THE ARABIDOPSIS NIM1 PROTEIN SHOWS HOMOLOGY TO A MAMMALIAN TRANSCRIPTION FACTOR INHIBITOR
L FRIEDRICH1, K LAWTON1, R CADE1, D ELLIS1 and J RYALS 2
1Novartis Crop Protection Inc., Research Triangle Park, NC 27709-2257, USA; 2Paradigm Genetics Inc., Research Triangle Park, NC 27709-4528, USA
The NIM1 (for non-inducible immunity) gene product is involved in the signal transduction cascade leading to both systemic acquired resistance (SAR) and gene-for-gene resistance in Arabidopsis. We have isolated and characterized five new alleles of nim1 that show a range of phenotypes, from weakly impaired in chemically induced pathogenesis-related protein-1 gene expression and fungal resistance, to very strongly blocked. We have isolated the NIM1 gene by using a map-based cloning procedure. Interestingly, the NIM1 protein shows sequence homology to the mammalian signal transduction factor IkappaB subclass alpha. NF-kappaB/IkappaB signalling pathways are implicated in disease resistance responses in a range of organisms from Drosophila to mammals, suggesting that the SAR signalling pathway in plants is representative of an ancient and ubiquitous defence mechanism in higher organisms.