Red and blue light treatments of ripening bilberry fruits reveal
differences in signaling through ABA regulated anthocyanin biosynthesis
Abstract
The biosynthesis of anthocyanins has been shown to be influenced by
light quality. However, the molecular mechanisms underlying the
light-mediated regulation of fruit anthocyanin biosynthesis are not well
understood. In this study, we analyzed the effects of supplemental red
and blue light on the anthocyanin biosynthesis in non-climacteric
bilberry (Vaccinium myrtillus L.). After six days of continuous
irradiation during fruit ripening, both red and blue light elevated
concentration of total anthocyanins, but especially red light promoted
accumulation of delphinidins. Transcriptomic analysis of ripening
berries showed that both light treatments up-regulated all the major
anthocyanin structural genes, the key regulatory MYB transcription
factors and abscisic acid (ABA) biosynthetic genes. However, higher
induction of specific genes of anthocyanin and delphinidin biosynthesis
alongside ABA signal perception and metabolism were found in red light.
The difference in red and blue light signaling was found in NCED, ABA
receptor PYL and catabolic ABA-8’hydroxylase gene expression. Red light
also up-regulated expression of SNARE domain transporters, which may
indicate involvement of these proteins in vesicular trafficking of
anthocyanins during fruit ripening. Our results suggest differential
signal transduction and transport mechanisms between red and blue light
in in ABA- regulated anthocyanin and delphinidin biosynthesis during
non-climacteric fruit ripening.