The efficient management by an organism of its energetic resources is crucial to ensure its development and reproduction. Plants as sessile organisms developed sophisticated mechanisms to optimize the balanced use of their available energetic resources in response to environmental changes. Carbohydrates such as sucrose and starch, which are end products of CO2 fixation by photosynthesis during daytime, are primary sources of energy. During the night period, in the model organism Arabidopsis thaliana (Arabidopsis), starch is degraded at a rate compatible with a constant and regular supply of carbohydrates to sustain growth until dawn. The regulation of this process involves the circadian clock and a mechanism which quantifies the available starch. We obtained evidences that the Arabidopsis bZIP type Transcription Factor (TF) AtbZIP63 is also involved in this regulatory scheme. In response to changes in carbohydrate levels, this TF modulates the expression of PRR7, a key component of the clock. On the other hand, AtbZIP63 is regulated by the clock and is also the main target of the SnRK1/KIN10 kinase which mediated energetic stress responses. We suggest that AtbZIP63, by regulating PRR7, adjusts the activity of the clock to the energetic status of the organism. The objective of the project is to describe into more details the Gene Regulatory Network related to AtbZIP63. Thus, the proposal follows up on the functional analysis of AtbZIP63, aiming to unravel the mechanisms of the interaction between the circadian clock and AtbZIP63 to control the use of energetic resources.
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