The Infectious Transcripts of Sweet Clover Necrotic Mosaic Virus Bipartite Genome Constructed by the Polymerase Chain Reaction.

Abstract

Based on the complete nucleotide sequences of sweet clover necrotic mosaic virus (SCNMV) genome, full-length cDNA clones derived from RNA-1 and RNA-2 were constructed by the polymerase chain reaction with proper primers. RNA-1 and RNA-2 transcripts capped or uncapped with m7GpppG were efficiently generated, were infectious and induced symptoms identical with those caused by native viral RNAs when coinoculated to test plants Chenopodium quinoa, C. amaranticolor and Phaseolus vulgaris 'Red Kidney' bean. However, infectivity of these transcripts were less than that of the native viral RNA. In addition, the uncapped transcripts were less infectious than the capped transcripts, particularly on Red Kidney bean. The progeny SCNMV particles derived from the transcript infection had infectivity similar to that of the native viral RNA-generated virions. Both the capped and the uncapped transcripts containing an artificial poly(A)61 tail were not infectious.