Dark induction of zeaxanthin-dependent nonphotochemical fluorescence quenching mediated by ATP.

Abstract

Zeaxanthin-dependent nonphotochemical fluorescence quenching is a light-induced activity in plants that apparently protects against the potentially damaging effects of excess light. We report a dark-induced nonphotochemical quenching in thylakoids of Lactuca satva L. cv. Romaine mediated by ATP. This effect is due to low lumen pH from hydrolysis-dependent proton pumping and hence required an active ATPase. The induction was optimal at 0.3 mM ATP, a physiological concentration, and occurred under conditions of little or no reverse electron flow. The properties of ATPinduced quenching were in all respects examined similar to light-induced quenching, including antimycin inhibition of quenching induction but not ApH. We conclude that zeaxanthin-dependent quenching depends directly on lumen pH and that the role of light is indirect. Although it is known that zeaxanthin and low lumen pH are insufficient for quenching to occur, the results apparently exclude the redox state of an electron-transport carrier or formation of light-induced carotenoid triplets as a further requirement. We propose that a slow pH-dependent conformational change together with zeaxanthin cause static quenching in the pigment bed; possibly antimycin inhibits this change. Furthermore, we suggest from the ability of ATP to sustain quenching in the dark for extended periods that persistent or slowly reversible zeaxanthin quenching often observed in vivo may be due to sustained ApH from ATP hydrolysis.High light intensity induces reversible changes in the level of violaxanthin in leaves via the so-called xanthophyll cycle (1-3). Zeaxanthin, which is formed in this cycle from violaxanthin (4) under low lumen pH (5), enhances nonradiative dissipation of excess absorbed energy and thus apparently serves the important function of protecting the photosystem against the potentially damaging effects of excess light (6). In vitro, the rate and extent of zeaxanthin formation are functions of lumen pH, ascorbate concentration, and violaxanthin availability (2). In vivo, zeaxanthin forms when photosynthesis becomes limiting (4,7,8), at high temperature (7, 9), or under other combined stresses (10). Zeaxanthin-forming capacity, thus protective capacity, varies with species and growth history. Plants that are well adapted to high light intensity have larger total pools of xanthophyll-cycle pigments (violaxanthin plus antheraxanthin plus zeaxanthin) than the same species grown under reduced light intensity (11).Nonradiative energy dissipation at photosystem II (PSII) is reflected in nonphotochemical quenching (NPQ) of roomtemperature fluorescence (12-15). The correlation of NPQ with zeaxanthin formation, first reported by Demmig et al. (16) in leaves, has since been observed in intact chloroplasts (17) and thylakoids (18). Zeaxanthin-dependent NPQ is of the "high-energy" or ApH-dependent type (17-19) as is zeaxanthin-independent or constitutive NPQ that is also present in many systems (17)(18)(19)(20). Lowering of the intrinsic quantum efficiency or "do...

Nonphotochemical Quenching of Chlorophyll Fluorescence inChlamydomonas reinhardtii

“…Moreover, this different capacity to generate a sustained nonphotochemical quenching in the light cannot be ascribed to the presence of a quenched state generated before illumination, which would originate from a trans-thylakoid ∆pH established by ATP hydrolysis in darkness. Indeed, uncoupling of dark-adapted Chlamydomonas cells by ionophores had no effect on the variable fluorescence, in contrast to plants placed in conditions where high-energy state quenching is induced in the dark (41).…”

The Xanthophyll Cycle Modulates the Kinetics of Nonphotochemical Energy Dissipation in Isolated Light-Harvesting Complexes, Intact Chloroplasts, and Leaves of Spinach1

“…From this and other evidence it is widely concluded that the effect of low pH is due to protonation-induced conformational changes in one or more of the components of the PSII antenna Gilmore and Yamamoto 1992;Noctor et al, 1993;Ruban et al, 1993;Bilger and Bjö rkman, 1994). Support for the view that both protonation and zeaxanthin induce conformational changes in the PSII antenna came later from an analysis of fluorescence lifetimes (Gilmore et al, 1995(Gilmore et al, , 1996a(Gilmore et al, , 1996b and steadystate fluorescence (Walters and Horton, 1993), which indicated that the qE was associated with a switch from an unquenched to a quenched conformation.…”

Higher Plant Light‐Harvesting Complexes LHCIIa and LHCIIc are Bound by Dicyclohexylcarbodiimide During Inhibition of Energy Dissipation

“…quenching of chlorophyll fluorescence (Horton and Bowyer, 1990;Krause and Weis, 1992) has shown that it is dependent on the acidification of the thylakoid lumen that results from light-induced proton translocation (Briantais et al, 1979 ;Gilmore and Yamamoto, 1992). This implies that protonation of pigments or amino-acid residues is a key event in the induction of qE.…”