Dean B B, Kolattukudy P E
Department of Agricultural Chemistry, Washington State University, Pullman, Washington 99163.
Plant Physiol. 1977 Jan;59(1):48-54. doi: 10.1104/pp.59.1.48.
Biosynthesis of the aliphatic components of suberin was studied in suberizing potato (Solanum tuberosum) slices with [1-(14)C]oleic acid and [1-(14)C]acetate as precursors. In 4-day aged tissue, [1-(14)C]oleic acid was incorporated into an insoluble residue, which, upon hydrogenolysis (LiA1H(4)), released the label into chloroform-soluble products. Radio thin layer and gas chromatographic analyses of these products showed that (14)C was contained exclusively in octadecenol and octadecene-1, 18-diol. OsO(4) treatment and periodate cleavage of the resulting tetraol showed that the labeled diol was octadec-9-ene-1, 18-diol, the product expected from the two major components of suberin, namely 18-hydroxyoleic acid and the corresponding dicarboxylic acid. Aged potato slices also incorporated [1-(14)C]acetate into an insoluble material. Hydrogenolysis followed by radio chromatographic analyses of the products showed that (14)C was contained in alkanols and alkane-alpha,omega-diols. In the former fraction, a substantial proportion of the label was contained in aliphatic chains longer than C(20), which are known to be common constituents of suberin. In the labeled diol fraction, the major component was octadec-9-ene-1,18-diol, with smaller quantities of saturated C(16), C(18), C(20), C(22), and C(24)-alpha,omega-diols. Soluble lipids derived from [1-(14)C]acetate in the aged tissue also contained labeled very long acids from C(20) to C(28), as well as C(22) and C(24) alcohols, but no labeled omega-hydroxy acids or dicarboxylic acids were detected. Label was also found in n-alkanes isolated from the soluble lipids, and the distribution of label among them was consistent with the composition of n-alkanes found in the wound periderm of this tissue; C(21) and C(23) were the major components with lesser amounts of C(19) and C(25). The amount of (14)C incorporated into these bifunctional monomers in 0-, 2-, 4-, 6-, and 8-day aged tissue were 0, 1.5, 2.5, 0.8, and 0.3% of the applied [1-(14)C]oleic acid, respectively. Incorporation of [1-(14)C]acetate into the insoluble residue was low up to the 3rd day of aging, rapid during the next 4 days of aging, and subsequently the rate decreased. These changes in the rates of incorporation of exogenous oleic acid and acetate reflected the development of diffusion resistance of the tissue surface to water vapor. As the tissue aged, increasing amounts of the [1-(14)C]acetate were incorporated into longer aliphatic chains of the residue and the soluble lipids, but no changes in the distribution of radioactivity among the alpha-omega-diols were obvious. The above results demonstrated that aging potato slices constitute a convenient system with which to study the biochemistry of suberization.
以[1-(14)C]油酸和[1-(14)C]乙酸盐作为前体，研究了马铃薯（Solanum tuberosum）切片中木栓质脂肪族成分的生物合成。在4日龄的组织中，[1-(14)C]油酸被掺入到一种不溶性残渣中，该残渣经氢解（LiA1H(4)）后，将标记物释放到氯仿可溶产物中。对这些产物进行放射性薄层和气相色谱分析表明，(14)C仅存在于十八碳烯醇和十八碳-1,18-二醇中。对所得四醇进行OsO(4)处理和高碘酸盐裂解表明，标记的二醇是十八碳-9-烯-1,18-二醇，这是木栓质两种主要成分即18-羟基油酸和相应二羧酸的预期产物。老化的马铃薯切片也将[1-(14)C]乙酸盐掺入到一种不溶性物质中。氢解后对产物进行放射性色谱分析表明，(14)C存在于链烷醇和链烷-α,ω-二醇中。在前一组分中，相当一部分标记物存在于碳链长度超过C(20)的脂肪族链中，已知这些是木栓质的常见成分。在标记的二醇组分中，主要成分是十八碳-9-烯-1,18-二醇，还有少量饱和的C(16)、C(18)、C(20)、C(22)和C(24)-α,ω-二醇。老化组织中源自[1-(14)C]乙酸盐的可溶性脂质还含有标记的碳链长度从C(20)到C(28)的非常长链酸，以及C(22)和C(24)醇，但未检测到标记的ω-羟基酸或二羧酸。在从可溶性脂质中分离出的正构烷烃中也发现了标记物，标记物在它们之间的分布与该组织创伤周皮中发现的正构烷烃组成一致；C(21)和C(23)是主要成分，C(19)和C(25)含量较少。在0、2、4、6和8日龄组织中，掺入到这些双功能单体中的(14)C量分别为所施加[1-(14)C]油酸的0、1.5、2.5、0.8和0.3%。在老化的第3天之前，[1-(14)C]乙酸盐掺入到不溶性残渣中的量较低，在接下来的4天老化过程中迅速增加，随后速率下降。外源油酸和乙酸盐掺入速率的这些变化反映了组织表面对水蒸气扩散阻力的发展。随着组织老化，越来越多的[1-(14)C]乙酸盐被掺入到残渣和可溶性脂质的较长脂肪族链中，但在α,ω-二醇之间放射性分布没有明显变化。上述结果表明，老化的马铃薯切片构成了一个研究木栓化生物化学的便利系统。
