Time of day modulates low-temperature Ca signals in Arabidopsis

Plant J. 2006 Dec;48(6):962-73. doi: 10.1111/j.1365-313X.2006.02933.x.


We tested the hypothesis that the circadian clock modulates Ca(2+)-based signalling pathways, using low-temperature (LT)-induced Ca(2+) signals. We investigated the relationship between diurnal and circadian modulation of LT-induced increases in cytosolic-free calcium ([Ca(2+)](cyt)), and regulation of [Ca(2+)](cyt)-dependent outputs of the LT-signalling network (RD29A transcript abundance and stomatal closure). We measured [Ca(2+)](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 [Ca(2+)](cyt). In guard cells, the LT-induced [Ca(2+)](cyt) elevation preceded stomatal closure. In whole plants, the magnitude of LT-induced [Ca(2+)](cyt) transients, measured from the entire plant or specifically the guard cell, varied with the time of day: LT-induced [Ca(2+)](cyt) transients were significantly higher during the mid-photoperiod than at the beginning or end. Diurnal variation in LT-induced guard cell [Ca(2+)](cyt) increases was not correlated to diurnal variation in LT-induced stomatal closure. There was circadian modulation of LT-induced whole plant [Ca(2+)](cyt) increases, which were correlated to the circadian pattern of RD29A induction. In order to understand the significance of LT-induced [Ca(2+)](cyt) increases, we used a computer simulation to demonstrate that, in guard cells, LT-induced [Ca(2+)](cyt) increases measured from a population of cells are likely to represent the summation of cold-induced single-cell [Ca(2+)](cyt) oscillations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aequorin / genetics
  • Aequorin / metabolism
  • Arabidopsis / anatomy & histology
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Calcium Signaling*
  • Circadian Rhythm*
  • Cold Temperature*
  • Gene Expression Profiling
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Plant Leaves / cytology
  • Plant Leaves / metabolism


  • Green Fluorescent Proteins
  • Aequorin