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

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 consis ts of 4,986 nucleotides. A computer-based study of the folding of pRS224-1 at both termini predicted hairpin-loop structures. The hairpin loops consis ted 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 th e locations of different expression signals. The 7.4-kb transcript is gener ated from the left terminal region of the complementary strand, via the ful l-length sense-strand, to the right terminal region of the complementary st rand. The 4.7-kb transcript is generated from the center region of the sens e 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 po tential coding capacity of 102 kDa. The ORF contains the highly conserved d omains characteristic of reverse transcriptase sequences, including the hig hly conserved YXDD sequence.