蓖麻蚕核糖体大亚基RNA基因3‘—端序列分析及进化研究

测定了蓖麻蚕核糖体大亚基ＲＮＡ编码区３’－端ＤＮＡ序列,分析了其二级结构,并与昆虫伊蚊、果蝇;线虫;脊椎动物人、小鼠、爪蟾;低等脊索动物海鞘以及真菌酵母、毛霉相应的保守区段进行了同源比较。邻接法分析表明,昆虫核糖体大亚基ＲＮＡ在进化上与５ＳｒＲＮＡ相似,有加快的趋势。     

A Simple and Rapid PCR-based Method to Isolate Complete Small Macronuclear Minichromosomes from Hypotrich Ciliates: 5S rDNA and S26 Ribosomal Protein Gene of Oxytricha (Sterkiella) nova

Hypotrich ciliates present a macronuclear genome consisting of gene-sized instead of chromosome-sized DNA molecules. Exploiting this unique eukaryotic genome feature, we introduce, for the first time in ciliates, a rapid and easy PCR method using telomeric primers to isolate small complete macronuclear DNA molecules or minichromosomes. Two presumably abundant macronuclear DNA molecules, containing ribosomal genes, were amplified from the Oxytricha (Sterkiella) nova complete genome after using this method, and then were cloned and sequenced. The 5S rDNA sequence of O. (S.) nova is the third one reported among hypotrich ciliates; its primary and secondary structure is compared with other eukaryotic 5S rRNAs. The ribosomal protein S26 gene is the first one reported among ciliates. This “End-End-PCR” method might be useful to obtain similar gene-sized macronuclear molecules from other hypotrich ciliates, and, therefore, to increase our knowledge on ribosomal genes in these eukaryotic microorganisms.