黄瓜线粒体DNA类质粒pC1的性质和核酸序列研究

津研四号黄瓜线粒体中除主环ＤＮＡ外，还有４种ＤＮＡ类质粒：ｐＣ１、ｐＣ２、ｐＣ３、ｐＣ４。将环形类质粒ｐＣ１ｌｐｋ ｇｃ ｐＵＣ１９的ＥｃｏＲⅠ位点上，克隆至Ｅ．ｃｏｌｉ ＪＭ１０９中。以克隆的ｐＣ１为探针，进行同源性检测，ｐＣ１与津研四号黄瓜的核基因组、叶绿体基因组、线粒体基因组和线粒体中其他类质粒不同源。对ｐＣ１进行序列测定和分析，ｐＣ１长度２ ８８９ｂｐ，含有多个正向和反向重复序列，有３个８

Properties and Nucleotide Sequence of Mitochondrial Plasmid-like DNA pC1 of Cucumber

Four kinds of plasmid-like DNA, designated pC1, pC2, pC3 and pC4 were found in the mitochondrion of cucumber Jinyan No.4. The circle plasmid-like DNA pC1 was cloned into the Eco R I site of pUC19 using E. coli JM109 as host. The cloned pC1 DNA was isolated and used as probes in Southern analyses of total mitochondrial DNA, nuclear DNA and chloroplast DNA. Evidences were obtained that the pC1 did not show any homology with nuclear, chloroplast, main mitochondrial genomes and the other plasmid-like DNAs. Sequence analysis revealed that pC1 was 2889bp long. It contained many forward and reverse repeat sequences. Three main open reading frames in pC1 were longer than 800bp. Computer-assisted searching the nucleotide sequence in GenBank database revealed PC1 had no significant homology with known sequences of mitochondrial and plasmid-like DNA, but had homology with the E. coli, Mycobaterium tuberculosis and Anacystis nidulans genomes. The predicted proteins of PC1 main ORFs show homology with the sulfate transport system in bacteria. alga and liverwort. It suggested that pC1 may encode functional proteins.