Chlorophyll a fluorescence decay in herbicide-resistant D1 mutants of Chlamydomonas reinhardtii and the formate effect

Govindjee, .; Eggenberg, P.; Pfister, Klaus; Strasser, Reto J.

doi:10.1016/0005-2728(92)90092-g

Cited by 23 publications

(10 citation statements)

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“…5A) exhibited complex kinetics which could be resolved into at least three different decay components (Table 2) similar to those reported by others (Cao and Govindjee 1990;Govindjee et al 1992). The estimated decay half-times for the ®rst two phases (fast and medium) of Q À A re-oxidation in SP were 230 and 2,370 ls, accounting for 48.0 and 32.1% of the decay, respectively.…”

Section: Decay Of the Variable Chlorophyll¯uorescencesupporting

confidence: 61%

“…1B), thus implying that the PQ pool is in a predominantly reduced state during darkness. In addition, the¯uorescence decay kinetics after a saturating¯ash, used as a measure of the dark re-oxidation of the primary electron acceptor Q A (Schreiber 1986;Mohanty et al 1991;Govindjee et al 1992), was retarded in WP needles (Fig. 5, Table 2), thus indicating that indeed Q A is in a more reduced state in WP.…”

Section: Discussionmentioning

confidence: 97%

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Photosynthetic electron transport adjustments in overwintering Scots pine ( Pinus sylvestris L.)

Ivanov

Sane

Zeinalov

et al. 2001

Planta

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As shown before [C. Ottander et al. (1995) Planta 197:176-183], there is a severe inhibition of the photosystem (PS) II photochemical efficiency of Scots pine (Pinus sylvestris L.) during the winter. In contrast, the in vivo PSI photochemistry is less inhibited during winter as shown by in vivo measurements of deltaA820/A820 (P700+). There was also an enhanced cyclic electron transfer around PSI in winter-stressed needles as indicated by 4-fold faster reduction kinetics of P700+. The differential functional stability of PSII and PSI was accompanied by a 3.7-fold higher intersystem electron pool size, and a 5-fold increase in the stromal electron pool available for P700+ reduction. There was also a strong reduction of the QB band in the thermoluminescence glow curve and markedly slower Q-A re-oxidation in needles of winter pine, indicating an inhibition of electron transfer between QA and QB. The data presented indicate that the plastoquinone pool is largely reduced in winter pine, and that this reduced state is likely to be of metabolic rather than photochemical origin. The retention of PSI photochemistry, and the suggested metabolic reduction of the plastoquinone pool in winter stressed needles of Scots pine are discussed in terms of the need for enhanced photoprotection of the needles during the winter and the role of metabolically supplied energy for the recovery of photosynthesis from winter stress in evergreens.

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Section: Decay Of the Variable Chlorophyll¯uorescencesupporting

confidence: 61%

Section: Discussionmentioning

confidence: 97%

Photosynthetic electron transport adjustments in overwintering Scots pine ( Pinus sylvestris L.)

Ivanov

Sane

Zeinalov

et al. 2001

Planta

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“…Erickson et al (1989) studied the fluorescence yield decay after a flash in D 1 mutants of Chlamydomonas reinhardtii. This study was extended by Govindjee et al (1992) and by Crofts et al (1993). The study of oxygen and thermoluminescence oscillations was undertaken by Gleiter et al (1992) in thylakoids of a series of herbicide resistant mutants produced by site directed mutagenesis in Synechococcus PCC 7942.…”

Section: Introductionmentioning

confidence: 95%

The primary structure of D1 near the QB pocket influences oxygen evolution

Étienne

Kirilovsky

1993

Photosynth Res

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Photosystem II (PS II) is the site of oxygen evolution. Activation of dark adapted samples by a train of saturating flashes produces oxygen with a yield per flash which oscillates with a periodicity of four. Damping of the oxygen oscillations is accounted for by misses and double hits. The mechanisms hidden behind these parameters are not yet fully understood. The components which participate in charge transfer and storage in PS II are believed to be anchored to the heterodimer formed by the D1 and D2 proteins. The secondary plastoquinone acceptor QB binds on D1 in a loop connecting the fourth and fifth helices (the QB pocket). Several D1 mutants, mutated in the QB binding region, have been studied over the past ten years.In the present report, our results on nine D1 mutants of Synechocystis PCC 6714 and 6803 are analyzed. When oxygen evolution is modified, it can be due to a change in the electron transfer kinetics at the level of the acceptor side of PS II and also in some specific mutants to a long ranging effect on the donor side of PS II. The different properties of the mutants enable us to propose a classification in three categories. Our results can fit in a model in which misses are substantially determined by the fraction of centers which have QA (-) before each flash due to the reversibility of the electron transfer reactions. This idea is not new but was more thoroughly studied in a recent paper by Shinkarev and Wraight (1993). However, we will show in the discussion that some doubts remain as to the true origin of misses and double hits.

