title: Biochemical and molecular analysis of pink tomatoes: deregulated expression of the gene encoding transcription factor SlMYB12 leads to pink tomato fruit color.
abstract: The color of tomato fruit is mainly determined by carotenoids and flavonoids. Phenotypic analysis of an introgression line (IL) population derived from a cross between Solanum lycopersicum 'Moneyberg' and the wild species Solanum chmielewskii revealed three ILs with a pink fruit color. These lines had a homozygous S. chmielewskii introgression on the short arm of chromosome 1, consistent with the position of the y (yellow) mutation known to result in colorless epidermis, and hence pink-colored fruit, when combined with a red flesh. Metabolic analysis showed that pink fruit lack the ripening-dependent accumulation of the yellow-colored flavonoid naringenin chalcone in the fruit peel, while carotenoid levels are not affected. The expression of all genes encoding biosynthetic enzymes involved in the production of the flavonol rutin from naringenin chalcone was down-regulated in pink fruit, suggesting that the candidate gene underlying the pink phenotype encodes a regulatory protein such as a transcription factor rather than a biosynthetic enzyme. Of 26 MYB and basic helix-loop-helix transcription factors putatively involved in regulating transcription of genes in the phenylpropanoid and/or flavonoid pathway, only the expression level of the MYB12 gene correlated well with the decrease in the expression of structural flavonoid genes in peel samples of pink- and red-fruited genotypes during ripening. Genetic mapping and segregation analysis showed that MYB12 is located on chromosome 1 and segregates perfectly with the characteristic pink fruit color. Virus-induced gene silencing of SlMYB12 resulted in a decrease in the accumulation of naringenin chalcone, a phenotype consistent with the pink-colored tomato fruit of IL1b. In conclusion, biochemical and molecular data, gene mapping, segregation analysis, and virus-induced gene silencing experiments demonstrate that the MYB12 transcription factor plays an important role in regulating the flavonoid pathway in tomato fruit and suggest strongly that SlMYB12 is a likely candidate for the y mutation.
authors.affiliation: Plant Research International, 6700 AA Wageningen, The Netherlands.
authors.forename: Ana-Rosa
authors.initials: AR
authors.lastname: Ballester
authors.forename: Jos
authors.initials: J
authors.lastname: Molthoff
authors.forename: Ric
authors.initials: R
authors.lastname: de Vos
authors.forename: Bas te Lintel
authors.initials: Bt
authors.lastname: Hekkert
authors.forename: Diego
authors.initials: D
authors.lastname: Orzaez
authors.forename: Josefina-Patricia
authors.initials: JP
authors.lastname: Fernández-Moreno
authors.forename: Pasquale
authors.initials: P
authors.lastname: Tripodi
authors.forename: Silvana
authors.initials: S
authors.lastname: Grandillo
authors.forename: Cathie
authors.initials: C
authors.lastname: Martin
authors.forename: Jos
authors.initials: J
authors.lastname: Heldens
authors.forename: Marieke
authors.initials: M
authors.lastname: Ykema
authors.forename: Antonio
authors.initials: A
authors.lastname: Granell
authors.forename: Arnaud
authors.initials: A
authors.lastname: Bovy
mesh_terms: D000595:Amino Acid Sequence; D047188:Chalcones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D044948:Flavonols / Q000737:chemistry / Q000378:metabolism; D005638:Fruit / Q000737:chemistry* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005838:Genotype; D018551:Solanum lycopersicum / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010860:Pigments, Biological / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020005:Propanols / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D047188:Chalcones; D044948:Flavonols; D010860:Pigments, Biological; D010940:Plant Proteins; D020005:Propanols; D014157:Transcription Factors; C027329:naringenin chalcone