THE PRODUCT OF THE TOBACCO MOSAIC-VIRUS RESISTANCE GENE-N - SIMILARITY TO TOLL AND THE INTERLEUKIN-1 RECEPTOR

The products of plant disease resistance genes are postulated to recog nize invading pathogens and rapidly trigger host defense responses. He re we describe isolation of the resistance gene N of tobacco that medi ates resistance to the viral pathogen tobacco mosaic virus (TMV). The N gene was isolated by transposon tagging using the maize Activator tr ansposon. A genomic DNA fragment containing the N gene conferred TMV r esistance to TMV susceptible tobacco. Sequence analysis of the N gene shows that it encodes a protein of 131.4 kDa with an amino-terminal do main similar to that of the cytoplasmic domain of the Drosophila Toll protein and the interleukin-1 receptor (IL-1R) in mammals, a nucleotid e-binding site (NBS), and 4 imperfect leucine-rich repeats (LRR). The sequence similarity of N, Toll, and IL-1 R suggests that N mediates ra pid gene induction and TMV resistance through a Toll-IL-1-like pathway .