Cutin monomers

Leaf discs from rapidly expanding V.faba leaves incorporated 14C-labeled palmitic acid into cutin. After removal of the soluble lipids and other materials, the insoluble residue was subjected to LiAlH4 hydrogenolysis and the labeled reduction products of cutin monomers were identified by chromatography as hexadecane-... 

Fig. 7. Biosynthesis of cutin monomers, and the polymer from the monomers (inset, bottom left). ACP = acyl carrier protein...

Based on the composition of the C18 family of cutin monomers we postulated that oleic acid would be > hydroxy la ted first, followed by epoxidation of the double bond at C-9 followed by the hydrolytic cleavage of the oxirane to yield 9,10,18-trihydroxy acid. This postulate was experimentally verified by the demonstration of specific incorporation of exogenous 18-hydroxyoleic acid into 18-hydroxy-9,10-epoxy C18 acid in grape berry skin slices and apple fruit skin disks, and incorporation of exogenous labeled 18-hydroxy-9,10-epoxy C18 acid into 9,10,18-trihydroxy C18 acid of cutin in apple fruit skin slices [61]. 

Conidia from pathogenic fungi that land on a plant surface carry low levels of cutinase to sense the contact with the host, and the cutin monomers generated upon contact of the conidia with the plant can be the inducers that allow the fungus to produce enough quantities of cutinase to gain access into the host (Fig. 12). This postulate was supported by many lines of evidence. Highly pa-... 

Fig. 13. Postulated mechanism by which cutin monomers produced by constitutive expression of c f2/3 induce cut ...

Lin TS, Kolattukudy PE (1978) Induction of a biopolyester hydrolase (cutinase) by low levels of cutin monomers in Fusarium solani f sp. pisi. J Bacteriol 133 942-951... 

P. Schweizer, A. Jeanguenat, D. Whitacre, J. P. Metraux, E. Mosinger, Induction of resistance in barley against Erysiphe graminis f.sp. hordei by free cutin monomers. Physiol. Mol. Plant Pathol. 49 (1996) 103. 

Table 2.7 Typical cutin monomers and their ability to form polyesters...

Cutin monomers (acids) capable of cross-linking a polyester polymer... 

Cutin monomers copoble forming only o Imeor polyester Monobasic a.tu-D bosic... 

Cutin is composed of chiefly a Cig family and/or a Cig family of monomers (Fig. 9). The usual meyor components of the former are palmitic acid, 16-hy-droxypalmitic acid, and 10,16-dihydroxypalmitic acid and/or its positional isomers, in which the midchain hydroxyl group is at C-9, C-8, or C-7 (Kolat-tukudy, 1977b Brieskom, 1978). The dihydroxy acid from papaya and tomato cutin showed a plain-positive rotation, and therefore the L configuration has been assigned to this major cutin monomer (Espelie and... 

Since AA is only a minor fatty acid in higher plants, eicosanoids are not of major importance for plant physiology. However, the oxygenation metabolites of linoleic acid and a-linolenic acid, called oxylipins [5,6], do play a role in plant defence reactions, in the formation of phytohormones and in the synthesis of cutin monomers [6,40-43]. Oxylipins constitute a family of lipids that are formed from free fatty acids by a cascade of reactions involving at least one step of dioxygen-dependent oxidation. The biosynthesis of oxylipins proceeds via a large number of metabolic pathways, most of which involve an unsaturated hydroperoxy fatty acid as intermediate (Scheme 10). Conversion of the hydroperoxide via the peroxide lyase pathway, the allene oxide pathway and the recently discovered peroxygenase pathway, leads to a complex pattern of oxidized lipid mediators. 

The epoxy compounds formed via the peroxygenase reaction may then be hydrolysed by epoxide hydrolases that are an integral part of the peroxygenase pathway, forming di- or trihydroxy fatty acids. This pathway is of importance for plant defence as it is hkely to be involved in the biosynthesis of cutin monomers, in the production of antifungal compounds and in detoxification mechanisms [6]. 

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