Poster: Clocks

Abs # 780: Photoperiodic information encoded by diurnal and circadian rhythms in cytoplasmic [Ca²⁺].

Presenter:	Love, John , john.love@plantsci.cam.ac.uk
Authors	Love, John  (A)   Dodd, Antony N (A)   Webb, Alex A.R (A)
Affiliations:	(A): Department of Plant Sciences, The University of Cambridge, Cambridge, CB2 9EA, U.K.

In temperate zones, the seasons are characterised by changes in day length. Since the work of Bünning in the 1930’s, it has been proposed that the seasonal, or “photoperiodic”, and daily, or “circadian”, rhythms of plant development are intimately linked; essentially that plants track and anticipate the seasons by measuring the annual changes in day length. Circadian clocks are complex and are set by multiple interacting pathways that include several input receptors, coupling factors, translational controls, cellular oscillators and signal transduction mechanisms. In plants, environmental stimuli can be transduced into cellular information as changes in cytoplasmic free [Ca²⁺] that vary in amplitude, duration and location. Circadian [Ca²⁺] oscillations have previously been observed in both the cytoplasm and the chloroplast, suggesting that [Ca²⁺] signalling networks may contribute to circadian signalling. Using Arabidopsis thaliana plants that constitutively express the bioluminescent Ca²⁺ reporter aequorin, we have shown that both diurnal and circadian Ca²⁺_cyt rhythms are differentially entrained by varying the photoperiod under which the plants were grown. These data indicate that circadian oscillations in cytoplasmic Ca²⁺ may play a fundamental role in encoding photoperiodic information in plants. This work was supported by the Broodbank Fellowship Trust, the Royal Society of London and the BBSRCUK, whom we gratefully acknowledge.