Synthesis of Suberin during Wound-healing in Jade Leaves, Tomato Fruit, and Bean Pods.

The structure and composition of the aliphatic monomers of the polymeric material deposited during wound-healing of tomato fruit, bean pods, and Jade leaves were examined. After removing the cuticle-containing layer of tissue, the wounds were healed for 14 days and the resulting surface layer was excised, lyophilized, solvent-extracted, and depolymerized by hydrogenolysis with LiAlH(4) or transesterified with BF(3) in methanol. The products obtained by the chemical depolymerization were subjected to thin layer chromatography and combined gas chromatography and mass spectrometry. The major aliphatic components isolated from the hydrogenolysate of the wound polymer produced by tomato fruit were hexadecane-1,16-diol and octadec-9-ene-1,18-diol, which were shown to be derived from a 1:1 mixture of omega-hydroxy and dicarboxylic acids of the appropriate chain length by LiAlH(4) reduction. Also identified in the wound polymer were long chain (>C(20)) fatty acids and alcohols. This monomer composition is typical of suberin polymers and is in sharp contrast with that of the cutin of tomato fruit which contains dihydroxy C(16) acid as the major aliphatic component. The hydrogenolysis of the wound material from bean pods gave octadecene-1,18-diol as the major aliphatic component, and smaller amounts of hexadecane-1,16-diol and long chain alcohols. Similar treatment of the normal cuticular tissue of these pods gave hexadecane triol, as well as C(16) and C(18) alcohols. Hydrogenolysis of wound material from the Jade leaves gave octadecene-1,18-diol, C(16) and C(22) diols, as well as alcohols from C(16) to C(26), whereas similar treatment of the cutin-containing tissue from these leaves gave C(16) triol as the major aliphatic component. Thus, the major aliphatic monomers of the polymeric material deposited during the wound-healing of bean pods and Jade leaves are very similar to those of suberin, although the natural protective polymer of these tissues is cutin. From these results, it is concluded that suberization is a fundamental process involved in wound-healing in plants, irrespective of the chemical nature of the natural protective polymer of the tissue.