Molecular characterization and analysis of conserved potyviral motifs in bean common mosaic virus (BCMV) for RNAi-mediated protection

Australian bean common mosaic virus (BCMV) isolates were sequenced, and the sequences were compared to global BCMV and bean common mosaic necrosis virus (BCMNV) sequences and analysed for conserved potyviral motifs to generate in planta RNA-interference (RNAi) resistance. Thirty-nine out of 40 previously reported potyvirus motifs were conserved among all 77 BCMV/BCMNV sequences. Two RNAi target regions were selected for dsRNA construct design, covering 920 bp of the nuclease inclusion b (NIb) protein and 461 bp of the coat protein (CP). In silico prediction of the effectiveness of these constructs for broad-spectrum defence against the 77 BCMV and BCMNV sequences was done via analysis of putative 21-nucleotide (nt) and 22-nt small-interfering RNAs (siRNAs) generated from the target regions. The effectiveness of both constructs for siRNA generation and BCMV RNAi-mediated resistance was validated in Nicotiana benthamiana transient assays.