The role of the transcription factor AtbZIP63 in the interaction between carbohydrates and the circadian clock in Arabidopsis thaliana

Abstract

The Arabidopsis thaliana (Arabidopsis) AtbZIP63 transcription factor is part of the response pathway to energy shortage which is coordinated by the energy deprivation central signal integrators, kinases KIN10/11. The expression of AtbZIP63 is repressed by glucose, indicating that the carbon status influences the activity of this gene. The gene expression profile and the levels of some metabolites of the T-DNA insertion mutant atbzip63-2 indicated that AtbZIP63 takes part in the control of starch degradation, regulating the expression of some key genes in starch degradation. Diurnal AtbZIP63 mRNA level fluctuation are possibly regulated by the circadian clock, and the phase oscillation is influenced by the availability of carbohydrates in the cells. In addition, to be controlled by the circadian clock, AtbZIP63 also induces the expression of PRR7, one of the key regulators of the core clock. We have therefore identified a reciprocal interaction between the clock and AtbZIP63 which is probably affecting the starch degradation process. This set of evidence reveals new aspects of the entrainment of the circadian clock by sugars, and is consistent with recent studies showing that sugars directly regulate the circadian clock. Our hypothesis is that AtbZIP63 is acting as a mediator between the energy status (availability of sugar) and the oscillatory mechanism of the Arabidopsis circadian clock. We intend to show more directly that the interaction between AtbZIP63 and PRR7, functions as an entrainment of the circadian clock.