Synthesis and accumulation of anthocyanins in sour cherries during ripening in accordance with antioxidant capacity development and chalcone synthase expression

Phytonutrient metabolism in sour cherries takes place during fruit ripening. This study demonstrated that total phenolic–flavonoid contents decline during ripening while total anthocyanin content significantly increases at the same period. There were no detectable anthocyanins in green cherry fruits. Anthocyanin biosynthesis started concurrently with color formation. Cyanidin-3-glucosylrutinoside and cyanidin-3-rutinoside were the early anthocyanins accumulated in fruits and were accompanied with cyanidin-3-sophoroside and cyanidin-3-glucoside in fully ripe fruits. Phenylpropanoid pathway involves anthocyanin biosynthesis, and chalcone synthase (CHS) is one of the key enzymes regulating the pathway. Three CHS genes (PcChs1, PcChs2, PcChs3) were isolated from sour cherry genome, and their transcription profiles were determined using the RT-PCR approach. There was no CHS gene expression before breaker stage, and PcChs1, PcChs2, PcChs3 transcription were upregulated in parallel with pigmentation in sour cherry cells and PcChs1 had the highest transcripts in fully ripe fruits.