Polyester composition

Mature seeds of Arabidopsis thaliana and Brassica napus contain a complex mixture of aliphatic monomers derived from the non-extractable lipid polyesters deposited by various seed tissues. Methods of polyester depolymerization of solvent-extracted seeds and analysis of aliphatic monomers were compared. Sodium methoxide-catalyzed depolymerization, followed by GC analysis of the acetylated monomers, was developed for routine quantitative analysis suitable for 0.5 g seed samples. In Arabidopsis seeds, the major C16 and C18 monomers identified included ω-hydroxy fatty acids and α, ω-dicarboxylic acids derived from palmitate, oleate and linoleate, and 9, 10, 18-trihydroxyoctadecenoic acid. Among monomers which can collectively be considered likely to be derived from suberin, docosan-1-ol, docosane-1, 22-diol, 22-hydroxydocosanoic acid, 24-hydroxytetracosanoic acid, tetracosane-1, 24-dioic acid and ferulic acid were the major species. Compared to Arabidopsis, Brassica seeds showed a roughly similar proportion of monomer classes, with the exception that alkan-1ols were 3-fold higher. Also, there were much less C24 aliphatic species and significant amounts of C14–C16 alkan-1ols, including iso- and anteiso-methyl branched compounds. Dissection and analysis of mature Brassica seeds showed that the trihydroxy C18:1 fatty acid was found mainly in the embryo, while ferulate, fatty alcohols and C22 and C24 species were specific to the seed coat plus endosperm.

Graphical abstract

Analysis of the presumed cutin and suberin monomers of the mature seeds of Brassica napus and Arabidopsis thaliana shows a similar grouping of monomer classes but some significant differences in molecular species compositions.

Keywords

• Arabidopsis thaliana;
• Brassica napus;
• Brassicaceae;
• Seeds;
• Lipid polyesters;
• Cutin;
• Suberin;
• Aliphatic monomers