Recombination between heterologous linear and circular mitochondrial plasmids in the fungus Neurospora.
A strain of Neurospora intermedia from China contains five prominent extragenomic mitochondrial plasmids: three linear elements called zhisi plasmids, and two circular plasmids, Harbin-1 and -2. In one subculture, levels of four plasmids (all three zhisis and Harbin-1) fell to undetectable values and two novel linear plasmids appeared, Harbin-L and -L2, as well as a new small circular plasmid, Harbin-0.9. Cross-hybridization of restriction fragments and DNA sequencing showed that the Harbin-L plasmid was composed of parts of the circular Harbin-1 plasmid and of one of the linear zhisi plasmids. A model is presented in which the Harbin-1 and zhisi plasmids are present within the same mitochondrion, and crossovers at two separate 7 bp sites of sequence identity effectively insert part of the circular Harbin-1 DNA into a zhisi linear plasmid, simultaneously deleting part of the zhisi element. The small plasmid Harbin-0.9 is a fragment of the Har-1 plasmid, and seems to be another product of the recombination process that created Har-L. Recombination of this type could have contributed to the wide array of mitochondrial plasmids found in natural populations of Neurospora.
Griffiths
A J
AJ
Botany Department, University of British Columbia, Vancouver, Canada.
Yang
X
X
D001483:Base Sequence; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009491:Neurospora / Q000235:genetics*; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D010957:Plasmids / Q000737:chemistry; D011995:Recombination, Genetic; D015183:Restriction Mapping; D013045:Species Specificity
D004271:DNA, Fungal; D004272:DNA, Mitochondrial