Premature death in Podospora anserina: sporadic accumulation of the deleted mitochondrial genome, translational parameters and innocuity of the mating types.
The Podospora anserina premature death syndrome was described as early growth arrest caused by a site-specific deletion of the mitochondrial genome (mtDNA) and occurring in strains displaying the genotype AS1-4 mat-. The AS1-4 mutation lies in a gene encoding a cytosolic ribosomal protein, while mat- is one of the two forms (mat- and mat+) of the mating-type locus. Here we show that, depending on culture conditions, death due to the accumulation of the deleted mtDNA molecule can occur in the AS1-4 mat+ context and can be delayed in the AS1-4 mat- background. Furthermore, we show that premature death and the classical senescence process are mutually exclusive. Several approaches permit the identification of the mat-linked gene involved in the appearance of premature death. This gene, rmp, exhibits two natural alleles, rmp- linked to mat- and rmp+ linked to mat+. The first is probably functional while the second probably carries a nonsense mutation and is sporadically expressed through natural suppression. A model is proposed that emphasizes the roles played by the AS1-4 mutation, the rmp gene, and environmental conditions in the accumulation of the deleted mitochondrial genome characteristic of this syndrome.
Contamine
V
V
Institut de Génétique et Microbiologie, CNRS URA 1354, Université Paris-Sud, Orsay, France.
Lecellier
G
G
Belcour
L
L
Picard
M
M
D000483:Alleles; D001203:Ascomycota / Q000235:genetics*; D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D004843:Epistasis, Genetic; D017353:Gene Deletion; D005799:Genes, Dominant; D005808:Genes, Recessive; D014176:Protein Biosynthesis; D013489:Suppression, Genetic
D004271:DNA, Fungal; D004272:DNA, Mitochondrial