Postharvest application of ultraviolet-A and blue light irradiations boosted the accumulation of acetylated anthocyanins in the blueberry fruit and its potential regulatory mechanisms

Abstract

Anthocyanins in blueberry fruit have strong antioxidant capacity which could provide health benefits. However, the instability of natural anthocyanins restricts their inherent benefits. Acylation could enhance the stability of anthocyanins, but how to increase the content of acylated anthocyanins in blueberry fruit and underlying regulatory mechanisms are far less known. In this study, two southern highbush blueberry cultivars, 'Gulfcoast' and 'O'neal', which exhibit notable variations in acetylated anthocyanins content, were employed to explore the method of boosting this content through spectral modulation and the underlying regulatory mechanisms. The findings indicated that postharvest exposure to ultraviolet (UV)-A or 440 nm blue light irradiations significantly increased the contents of acetylated anthocyanins in both blueberry cultivars. Through the analysis of acetylated anthocyanins content and corresponding transcriptomic data from 'Gulfcoast' and 'O'neal' fruit across various developmental stages, it was identified that four candidate genes encoding anthocyanin acyltransferase (AAT) might be responsible for the accumulation of acetylated anthocyanins in blueberries. Furthermore, higher levels of acetylated anthocyanin content in blueberry fruit after UV-A or 440 nm blue light irradiations was found to be strong positively correlated with the induced expression of VcAAT2 in cultivar 'O'neal', implying that UV-A or 440 nm blue light irradiations effectively boosted acetylated anthocyanins in postharvest blueberry fruit, likely through upregulating AAT genes like VcAAT2 in 'O'neal'. The study provided insights into the potential mechanisms by which acylation can be promoted to stabilize anthocyanins and thereby maximize their health-promoting antioxidant properties in blueberries.