Abstract: Tobacco N gene, cloned from wild tobacco Nicotiana glutinosa, confers resistance to tobacco mosaic virus (TMV) by recognizing the helicase domain of 126 kDa TMV replicase and triggering the hypersensitive reaction at the infection site in plants. The N-TMV interaction is one of the earliest and most studied models of plant-pathogen interaction. Here, we review the isolation, expression, protein structure-function analysis of N gene and the current understanding of the N-mediated signal transduction and other aspects.