Autoactive alleles of the flax L6 rust resistance gene induce non-race-specific rust resistance associated with the hypersensitive response.
L6 is a nucleotide binding site-leucine rich repeat (NBS-LRR) gene that confers race-specific resistance in flax (Linum usitatissimum) to strains of flax rust (Melampsora lini) that carry avirulence alleles of the AvrL567 gene but not to rust strains that carry only the virulence allele. Several mutant and recombinant forms of L6 were made that altered either the methionine-histidine-aspartate (MHD) motif conserved in the NBS domain of resistance proteins or exchanged the short domain C-terminal to the LRR region that is highly variable among L allele products. In transgenic flax some of these alleles are autoactive; they cause a gene dosage-dependent dwarf phenotype and constitutive expression of genes that are markers for the plant defense response. Their effects and penetrance ranged from extreme to mild in their degree of plant stunting, survival, and reproduction. Dwarf plants were also resistant to flax rust strains virulent to wild-type L6 plants, and this nonspecific resistance was associated with a hypersensitive response (HR) at the site of rust infection. The strongest autoactive allele, expressed in Arabidopsis from an ethanol-inducible promoter, gave rise to plant death dependent on the enhanced disease susceptibility 1 (EDS1) gene, which indicates that the mutant flax (Linaceae) L6 gene can signal cell death through a defined disease-resistance pathway in a different plant family (Brassicaceae).
Howles
Paul
P
CSIRO, Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia.
Lawrence
Greg
G
Finnegan
Jean
J
McFadden
Helen
H
Ayliffe
Michael
M
Dodds
Peter
P
Ellis
Jeff
J
D000483:Alleles; D000595:Amino Acid Sequence; D017124:Conserved Sequence / Q000235:genetics; D019597:Flax / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics
C095731:L6 protein, Linum usitatissimum; D010940:Plant Proteins