The role of the chloroplast coupling factor in the inactivation of thylakoid membranes at low temperatures

Abstract

Thylakoids isolated from spinach leaves (Spinacia oleracea L. cv. Monatol) were exposed to variable low temperatures under non‐freezing conditions. After incubation, changes in the activities of several photochemical reactions and physical properties of the membranes were measured at room temperature. Cyclic photophosphorylation was strictly dependent on the temperature and the electrolyte concentration: decrease in temperature and increase in NaCl concentration enhanced membrane damage. Inactivation of photophosphorylation was accompanied by stimulation of non‐cyclic electron transport, increase in proton permeability and decrease in δpH. When dicyclohexylcarbodiimide was added, the proton gradient became completely restored. The temperature‐ and salt‐dependent breakdown of photophosporylation was closely related to the release of the chloroplast coupling factor (CF1) from the membranes. The addition of Mg2+, very low concentrations of ATP or ADP, or higher concentrations of low‐molecular‐weight polyols prior to temperature treatment prevented thylakoid damage. The data indicate that inactivation of photophosphorylation of thylakoids at low temperatures is determined to a considerable extent by the cold lability of the CF1. As a consequence, it must be concluded that damage of biomembranes caused by freezing is not due solely to changes resulting from the ice formation but additionally by temperature‐dependent alterations of cold‐labile proteins. Moreover, the data explain the mechanism of non‐colligative cryoprotection of isolated thylakoid membranes.

Mechanical freeze‐thaw damage and frost hardening in leaves and isolated thylakoids from spinach. I. Mechanical freeze‐thaw damage in an artificial stroma medium

“…This was accompanied by a loss of 64% of the CFI from the membranes, irrespective of whether ATP was present or not (data not shown). Solubilization of CFI by high NaCl concentrations under non-freezing conditions has been described before (Santarius, 1984b).…”

Changes in Protein Synthesis Induced in Tomato by Chilling

“…Santarius (30) has reported that low temperatures can release the coupling factor from isolated spinach thylakoid membranes. Although this may occur in tomato, we cannot disclude the possibility that chilling may alter the turnover rates of these proteins.…”

Photosynthetic characteristics of detached barley leaves during greening in the presence of SAN 9785

“…The 3.1-ml reaction mixture contained 0.33 M sorbitol, 50mM tricine, 5 mM MgCI2 and 0.5 mM K3[Fe(CN)6], pH 7.8. For phosphorylation conditions, 2.2 mM ADP and 2.2 mM KH/PO4 were added (Santarius 1984). Samples containing thylakoids equivalent to 40 lag chlorophyll were illuminated with white light of irradiance 10 roW" cm-2 at a constant temperature of 25 ~ C. The activity of the PSI-dependent electron transport (in vitro Mehler reaction) was measured polarographically as lightinduced oxygen consumption in the presence of 2,6-dichlorophenol indophenol (DPIP) ascorbate and methylviologen.…”