A wild 'albino' bilberry (Vaccinium myrtillus L.) from Slovenia shows three bottlenecks in the anthocyanin pathway and significant differences in the expression of several regulatory genes compared to the common blue berry type.

PLoS One. 2017 Dec 22;12(12):e0190246. doi: 10.1371/journal.pone.0190246. eCollection 2017. Zorenc Z1, Veberic R1, Slatnar A1, Koron D2, Miosic S3, Chen MH3, Haselmair-Gosch C3, Halbwirth H3, Mikulic-Petkovsek M1. Author information 1 Department of Agronomy, Chair for Fruit, Wine and Vegetable Growing, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia. 2 Department of Fruit Growing, Viticulture and Oenology, Agricultural Institute of Slovenia, Ljubljana, Slovenia. 3 Institute of Chemical, Environmental and Biological Engineering, Technische Universität Wien, Vienna, Austria. Abstract Relative expressions of structural genes and a number of transcription factors of the anthocyanin pathway relevant in Vaccinium species, and related key enzyme activities were compared with the composition and content of metabolites in skins of ripe fruits of wild albino and blue bilberry (Vaccinium myrtillus) found in Slovenia. Compared to the common blue type, the albino variant had a 151-fold lower total anthocyanin and a 7-fold lower total phenolic content in their berry skin, which correlated with lower gene expression of flavonoid 3-O-glycosyltransferase (FGT; 33-fold), flavanone 3-hydroxylase (FHT; 18-fold), anthocyanidin synthase (ANS; 11-fold), chalcone synthase (CHS, 7.6-fold) and MYBPA1 transcription factor (22-fold). The expression of chalcone isomerase (CHI), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin reductase (LAR), anthocyanidin reductase (ANR) and MYBC2 transcription factor was reduced only by a factor of 1.5-2 in the albino berry skins, while MYBR3 and flavonoid 3',5'-hydroxylase (F3'5'H) were increased to a similar extent. Expression of the SQUAMOSA class transcription factor TDR4, in contrast, was independent of the color type and does therefore not seem to be correlated with anthocyanin formation in this variant. At the level of enzymes, significantly lower FHT and DFR activities, but not of phenylalanine ammonia-lyase (PAL) and CHS/CHI, were observed in the fruit skins of albino bilberries. A strong increase in relative hydroxycinnamic acid derivative concentrations indicates the presence of an additional bottleneck in the general phenylpropanoid pathway at a so far unknown step between PAL and CHS. PMID: 29272302 DOI: 10.1371/journal.pone.0190246