Phylogenetic implication of heterogeneity of the nontranscribed spacer of rDNA repeating unit in various Neurospora and related fungal species.

Nontranscribed spacer (NTS) regions of ribosomal (r)RNA genes are non-conserved and are shown to be useful for phylogenetic studies. 32P-labelled N. crassa NTS pCC3400 DNA, was used as a molecular probe to hybridize Southern blots of genomic DNAs obtained from Neurospora, Gelacinospora, Sordaria, bacteria, plants, and animals. Our studies conclude that: (a) the homotahllic species of Neurospora should not belong to genus Gelacinospora (a historical question) and that Neurospora homothallic species are closer to Gelacinospora than to Sordaria; and that (b) all of the filamentous fungal species tested are indeed closer to the higher plant genome than to higher primate animal genome based on shared restriction sites of 12 enzymes. Our studies also demonstrate the usefulness of nontranscribed rRNA gene probes in resolving questions regarding phylogenetic relatedness between widely separated organisms using the parsimony principle based on mutation sites from DNA restriction maps; it has not been possible to do this using DNA: DNA hybridization procedures that involved the total genome.