Abstract
Circadian clock circuitry intersects with a plethora of signaling pathways to adequately time physiological processes to occur at the most appropriate time of the day and year. However, our mechanistic understanding of how the clockwork is wired to its output is limited. Here we uncover mechanistic connections between the core clock component GIGANTEA (GI) and hormone signaling through the modulation of key components of the transduction pathways. Specifically, we show how GI modulates gibberellin (GA) signaling through the stabilization of the DELLA proteins, which act as negative components in the signaling of this hormone. GI function within the GA pathway is required to precisely time the permissive gating of GA sensitivity, thereby determining the phase of GA-regulated physiological outputs.
Highlights
Circadian clock circuitry intersects with a plethora of signaling pathways to adequately time physiological processes to occur at the most appropriate time of the day and year
The DELLA proteins are a set of GRAS transcription regulators that function as negative components of GA signaling and repress GA-responsive genes, including growth-promoting genes [21, 22]
DELLAs are proposed to function as hubs in plant development and physiology because they interact with multiple transcription factors from
Summary
Circadian clock circuitry intersects with a plethora of signaling pathways to adequately time physiological processes to occur at the most appropriate time of the day and year. Phytohormones are signaling molecules that play a pivotal role in intrinsic plant developmental programs, as well as in the modulation of such programs in response to environmental cues, including biotic and abiotic stresses [3,4,5] Both clock and hormone pathways are indispensable for the response to short- and long-term environmental challenges, and adequate crosstalk between them is crucial for plant adaptation to the local habitat. Specific hormones have been shown to affect circadian function [7], and, levels of many hormones display diel oscillatory patterns of accumulation, which are often circadian [8,9,10,11] These rhythms likely arise, at least partially, from transcriptional regulation by the clock, which broadly regulates the expression of hormone biosynthetic genes and signaling components [12,13,14,15,16,17]. GI affects GA signaling through the stabilization of the DELLAs and is required to precisely time the gating of GA sensitivity to the early night, affecting the rhythmicity of physiological outputs such as hypocotyl elongation
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