title: Characterization and prevalence of a circular mitochondrial plasmid in senescence-prone isolates of Neurospora intermedia.
abstract: Genetic and molecular analyses of the phenomenon of senescence-i.e., irreversible loss of growth and reproductive potential upon subculturing-in Neurospora intermedia strain M1991-60A, collected from Maddur in southern India, showed the presence of plasmid pMaddur1, which is homologous to the senescence-inducing circular mitochondrial plasmid, pVarkud. Maternal inheritance of senescence in M1991-60A correlated to the formation of variant pMaddur1, its subsequent insertion into mitochondrial (mt)DNA and the accumulation of defective mtDNA with the pMaddur1insert. PCR-based analyses for similar plasmids in 147 natural isolates of Neurospora from Maddur showed that nearly 40% of the strains had pMaddur1 or pMaddur2 that shared 97-98% sequence homology with pVarkud and pMauriceville. Nearly 50% of the strains that harbored either pMaddur1 or pMaddur2, also contained a circular Varkud satellite plasmid (pVS). Size polymorphism maps to the cluster of PstI sites in the non-coding region. Whereas senescence of nearly 40% of N. intermedia strains may be due to pMaddur, the presence in seven strains of pVS but not pMaddur and the absence of either of these two plasmids in other senescence-prone isolates suggests yet undiscovered mechanisms of senescence in the Maddur strains.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: D'Souza
authors.forename: Shahana
authors.initials: S
authors.lastname: Sultana
authors.forename: Ramesh
authors.initials: R
authors.lastname: Maheshwari
mesh_terms: D016922:Cellular Senescence / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D005800:Genes, Fungal / Q000235:genetics*; D009491:Neurospora / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial