title: Foliar-applied ethephon enhances the content of anthocyanin of black carrot roots (Daucus carota ssp. sativus var. atrorubens Alef.).
abstract: Black carrots (Daucus carota ssp. sativus var. atrorubens Alef.) constitute a valuable source of anthocyanins, which are used as natural red, blue and purple food colourants. Anthocyanins and phenolic compounds are specialised metabolites, accumulation of which often requires elicitors, which act as molecular signals in plant stress responses. In the present study, ethephon, an ethylene-generating compound was explored as enhancer of anthocyanin and phenolic contents during growth of 'Deep Purple' black carrots. The effects of ethephon on several parameters were investigated, and the expression of biosynthetic anthocyanin genes was studied during growth and anthocyanin accumulation.
  
  
  
  Roots of ethephon-treated carrot plants exhibited an increase in anthocyanin content of approximately 25%, with values ranging from 2.25 to 3.10 mg g-1fresh weight, compared with values ranging from 1.50 to 1.90 mg g-1fresh weight in untreated roots. The most rapid accumulation rate for anthocyanins, phenolic compounds, soluble solids and dry matter was observed between 10 and 13 weeks after sowing in both untreated and ethephon-treated carrots. The differences in anthocyanin contents between untreated and treated carrots increased for several weeks after the ethephon treatment was terminated. Five cyanidin-based anthocyanin forms were identified, with variable relative abundance values detected during root growth. Overall, the expression of the anthocyanin biosynthetic genes analysed (PAL1, PAL3, F3H1, DFR1, LDOX2) increased in response to ethephon treatment, as did the expression of the MYB1 transcription factor, which is associated with activation of the phenylpropanoid pathway under stress conditions. In addition, a correlation was proposed between ethylene and sugar contents and the induction of anthocyanin synthesis.
  
  
  
  This study presents a novel method for enhancing anthocyanin content in black carrots. This finding is of economic importance as increased pigment concentration per unit of biomass implies improved profitability parameters in food colour production. We provide new insight into the accumulation patterns of the different cyanidin-based anthocyanins and phenolic compounds during root growth. Moreover, we show that enhanced anthocyanin content in ethephon-treated carrots is accompanied by increased expression of anthocyanin biosynthetic genes.
authors.affiliation: Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Alle 9-13, 2630, Taastrup, Denmark. grbe@plen.ku.dk.
authors.forename: Gregorio
authors.identifier: 0000-0001-9229-9668
authors.initials: G
authors.lastname: Barba-Espín
authors.affiliation: Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Alle 9-13, 2630, Taastrup, Denmark.
authors.forename: Stephan
authors.initials: S
authors.lastname: Glied
authors.affiliation: DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark.
authors.forename: Christoph
authors.initials: C
authors.lastname: Crocoll
authors.affiliation: Natural Colors Division, Chr. Hansen A/S, Agern Allé 24, 2970, Hørsholm, Denmark.
authors.forename: Tsaneta
authors.initials: T
authors.lastname: Dzhanfezova
authors.affiliation: Natural Colors Division, Chr. Hansen A/S, Agern Allé 24, 2970, Hørsholm, Denmark.
authors.forename: Bjarne
authors.initials: B
authors.lastname: Joernsgaard
authors.affiliation: Natural Colors Division, Chr. Hansen A/S, Agern Allé 24, 2970, Hørsholm, Denmark.
authors.forename: Finn
authors.initials: F
authors.lastname: Okkels
authors.affiliation: Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Alle 9-13, 2630, Taastrup, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Lütken
authors.affiliation: Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Alle 9-13, 2630, Taastrup, Denmark.
authors.forename: Renate
authors.initials: R
authors.lastname: Müller
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D018552:Daucus carota / Q000187:drug effects* / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D005030:Ethylenes; D009943:Organophosphorus Compounds; C036216:ethylene; C005073:ethephon
keywords: Anthocyanin accumulation; Black carrot; Ethephon; Ethylene; Gene expression