NUCLEOTIDE-SEQUENCE RELATIONSHIPS OF DOUBLE-STRANDED RNAS IN FLAX RUST, MELAMPSORA-LINI

Flax rust, Melampsora lini strain SP6, contains 11 double-stranded (ds) RNA molecules with a total length of about 25 kbp. The dsRNAs are inherited in three genetic units: the L unit comprising a single 5.2 kbp dsRNA and contained within a 40-nm virus-like particle, and the A and B units each consisting of five dsRNAs (A1-A5, and B1-B5) ranging in size from 1.2 to 2.7 kbp. This paper reports the isolation of a cDNA library representing 10 of the 11 dsRNAs. By nucleic-acid hybridization techniques it has been shown that all ten sequences are unique showing no detectable cross-hybridization with any other dsRNA present in the rust. A near full-length sequence of 1932 bp of the B3 dsRNA is reported and contains several open reading frames, the largest of which comprises most of the molecule.