MITOCHONDRIAL-DNA REARRANGEMENTS OF PODOSPORA-ANSERINA ARE UNDER THE CONTROL OF THE NUCLEAR GENE GRISEA

Podospora anserina is a filamentous fungus with a limited life span. L ife span is controlled by nuclear and extranuclear genetic traits, Her ein we report the nature of four alterations in the nuclear gene grise a that lead Po an altered morphology, a defect in the formation of fem ale gametangia, and an Increased life span. Three sequence changes are located in the 5' upstream region of the grisea ORF. One mutation is a G --> A transition at the 5' splice site of the single intron of the gene, Beading to a RNA splicing defect. This loss-of-function affects the amplification of the first intron of the mitochondrial cytochrome c oxidase subunit I gene (COI) and the specific mitochondrial. DNA re arrangements that occur during senescence of wild-type strains. Our re sults indicate that the nuclear gene grisea is part of a molecular mac hinery involved in the control of mitochondrial DNA reorganizations. T hese DNA instabilities accelerate hut are not a prerequisite for the a ging of P. anserina cultures.