Wax Ester Synthases/Acyl-CoA:Diacylglycerol Acyltransferases (WS/DGATs) from <em>Arabidopsis thaliana</em>

Abstract

Wax esters occur in the surface wax of plants and are involved amongst others in the plant’s response to drought. In <em>Arabidopsis thaliana</em>, a family of 11 genes are annotated as bifunctional wax ester synthases/acyl-CoA diacylglycerol acyltransferases (WS/DGATs) and designated as <em>WSD1</em> – <em>WSD11</em>. WSD1 was previously characterized to contribute wax esters to the surface wax of stem. <br /> In this study, the surface waxes of <em>Arabidopsis thaliana</em> stem, silique and flowers were analyzed from wild type and <em>wsd</em> insertion mutants regarding the amount and species composition of wax esters by quadrupole time-of-flight mass spectrometry. In wild type, wax ester species with 16:0 acyl moiety were most abundant in the surface waxes of stem, silique and flower. The mutant <em>wsd1</em> revealed a reduction of wax ester species with 16:0 acyl moieties in the surface waxes of stem, flower and silique. <em>WSD</em> gene expression was measured for <em>WSD1</em> – <em>WSD11</em> in root, stem, leaf, inflorescence and seed under normal growth conditions and in root and leaf after exposure to drought, salt and abscisic acid (ABA). The expression of <em>WSD1</em> was induced in leaf and the expression of <em>WSD6</em> and <em>WSD7</em> increased in both root and leaf after exposure to drought, salt and ABA. Heterologous expression of WSD1 in yeast led to the detection of an unknown lipid 1 (UL1) while wax ester synthase activity was not detected. Subcellular localization studies of WSD3, WSD4 and WSD9 indicated the three WSD proteins reside at the endoplasmic reticulum. Furthermore, the wax ester load of leaves from drought-stressed <em>Hordeum vulgare</em> was measured revealing an increased wax ester load in leaf surface wax compared to the control.