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Distinct Light and Clock Modulation of Cytosolic Free $\text{Ca}^{2+}$ Oscillations and Rhythmic CHLOROPHYLL A/B BINDING PROTEIN2 Promoter Activity in Arabidopsis

Xiadong Xu, Carlos T. Hotta, Antony N. Dodd, John Love, Robert Sharrock, Young Wha Lee, Qiguang Xie, Carl H. Johnson and Alex A. R. Webb
The Plant Cell
Vol. 19, No. 11 (Nov., 2007), pp. 3474-3490
Stable URL: http://www.jstor.org/stable/20077213
Page Count: 17
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Distinct Light and Clock Modulation of Cytosolic Free $\text{Ca}^{2+}$ Oscillations and Rhythmic CHLOROPHYLL A/B BINDING PROTEIN2 Promoter Activity in Arabidopsis
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Abstract

Plants have circadian oscillations in the concentration of cytosolic free calcium ($[\text{Ca}^{2+}]_{\text{cyt}}$). To dissect the circadian $\text{Ca}^{2+}$-signaling network, we monitored circadian $[\text{Ca}^{2+}]_{\text{cyt}}$ oscillations under various light/dark conditions (including different spectra) in Arabidopsis thaliana wild type and photoreceptor and circadian clock mutants. Both red and blue light regulate circadian oscillations of $[\text{Ca}^{2+}]_{\text{cyt}}$. Red light signaling is mediated by PHYTOCHROME B (PHYB). Blue light signaling occurs through the redundant action of CRYPTOCHROME1 (CRY1) and CRY2. Blue light also increases the basal level of $[\text{Ca}^{2+}]_{\text{cyt}}$, and this response requires PHYB, CRY1, and CRY2. Light input into the oscillator controlling $[\text{Ca}^{2+}]_{\text{cyt}}$ rhythms is gated by EARLY FLOWERING3. Signals generated in the dark also regulate the circadian behavior of $[\text{Ca}^{2+}]_{\text{cyt}}$. Oscillations of $[\text{Ca}^{2+}]_{\text{cyt}}$ and CHLOROPHYLL A/B BINDING PROTEIN2 (CAB2) promoter activity are dependent on the rhythmic expression of LATE ELONGATED HYPOCOTYL and CIRCADIAN CLOCK-ASSOCIATED1, but $[\text{Ca}^{2+}]_{\text{cyt}}$ and CAB2 promoter activity are uncoupled in the timing of cab1 (toc1-1) mutant but not in toc1-2. We suggest that the circadian oscillations of $[\text{Ca}^{2+}]_{\text{cyt}}$ and CAB2 promoter activity are regulated by distinct oscillators with similar components that are used in a different manner and that these oscillators may be located in different cell types in Arabidopsis.

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