Distribution and evolutionary significance of mitochondrial plasmids in Neurospora spp.

A mitochondrial plasmidline in the fungal genus Neurosporais geographically widely distributed and occurs in isolates of at least two species. On the basis of characterization with restriction endonucleases, it is apparent that plasmidsfrom isolates of Neurosporatetrasperma are more closely related to one another than to an evolutionarily homologous plasmidfrom Neurospora intermedia; N. tetrasperma plasmidsfrom Surinam and Hawaii differed from one another only slightly by our analysis, whereas the plasmidfrom N. intermedia(Fiji) exhibited substantial restriction sitedivergence from all N. tetrasperma plasmids. We believe these observations strengthen the presumption that four-spored isolates of Neurosporaspp. represent a natural taxonomic grouping (N. tetrasperma). The plasmidsfrom N. tetrasperma and N. intermedia(Fiji), although clearly related to each other as shown by hybridization studies, exhibited no detectable homology with either of two additional plasmidlines from isolates of Neurosporaspp. Nor did they exhibit homology with the mitochondrial genome. Despite this lack of homology among three distinct plasmidlines, all the plasmidsmay possess a common mode of replication. Images