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“…1992;Strasser et al 1992;Crofts et al 1993). Govindjee et al (1992) suggested that the amino acid substitutions at $264 and at G256 in C. reinhardtii altered the equilibrium for QA QB : QAQB reaction and the ratio of slow to the fast PS II centers showing a modification at the QB binding site. By the analysis of the electron transfer kinetics, Crofts et al (1993) showed a marked decrease in the rate of reduction of bound plastoquinone to the bound semiquinone in A251V and $264A mutants.…”

Section: Introductionmentioning

confidence: 99%

Polyphasic rise of chlorophyll a fluorescence in herbicide-resistant D1 mutants of Chlamydomonas reinardtii

1995

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Chlorophyll (Chl) a fluorescence transient, a sensitive and non-invasive probe of the kinetics and heterogeneity of the filling up of the electron acceptor pool of Photosystem II (PS II), was used to characterize D1-mutants of Chlamydomonas reinhardtii. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK), which provides the first measured data point at 10 μs and allows data accumulation over several orders of magnitude of time, we have characterized, for the first time, complete Chl a fluorescence transients of wild type (WT), cell wall less (CW-15) C. reinhardtii and several herbicide-resistant mutants of the D1 proteins: D1-V219I The mutants are labeled as follows: the single letter code for the wild type amino acid, followed by the residue number, then the code for the mutated amino acid. A251V, F255Y, S264A G256D and L275F. In all cases, the Chl a fluorescence induction transients follow a pattern of O-J-I-P where J and I appear as two steps between the minimum Fo (O) and the maximum Fmax (Fm, P) levels. The differences among the mutants are in the kinetics of the filling up of the electron acceptor pool of PS II (this paper) in addition to those in the re-oxidation kinetics of QA (-) to QA, published elsewhere (Govindjee et al. (1992) Biochim Biophys. Acta: 1101: 353-358; Strasser et al. (1992) Archs. Sci. Genève 42: 207-224) and not in the ratio of the maximal fluorescence Fm to the initial fluorescence Fo. The value of this experimental ratio is Fm/Fo = 4.4±0.21 independent of the mutation. At 600 W m(-2) of 650 nm excitation, distinct hierarchy in the fraction of variable Chl a fluorescence at the J level is observed: S264A > A251V ∼ G256A > L275F ∼ V219I > F255Y ∼ CW-15 ∼ WT. At 300 and 60 W m(-2) excitation, a somewhat similar hierarchy among the mutants was observed for the intermediate levels J and I. Addition of bicarbonate-reversible inhibitor formate did not change the O to J phases, slowed the I to P rise, and in many cases, slowed the decay of fluorescence beyond the P level. These observations are interpreted in terms of formate effect being on the acceptor rather than on the donor side (S-states) of PS II. The formate effect was different in different mutants, with L275F being the most insensitive mutant followed by others (V219I, F255Y, WT, A251V and S264A). Further, in the presence of high concentrations of DCMU, identical transients were observed for all the mutants and the WT.The quantum yield of photochemistry of PS II, calculated from 1-(Fo/Fm), is in the range of 0.73 to 0.82 for the WT as well as for the mutants examined. Thus, in contrast to differences in the kinetics of the electron acceptor side of PS II, there were no significant differences in the maximum quantum yield of PS II, among the mutants tested. We suggest that earlier photochemistry yield values were much lower (0.4-0.6) than those reported here due to either higher measured values of Fo by instruments using camera shutters, or due to the use of cells grown in less than-optimal conditions.

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Chlorophyll a fluorescence decay in herbicide-resistant D1 mutants of Chlamydomonas reinhardtii and the formate effect

Cited by 23 publications

References 0 publications

Photosynthetic electron transport adjustments in overwintering Scots pine ( Pinus sylvestris L.)

Photosynthetic electron transport adjustments in overwintering Scots pine ( Pinus sylvestris L.)

The primary structure of D1 near the QB pocket influences oxygen evolution

Polyphasic rise of chlorophyll a fluorescence in herbicide-resistant D1 mutants of Chlamydomonas reinardtii

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