The composition of surface wax on trichomes of Arabidopsis thaliana differs from wax on other epidermal cells

To protect plants against biotic and abiotic stress, the waxy cuticle must coat all epidermis cells. Here, two independent approaches addressed whether cell-type-specific differences exist between wax compositions on trichomes and other epidermal cells of Arabidopsis thaliana, possibly with different protection roles. First, the total waxes from a mutant lacking trichomes (gl1) were compared to waxes from wild type and a trichome-rich mutant (cpc tcl1 etc1 etc3). In the stem wax, compounds with aliphatic chains longer than 31 carbons (derived from C-32 precursors) increased in relative abundance in cpc tcl1 etc1 etc3 over gl1. Similarly, the leaf wax from the trichome-rich mutant contained higher amounts of C32+ compounds as compared to gl1. Second, leaf trichomes were isolated, and their waxes were analyzed. The wax mixtures of the trichome-rich mutant and the wild type were similar, comprising alkanes and alkenes as well as branched and unbranched primary alcohols. The direct analyses of trichome waxes confirmed that they contained relatively high concentrations of C32+ compounds, compared with the pavement cell wax inferred from analysis of gl1 leaves. Finally, the cell-type-specific wax compositions were put into perspective with expression patterns of wax biosynthesis genes in trichomes and pavement cells. Analyses of published transcriptome data (Marks etal., ) revealed that core enzymes involved in elongation of wax precursors to various carbon chain lengths are expressed differentially between epidermis cell types. By combining the chemical and gene expression data, we identified promising gene candidates involved in the formation of C32+ aliphatic chains. Significance Statement Surface properties of different epidermal cells differ. Cuticular wax analyses distinguish between the compositions of lipid mixtures coating Arabidopsis leaf trichomes and neighbouring pavement cells. Integrating wax compositions of different epidermal cell types with gene expression data shows that trichome cells have an autonomous wax biosynthesis machinery and gene candidates involved in the formation of aliphatic chains longer then C-32 were identified.