A saponin-detoxifying enzyme mediates suppression of plant defences.
Plant disease resistance can be conferred by constitutive features such as structural barriers or preformed antimicrobial secondary metabolites. Additional defence mechanisms are activated in response to pathogen attack and include localized cell death (the hypersensitive response). Pathogens use different strategies to counter constitutive and induced plant defences, including degradation of preformed antimicrobial compounds and the production of molecules that suppress induced plant defences. Here we present evidence for a two-component process in which a fungal pathogen subverts the preformed antimicrobial compounds of its host and uses them to interfere with induced defence responses. Antimicrobial saponins are first hydrolysed by a fungal saponin-detoxifying enzyme. The degradation product of this hydrolysis then suppresses induced defence responses by interfering with fundamental signal transduction processes leading to disease resistance.
Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, UK.
K
K
Bouarab
R
R
Melton
J
J
Peart
D
D
Baulcombe
A
A
Osbourn
D000890:Anti-Infective Agents / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001203:Ascomycota / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D016923:Cell Death / Q000187:drug effects; D004198:Disease Susceptibility; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D006790:Host-Parasite Interactions; D006868:Hydrolysis; D007113:Immunity, Innate / Q000187:drug effects; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012503:Saponins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D014053:Tomatine / Q000378:metabolism / Q000494:pharmacology
D000890:Anti-Infective Agents; D012333:RNA, Messenger; D018749:RNA, Plant; D012503:Saponins; D014053:Tomatine; D006026:Glycoside Hydrolases; C099475:tomatinase