Suberin aliphatic components

Inhibition of synthesis of the aromatic matrix by inhibitors of phenylalanine ammonia lyase causes the inhibition of deposition of aliphatic components and prevents development of diffusion resistance. Inhibition of synthesis of peroxidase, the enzyme involved in the deposition of the polymeric phenolic matrix, caused by iron deficiency, prevents deposition of aliphatic components of suberin. 

The time-course of deposition of aromatic monomers into the polymer laid down by suberizing tissue slices indicates that the phenolic matrix is deposited simultaneously with or slightly before the aliphatic components. The specific anionic peroxidase appeared with a time-course consistent with its involvement in the polymerization and deposition of the phenolic matrix of the suberin. Increase or decrease in suberin content involves similar changes in both the aliphatic and aromatic components and such changes are associated with the expected increase or decrease in the anionic peroxidase activity caused by physical or biological stress. 

Removal of the aliphatic materials by hydrogenolysis leaves a residue that contains low amounts of polymethylenic components, suggesting that the suberized material contains some aliphatic components not susceptible to cleavage by such methods [3]. On the other hand, removal of suberin from cork cell wall preparations was examined by CPMAS and the results showed that the aliphatic components were nearly completely removed from this suberin preparation as the spectra showed that the residual material was virtually devoid of methyl... 

In suberizing potato tuber disks, labeled oleic acid was incorporated into co-hy-droxyoleic acid and the corresponding dicarboxylic acid, the two major aliphatic components of potato suberin [73]. Exogenous labeled acetate was also incorporated into all of the aliphatic components of suberin, including the very long chain acids and alcohols in the wound-healing potato slices. The time-course of incorporation of the labeled precursors into the suberin components was consistent with the time-course of suberization. The biosynthetic pathway for the major aliphatic components of suberin is shown in Fig. 8a. 

Fig. 8a, b. a Biosynthetic pathways for the major aliphatic components of suberin. b Representation of the active site of co-hydroxy acid dehydrogenase involved in the synthesis of the dicarboxylic acids characteristic of suberin. From [74]... 

The major aliphatic components of suberins are Cf>-hydroxy acids and dicarboxylic acids. Octadec-9-ene-dioic acid is the usual dicarboxylic acid, and 18-hydroxyoleic the major hydroxy fatty acid. The... 

Hydroxy acids are major aliphatic components of cutin and suberin and these are readily identified by GLC-mass spectrometry. Major ions generated from the usual cutin components are listed in Kolattukudy (1977). The position of the hydroxyl group in the chain is easily seen because cleavage occurs on either side of the substituent (Fig. 6.13). The rather simple phenolic compounds yielded by reductive depolymerization of cutin and suberin are also very... 

The major aliphatic components of suberin are to-hydroxy acids, the corresponding dicarboxylic acids, very long acids (greater than C20), and similarly long alcohols. Among the u)-hydroxy and dicarboxylic acids, monounsaturated C18 and... 

Composition of the Aliphatic Components of Suberin and Comparison with That of Cutin°... 

H00C(CH2) 4C00H H00C(CH2)tCH =CH(CH2)tC00H Fig. 17. Proposed biosynthetic pathways for the major aliphatic components of suberin. 

Fernando G, Zimmermann W, Kolattukudy PE (1984) Suberin-grown Fusarium solani f. sp. pisi generates a cutinase like esterase which depolymerizes the aliphatic components of suberin. Plant Pathol 24 143-155... 

HCA may also be covalenty attached to aliphatic components of cutin and suberin. The amount of covalently bound phenolic compounds m-, /7-coumaric acids and flavonoids) in tomato fruit cutin increased during fruit development and accounted for as much as 6% of cutin membranes. Protoplasts isolated from immature tomato fruit secrete a wall that has been shown to contain suberin, in which phenolic compounds formed 25% of total monomers [3]. 

Fig. 6.4.5. Methods used to analyze the aliphatic components of suberin. Top left chemical methods used to depolymerize suberin. Top right gas-liquid chromatogram of the mixture of monomers generated by LiAlD4 treatment of suberin from the chalazal region of the inner seed coat of Citrus paradisi the components are trimethylsilyl ethers of 1,16-dihydroxyhexadecane (1), 1,18-dihydroxy-octadecene (2), 1,9,18-trihydroxyoctadecene (3), 1,9,18-trihydroxyoctadecane (4), 1,9,10,18-tetrahy-droxyoctadecane (5), 1,22-dihydroxydocosane (6), 1,24-dihydroxytetracosane (7). Bottom mass spectrum of component 2 from gas chromatogram (111)...

Table 6.4.5. Composition of the aliphatic components of suberin from the periderm of the underground storage organs of three plants...

A fraction analogous to BjOrkman lignin (39) was obtained when a portion of finely-powdered suberin polymer from the periderm of 5. tuberosum was solubilized with dioxane. This soluble fraction, however, was not enriched in either aromatic or aliphatic components over the insoluble residue (unpublished results). Other procedures from lignin chemistry - including refluxing in HCl/dioxane or HCl/dimethylformamide, and dioxane treatment at 160 C and high pressure (268, 396) - resulted in 20 o to 50% solubilization of the suberin preparation, but with each method the insoluble material contained the majority... 

Initial studies, primarily done on suberin from the periderm of S. tuberosum give additional indication of the secondary structure of the polymer. Enriched preparations of suberin always contain high levels of carbohydrate (as much as 50 o). Obviously the suberin-enriched preparations contain covalently attached cell wall carbohydrates and the linkages between suberin and carbohydrate may be similar to those proposed for the attachment of lignin to carbohydrate (132, 268). Chemical studies on the polymer have shown that very few of the hydroxyl groups of cu-hydroxy acids are free and that the polymer has very few (< 5%) free aliphatic carboxyl moieties (230). Fractionation of S. tuberosum suberin by partial solubilization with 1 % HCl/dioxane has indicated that the aliphatic components may be in separate domains, for polymeric fractions that contained a larger proportion of fatty acids and fatty alcohols but a lower proportion of cu-hydroxy acids and dicarboxylic acids have been isolated. These fatty acids and fatty alco-... 

A high content of dicarboxylic acid is the most characteristic feature of the composition of aliphatic components of suberin (231). The generation of dicarboxylic acids by oxidation of endogenous cu-hydroxy fatty acids has been demonstrated in cell-free preparations from the excised epidermis of Vida faba leaves (242). This dehydrogenase activity, which showed a strong preference for NADP, was located in the 100000-g supernatant. Modification of the substrate, o>-hydroxyhex-adecanoic acid, by removal or esterification of the carboxyl or incorporation of a hydroxyl moiety at C-10, rendered it a poor substrate. cu-Oxohexadecanoic acid could be trapped by dinitrophenylhydrazine, indicating that the oj-oxo acid was probably an intermediate in the reaction. Additionally, synthetic co-oxohex-adecanoic acid was converted to Cjg dicarboxylic acid by the enzyme preparation. 

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