Flavonoid Biosynthesis in Bilberry (Vaccinium Myrtillus L.)

Abstract

Flavonoids are a class of secondary metabolites in plants that are involved in many important functions. Various flavonoid compounds have also been reported to be beneficial for human health. Bilberry (Vaccinium myrtillus L.) is the characteristic field layer species in boreal forests and the fruits of bilberry are rich in anthocyanin pigments, a subclass of flavonoids. In the present work, flavonoid biosynthesis was examined in different tissues of bilberry. The focus was on the developing fruits of wild type and natural color mutants of bilberry, and on effect of solar radiation on flavonoid biosynthesis in bilberry leaves.For the isolation of RNA for gene expression analysis, a method was optimized for different tissues of bilberry. The cDNA fragments of five genes from the flavonoid pathway, coding phenylalanine ammonia-lyase, chalcone synthase, flavanone 3-hydroxylase, dihydroflavanol 4-reductase and anthocyanidin synthase, were isolated from bilberry using polymerase chain reaction technique, sequenced, and labelled with dioxigenin-dUTP label. These homologous, bilberry-specific probes were used for determining the expression of the flavonoid pathway genes in bilberry fruits, flowers and leaves with a modified non-radioactive method developed in the course of the study. The anthocyanins, catechins, proanthocyanidins, flavonols and hydroxycinnamic acids in fruits, leaves and different fractions of bilberry were identified and quantified with high-performance liquid chromatography combined with a diode array detector and mass spectrometer.The results demonstrate a correlation between anthocyanin accumulation and expression of the flavonoid pathway genes during the ripening of berries. A correlation between flavonol and anthocyanin biosynthesis was detected in bilberry and also in previous literature collected from flavonol and anthocyanin analyses from other fruits. Accordingly, models for the connection between flavonol and anthocyanin synthesis in fruit species were suggested. Activation of the expression of flavonoid pathway genes and accumulation of flavonoids and hydroxycinnamic acids was detected in leaves growing under direct solar radiation, compared to the shadow leaves of the same plants. Based on the results, it is suggested that cyanidin of anthocyanins and flavonol quercetin play a predominant role in the defence against high solar radiation in Vaccinium leaves.The results give new information about the biosynthesis of flavonoids in bilberry at the gene level, in addition to the information of the composition and content of flavonoids during fruit development and in different parts of the bilberry plant. Also, new information was obtained of the roles of flavonoids in protecting plants from excess solar radiation.

Content of phenolic compounds in wild populations ofEpilobium angustifoliumgrowing at different altitudes

“…Several experimental data support that enhanced solar, UV-B radiation is correlated to accumulation of highly antioxidative flavonoids (Jaakola et al, 2004;Markham et al, 1998;Spitaler et al, 2006). Previously, we showed that flavonols revealed significant differences in samples of Calluna vulgaris L. (Ericaceae) collected at different altitudes with increased levels of quercetin glycosides at higher altitudes whereas no significant correlation could be found for caffeoyl quinic acids and the dihydroflavonol glycoside callunin ( However, in the current study, we could not confirm the assumption that only the content of flavonol 3-Oglycosides with adjacent hydroxyl groups in ring B rise with increasing altitude (Ganzera et al, 2008b;Rieger et al, 2008) as also for compounds 11 and 13 a similar trend as for compound 12 was observed.…”

Functional Promiscuity of Two Divergent Paralogs of Type III Plant Polyketide Synthases

“…The increased concentration of phenolic compounds and carotenoids with increasing altitude has been suggested as a response to high light intensity and escalating UV radiation. In particular, flavonoids have been reported as UV-B light-absorbing compounds (Jaakola et al, 2004).…”

Antibacterial and antioxidant activities of bilberry (Vaccinium myrtillus L.) in vitro

“…Although there are papers on phytochemical analysis of leaves and fruits of this plant (Jaakola et al, 2002;Jaakola et al, 2004), the aim of this study was to determine and compare the antibacterial and antioxidant activity of different extracts of fruits and leaves of this plant collected on Borja Mountain (RS, Bosnia and Herzegovina, W. Balkans). The second aim of this paper was to determine the total phenol and flavonoid content in water, ethanol and ethyl acetate extracts using spectrophotometric methods.…”