Universal Primers for Amplification of Mitochondrial Small Subunit Ribosomal RNA-Encoding Gene in Scleractinian Corals

We describe the construction of polymerase chain reaction primers designed to amplify a portion of the mitochondrial (mt) small subunit ribosomal (SSU) RNA-encoding genes in scleractinian corals. Combinations of cloning and sequencing show that the amplified fragments are between 694 and 896 bp in length. Alignment of the amplified DNA sequences to the published mt SSU rRNA genes of Metridium senile and Sarcophyton glaucum indicates several conserved regions among actiniarian, corallimorpharian, octocorallian, and scleractinians, suggesting this primer set can successfully amplify over 80% of the mt SSU rDNA region of scleractinian corals. Surveys of sequence variation and estimation of the rate of evolution show an extremely slow divergence of the SSU rRNA gene in the family Acroporidae. Received June 11, 1999; accepted October 4, 1999.     

The Ribonucleic Acids of Crithidia fasciculata*

SYNOPSIS. Crithidia fasciculata ribosomes were found to be 80S and to dissociate into 58 and 41S subunits; on 5 to 50% sucrose gradients, rRNA was separated into 25, 18, and 5S components. The molecular sizes of the heavier rRNA species, estimated by polyacrylamide gel electrophoresis were 1.24 and 0.84 M (×10⁶ daltons). The 25S RNA has a tendency to interact with the 18S RNA to give a complex that is difficult to separate by sucrose gradient centrifugation. The 25S RNA is also unstable and dissociates into 0.73 and 0.57 M components. The 18S RNA has molecular size (0.84 M) higher than the 0.7 M reported for most eukaryotes, but similar to that of Euglena and Amoeba. Ribosomal RNA hybridized 0.29% of the nuclear DNA. Mitochondrial RNA, extracted by a rapid procedure was resolved into 16 and 5S components in sucrose gradients.     

Identification of RNA species in the RNA-toxin complex and structure of the complex in Clostridium botulinum type E

Clostridium botulinum type E toxin was isolated in the form of a complex with RNA(s) from bacterial cells. Characterization of the complexed RNA remains to be elucidated. The RNA is identified here as ribosomal RNA (rRNA) having 23S and 16S components. The RNA-toxin complexes were found to be made up of three types with different molecular sizes. The three types of RNA-toxin complex are toxin bound to both the 23S and 16S rRNA, toxin bound to the 16S rRNA and a small amount of 23S rRNA, and toxin bound only to the 16S rRNA.     

基于18S rRNA和线粒体16S rRNA基因序列的柳蚕进化分析

为探讨柳蚕Actias selene Hübner与鳞翅目昆虫的系统发育关系,本研究利用PCR扩增获得了柳蚕核糖体18S rRNA和线粒体16S rRNA基因的部分序列,长度分别为391bp和428bp。并采用邻近距离法(NJ)、最大简约法(MP)、类平均聚类法(UPGMA)构建系统进化树。结果表明,柳蚕线粒体16SrRNA基因序列与大蚕蛾科昆虫的16SrRNA基因序列均表现出偏好于碱基AT的倾向。柳蚕与所研究的其它蚕类的遗传距离介于0.016至0.140之间,其中与温带柞蚕Antheraea roylii的遗传距离最小,与野桑蚕Bombyx mandarina的遗传距离最大。而基于鳞翅目昆虫18S rRNA基因部分序列的进化分析显示,柳蚕与柞蚕Antheraea pernyi之间的遗传距离最小(0.010),与蓖麻蚕Samia ricini的遗传距离最大(0.017)。     

Isolation of cDNA clones coding for mitochondrial 16S ribosomal RNA from the crustacean Artemia

cDNA clones coding for Artemia mitochondrial 16S ribosomal RNA (rRNA) have been isolated. The clones cover from nucleotide 650 of the RNA molecule to its 3' end. The comparison of Artemia sequence with both vertebrate and invertebrate mitochondrial 16S rRNA sequences has shown the existence of regions of high similarity between them. A model for the secondary structure of the 3' half of Artemia mitochondrial 16S rRNA is proposed. The size of the rRNA molecule has been estimated at 1.35 kb. Despite the similarity of the Artemia gene to insect rRNA in size, sequence and secondary structure, the G + C content of the Artemia gene (42%) is closer to that of mammals than to the insect genes. The number of mitochondria in Artemia has been estimated at 1500 per diploid genome in the cyst and 4000 in the nauplius. In contrast, the amount of mt 16S rRNA is constant at all stages of Artemia development.     

Nuclear pseudogenes of mitochondrial DNA as a variable part of the human genome

INTRODUCTIONNuclearpseudogenesofmitochondrial(mt)DNAwereinitiallydiscoveredintheearly80's[1--6].However,mechanismsforthegenerationofmtDNApseudogenesarestillnotclearandmayvaryindifferentcases.BothRNA--[7--8]andDNAmediated[9--11]processeshavebeensugges...     

Molecular structures of mitochondrial-DNA-like sequences in human nuclear DNA.

Two lambda phage clones carrying mitochondrial-DNA-like (mtDNA-like) sequences isolated from a human gene library were named Lm E-1 and Lm C-2, and their DNA structures were characterized. Lm E-1 contains about 0.4 kb DNA homologous to the 5' portion of the mitochondrial 16S ribosomal RNA (rRNA) gene and Lm C-2, a 1.6 kb DNA homologous to the 3' portion of the 12S rRNA gene and to almost all of the 16S rRNA gene. Comparisons of their nucleotide sequences with those of the corresponding regions of the human mtDNA revealed no detectable DNA rearrangement and their homologies to the human mtDNA are 84% and 80%, respectively. There are neither terminal repeats in the nuclear mtDNA-like sequences nor duplications of the nuclear DNAs flanking the mtDNA-like sequences. Evolutionary relationship between these two human nuclear mtDNA-like sequences and the human and bovine mtDNAs is discussed.