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Effects of plasma membrane excitation on spatially distributed H+ fluxes, photosynthetic electron transport and non-photochemical quenching in the plant cellстатья
- Авторы: Bulychev Alexander A., Krupenina Natalia A.
- Сборник: Bioelectrochemistry Research Developments
- Год издания: 2008
- Место издания: Nova Scince Publishers, Inc Hauppauge, NY, United States
- Первая страница: 159
- Последняя страница: 188
- Аннотация: The electrical excitation of plant cell membranes is a multifunctional signal whose significance and operational pathways are not yet fully recognized. Chemical, mechanical or thermal stimuli induce electric signals – action potentials (AP) – that propagate over plants and temporally suppress photosynthesis. Unlike higher plants, characean algae combine the properties of membrane excitation, photosynthesis, and self-organization on the single cell level. Isolated cells of Chara corallina represent a unique model for studying the influence of AP on spatial patterns of proton flows, photosynthesis, and cell protection against excess light. The key event during AP is nearly a 100-fold increase in the cytosolic Ca2+ level, while concentration changes from the ensuing Cl– and K+ fluxes are less significant. By applying pulse-modulated microfluorometry, pH microelectrodes, and other methods, two principal effects of AP have been found and assigned to the plasma membrane and the chloroplast layer, respectively. Under resting conditions, photosynthesis and protective non-photochemical quenching in Chara cells are subject to spatial patterns coordinated with the light-dependent pH banding. The generation of AP was found to temporally extinguish the external pH pattern without smoothing the heterogeneity in the chloroplast layer. By mobilizing ion flux-mediated pathways, the membrane excitation induced a large transient drop in maximal chlorophyll fluorescence (energy-dependent quenching) and inhibited photosynthetic linear electron transport in chloroplasts. Unlike the influence on pH banding, the effect of membrane excitation on chloroplasts was strictly light dependent and disappeared upon inhibition of photosynthetic electron transport with diuron. Relations between the AP-induced quenching and electron transport were examined in the presence of electron acceptor methyl viologen (MV). This divalent cationic acceptor was inaccessible to the chloroplast thylakoids under resting cell conditions, even at high (~1 mM) external concentrations. However, the generation of a single AP, made MV immediately accessible inside the chloroplasts, which was evident from irreversible non-photochemical quenching at a wide range of irradiances, including the low irradiance range. Thus, the plasma membrane excitation inhibited native electron flow and activated electron flux to MV in a triggered mode, acting as a switch of electron transport pathways. Possible mechanisms underlying effects of AP on the plasma membrane and chloroplasts are discussed.
- Добавил в систему: Булычев Александр Александрович