Abstract
Anthocyanins are essential contributors to fruit coloration, an important quality feature and a breed determining trait of a sweet cherry fruit. It is well established that the biosynthesis of anthocyanins is regulated by an interplay of specific transcription factors belonging to MYB and bHLH families accompanied by a WD40 protein. In this study, we isolated and analyzed PaWD40, PabHLH3, PabHLH33, and several closely related MYB10 gene variants from different cultivars of sweet cherry, analyzed their expression in fruits with different anthocyanin levels at several developmental stages, and determined their capabilities to modulate anthocyanin synthesis in leaves of two Nicotiana species. Our results indicate that transcription level of variant PaMYB10.1-1 correlates with fruit coloration, but anthocyanin synthesis in Nicotiana was induced by another variant, PaMYB10.1-3, which is moderately expressed in fruits. The analysis of two fruit-expressed bHLH genes revealed that PabHLH3 enhances MYB-induced anthocyanin synthesis, whereas PabHLH33 has strong inhibitory properties.
Highlights
Sweet cherry (Prunus avium L.) is an important crop valued primarily for the fleshy fruits, an excellent source of many nutrients and phytochemicals
At the start of this research, sequence information on some cherry anthocyanin synthesis genes as well as raw genome sequence of closely related peach species was already available in public databases
The gene for UDP-glucose:flavonoid 3-Oglucosyltransferase (UFGT) enzyme appeared to be extremely conserved with no nucleotide differences across all coding sequence and the only short intron in our sweet and sour cherries and another publicly available sweet cherry gene sequence
Summary
Sweet cherry (Prunus avium L.) is an important crop valued primarily for the fleshy fruits, an excellent source of many nutrients and phytochemicals. There are hundreds of sweet cherry varieties with fruit skin and flesh colors ranging from dark red to pale yellow, and this important quality is determined primarily by the accumulation of red anthocyanin pigments. Anthocyanins belong to flavonoids, an important group of plant secondary metabolites possessing antioxidant activity and other health-promoting qualities [1]. The general pathway of flavonoid synthesis is already well established in a model plant Arabidopsis thaliana [2] and has been studied in important fruit crops such as grapevine (Vitis vinifera) [3] and apple (Malus domestica) [4]. The flavonoid pathway branches from the general phenylpropanoid pathway when enzyme chalcone synthase (CHS) generates tetrahydroxychalcone from 4-coumaroyl-CoA and PLOS ONE | DOI:10.1371/journal.pone.0126991 May 15, 2015
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