Biosynthesis of Proanthocyanidins in White Clover Flowers: Cross Talk within the Flavonoid Pathway

Abstract

Proanthocyanidins and anthocyanins are produced by closely related branches of the flavonoid pathway and utilize the same metabolic intermediates. Previous studies have shown a flexible mechanism of flux diversion at the branch-point between the anthocyanin and proanthocyanidin pathways, but the molecular basis for this mechanism is poorly understood. Floral tissues in white clover plants (Trifolium repens) produce both proanthocyanidins and anthocyanins. This makes white clover amenable to studies of proanthocyanidin and anthocyanin biosynthesis and possible interactions within the flavonoid pathway. Results of this study show that the anthocyanin and proanthocyanidin pathways are spatially colocalized within epidermal cells of petals and temporally overlap in partially open flowers. A correlation between spatiotemporal patterns of anthocyanin and proanthocyanidin biosynthesis with expression profiles of putative flavonoid-related genes indicates that these pathways may recruit different isoforms of flavonoid biosynthetic enzymes. Furthermore, in transgenic white clover plants with downregulated expression of the anthocyanidin reductase gene, levels of flavan 3-ols, anthocyanins, and flavonol glycosides and the expression levels of a range of genes encoding putative flavonoid biosynthetic enzymes and transcription factors were altered. This is consistent with the hypothesis that flux through the flavonoid pathway may be at least partially regulated by the availability of intermediates.

Effects of Salt Stress after Late Booting Stage on Yield and Antioxidant Capacity in Pigmented Rice Grains and Alleviation of the Salt-Induced Yield Reduction by Exogenous Spermidine

“…Cross talk between anthocyanin-and proanthocyanidin-specific branches existed where down-regulation of anthocyanidin reductase resulted in the accumulation of anthocyanins and inhibition of proanthocyanidin synthesis (Abrahams et al, 2002) while its overexpression led to down-regulation of anthocyanin and accumulation of proanthocyanidins (Xie et al, 2003). Regulation of flavonoid pathway branch is regulated by complex network of signals triggered by internal metabolic cues and external signals including abiotic stress factors (Abeynayake et al, 2012). Flavonoid pigments particularly anthocyanins and proanthocyanidins have been reported to be highly correlated with antioxidant capacities of colored rice grains (Finocchiaro et al, 2007;Min et al, 2012).…”

Flavonoids: a metabolic network mediating plants adaptation to their real estate

“…Proanthocyanidins are found in the leaves, flowers, fruit, seeds, bark, and roots of many plant species (Abeynayake et al, 2011, 2012; Hancock et al, 2014). Legumes offer opportunities for studying proanthocyanidin biosynthesis accumulating them across a broad range of tissues [for reviews, see (Marles et al, 2003; Lepiniec et al, 2006; Routaboul et al, 2006].…”

An Atlas of Soybean Small RNAs Identifies Phased siRNAs from Hundreds of Coding Genes

“…MYB5 has been reported previously to be involved in differentiation of the outer seed coat (Gonzalez et al, 2009) and anthocyanin biosynthesis (Dubos et al, 2010;Abeynayake et al, 2012), whereas miR828 in Arabidopsis functions to generate MYB-targeting tasiRNAs from TAS4 . Thus, relative to soybean, the Arabidopsis TAS4 locus may have evolved to separate the miR828-dependent phasiRNA generation and MYB suppression activities.…”