Extracellular lipids ofCamelina sativa: Characterization of cutin and suberin reveals typical polyester monomers and novel functionalized dicarboxylic fatty acids

Camelina sativa is relatively drought tolerant and requires less fertilizer than other oilseed crops. Various lipid- and phenolic-based extracellular barriers of plants help to protect them against biotic and abiotic stresses. These barriers, which consist of solvent-insoluble polymeric frameworks and solvent-extractable waxes, include the cuticle of aerial plant surfaces and suberized cell walls found, for example, in periderms and seed coat. Cutin, the polymeric matrix of the cuticle, and the aliphatic domain of suberin are fatty acid- and glycerol-based polyesters. These polyesters were investigated by base-catalyzed transesterification of C. sativa aerial and underground delipidated tissues followed by gas chromatographic analysis of the released monomer mixtures. Seed coat and root suberin had similar compositions, with 18-hydroxyoctadecenoic and 1,18-octadecenedioic fatty acids being the dominant species. Root suberin presented a typical lamellar ultrastructure, but seed coats showed almost imperceptible, faint dark bands. Leaf and stem lipid polyesters were composed of fatty acids (FA), dicarboxylic acids (DCA), ω-hydroxy fatty acids (OHFA) and hydroxycinnamic acid derivatives (HCA). Dihydroxypalmitate (DHP) and caffeic acid were the major constituents of leaf cutin, whereas stem cutin presented similar molar proportions in several monomers across the four classes. Unlike the leaf cuticle, the C. sativa stem cuticle presented lamellar structure by transmission electron microscopy. Flower cutin was dominated by DHP and did not contain aromatics. We found striking differences between the lipid polyester monomer compositions of aerial tissues of C. sativa and that of its close relatives Arabidopsis thaliana and Brassica napus . Graphical Abstract Camelina sativa leaf and stem cutin is dominated by 16:0 dihydroxy fatty acid and aromatics, with dicarboxylic fatty acids representing 20-30 % of the monomers. Suberin of root and seed coat is largely composed of 18:1 dicarboxylic and ω-hydroxy fatty acids. Highlight bullet points Camelina sativa is an oil crop tolerant to biotic and abiotic stresses Extracellular lipid polyesters may in part confer these attributes Dihydroxypalmitate and caffeic acid were major components of C. sativa leaf cutin Flower cutin lacked aromatics and contained monomers not previously reported Root and seed coat suberin was dominated by 18:1 ω-hydroxy and dicarboxylic fatty acids C18 monounsaturated photo-oxidation products were found in leaf cutin and suberin