Cuticular wax biosynthesis is positively regulated by WRINKLED4, an AP2/ERF‐type transcription factor, in Arabidopsis stems

Abstract

The aerial surfaces of terrestrial plants are covered by a cuticular wax layer, which protects the plants from environmental stresses such as desiccation, high irradiance, and UV radiation. Cuticular wax deposition is regulated in an organ-specific manner; Arabidopsis stems have more than 10-fold higher wax loads than leaves. In this study, we found that WRINKLED4 (WRI4), encoding an AP2/ERF (ethylene-responsive factor) transcription factor (TF), is predominantly expressed in stem epidermis, is upregulated by salt stress, and is involved in activating cuticular wax biosynthesis in Arabidopsis stems. WRI4 harbors a transcriptional activation domain at its N-terminus, and fluorescent signals from a WRI4:eYFP construct were localized to the nuclei of tobacco leaf protoplasts. Deposition of epicuticular wax crystals on stems was reduced in wri4-1 and wri4-3 knockout mutants. Total wax loads were reduced by ~28% in wri4 stems but were not altered in wri4 siliques or leaves compared to the wild type. The levels of 29-carbon long alkanes, ketones, and secondary alcohols, which are the most abundant components of stem waxes, were significantly reduced in wri4 stems relative to the wild type. A transactivation assay in tobacco protoplasts and a chromatin immunoprecipitation (ChIP) assay showed that the expression of long-chain acyl-CoA synthetase1 (LACS1), β-ketoacyl CoA reductase1 (KCR1), PASTICCINO2 (PAS2), trans-2,3-enoyl-CoA reductase (ECR), and bifunctional wax synthase/acyl-CoA: diacylglycerol acyltransferase (WSD1) is positively regulated by direct binding of WRI4 to their promoters. Taken together, these results suggest that WRI4 is a transcriptional activator that specifically controls cuticular wax biosynthesis in Arabidopsis stems.

An Expanded Role for WRINKLED1 Metabolic Control Based on Combined Phylogenetic and Biochemical Analyses

“…Another aspect of 478 functional overlap not explored here is cuticular wax biosynthesis. It has been shown that A. thaliana 479 WRINKLED4, a close homolog to WRI1, regulates cuticular wax biosynthesis and has many gene targets in 480 common with WRI1 (Park et al, 2016). Since Fig.…”

Effect of Ethylene on Cell Wall and Lipid Metabolism during Alleviation of Postharvest Chilling Injury in Peach

“…Some ERFs, such as AtWRI1/3/4, have been found to directly or indirectly regulate lipid genes in Arabidopsis [36,37]. However, reports on ERF regulation of lipid genes have focused mainly on Arabidopsis [36,[38][39][40], and the investigation of the regulation of lipid genes by ERFs have rarely been reported in fruits.…”

Expression of Arabidopsis SHN1 in Indian Mulberry (Morus indica L.) Increases Leaf Surface Wax Content and Reduces Post-harvest Water Loss

“…Considerable progress has been made in understanding the genetic determinants of the biosynthesis of cutin and cuticular waxes in model plants (Kunst et al, 2006; Kunst and Samuels, 2009; Yeats and Rose, 2013; Lee and Suh, 2015a). A number of upstream regulatory proteins such as transcriptions factors (TFs) that coordinate the expression of downstream target genes associated with wax biosynthesis have been shown to alter leaf surface wax load (Broun et al, 2004; Seo et al, 2011; Borisjuk et al, 2014; Park et al, 2016). Many regulatory proteins, such as, SHINE1/Wax Inducer1 ( SHN1/WIN1 ) in Arabidopsis thaliana (Aharoni et al, 2004; Broun et al, 2004), WXP1/2 in Medicago (Zhang et al, 2005, 2007), Outer Cell Layer 1 ( OCL1 ) in Zea mays (Javelle et al, 2010), MYB96 in Arabidopsis and Camelina sativa (Seo et al, 2011; Lee et al, 2014), MYB94 in Arabidopsis (Lee and Suh, 2015b), MYB106 and MYB16 in Arabidopsis and Torenia fournieri , respectively (Oshima et al, 2013), have been shown to be associated with surface wax deposition.…”