title: 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.
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea.
authors.forename: Chan Song
authors.initials: CS
authors.lastname: Park
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea.
authors.forename: Young Sam
authors.initials: YS
authors.lastname: Go
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea.
authors.forename: Mi Chung
authors.initials: MC
authors.lastname: Suh
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism*; D050656:Transcription Factor AP-2 / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014885:Waxes / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D014885:Waxes
keywords: 
  Arabidopsis thaliana
  ; WRI4; WRINKLED4; cuticular wax; organ-specific; transcription factor