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[Properties and nucleotide sequence of mitochondrial plasmid-like DNA pC1 of cucumber]
1Institude for Molecular Biology, Nankai University, Tianjin 300071, China.
Abstract:
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 EcoR 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 2,889 bp long. It contained many forward and reverse repeat sequences. Three main open reading frames in pC1 were longer than 800 bp. 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.
Insights
Cucumber plants contain novel plasmid-like DNA (pC1) in their mitochondria. This DNA shows no homology to other genomes but shares similarities with bacterial and algal genes, suggesting it may encode functional proteins.
Area of Science:
- * Plant molecular biology
- * Genetics
- * Genomics
Context:
- * Mitochondria harbor unique genetic elements beyond the main genome.
- * Plasmid-like DNAs in plant mitochondria are not fully characterized.
- * Cucumber (Jinyan No. 4) mitochondrial DNA was investigated for novel sequences.
Purpose:
- * To isolate, clone, and characterize plasmid-like DNA from cucumber mitochondria.
- * To determine the genomic origin and homology of the isolated plasmid-like DNA.
- * To investigate the potential function of the identified DNA sequences.
Summary:
- * Four plasmid-like DNAs (pC1-pC4) were identified in cucumber mitochondria.
- * Plasmid-like DNA pC1 was cloned and analyzed, revealing a 2,889 bp circular molecule.
- * Southern blot analysis confirmed pC1's lack of homology with nuclear, chloroplast, or main mitochondrial genomes.
- * Sequence analysis showed pC1 contains repeat sequences and three large open reading frames (ORFs).
- * pC1 exhibited homology to bacterial and algal genomes, particularly with sulfate transport systems, suggesting functional protein encoding.
Impact:
- * Discovery of novel mitochondrial plasmid-like DNA in plants.
- * Characterization of pC1 provides insights into plant mitochondrial genetics.
- * Potential functional proteins encoded by pC1 could have implications for plant biology and biotechnology.
- * Findings contribute to understanding extrachromosomal DNA in eukaryotic organelles.