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Plant Physiology 56:157-159 (1975)
© 1975 American Society of Plant Biologists

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Articles

Acceleration of Dark Reversion of Phytochrome in Vitro by Calcium and Magnesium 1

Moshé Negbi2, David W. Hopkins3 and Winslow R. Briggs4

a The Biological Laboratories, Harvard University, Cambridge, Massachusetts, 02138

Rates of dark reversion of the far red-absorbing form of phytochrome, Pfr, to the red-absorbing form, Pr, have been determined in the presence of several salts. Low concentrations of calcium chloride and magnesium chloride (up to 3 mM) accelerated the rate of dark reversion at all stages of purification of phytochrome from etiolated rye (Secale cereale L. cv. Balbo) seedlings. The complex kinetics of the dark reversion could be resolved into two first-order components. The effect of the added divalent cations was on the relative proportion of the fast and slow reacting components, rather than on the rate constants of the two populations. It was possible to reverse the effects of the cations by adding the chelating agents ethylene-bis-(oxyethylene-nitrilo) tetraacetic acid or ethylenediaminetetraacetate. The effect of the divalent cations is not a nonspecific ionic strength effect. The relative proportion of the two populations was also affected by the degree of purity of the phytochrome samples.

2 Present address: Department of Agricultural Botany, The Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, Israel.

3 Present address: Institut für Biologie III der Universität, 78 Freiburg i. Br., Schänzlestrasse 9-11, W. Germany.

4 Present address: Department of Plant Biology, Carnegie Institute of Washington, Stanford, Calif. 94305.

1 This work was supported by National Science Foundation Grant GB-30964X to W.R.B., and by the Department of Plant Biology, Carnegie Institute of Washington, Stanford, California. M.N. and D.W.H. held fellowships from the Maria Moors Cabot Foundation, Harvard University.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1975 by the American Society of Plant Biologists