Drought stress modulates cuticular wax composition of the grape berry.

Gregory A Gambetta,Changzheng Song,Nicolas Dimopoulos,Till Matzat,Simone D Castellarin,Tegan Haslam,Ljerka Kunst,Ricco Tindjau,Darren C J Wong,Fabrizio Costa

doi:10.1093/jxb/eraa046

Abstract

Drought events are a major challenge for many horticultural crops, including grapes, which are often cultivated in dry and warm climates. It is not understood how the cuticle contributes to the grape berry response to water deficit (WD); furthermore, the cuticular waxes and the related biosynthetic pathways are poorly characterized in this fruit. In this study, we identified candidate wax-related genes from the grapevine genome by phylogenetic and transcriptomic analyses. Developmental and stress response expression patterns of these candidates were characterized across pre-existing RNA sequencing data sets and confirmed a high responsiveness of the pathway to environmental stresses. We then characterized the developmental and WD-induced changes in berry cuticular wax composition, and quantified differences in berry transpiration. Cuticular aliphatic wax content was modulated during development and an increase was observed under WD, with wax esters being strongly up-regulated. These compositional changes were related to up-regulated candidate genes of the aliphatic wax biosynthetic pathway, including CER10, CER2, CER3, CER1, CER4, and WSD1. The effect of WD on berry transpiration was not significant. This study indicates that changes in cuticular wax amount and composition are part of the metabolic response of the grape berry to WD, but these changes do not reduce berry transpiration.

Highlights

The plant cuticle covers all primary aerial organs forming the outermost layer of a plant’s ‘skin’, and is the interface between the plant and environment, protecting it from biotic and abiotic stresses
These waxes are intercalated within the cutin polymer and deposited on the Abbreviations: ABA, abscisic acid; BAS, β-amyrin synthase; CER10, an ECR; CER2, BAHD acyltransferase; CER2-LIKE1, ECERIFERUM2-LIKE1; CER2-LIKE2, ECERIFERUM2-LIKE2; CER4, fatty acyl-CoA reductase; CER6, a KCS; CT, control; DAA, days after anthesis; DE, differential expression; ECR, enoyl-CoA reductase; ER, endoplasmic reticulum; FAAR, fatty acyl-CoA reductase; FAE, fatty acid elongase complex; FPKM, fragments per kilobase of transcript per million mapped reads; HCD, β-hydroxyacyl-CoA dehydratase; KCR, β-ketoacyl-CoA reductase; KCS, ketoacyl-CoA synthase; Oleanolic acid (OA), oleanolic acid; PAS2, an HCD; RPKM, reads per kilobase of transcript per million mapped reads; TF, transcription factor; VLC, very long chain; VLCFA, very long chain fatty acid; WD, water deficit; WSD1, wax ester synthase/acyl-CoA:diacylglycerol acyltransferase
The general trend of WD stress was an up-regulation of genes predicted to function in cuticular wax biosynthesis, and down-regulation of those predicted to be involved in OA biosynthesis

Summary

Introduction

The plant cuticle covers all primary aerial organs forming the outermost layer of a plant’s ‘skin’, and is the interface between the plant and environment, protecting it from biotic and abiotic stresses (reviewed in Yeats and Rose, 2013). The cuticle is a specialized lipidic modification of plant cell walls, which is largely composed of a cutin polymer that acts as a macromolecular scaffold for cuticular waxes These waxes are intercalated within the cutin polymer and deposited on the Abbreviations: ABA, abscisic acid; BAS, β-amyrin synthase; CER10, an ECR; CER2, BAHD acyltransferase; CER2-LIKE1, ECERIFERUM2-LIKE1; CER2-LIKE2, ECERIFERUM2-LIKE2; CER4, fatty acyl-CoA reductase; CER6, a KCS; CT, control; DAA, days after anthesis; DE, differential expression; ECR, enoyl-CoA reductase; ER, endoplasmic reticulum; FAAR, fatty acyl-CoA reductase; FAE, fatty acid elongase complex; FPKM, fragments per kilobase of transcript per million mapped reads; HCD, β-hydroxyacyl-CoA dehydratase; KCR, β-ketoacyl-CoA reductase; KCS, ketoacyl-CoA synthase; OA, oleanolic acid; PAS2, an HCD; RPKM, reads per kilobase of transcript per million mapped reads; TF, transcription factor; VLC, very long chain; VLCFA, very long chain fatty acid; WD, water deficit; WSD1, wax ester synthase/acyl-CoA:diacylglycerol acyltransferase. The cuticular aliphatic wax biosynthetic pathway synthesizes a range of VLC compounds, including fatty acids, primary alcohols, acyl esters (wax esters), alkanes, aldehydes, secondary alcohols, and ketones

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Discussion

Conclusion