Clock Control Over Plant Gene Expression

Endogenous time-keepers known as circadian clocks are setting the pace of multiple metabolic and physiological processes. These complex biological oscillators have arisen in eukaryotic organisms and have been shown to enhance fitness and to confer a competitive advantage by several mechanisms. In general, the plant circadian clock participates in the resonance of the internal biology with optimal time-of-day, in coupling the different steps common to one pathway, in gating or partitioning incompatible physiological activities to distinct phases, and in sensing the changes in the seasons and when to flower. Original transcriptional as well as post-transcriptional mechanisms are involved in the different steps of clock function, from the integration of environmental clues (light quality, temperature) to the interlocked feedback loops composing the core of the oscillator, and the resulting genome scale changes in gene expression. Our current understanding of the intimate mechanisms influencing gene expression at these different steps of clock progression is the focus of this chapter.