Cause for Dark, Chilling-Induced Inactivation of Photosynthetic Oxygen-Evolving System in Cucumber Leaves

Abstract

Effects on oxygen evolution of the storage of detached cucumber (Cucumis sativus) leaves at 0°C in the dark were investigated with thylakoids and oxygen-evolving photosystem 11 membranes isolated from stored leaves. The cold and dark treatment of leaves selectively inactivated electron transport on the oxidizing side of photosystem I. Photosystem II membranes isolated from treated leaves were largely depleted of two proteins of 20 and 14 kilodaltons, which correspond to the extrinsic 23-and 17-kilodalton proteins of spinach functioning in oxygen evolution. The manganese content of photosystem 11 membranes was also markedly reduced by the treatment. Thus, the inactivation of oxygen evolution induced by the dark, chilling treatment is ascribed to solubilization of the 20-and 14-kilodalton proteins and extraction of manganese.Photosynthetic oxygen evolution takes place in a discrete multiprotein complex of thylakoid membranes, which carries Chl a, carotenoids, and various reaction components or cofactors. Among others, four Mn atoms bound to the complex play a central role in cleavage of water molecules, which leads to the production of molecular oxygen. The Mn atoms are considered to be located on the Dl and D2 proteins of the PSII reaction center complex (13,19). Three extrinsic proteins of 33, 23, and 17 kD, which are associated with the lumenal side ofthe thylakoid membranes, are also essential for oxygen evolution. The 33-kD protein is needed to maintain the functional conformation of the Mn cluster, whereas the extrinsic 23-and 17-kD proteins have regulatory roles in oxygen evolution (8). Removal of the two proteins from inside-out thylakoid vesicles or PSII membranes, with a high concentration of NaCl, strongly suppresses oxygen evolution (1), but the lost activity is largely restored by addition of Ca2' and Cl- (6,14,16 cluster becomes unstable in the presence of exogenous reductants (7).Treatment of cucumber (Cucumis sativus L.) leaves at 0°C in the dark is known to inactivate selectively the oxygenevolving system because thylakoid membranes isolated from treated leaves are capable of photoreducing DCIP3 only in the presence of exogenous electron donors, such as DPC (4,10,20). Fluorescence induction determined at 77 K and 25°C also demonstrated that the chilling-sensitive site is not the PSII reaction center but electron transport on the oxidizing side of the reaction center (4, 20). The mechanism of the inactivation, however, still remains unclear. Kaniuga et al. (I 1) have shown that the Mn content of isolated chloroplasts decreased by 40 to 50% upon the cold and dark storage of tomato leaves, concomitant with an almost complete inactivation of the Hill reaction, and the changes were largely reversed by illumination of the treated leaves. The results suggest that loss of the Mn is the cause of inactivation. However, Mn atoms present in chloroplasts are heterogeneous in terms of both function and binding stability and there is a significant amount of Mn not related to photosynthetic oxygen evoluti...

The site of photoinhibition in leaves of Cucumis sativus L. at low temperatures is photosystem I, not photosystem II

“…Even at the highest PPFD used in the present study, the decrease in the QY(PSII) was not marked except when the leaves had been kept in the dark. This slight decrease by the chilling treatment in the dark is probably attributable to the dissociation of extrinsic proteins of PSII and release of some manganese, as has already been described (Shen et al 1990). In contrast to the slight changes in QY(PSII), a marked decrease in QY(PSI) was observed even at the lowest PPFD tested, 44 pmol.…”

“…When cucumber leaves are treated at low temperatures in the dark, selective inactivation of the oxygenevolving system of PSII occurs (Kaniuga et al 1978a, b;Terashima et al 1989a, b;Shen et al 1990). A similar phenomenon was also reported for Phaseolus vulgaris L. (Margulies and Jagendorf 1960;Margulies 1972) and for Lycopersicon esculentum Mill.…”

“…Margulies (1972) and Kaniuga et al (1978a, b) showed that chilling of leaves in the dark causes a marked decrease in the amount of manganese bound to thylakoids. Recently, we prepared PSII membranes from cucumber leaves which had been treated at 0~ for 24 or 48 h in the dark, and revealed that the manganese is released from the oxygen-evolving complex of PSII by the chilling treatment (Shen et al 1990). It was also shown that the release of manganese is preceded by the dissociation of the extrinsic 14-and 20-kDa proteins, which correspond to the 17-and 23-kDa proteins of spinach (Spinacia oleracea L.) and are involved in oxygen evolution.…”

Contrasting effect of dark-chilling on chloroplast structure and arrangement of chlorophyll–protein complexes in pea and tomato: plants with a different susceptibility to non-freezing temperature

“…The decrease in PSII activity in leaves of CS plants chilled in the dark for 3-5 days was associated with the release of manganese from the oxygen-evolving complex (OEC) of PSII (Kaniuga et al 1978) and with the destabilization of PSII extrinsic proteins (Shen et al 1990;Garstka and Kaniuga 1991). Moreover, dark-chilling of detached leaves of CS, but not CT plants, induced the accumulation of free fatty acids (FFA) in chloroplast membranes, due to a high activity of endogenous galactolipase (Gemel and Kaniuga 1987;Kaniuga 1997).…”

Synergic effect of salinity and light-chilling on photosystem II photochemistry of the halophyte, Sarcocornia fruticosa

“…1a and b; except the second day in the case of plants grown with 1030 mM NaCl) and higher than the control. Shen et al (1990) found that in the case of dark-chilling treatment in cucumber leaves, a long incubation (24-48 h) at 0 C was necessary for the inhibition. The reduction in F v /F m values of S. fruticosa indicated that those plants with no or low salt (170 mM NaCl) under light-chilling treatment and the control plants along the overall NaCl concentrations experienced higher photoinhibition.…”