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

Abstract

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 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 C 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 C 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 et al., ) 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 C aliphatic chains.

Arabidopsis ketoacyl‐CoA synthase 16 (KCS16) forms C36/C38 acyl precursors for leaf trichome and pavement surface wax

“…Leaf wax of the Arabidopsis mutant gl1 , lacking trichomes, contains small but significant amounts of C 36 and C 38 products (Hegebarth et al . ; Busta et al . ), showing that pavement and guard cells also harbour elongation machineries that can produce such chain lengths.…”

“…The wax was extracted following the protocol described in Hegebarth et al . (). For quantitative and qualitative analysis, the samples were loaded onto gas chromatography (GC) systems equipped with flame ionization detector (FID) and mass spectrometric detector (MS), respectively, and analysed as described by Buschhaus & Jetter ().…”

“…() with minor modifications described in Hegebarth et al . (). In brief, trichomes were removed mechanically by vortexing a suspension of leaves and silica beads in 0.5 m ethylene glycol‐bis( β ‐aminoethyl ether)‐ N , N , N ′, N ′‐tetraacetic acid solution (pH 7.8), and the resulting mixture was strained through a wire mesh (mesh size 1 mm) to remove plant organs and filtered to collect the trichomes.…”

“…The samples were derivatized as described in Hegebarth et al . (), and the wax was re‐dissolved in 10 μ L of chloroform. For quantitative and qualitative analyses of the trichome wax mixtures, GC‐FID and GC–MS were used as described by Buschhaus & Jetter ().…”

“…) and isolated leaf trichomes (Hegebarth et al . ) contain such extra‐long compounds, leading us to hypothesize a trichome‐specific KCS dedicated to the formation of C 36 and C 38 acyl‐CoAs. Analysis of microarray data (Jakoby et al .…”