At GRP7, a nuclear RNA-binding protein as a component of a circadian-regulated negative feedback loop in Arabidopsis thaliana

Abstract

The endogenous clock that drives circadian rhythms is thought to communicate temporal information within the cell via cycling downstream transcripts. A transcript encoding a glycine-rich RNA-binding protein, Atgrp7, in Arabidopsis thaliana undergoes circadian oscillations with peak levels in the evening. The AtGRP7 protein also cycles with a time delay so that Atgrp7 transcript levels decline when the AtGRP7 protein accumulates to high levels. After AtGRP7 protein concentration has fallen to trough levels, Atgrp7 transcript starts to reaccumulate. Overexpression of AtGRP7 in transgenic Arabidopsis plants severely depresses cycling of the endogenous Atgrp7 transcript. These data establish both transcript and protein as components of a negative feedback circuit capable of generating a stable oscillation. AtGRP7 overexpression also depresses the oscillation of the circadianregulated transcript encoding the related RNA-binding protein AtGRP8 but does not affect the oscillation of transcripts such as cab or catalase mRNAs. We propose that the AtGRP7 autoregulatory loop represents a ''slave'' oscillator in Arabidopsis that receives temporal information from a central ''master'' oscillator, conserves the rhythmicity by negative feedback, and transduces it to the output pathway by regulating a subset of clock-controlled transcripts.

The PAS/LOV protein VIVID controls temperature compensation of circadian clock phase and development in Neurospora crassa

“…VVD is strongly temperature regulated, and data presented here and in previously reported studies suggest that it is part of an autoregulatory feedback loop Elvin et al 2005). Slave oscillatory feedback loops have been described in other circadian systems (Heintzen et al 1997;Staiger et al 2003;Kornmann et al 2007), but whether they play a role in certain aspects of temperature compensation is not known.…”

Conservation and Divergence of Circadian Clock Operation in a Stress-Inducible Crassulacean Acid Metabolism Species Reveals Clock Compensation against Stress

“…However, McCCR1/2 transcript levels do cycle in CAM leaves under driven LD conditions, so it is clear that McCCR1/2 may be specifically uncoupled from its clock in CAM-induced leaves. In Arabidopsis, AtCCR2 expression is controlled in part by its own protein in a suboscillator feedback loop (Heintzen et al, 1997). This makes it possible that the autoregulation of McCCR1/2 is lost in salt-stressed, CAM-induced leaves even though the central clock itself is largely compensated against stress and continues to operate robustly in CAM-induced leaves.…”

ELF4Is Required for Oscillatory Properties of the Circadian Clock

“…Under short days, only a marginal rhythm is seen for CCR2:LUC in elf4-1; however, a weak rhythm that apparently is able to anticipate dusk is seen in long photoperiod conditions (Fig. 4, E and F), suggesting that the slave oscillator of CCR2 (Heintzen et al, 1997) still runs under these conditions even in the elf4-1 mutant. Again, the same phase of the CCR2 peak was seen in ELF4-ox plants compared to wild type (Fig.…”