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Resetting of the Circadian Clock by Phytochromes and Cryptochromes in Arabidopsis

IFEVA, Faculty of Agronomy, University of Buenos Aires, Avenida San Martn 4453, 1417-Buenos Aires, Argentina; Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA

M. Agustina Mazzella

IFEVA, Faculty of Agronomy, University of Buenos Aires, Avenida San Martn 4453, 1417-Buenos Aires, Argentina

Garry C. Whitelam

Department of Biology, University of Leicester University Road, Leicester LE1 7RH, United Kingdom

Jorge J. Casal

IFEVA, Faculty of Agronomy, University of Buenos Aires, Avenida San Martn 4453, 1417-Buenos Aires, Argentina; casal{at}ifeva.edu.ar

The authors sought to investigate the role of phytochromes A and B (phyAand phyB) and cryptochromes 1 and 2 (cry1 and cry2) in the synchronization of the leaf position rhythm in Arabidopsis thaliana. The seedlings were transferred from white light–dark cycles to free-running conditions with or without exposure to a light treatment during the final hours of the last dark period. The phase advance caused by a far-red light treatment was absent in the phyA mutant, deficient in the fhy1 and fhy3 mutants involved in phyAsignaling, and normal in the cry1 and cry1 cry2 mutants. The phase shift caused by blue light was normal in the cry2 mutant; reduced in the phyA, cry1, phyA cry1, and cry1 cry2 mutants; and abolished in the phyA cry1 cry2 triple mutant. The phase shift caused by red light was partially retained by the phyA phyB double mutant. The authors conclude that cry1 and cry2 participate as photoreceptors in the blue light input to the clock but are not required for the phyA-mediated effects on the phase of the circadian rhythm of leaf position. The signaling proteins FHY1 and FHY3 are shared by phyA-mediated photomorphogenesis and phyA input to the clock.

Key Words: Arabidopsis • circadian rhythms • cryptochrome • leaf movement • light input • phytochrome

Journal of Biological Rhythms, Vol. 16, No. 6, 523-530 (2001)
DOI: 10.1177/074873001129002213


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