title: Pectic-β(1,4)-galactan, extensin and arabinogalactan-protein epitopes differentiate ripening stages in wine and table grape cell walls.
abstract: OBJECTIVE
  Cell wall changes in ripening grapes (Vitis vinifera) have been shown to involve re-modelling of pectin, xyloglucan and cellulose networks. Newer experimental techniques, such as molecular probes specific for cell wall epitopes, have yet to be extensively used in grape studies. Limited general information is available on the cell wall properties that contribute to texture differences between wine and table grapes. This study evaluates whether profiling tools can detect cell wall changes in ripening grapes from commercial vineyards.
  
  
  METHODS
  Standard sugar analysis and infra-red spectroscopy were used to examine the ripening stages (green, véraison and ripe) in grapes collected from Cabernet Sauvignon and Crimson Seedless vineyards. Comprehensive microarray polymer profiling (CoMPP) analysis was performed on cyclohexanediaminetetraacetic acid (CDTA) and NaOH extracts of alcohol-insoluble residue sourced from each stage using sets of cell wall probes (mAbs and CBMs), and the datasets were analysed using multivariate software.
  
  
  RESULTS
  The datasets obtained confirmed previous studies on cell wall changes known to occur during grape ripening. Probes for homogalacturonan (e.g. LM19) were enriched in the CDTA fractions of Crimson Seedless relative to Cabernet Sauvignon grapes. Probes for pectic-β-(1,4)-galactan (mAb LM5), extensin (mAb LM1) and arabinogalactan proteins (AGPs, mAb LM2) were strongly correlated with ripening. From green stage to véraison, a progressive reduction in pectic-β-(1,4)-galactan epitopes, present in both pectin-rich (CDTA) and hemicellulose-rich (NaOH) polymers, was observed. Ripening changes in AGP and extensin epitope abundance also were found during and after véraison.
  
  
  CONCLUSIONS
  Combinations of cell wall probes are able to define distinct ripening phases in grapes. Pectic-β-(1,4)-galactan epitopes decreased in abundance from green stage to véraison berries. From véraison there was an increase in abundance of significant extensin and AGP epitopes, which correlates with cell expansion events. This study provides new ripening biomarkers and changes that can be placed in the context of grape berry development.
authors.affiliation: Institute for Wine Biotechnology, Department of Viticulture and Oenology, Faculty of AgriSciences, Stellenbosch University, Matieland 7602, South Africa moorejp@sun.ac.za.
authors.forename: John P
authors.initials: JP
authors.lastname: Moore
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Copenhagen DK-1001, Denmark.
authors.forename: Jonatan U
authors.initials: JU
authors.lastname: Fangel
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Copenhagen DK-1001, Denmark.
authors.forename: William G T
authors.initials: WG
authors.lastname: Willats
authors.affiliation: Institute for Wine Biotechnology, Department of Viticulture and Oenology, Faculty of AgriSciences, Stellenbosch University, Matieland 7602, South Africa.
authors.forename: Melané A
authors.initials: MA
authors.lastname: Vivier
mesh_terms: D015415:Biomarkers; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D000939:Epitopes; D005638:Fruit / Q000254:growth & development; D005685:Galactans / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006023:Glycoproteins / Q000378:metabolism*; D009088:Mucoproteins / Q000235:genetics / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D027843:Vitis / Q000235:genetics / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism
chemical_list: D015415:Biomarkers; D000939:Epitopes; D005685:Galactans; D006023:Glycoproteins; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins; C005488:extensin protein, plant; D010368:Pectins
keywords: AGP; Cabernet Sauvignon; Crimson Seedless; Profiling; Vitis vinifera; arabinogalactan–protein; berry ripening; extensin; pectic-β-(1,4)-galactan; plant cell wall; table grapes; wine grapes