Calcium dependent sucrose uptake links sugar signaling to anthocyanin biosynthesis in Arabidopsis

Abstract

Sugars enhance light signaling-induced anthocyanin accumulation in Arabidopsis seedlings via differential regulation of several positive and negative transcription factors. Ca2+ plays a role as a second messenger in sugar signaling in grape and wheat. However, whether anthocyanin pigmentation is modulated by changes in intracellular Ca2+ level in Arabidopsis is not known. Here, we used a pharmaceutical approach that Ca2+ antagonists strongly interfered with sucrose uptake and anthocyanin accumulation by down-regulating the expression of sucrose transporter 1 (SUC1) and transcriptional regulatory factors, such as PAP1. Time course analysis of the effect of Ca2+ antagonists showed the early inhibition of sucrose-induced sugar uptake leading to decreased anthocyanin accumulation, indicating that Ca2+ signals play a role in sugar uptake rather than in anthocyanin biosynthesis. An early increase in cytosolic Ca2+ level in Arabidopsis roots in response to sucrose feeding was significantly inhibited by Ca2+ antagonists. Taken together, these results indicate that sucrose-induced sugar uptake in Arabidopsis is modulated by changes in endogenous Ca2+ levels, which in turn regulate anthocyanin accumulation. (C) 2012 Elsevier Inc. All rights reserved.