Complete nucleotide sequence of the linear DNA plasmid pRS224 with hairpin loops from Rhizoctonia solani and its unique transcriptional form.

ABSTRACT

The complete nucleotide sequence of the linear DNA plasmid (pRS224-1) from the plant-pathogenic fungus Rhizoctonia solani isolate H-16 was determined; and its unique RNA transcripts were characterized. The pRS224-1 DNA consists of 4,986 nucleotides. A computer-based study of the folding of pRS224-1 at both termini predicted hairpin-loop structures. The hairpin loops consisted of the left and right termini of 236 and 264 nucleotides, respectively, and share no sequence homology. Unique poly(A) RNAs, 4.7 kb and 7.4 kb in length and hybridizing with the pRS224 DNA, were found in mycelial cells of R. solani H-16. Transcript product-mapping allowed the prediction of the locations of different expression signals. The 7.4-kb transcript is generated from the left terminal region of the complementary strand, via the full-length sense-strand, to the right terminal region of the complementary strand. The 4.7-kb transcript is generated from the center region of the sense strand to the right terminal region of the complementary strand. One open reading frame (ORF) found in pRS224-1 is 887 amino acids long and has a potential coding capacity of 102 kDa. The ORF contains the highly conserved domains characteristic of reverse transcriptase sequences, including the highly conserved YXDD sequence.