Escape from premature death due to nuclear mutations in Podospora anserina:: Repeal versus respite

Premature death has been defined as a growth stoppage linked to the accumulation of specific deletions of the mitochondrial genome (mtDNA) in Podospora anserina, This occurs only in strains carrying the AS1-4 mutation which lies in a gene encoding a cytosolic ribosomal protein, Here we describe the isolation and genetic characterization of 10 nuclear mutations which either delay the appearance of this syndrome (respite from premature death) or cause a switch to the classical senescence process (repeal of premature death), These mutations lie in at least six genes. Some cause defects at the levels of ascospore germination, growth rates, and/or sensitivity toward inhibitors of protein syntheses. AII modify the onset of senescence in wild-type (AS1(+)) strains. The role played by these genes is discussed with respect to the control of diseases due to mtDNA rearrangements in filamentous fungi, (C) 1998 academic Press.