Membrane associated stigmasterol plays an important role in plantinnate immunity

Plant nonhost resistance, a form of innate immunity, is the most common form of disease resistance exhibited by plants against the majority of potential pathogens in nature. We used virus-induced gene silencing in Nicotiana benthamiana to identify genes involved in nonhost resistance. We individuall...

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Bibliographic Details
Published in:Phytopathology 2008-06, Vol.98 (6), p.S165-S165
Main Authors: Wang, K, Ryu, C, Kang, L, Muthappa, S, Mysore, K S
Format: Article
Language:English
Subjects:
Arabidopsis
Lycopersicon esculentum
Nicotiana benthamiana
Pseudomonas syringae
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Summary:Plant nonhost resistance, a form of innate immunity, is the most common form of disease resistance exhibited by plants against the majority of potential pathogens in nature. We used virus-induced gene silencing in Nicotiana benthamiana to identify genes involved in nonhost resistance. We individually silenced similar to 4,000 genes by using cDNA clones from a normalized NbcDNA library. Eleven genes were identified to be involved in type I and/or type II nonhost resistances. One of them encodes squalene synthase (SQS), a key enzyme catalyzing the first enzymatic step in sterol biosynthesis. The Arabidopsis SQS1 RNAi lines were not only susceptible to nonhost pathogens, Pseudomonas syringae pv. tabaci and P. syringae pv. syringae, but also more susceptible to pathogens, P. syringae pv. tomato DC3000 and P. syringae pv. macuticola, when compared to wild-type Arabidopsis. We also discovered that a mutation in Arabidopsis SMT2, a gene encoding sterol methyltransferase (downstream enzyme in phytosterol biosynthesis), also compromised nonhost resistance. Silencing SQS gene resulted in plant cell membrane leakage in both Arabidopsis and N. benthamiana. Metabolite analysis indicated that, compared to the wild-type Arabidopsis, SQSI RNAi lines and a smt2 mutant produced less stigmasterol. Strikingly, we found more stigmasterol accumulation in the wild-type plants upon inoculation with a nonhost pathogen. Our data suggest that the membrane associated stigmasterol plays an important role in plant immunity against bacterial infections.
ISSN:0031-949X