Harmless High Molecular Weight Double-stranded RNA in Phaseolus vulgaris: A Cryptic Virus or RNA Plasmid?

The 1980s presented a perplexing discovery within Phaseolus vulgaris (common bean) in the form of high molecular weight double-stranded RNA (dsRNA). The sequencing of P. vulgaris dsRNA was attempted in 1990 (Wakarchuk and Hamilton, 1990), producing 630 base pairs of the only P. vulgaris dsRNA known sequence to date. The sequence of high MW dsRNA in symptomless plants is desired for its classification as the genome of a cryptic virus or an RNA plasmid. Protein motifs for viral coat proteins may be compared with this sequence to help classify the dsRNA as viral. Obtaining sequence information for an entire P. vulgaris dsRNA molecule was the central goal of this research project, although progress has been slow. However, new information has been discovered regarding sequence homology of P. vulgaris (cv. Midnight) dsRNA with similar molecules of fully sequenced high MW dsRNA in rice (Oriza sativa and Oriza rufipogon). With a substanial 30% sequence homology at the amino acid level, the small 630bp segment of P. vulgaris dsRNA has indicated that use of primers based upon O. sativa sequence information (GenBank accession number S57908) is now possible for the expansion of P. vulgaris\u27 dsRNA sequence