Time of day modulates low‐temperature Ca2+ signals in Arabidopsis

• Published in: The Plant journal : for cell and molecular biology 2006-12, Vol.48 (6), p.962-973
• Main Authors: Dodd, Antony N., Jakobsen, Mia Kyed, Baker, Andrew J., Telzerow, Anja, Hou, Sui‐Wen, Laplaze, Laurent, Barrot, Laure, Scott Poethig, R., Haseloff, Jim, Webb, Alex A. R.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Botany; Calcium; circadian; Circadian rhythm; cold; Flowers & plants; Fundamental and applied biological sciences. Psychology; guard cell; Hypothesis testing; Physical agents; Plant physiology and development; Signal transduction; signalling; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.02933.x

Summary We tested the hypothesis that the circadian clock modulates Ca2+‐based signalling pathways, using low‐temperature (LT)‐induced Ca2+ signals. We investigated the relationship between diurnal and circadian modulation of LT‐induced increases in cytosolic‐free calcium ([Ca2+]cyt), and regulation of [Ca2+]cyt‐dependent outputs of the LT‐signalling network (RD29A transcript abundance and stomatal closure). We measured [Ca2+]cyt non‐invasively using aequorin, and targeted aequorin to the guard cell using a guard cell‐specific GAL4‐green fluorescent protein enhancer trap line. LT caused transient increases in whole plant and guard cell [Ca2+]cyt. In guard cells, the LT‐induced [Ca2+]cyt elevation preceded stomatal closure. In whole plants, the magnitude of LT‐induced [Ca2+]cyt transients, measured from the entire plant or specifically the guard cell, varied with the time of day: LT‐induced [Ca2+]cyt transients were significantly higher during the mid‐photoperiod than at the beginning or end. Diurnal variation in LT‐induced guard cell [Ca2+]cyt increases was not correlated to diurnal variation in LT‐induced stomatal closure. There was circadian modulation of LT‐induced whole plant [Ca2+]cyt increases, which were correlated to the circadian pattern of RD29A induction. In order to understand the significance of LT‐induced [Ca2+]cyt increases, we used a computer simulation to demonstrate that, in guard cells, LT‐induced [Ca2+]cyt increases measured from a population of cells are likely to represent the summation of cold‐induced single‐cell [Ca2+]cyt oscillations.