Red clover necrotic mosaic virus infectious transcripts synthesized in vitro

Area of Science:

• Plant Virology
• Molecular Biology
• RNA Virus Research

Background:

• The red clover necrotic mosaic dianthovirus (RCNMV) has a bipartite genome composed of two single-stranded RNAs (RNA-1 and RNA-2).
• Efficient in vitro synthesis of full-length viral RNAs is essential for reverse genetics studies.

Purpose of the Study:

• To develop efficient methods for in vitro transcription of RCNMV RNAs.
• To generate infectious RCNMV transcripts for further biological studies.

Main Methods:

• Generation of full-length cDNA clones for RCNMV RNA-1 and RNA-2.
• Oligonucleotide-directed mutagenesis to introduce T7 RNA polymerase promoter.
• Engineering of nonviral guanosine residues at the transcription start site.
• In vitro transcription and inoculation assays on host plants.

Main Results:

• Low yields of in vitro transcripts were obtained with the authentic viral start site.
• Efficient transcription was achieved by adding one or two nonviral guanosines at the 5' end.
• Both capped and uncapped transcripts were infectious, inducing typical RCNMV symptoms.
• Uncapped transcripts showed slightly reduced infectivity.
• Progeny virus retained wild-type infectivity, and nonviral guanosines were not maintained.

Conclusions:

• Nonviral guanosine residues at the transcription start site significantly enhance RCNMV RNA synthesis in vitro.
• Infectious RCNMV RNAs can be produced efficiently using this modified transcription strategy.
• This method facilitates the study of RCNMV replication and pathogenesis through reverse genetics.