title: Functional effect of grapevine 1-deoxy-D-xylulose 5-phosphate synthase substitution K284N on Muscat flavour formation.
abstract: Grape berries of Muscat cultivars (Vitis vinifera L.) contain high levels of monoterpenols and exhibit a distinct aroma related to this composition of volatiles. A structural gene of the plastidial methyl-erythritol-phosphate (MEP) pathway, 1-deoxy-D-xylulose 5-phosphate synthase (VvDXS), was recently suggested as a candidate gene for this trait, having been co-localized with a major quantitative trait locus for linalool, nerol, and geraniol concentrations in berries. In addition, a structured association study discovered a putative causal single nucleotide polymorphism (SNP) responsible for the substitution of a lysine with an asparagine at position 284 of the VvDXS protein, and this SNP was significantly associated with Muscat-flavoured varieties. The significance of this nucleotide difference was investigated by comparing the monoterpene profiles with the expression of VvDXS alleles throughout berry development in Moscato Bianco, a cultivar heterozygous for the SNP mutation. Although correlation was detected between the VvDXS transcript profile and the accumulation of free monoterpenol odorants, the modulation of VvDXS expression during berry development appears to be independent of nucleotide variation in the coding sequence. In order to assess how the non-synonymous mutation may enhance Muscat flavour, an in vitro characterization of enzyme isoforms was performed followed by in vivo overexpression of each VvDXS allele in tobacco. The results showed that the amino acid non-neutral substitution influences the enzyme kinetics by increasing the catalytic efficiency and also dramatically affects monoterpene levels in transgenic lines. These findings confirm a functional effect of the VvDXS gene polymorphism and may pave the way for metabolic engineering of terpenoid contents in grapevine.
authors.affiliation: Fondazione Edmund Mach, Research and Innovation Centre, Genomic and Biology of Fruit Crops Department, Via Mach, 1, 38010 San Michele all'Adige (TN), Italy. juri.battilana@iasma.it
authors.forename: Juri
authors.initials: J
authors.lastname: Battilana
authors.forename: Francesco
authors.initials: F
authors.lastname: Emanuelli
authors.forename: Giorgio
authors.initials: G
authors.lastname: Gambino
authors.forename: Ivana
authors.initials: I
authors.lastname: Gribaudo
authors.forename: Flavia
authors.initials: F
authors.lastname: Gasperi
authors.forename: Paul K
authors.initials: PK
authors.lastname: Boss
authors.forename: Maria Stella
authors.initials: MS
authors.lastname: Grando
mesh_terms: D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism; D039821:Monoterpenes / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics; D014166:Transferases / Q000235:genetics / Q000378:metabolism*; D027843:Vitis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D039821:Monoterpenes; D010940:Plant Proteins; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase