Related Experiment Videos
Genetic organization of a linear mitochondrial plasmid (mF) that promotes mitochondrial fusion in Physarum
H Takano1, S Kawano, T Kuroiwa
1Department of Plant Sciences, Graduate School of Science, University of Tokyo, Japan.
Abstract:
The mF plasmid which promotes mitochondrial fusion in Physarum polycephalum is a linear molecule with complex terminal inverted repeats (TIRs). Its nucleotide sequence was determined. The mF plasmid is 14,503 bp in size, and contains ten open reading frames (ORFs). All of the ORFs except one are encoded on the same DNA strand (coding strand). The number of amino-acid residues in the putative proteins derived from the nine ORFs on the coding strand are 231, 163, 640, 235, 118, 1130, 366, 309, and 547 from left (5' end) to right (3' end) on the map. The amino-acid sequences of newly-identified ORFs on the mF plasmid did not show significant homology to any amino-acid sequences in the databases. A brief transcriptional map of the mF plasmid was constructed, and the following features were noted. (1) The transcription initiation site was located just inside the end of the left TIRs, but not within the TIRs themselves. (2) Three major transcripts of 1.0, 3.4 and 4.6 knt corresponded to the left region of the mF plasmid, and long, low-abundance (more than 4.6 knt), heterogenous transcripts corresponded to almost the entire mF plasmid. A low-abundance, 3.5-knt transcript corresponding to the coding region of ORF1 130 (a 1 130-amino-acid polypeptide) was also detected, and may be derived from the long transcripts. (3) The quantity of transcripts which included the region near the transcription initiation site was about 500-times more than that which included the region near the inner end of the right TIRs.
Insights
The mF plasmid, crucial for mitochondrial fusion in Physarum polycephalum, has a determined nucleotide sequence. This linear molecule contains ten open reading frames (ORFs) with unique amino acid sequences, suggesting novel functions.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The mF plasmid in Physarum polycephalum is known to promote mitochondrial fusion.
- This plasmid is a linear molecule characterized by complex terminal inverted repeats (TIRs).
Purpose of the Study:
- To determine the complete nucleotide sequence of the mF plasmid.
- To identify and characterize the open reading frames (ORFs) encoded by the mF plasmid.
- To construct a transcriptional map of the mF plasmid.
Main Methods:
- DNA sequencing to determine the nucleotide sequence of the mF plasmid.
- Bioinformatic analysis to identify open reading frames (ORFs) and predict protein sequences.
- Transcriptional mapping to analyze gene expression patterns.
Main Results:
- The mF plasmid is 14,503 bp long and contains ten ORFs, mostly on the same DNA strand.
- Predicted protein sequences from the ORFs showed no significant homology to existing database sequences.
- A transcriptional map revealed a transcription initiation site near the left TIRs and major transcripts of 1.0, 3.4, and 4.6 knt, along with longer, low-abundance transcripts.
Conclusions:
- The mF plasmid harbors novel genes with potentially unique functions in mitochondrial fusion.
- The transcription patterns suggest complex gene regulation within the mF plasmid.
- Further research is needed to elucidate the specific roles of the identified ORFs and their products.