Aliphatic components of suberin

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. 

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... 

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... 

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 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. 

The aliphatic components of suberin form polyester domains that are attached to the phenolics as indicated above (see Fig. 6.4.7). Activated cu-hydroxy acids and dicarboxylic acids are probably involved in the esterification as shown in cutin biosynthesis (232). It was proposed that the long-chain fatty alcohols found in suberin might be incorporated into the suberin polymer by peroxidase-catalyzed polymerization of phenylpropanoic acid esters of these alcohols (232), such as the ferulic acid esters of C18-C28 alcohols frequently found in suberin-as-sociated waxes (Table 6.4.2). 

Dean B B, Kolattukudy P E 1977 Biochemistry of suberization. Incorporation of [l- CJoleic acid and [l- C]acetate into the aliphatic components of suberin in potato tuber disks Solarium tuberosum). Plant Physiol 59 48-54... 

Kolattukudy P E 1978 Chemistry and biochemistry of the aliphatic components of suberin. In Kahl G (ed) Biochemistry of wounded plant tissues, de Gruyter Berlin New York, 43-84... 

HHT activity was not detectable in intact potato tuber tissue but was induced upon wounding after a lag period of three days (Fig.2). The time course of induction of HHT was therefore comparable with the kinetics of accumulation of alkyl ferulates [3] and of deposition of the aliphatic components of suberin [1]. HHT activity being restricted to the outermost cell layers of the wound-healing tuber discs, the development of HHT activity was both temporally and spatially coincident with the suberization process. The... 

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