Sucrose Signaling Regulates Anthocyanin Biosynthesis Through a MAPK Cascade in <i>Arabidopsis thaliana</i>

Abstract

Anthocyanin accumulation specifically depends on sucrose (Suc) signaling. However, the molecular basis of this process remains unknown. In this study, <i>in vitro</i> pull-down assays identified ETHYLENE-INSENSITIVE3 (EIN3), a component of both sugar signaling or/and metabolism. This protein interacted with YDA, and the physiological relevance of this interaction was confirmed by <i>in planta</i> co-immunoprecipitation, yeast two-hybrid (Y2H) assay, and bimolecular fluorescence complementation. <i>Ethylene insensitive3-like 1</i> (<i>eil1</i>) <i>ein3</i> double-mutant seedlings, but not <i>ein3-1</i> seedlings, showed anthocyanin accumulation. Furthermore, <i>ein3-1</i> suppressed anthocyanin accumulation in <i>yda-1</i> plants. Thus, <i>EMB71/YDA-EIN3-EIL1</i> may form a sugar-mediated gene cascade integral to the regulation of anthocyanin accumulation. Moreover, the <i>EMB71/YDA-EIN3-EIL1</i> gene cascade module directly targeted the promoter of <i>Transparent Testa 8</i> (<i>TT8</i>) by direct EIN3 binding. Collectively, our data inferred a molecular model where the signaling cascade of the YDA-EIN3-TT8 appeared to target <i>TT8</i> via EIN3, thereby modulating Suc signaling-mediated anthocyanin accumulation.