Open AccessStructure–function analysis of the tobacco mosaic virus resistance gene N
Author(s) -
Savithramma P. DineshKumar,
WaiHong Tham,
Barbara Baker
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.97.26.14789
Subject(s) - tobacco mosaic virus , biology , mutant , point mutation , gene , genetics , wild type , amino acid , mutation , allele , virus , microbiology and biotechnology
The tobaccoN gene is a member of the Toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat (TIR-NBS-LRR) class of plant resistance (R ) genes and confers resistance to tobacco mosaic virus (TMV). We investigated the importance of specific domains ofN in inducing TMV resistance, by examining variousN deletion and point mutations that introduce single amino acid substitution mutantsin vivo . Our deletion analysis suggests that the TIR, NBS, and LRR domains play an indispensable role in the induction of resistance responses against TMV. We show that amino acids conserved among the Toll/IL-1R/plantR gene TIR domain and NBS-containing proteins play a critical role inN -mediated TMV resistance. Some loss-of-functionN alleles such as the TIR deletion and point mutations in the NBS (G216A/E/V/R, G218R, G219D, K222E/N, and T223A/N) interfere with the wild-typeN function and behave like dominant negative mutations. These F1 plants mount a hypersensitive response (HR) that is indistinguishable from that of the wild-typeN plants, yet TMV was able to move systemically, causing a systemic hypersensitive response (SHR). Many amino acid substitutions in the TIR, NBS, and LRR domains ofN lead to a partial loss-of-function phenotype. These mutant plants mount delayed HR compared with the wild-typeN plants and fail to contain the virus to the infection site. In addition, some partial loss-of-function alleles (W82S/A, W141S/A, G218V/S, and G219V) interfere with the wild-typeN function, leading to SHR. The partial loss-of-function and dominant negative mutant alleles described in this report will be useful in furthering our understanding of the TIR-NBS-LRR class ofR genes.