4. Discussion
It has been shown in many fruits that specific light spectral wavelengths can influence the biosynthesis of anthocyanins and other polyphenolic compounds (Jeong et al., 2004; Kokalj et al., 2019; Koyama et al., 2012; Tao et al., 2018). However, the molecular mechanisms underlying the light quality regulated fruit anthocyanin biosynthesis are not well understood. In this study, we used a comparative transcriptomics approach to analyze the effect of light quality on anthocyanin biosynthesis in ripening fruit of bilberry producing anthocyanins from both cyanidin and delphinidin branches. The light treatments were given to unripe green (S3) bilberry fruits, as this stage has been shown earlier to be reactive towards changes in spectral light wavelengths affecting anthocyanin biosynthesis (Zoratti et al., 2014b). Here, we showed that the anthocyanin concentration and profile in ripening berries was affected especially by red light but also blue light treatment, and our results indicate differences in light signaling pathways between red and blue light in regulation of anthocyanin biosynthesis.