度精简的基因组中的作用的猜测，尤其是当已知长微卫星的精确变化会调节几种原核生物中的关键毒力因子时。无论其生物学意义如何，简单生物微卫星可能提供一个通用的分子标记来源，以前所未有的细节追踪疾病爆发和微生物的进化。
