Several inositol sphingophospholipids (ISPL) were isolated from mycelia ofPhytophthora capsici, a phytopathogenic fungus of pepper (Capsicum annuum c.v. Yolo Wonder). The sphingophospholipids induce a protective response by cotyledons of young peppers against necrotic lesions caused by the pathogenP. capsici. The ISPL structures were determined by chemical methods, fast atom bombardment mass spectrometry and by fast atom bombardment collision‐induced tandem mass spectrometry. All ISPL consisted of ceramides linked to inositol phosphate. The amidelinked fatty acids were found to have 16, 20 and 22 carbon chains. The long chain bases were identified as trimethylsilyl derivatives and shown to be C16‐sphingosine and C16‐dihydrosphingosine. The protective effect of the ISPL on cotyledons of young peppers against necrotic lesions caused by the pathogenP. capsici was shown not to be dependent on the unsaturation of the C16‐sphingosine base and the nature of the acyl chain. We also investigated the effect of growth conditions on the ISPL produced in three different, chemically defined media that are commonly used for fungi cultures. We showed thatP. capsici synthesized one major class of compounds with molecular weights of Mr=833 and 835 containing the 16∶1 base and the 22∶1 or the 22∶0N‐acyl group, independent of the growth medium used. The presence of phosphite or fosetyl‐A1 did not affect the result.
Inositol sphingophospholipids that protect pepper (Capsicum annuum c. v. Yo10 Wonder) against pathogen have been isolated by chromatographic methods from the mycelium of Phytophthora capsici. The structure of the major compound was determined by chemical methods and mass spectrometry. Phosphodiester bond cleavage of the phospholipid by mild alkaline hydrolysis liberated a ceramide which contained a C16-sphingosine. This longchain base was identified by gas chromatography and mass spectrometry of its trimethylsilyl derivative. One of the amide-linked fatty acids was found to be 4-hydroxy-2 docosenoic acid. Fast-atom-bombardment mass spectrometry and fast-atom-bombardment collison-induced tandem mass spectrometry were used to characterize the ceramide as N(4-hydroxy-2-docosenoyl)C1 6-sphingosine. These sphingolipids have a protective effect on cotyledons of young peppers against necrotic lesions induced by the pathogen P . capsici.Various lipids from parasitic fungi have been found to be elicitors of plant defense reactions [l -41 and the polyunsaturated fatty acids, arachidonic and eicosapentaenoic acids, found in mycelial extracts of Phytophthora injestans, are highly active elicitors of the hypersensitive response in potato tuber tissue [5 -71. Creamer and Bostock [8] reported that triacylglycerols and phospholipids of the mycelium of P. infestans, containing arachidonic and eicosapentaenoic acids, elicit a hypersensitive response with sesquiterpenoid phytoalexins accumulation in potato tubers. Molot et al. [9, 101 isolated a mycelial extract from Phytophthora capsici which induced protection in cotyledons of pepper infected by a zoospores suspension. Lhomme et al. [ll] found that the lipid components of this mycelial extract induced protection in pepper against the pathogen P. capsici.The present paper describes the isolation and the characterization of the most active fraction as inositol sphingophospholipids.
La résistance du piment (Capsicum annum L.) à Phytophthora capsici Léon. X. -Influence de la température sur l'accumulation du capsidiol et les variations de l'induction de résistance
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