ArabidopsisCuticular Wax Biosynthesis Is Negatively Regulated by theDEWAXGene Encoding an AP2/ERF-Type Transcription Factor

Young Sam Go,Hae Jin Kim,Mi Chung Suh,Hyojin Kim

doi:10.1105/tpc.114.123307

Abstract

The aerial parts of plants are protected from desiccation and other stress by surface cuticular waxes. The total cuticular wax loads and the expression of wax biosynthetic genes are significantly downregulated in Arabidopsis thaliana under dark conditions. We isolated Decrease Wax Biosynthesis (DEWAX), which encodes an AP2/ERF-type transcription factor that is preferentially expressed in the epidermis and induced by darkness. Disruption of DEWAX leads to an increase in total leaf and stem wax loads, and the excess wax phenotype of dewax was restored to wild type levels in complementation lines. Moreover, overexpression of DEWAX resulted in a reduction in total wax loads in leaves and stems compared with the wild type and altered the ultrastructure of cuticular layers. DEWAX negatively regulates the expression of alkane-forming enzyme, long-chain acyl-CoA synthetase, ATP citrate lyase A subunit, enoyl-CoA reductase, and fatty acyl-CoA reductase, and chromatin immunoprecipitation analysis suggested that DEWAX directly interacts with the promoters of wax biosynthesis genes. Cuticular wax biosynthesis is negatively regulated twice a day by the expression of DEWAX, throughout the night and at stomata closing. Significantly higher levels (10- to 100-fold) of DEWAX transcripts were found in leaves than in stems, suggesting that DEWAX-mediated transcriptional repression may be an additional mechanism contributing to the different total wax loads in leaves and stems.

Highlights

During the transition from an aquatic to a terrestrial environment, land plants developed a hydrophobic cuticle layer that resists desiccation and high irradiation (Pollard et al, 2008; Samuels et al, 2008; Yeats and Rose, 2013)
Cuticular waxes were extracted with chloroform and analyzed by gas chromatography–flame ionization detection (GC-FID) and gas chromatography–mass spectrometry (GC-Murashige and Skoog (MS))
It has been reported that cuticular wax deposition increases more in the light than in the dark (Giese, 1975; Shepherd et al, 1995), little is known about the molecular mechanisms underlying the regulation of cuticular wax biosynthesis

Summary

Introduction

During the transition from an aquatic to a terrestrial environment, land plants developed a hydrophobic cuticle layer that resists desiccation and high irradiation (Pollard et al, 2008; Samuels et al, 2008; Yeats and Rose, 2013). Cutin is a polyester mainly composed of hydroxy, epoxy, and dicarboxylic fatty acids, while cuticular waxes include very-long-chain fatty acids (VLCFAs) and their derivatives such as alkanes, ketones, primary and secondary alcohols, aldehydes, and wax esters (Pollard et al, 2008; Samuels et al, 2008; Li-Beisson et al, 2013). In the alcohol-forming pathway, fatty acyl-CoA reductase (FAR3/CER4) converts the VLCFAs into primary alcohols (Aarts et al, 1997; Rowland et al, 2006), and the resulting fatty alcohols and C16:0 acyl-CoA are condensed into wax esters by the bifunctional wax synthase/ acyl-CoA:diacylglycerol acyltransferase enzyme, WSD1 (Li et al, 2008). The cuticular wax components, which are generated in the endoplasmic reticulum, are transported to the epidermal surface by the adenosine triphosphate binding cassette transporters ABCG11/ CER5 in the plasma membrane

Methods

Results

Conclusion