Fig 1.
Relative expression of genes from the anthocyanin pathway (CHS, CHI, FHT, F3’5’H, DFR, LAR, ANR, ANS and FGT) of blue and albino bilberry normalized to GAPDH.
Different letters (a, b) above the columns denote significant differences among bilberries (LSD test P < 0.05).
Fig 2.
Relative expression of transcription factors (MYBC2, MYBPA1, MYBR3 and TDR4) of blue and albino bilberry normalized to GAPDH.
Different letters (a, b) above the columns denote significant differences among bilberries (LSD test P < 0.05).
Fig 3.
Specific enzyme activities (PAL, CHS/CHI, FHT and DFR (with DHQ and DHM as substrates) (nkat kg-1 protein) of blue and albino bilberry.
Different letters (a, b) above the columns denote significant differences among bilberries (LSD test P < 0.05).
Fig 4.
Relative levels of the main polyphenol classes of bilberry fruit skins.
(A) Blue bilberry. (B) Albino bilberry.
Fig 5.
Simplified flavonoid biosynthesis pathway (combined studies of gene expression, enzyme activity and metabolite analysis) leading to anthocyanin accumulation in Vaccinium myrtillus L.
Abbreviations: ANR, anthocyanidin reductase; ANS, anthocyanidin synthase; C4H, cinnamate 4-hydroxylase; CHI, chalcone isomerase; CHS, chalcone synthase; 4CL, hydroxycinnamate: CoA ligase; DFR, dihydroflavonol reductase; F3′H, flavonoid 3′-hydroxylase; F3′5′H, flavonoid 3′, 5′-hydroxylase; FGT, flavonoid-3-O-glucosyltransferase; FHT, flavanone 3-hydroxylase; FLS, flavonol synthase; LAR, leucoanthocyanidin reductase; PAL, phenylalanine ammonia lyase. *leading to small amounts of kaempferol-3-O-glucuronide. The three bottlenecks identified in the anthocyanin pathway of the albino type berry skins are numbered with 1 (a, b: ANS, FGT), 2 (FHT) and 3 (a so far unknown step located in the general phenylpropanoid pathway between PAL and CHS). Grey shaded boxes, enzymes/genes analyzed in our work.