Changes in the abscisic acid levels and related gene expression during fruit development and ripening in bilberry (Vaccinium myrtillus L.)

Five ABA biosynthetic genes were isolated and their expression studied in bilberry. Expression of 9-cis-epoxycarotenoid dioxygenase (VmNCED1) and putative neoxanthin synthase (VmNSY) increased at the onset of berry ripening along with the accumulation of ABA. •Five ABA biosynthetic genes were isolated from bilberry.•ABA content and expression of ABA biosynthetic genes were analyzed in bilberry.•ABA accumulated highly at the onset of bilberry fruit ripening.•Expression of VmNCED1 and VmNSY increased simultaneously with ABA accumulation.•ABA may have a regulatory role in non-climacteric bilberry fruit ripening. Abscisic acid (ABA) is a natural plant hormone playing an important role in many physiological processes including fruit ripening and is also recently found to be potential for biomedical applications. This study was aimed to measure ABA levels and its biosynthesis in bilberry (Vaccinium myrtillus L.), which is one of the best sources of anthocyanins. Five ABA biosynthetic genes were isolated from bilberry and their expression profiles were studied in bilberry tissues, particularly during berry development. The level of ABA highly increased at the onset of bilberry fruit ripening, at the stage when expression of anthocyanin biosynthetic genes, chalcone synthase (VmCHS) and anthocyanidin synthase (VmANS), also increased. In fully ripe berries and leaves, ABA levels were lower but none was detected in bilberry stem or rhizome. The expression of 9-cis-epoxycarotenoid dioxygenase (VmNCED1) and putative neoxanthin synthase (VmNSY) was high in berry tissues and their expression increased markedly at the onset of berry ripening along with the accumulation of ABA. In contrast, the expression of zeaxanthin epoxidase (VmZEP), short-chain dehydrogenase/reductase (VmSDR/ABA2) and aldehyde oxidase (VmAO) were most highly associated with leaf tissues with no obvious relation to ABA content during berry development. The obtained results indicate that the ABA biosynthesis may play an important role in the regulation of ripening of non-climacteric bilberry fruits through transcriptional regulation of key ABA biosynthetic genes.