N gene

Abbink, T.E.M., deVogel, J., Bol. J.F., Linthorst, J.M. Induction of a hypersensitive response by chimeric helicase sequences of tobamoviruses U1 and Ob in N-carrying tobacco. MPMI 14, 1086-95 (2001)
Dinesh-Kumar, S.P., Tham, W-H., Baker, B.J. Structure-function analysis of the tobacco mosaic virus resistance gene N. PNAS 97, 14789-94 (2000)
Liu, Y., Schiff, M., Marathe, R., Dinesh-Kumar, S.P. Tobacco Rar1, EDS1 and NPR1/NIM1 like genes are required for N-mediated resistance to tobacco mosaic virus. Plant J. 30, 415 (2002)
Marathe, R., Anandalakshmi, R., Liu, Y.L., Dinesh-Kumar, S.P. The tobacco mosaic virus resistance gene, N Mol. Plant Path. 3, 167-72 (2002)
Whitham, S., McCormick, Baker, B. The N gene of tobacco confer resistance to tobacco mosaic in transgenic tomato. PNAS 93, 8776-81 (1996)


I- Basics of N gene
1- Confers local lesion based "hypersensitive" resistance to most tobamoviruses
2- Originally isolated from N. glutinosa and bred into tobacco
3- Normal TMV has not overcome the N gene
4- The N gene is inactive above 28oC - inoculating above 28oC and shifting down after systemic invasion yields systemic necrosis
5- The hypersensitive response is complex and involves many genes
6- "N" appears to be one of many switches which turn on the battery of genes
7- "N" response also yields systemic acquired resistance, SAR.
II- Region of TMV that induces N
1- Ob (a pepper strain) fails to recognize the N gene
2- By constructing chimeras show that helicase region induces hypersensitivity
3- By constructing chimeras at higher resolution show that several helicase regions are essential
III- Isolation and sequencing of N gene
1- N gene is a "classical" toll receptor (a membrane protein)
2- Resembles other resistance genes
3- Introducing N gene into tomato or N. benthamiana confers resistance
4- Strategies for identifying genes required for "N" action are now available.
5- N gene activates pathways common to many resistance systems including apoptosis.

E-mail: llane1@unl.edu