title: System level analysis of cacao seed ripening reveals a sequential interplay of primary and secondary metabolism leading to polyphenol accumulation and preparation of stress resistance.
abstract: Theobroma cacao and its popular product, chocolate, are attracting attention due to potential health benefits including antioxidative effects by polyphenols, anti-depressant effects by high serotonin levels, inhibition of platelet aggregation and prevention of obesity-dependent insulin resistance. The development of cacao seeds during fruit ripening is the most crucial process for the accumulation of these compounds. In this study, we analyzed the primary and the secondary metabolome as well as the proteome during Theobroma cacao cv. Forastero seed development by applying an integrative extraction protocol. The combination of multivariate statistics and mathematical modelling revealed a complex consecutive coordination of primary and secondary metabolism and corresponding pathways. Tricarboxylic acid (TCA) cycle and aromatic amino acid metabolism dominated during the early developmental stages (stages 1 and 2; cell division and expansion phase). This was accompanied with a significant shift of proteins from phenylpropanoid metabolism to flavonoid biosynthesis. At stage 3 (reserve accumulation phase), metabolism of sucrose switched from hydrolysis into raffinose synthesis. Lipids as well as proteins involved in lipid metabolism increased whereas amino acids and N-phenylpropenoyl amino acids decreased. Purine alkaloids, polyphenols, and raffinose as well as proteins involved in abiotic and biotic stress accumulated at stage 4 (maturation phase) endowing cacao seeds the characteristic astringent taste and resistance to stress. In summary, metabolic key points of cacao seed development comprise the sequential coordination of primary metabolites, phenylpropanoid, N-phenylpropenoyl amino acid, serotonin, lipid and polyphenol metabolism thereby covering the major compound classes involved in cacao aroma and health benefits.
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.|Vienna Metabolomics Center (VIME); University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nägele
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Doerfler
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Lena
authors.initials: L
authors.lastname: Fragner
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Palak
authors.initials: P
authors.lastname: Chaturvedi
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Ella
authors.initials: E
authors.lastname: Nukarinen
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.|Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030, Vienna, Austria.
authors.forename: Anke
authors.initials: A
authors.lastname: Bellaire
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030, Vienna, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Huber
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Jakob
authors.initials: J
authors.lastname: Weiszmann
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Doris
authors.initials: D
authors.lastname: Engelmeier
authors.affiliation: Department of Systems Biology and Biotechnology, National Institute of Biology, Vecna pot 111, 1000, Ljubljana, Slovenia.
authors.forename: Ziva
authors.initials: Z
authors.lastname: Ramsak
authors.affiliation: Department of Systems Biology and Biotechnology, National Institute of Biology, Vecna pot 111, 1000, Ljubljana, Slovenia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Gruden
authors.affiliation: Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria. wolfram.weckwerth@univie.ac.at.|Vienna Metabolomics Center (VIME); University of Vienna, Althanstrasse 14, 1090, Vienna, Austria. wolfram.weckwerth@univie.ac.at.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Weckwerth
mesh_terms: D002099:Cacao / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D059808:Polyphenols / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism*
chemical_list: D059808:Polyphenols
keywords: GC-MS; LC-MS; Theobroma cacao; metabolomics; multivariate statistics; plant systems biology; primary metabolism; proteomics; secondary metabolism; seed development