INHERITANCE OF MITOCHONDRIAL-DNA AND PLASMIDS IN THE ASCOMYCETOUS FUNGUS, EPICHLOE-TYPHINA

We analyzed the inheritance of mitochondrial DNA (mtDNA) species in ma tings of the grass symbiont Epichloe typhina. Eighty progeny were anal yzed from a cross in which the maternal (stromal) parent possessed thr ee linear plasmids, designated Callan-a (7.5 kb), Aubonne-a (2.1 kb) a nd Bergell (2.0 kb), and the paternal parent had one plasmid, Aubonne- b (2.1 kb). Maternal transmission of all plasmids was observed in 76 p rogeny; two progeny possessed Bergell and Callan-a, but had the matern al Aubonne- a replaced with the related paternal plasmid Aubonne-b; tw o progeny lacked Callan-a, but had the other two maternal plasmids. A total of 34 progeny were analyzed from four other matings, including a reciprocal pair, and in each progeny the plasmid transmission was mat ernal. The inheritance of mitochondrial genomes in all progeny was ana lyzed by profiles of restriction endonuclease-cleaved mtDNA. In most p rogeny the profiles closely resembled those of the maternal parents, b ut some progeny had nonparental mtDNA profiles that suggested recombin ation of mitochondrial genomes. These results indicate that the fertil ized stroma of E. typhina is initially heteroplasmic, permitting paren tal mitochondria to fuse and their genomes to recombine.