Submitted to: Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2002
Publication Date: 6/1/2002
Citation: Fellers, J.P., Tremblay, D., Handest, M.F., Lommel, S.A. 2002. The potato virus ymsnr nib-replicase is the elicitor of a veinal necrosis-hypersensitive response in root knot nematode resistant tobacco. Molecular Plant Pathology. 3:145-152. Interpretive Summary: In recent years, scientists have found that plant resistance to pathogens is controlled by a single gene. Also, that the ability of a pathogen to cause disease or to induce resistance is also caused by a single protein. This "lock and key" relationship determines whether a plant gets sick or if it will be resistant to disease. Tobacco plants can be resistant to root knot nematodes. It is controlled by a single gene; however, this gene also provides resistance to a virus, Potato Virus Y. The research reported evaluated the eight different proteins of PVY strain MN to determine which was the "key" to induce the resistance response. We found that the protein that replicates the RNA strand was responsible. The same protein from other PVY strains did not induce resistance. The resistance is probably due to a single amino acid.
Technical Abstract: A root knot nematode resistance gene in Nicotiana tabacum, Rk, providing resistance to the nematode parasite Meloidogyne incognita is tightly linked to, or is a pleiotropic gene with a veinal necrosis systemic hypersensitive response to infection by Potato virus Y (PVY) MSNR. The single PVY MSNR open reading frame was sequenced and found to have 89% protein identity to PVY N. Individual PVY MSNR polypeptides were deduced and the corresponding cDNA were cloned into a Potato virus X (PVX) based expression vector and used as templates for in vitro transcriptions. Infected plant sap, from N. benthamiana inoculated with infectious RNA, was used to inoculate both root knot nematode (RKN) resistant and susceptible tobacco lines. Lines were then evaluated for the induction of the hypersensitive response. The PVY MSNR Nib-replicase protein was found to induce a hypersensitive response 10 days post inoculation in nematode resistant tobacco. None of the other PVX/PVY MSNR constructs induced a hypersensitive response. The Nib-replicase of PVY N, which shares 93% identity to PVY MSNR, did not induce a hypersensitive response when expressed from the PVX vector. This confirmed that the PVY MSNR Nib-replicase is the elicitor of PVY MSNR veinal necrosis on RKN plants and thus the first report of a Potyvirus replicase functioning as an avirulence factor.