Oxylipin profiling of the hypersensitive response in Arabidopsis thaliana. Formation of a novel oxo-phytodienoic acid-containing galactolipid, arabidopside E.
Oxidation products of unsaturated fatty acids, collectively known as oxylipins, function as signaling molecules in plants during development, wounding, and insect and pathogen attack. Certain oxylipins are also known to have direct cytotoxic effects on pathogens. We used inducible expression of bacterial avirulence proteins in planta to study the involvement of oxylipins in race-specific defense against bacterial pathogens. We demonstrate that recognition of the Pseudomonas syringae avirulence protein AvrRpm1 induces 9- and 13-lipoxygenase-dependent oxylipin synthesis in Arabidopsis thaliana. The major oxylipins accumulated were jasmonic acid, 12-oxo-phytodienoic acid, and dinor-oxo-phytodienoic acid. The majority of the newly formed oxylipins (>90%) was found to be esterified to glycerolipids, whereby 12-oxo-phytodienoic acid and dinor-oxo-phytodienoic acid were found to be esterified to a novel galactolipid. The structure of the substance was determined as a monogalactosyldiacylglycerol containing two 12-oxo-phytodienoic acids and one dinor-oxo-phytodienoic acid acyl chain and was given the trivial name arabidopside E. This substance accumulated to surprisingly high levels, 7-8% of total lipid content, and was shown to inhibit growth of a bacterial pathogen in vitro. Arabidopside E was formed also after recognition of the avirulence protein AvrRpt2, suggesting that this could be a conserved feature of defense reactions against bacterial pathogens. In conclusion, the data presented suggest a role of enzymatically formed oxylipins, especially the octadecanoids and arabidopside E in race-specific resistance against bacterial pathogens.
Andersson
Mats X
MX
Department of Plant and Environmental Sciences, Göteborg University, SE-405 30 Göteborg, Sweden.
Hamberg
Mats
M
Kourtchenko
Olga
O
Brunnström
Asa
A
McPhail
Kerry L
KL
Gerwick
William H
WH
Göbel
Cornelia
C
Feussner
Ivo
I
Ellerström
Mats
M
D017360:Arabidopsis / Q000378:metabolism* / Q000382:microbiology; D005227:Fatty Acids / Q000737:chemistry; D038983:Galactolipids / Q000737:chemistry* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008055:Lipids / Q000737:chemistry; D008956:Models, Chemical; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000378:metabolism; D013997:Time Factors; D019076:Transgenes
D005227:Fatty Acids; D038983:Galactolipids; D008055:Lipids; D010940:Plant Proteins; C515116:arabidopside E