The nucleotide sequence of the 5S ribosomal RNA geneof Pyrenophora graminea

The distribution ofthe 5S ribosomal RNA genes in fungi is known to follow two patterns: either most or all of the 5S genes are part of the cluster (rDNA) which also encodes the large 17S and 25S ribosomal RNAs, or they are dispersed within the genome, away from the major rDNA transcript (1, 2). The first pattern is followed by Hansenula wingei, Kluyveromyces lactis, Saccharomyces cerevisiae, S. carlsbergensis, S. rosei, Torulopsis utilis (ascomycetous yeasts), Armillaria mellea, Coprinus cinereus, Schizophyllum commune, 7hanatephorus praticola (Basidiomycotina), Mucor racemosus (Zygomycetina) and Achlya ambisexualis (Oomycetina) whereas the second is followed by all the filamentous Ascomycotina studied to date (Aspergillus nidulans, Cochliobolus heterostrophus, Neurospora crassa, as well as by two ascomycetous yeasts Schizosaccharomyces pombe and Yarrowia lipolytica). The filamentous ascomycete Pyrenophora graminea (anamorph: Drechslera graminea) is a plant pathogen responsible for the leaf stripe disease of barley. During sequence analysis of a 2.4 kb EcoRI-SmaI fragment, part of a larger EcoRI genomic clone of the fungus, encompassing a 0.5 Kb portion of the 25S gene and the intergenic spacer of the rDNA gene cluster, we have detected a 118 bp long 5S gene (Figure la) which is located at 0.6 kb from the 3' end of the 25S gene (Figure lb). This finding demonstrates that, in contrast to what was known till now, both distribution patterns are present also in the filamentous Ascomycotina.