Characterization of DNA Sequences Cloned From Resting Spores of Plasmodiophora brassicae

Forty-four clones coittaining P. brassicae genomic DNA fragments were isolated from a partial genomic library (pUC118) of the fungus. Eleven DNA fragments were arbitrarily selected from them and partially sequenced. Southern blot analysis was performed using the 11 DNA fragments as probes to estimate the copy number of these DNA fragments in the P. brassicae genome and to see if they hybridized also to genomic DNA of host plant (Chinese cabbage). Five of those (Nos 24, 48, 54, 57, and 108) were of single-copy and hybridized only to DNA bands of P. brassicae. Two fragments (Nos 4 and 15) were found to contain repetitive sequence of/", brassicae. Three fragments (Nos 69,73, and 82) hybridized to DNA bands of both host and P. brassicae while the size and the number of the bands were different between host and P. brassicae. Data base searches revealed that one of the single-copy fragments (No. 48) had high homology with yeast RNA polymerase II gene