A resistance-breaking potyvirus uses a eukaryotic translation initiation factor different from that of a non-breaking virus: evidence obtained from interaction of potato virus Y and Nicotiana tabacum
Success of the viral infection cycle depends on complex interplay between components encoded by viral and host genomes. Potyviruses use host eukaryotic translation initiation factors (eIFs) for their infection cycle. Many reports have described that impaired eIFs in host plants confer enhanced resistance (reduced susceptibility) to potyviruses. However, no eIF that interacts with a host resistance-breaking (RB) potyvirus has ever been reported. In Nicotiana tabacum, Virgin A Mutant (VAM) has been used as a genetic resource for resistance to potato virus Y (PVY). The resistance is conferred by a recessive locus “va” that has been shown recently to result from the loss of eIF4E-S gene. In recent years, a strain of PVY that breaks the VAM resistance has been reported worldwide. Results of this study show that an RB strain of potato virus Y (PVY-RB) uses eIF(iso)4E, although PVY uses eIF4E in N. tabacum. Therefore, an isoform of eIF plays a key role in the emergence of resistance-breaking PVY. The loss-of-function of eIF(iso)4E-T gene conferred enhanced resistance to PVY-RB, although that of eIF(iso)4E-S gene did not. This homeologous gene-specific resistance implies that PVY and PVY-RB recruit each specific eIF in N. tabacum for their infection cycle. To our knowledge, this report is the first demonstrating that a host resistance-breaking potyvirus uses a eukaryotic translation initiation factor different from that of a non-breaking virus.