Dependence of Delayed Luminescence upon Adenosine Triphosphatase Activity in Chlorella

Abstract

Delayed luminescence and fluorescence yield after illumination by a short flash were measured in Chiorella pyrenoidosa in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Addition of tri-N-butyl-tin ( It is generally accepted that delayed luminescence emission is due to charge recombination between the oxidized donor and the reduced acceptor of PSII centers (1, 29). Delayed luminescence is thus an increasing function of the rate of back reactions occurring at the level ofPSII centers. Several parameters control the intensity of this delayed luminescence, among them the concentration of PSII centers which include simultaneously oxidized donors and reduced acceptors, the number of oxidizing equivalents stored on the donor side of PSII (7, 21, 36), the fluorescence yield (29), the electrical potential, and the pH gradient across the thylakoid membrane. Miles and Jagendorf (31) first described a stimulation of delayed luminescence by a membrane potential induced by an ion gradient. This effect has been more quantitatively studied by Barber and Kraan (5), Kraan (26), and Kraan et al. (27) detected by the 520 nm absorption change (23), when other parameters which control delayed luminescence are kept constant. Delayed luminescence can also be stimulated by acid-base transition (26,27,30) or by a light-induced proton gradient as shown by Wraight and Crofts (35).Living cells differ from chloroplasts isolated either from algae or from higher plants with respect to the rates of the back reaction and of the intensity of delayed luminescence. After a preillumination in the presence of DCMU, the reoxidation of reduced acceptor Q-can only occur by the back reaction, which is faster in living cells (ti/2 -0.75 s) than in isolated chloroplasts (t1/2 -2.5 s) (8). The measurement of the lifetime of the S states (25) with an 02 electrode in the absence of DCMU yields the same conclusion: the tl/2 for the reduction of state S2 to state Si is about 20 s in Chlorella and 60-100 s in isolated chloroplasts (13,21).It is possible to interpret these differences by assuming that in living cells, there exists, even in dark-adapted material, a permanent proton gradient and membrane potential which would stimulate the charge recombination. Carmeli (9) has shown in isolated chloroplasts that after light activation of the latent ATPases (4), hydrolysis of ATP can actually generate a proton gradient. To verify if in dark-adapted algae there exists a permanent proton gradient which originates from ATP hydrolysis, we studied the effect of a specific inhibitor of the ATPase, TNBT3 (24) which, like other trialkyl compounds probably blocks the proton channel located in a hydrophobic region of the membrane (15). In living cells, the decay of the light-induced membrane potential as measured by the electrochromic effect at 520 nm (23) is markedly slowed down by TNBT (Diner, personal communication quoted in ref. 17), which indicates the blockage of the specific ion channel of the ATPases. MATERIALS AND METHODSChlorella pyrenoidosa were ...

A New Electrochemical Gradient Generator in Thylakoid Membranes of Green Algae

“…We have studied the permanent electrochemical gradient (∆μ) 1 under strict anaerobic conditions to investigate the role of respiration processes in its formation. In wild-type Chlorella sorokiniana, a ∆μ has even been observed under anaerobic conditions (5).…”

Photosynthesis in Microalgae as Measured with Delayed Fluorescence Technique

“…OEC reacts with quinone molecules and their reduction state is in the equilibrium with PQ. The increase of PQH 2 concentration induces reverse electron flow, producing Q A -and Q B -states (Joliot & Joliot, 1980), which contribute to DF. The reduction state of PQ pool is influenced by many reactions including electron transport in PSI and dark reactions of photosynthesis.…”

“…The exact physiological interpretation of transient peaks is quite difficult due to complex electron pathways and their interactions, however they appear to be formed when the metabolic conditions affect the redox status of Q A and Q B directly or indirectly. It has been reported that ATP and NADPH can reduce quinones (Joliot & Joliot, 1980). Degradation of starch to PGA begins immediately after switching off the light.…”

“…In many cases, DFI can be utilized as a measure of living cell concentration (Berden- Zrimec et al, 2009). It also reflects the number of PSII centers, the fluorescence yield, and the rate of back reactions, which are influenced by the membrane potential and pH gradient (Avron & Schreiber, 1979;Joliot et al, 1971;Joliot & Joliot, 1980;Wraight & Crofts, 1971). In DF kinetics, the changes are most obvious when observing the position and intensity of the transient peak.…”

“…An important feature of DF is that it is emitted only by a functionally active chlorophyll -in other words, when photosynthesis is active (Bertsch, 1962). The emission depends on the number of PSII centers and the rate of back reactions in the photosynthetic chain, which are influenced by the membrane potential and pH gradient (Avron & Schreiber, 1979;Joliot & Joliot, 1980). Delayed fluorescence is affected by many chemical and physical variables, such as ATP (Avron & Schreiber, 1979), proton gradient in the thylakoids (Wraight & Crofts, 1971), chill stress (Melcarek & Brown, 1977), different xenobiotics (Berden-Zrimec et al, 2007;Drinovec et al, 2004a;Katsumata et al, 2006), excitation light spectral and intensity characteristics (Wang et al, 2004;Zrimec et al, 2005), cell culture growth stage (Berden-Zrimec et al, 2008b;Monti et al, 2005), and nutrient status (Berden-Zrimec et al, 2008a).…”