Downy mildew resistance in Arabidopsis by mutation of HOMOSERINE KINASE.
Plant disease resistance is commonly triggered by early pathogen recognition and activation of immunity. An alternative form of resistance is mediated by recessive downy mildew resistant 1 (dmr1) alleles in Arabidopsis thaliana. Map-based cloning revealed that DMR1 encodes homoserine kinase (HSK). Six independent dmr1 mutants each carry a different amino acid substitution in the HSK protein. Amino acid analysis revealed that dmr1 mutants contain high levels of homoserine that is undetectable in wild-type plants. Surprisingly, the level of amino acids downstream in the aspartate (Asp) pathway was not reduced in dmr1 mutants. Exogenous homoserine does not directly affect pathogen growth but induces resistance when infiltrated in Arabidopsis. We provide evidence that homoserine accumulation in the chloroplast triggers a novel form of downy mildew resistance that is independent of known immune responses.
van Damme
Mireille
M
Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands.
Zeilmaker
Tieme
T
Elberse
Joyce
J
Andel
Annemiek
A
de Sain-van der Velden
Monique
M
van den Ackerveken
Guido
G
D000596:Amino Acids / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000382:microbiology
D000596:Amino Acids; D029681:Arabidopsis Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C021370:homoserine kinase