An Application of Thermoluminescence to Herbicide Studies

Gleiter, Hermann M.; Ohadh, N.; Hirschberg, Joseph; Fromme, Raimund; Ренгер, Г.; Koike, Hiroyuki; Inoue, Yorinao

doi:10.1515/znc-1990-0508

Cited by 23 publications

(13 citation statements)

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“…Studies with mutants have shown that R2K1, a strain that has psbAI inactivated and thus produces just form II of Dl, is more resistant to photoinhibition than the wild type or R2S2C3, which has both psbAII and psbAIII inactivated (10,23). Thermoluminescence studies on mutants lacking form I or form II indicate that there may be a functional difference between these two forms (13). We have shown that there is a difference in the turnover of the two proteins at high PPFD (Fig.…”

Section: Discussionmentioning

confidence: 70%

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

1994

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The three psbA genes in the cyanobacterium Synechococcus sp. strain PCC 7942 encode two distinct forms of the DI protein of photosystem II. ThepsbAI message, which encodes form I, dominates the psbA transcript pool at low to moderate light intensities; however, exposure to high light triggers a response in which the psbAI message is actively degraded while psbAII and psbAIII, which encode form II, are transcriptionally induced. We addressed whether these changes result from a generalized stress response and examined the consequence of light-responsive psbA regulation on the composition of DI in thylakoid membranes. Heat shock and oxidative stress had some effect on levels of the three psbA transcripts but did not produce the responses generated by an increase in light intensity. Prolonged exposure to high light (24-h time course) was characterized by elevated levels of all psbA transcripts through maintenance of high levels ofpsbAII and psbAIII messages and a rebound of the psbAI transcript after its initial decline. Form II-encoding transcripts were enriched relative to those encoding form I at all high-light time points. Form II replaced form I in the thylakoid membrane at high light despite an abundance of psbAI transcript at later time points; this may be explained by the observed faster turnover of form I than form II in the membrane. We propose that form II is less susceptible to damage at high light and that this qualitative alteration, coupled with increased turnover of Dl, protects the cells from photoinhibition.Photosystem II (PSII) is a membrane-embedded proteinpigment complex involved in key reactions of oxygenic photosynthesis: charge separation in response to excitation of a chlorophyll molecule by light and by oxygen evolution. This mode of photosynthesis, which requires two photosystems (PSII and photosystem I), is conserved in cyanobacteria, algae, and higher plants. The reaction center of PSII contains two structurally similar proteins, Dl and D2, which harbor the photoreactants involved in the primary reactions. Dl and D2, along with cytochrome b559 and the 4.8-kDapsbI gene product, form the core of the PSII reaction center (16,31,33).Light intensity modulates the composition of thylakoid membranes in plants as well as in cyanobacteria to best use the available light (2,3,30). This involves variation in the relative proportions of light-harvesting pigments, PSII and photosystem I reaction centers, electron carriers, and ATP synthase (2). On exposure to light intensities in excess of those found in optimal growth conditions, a decline in photosynthetic capacity, i.e., oxygen evolution and CO2 fixation, which is termed photoinhibition, occurs. The Dl protein is believed to be the initial site of photoinhibition, with its damage reflected in the loss of PSII activity (26,35). The DI protein of plants is rapidly turned over in the light, with the rate being proportional to light intensity. Thus, it is thought to play a role in protection of PSII against photoinhibition and may be designed to be re...

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Section: Discussionmentioning

confidence: 70%

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

1994

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“…Flash‐induced changes of the relative fluorescence quantum yield were monitored with home‐built equipment [14].…”

Section: Methodsmentioning

confidence: 99%

Indirect evidence for structural changes coupled with Q^−⋅_B formation in photosystem II

Reifarth

Ренгер

1998

FEBS Letters

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The thermal blockage of 3c e oxidation was analysed in PS II membrane fragments by monitoring flash-induced changes of the relative fluorescence quantum yield as a function of temperature. The results obtained reveal: (a) in dark-adapted samples the fraction of 3c e that is not reoxidised within a time domain of 10 s after the actinic flash increases with lowering the temperature (half-maximum effect at 250^260 K), (b) at low temperatures where 3c e generated in dark-adapted samples remains almost completely reduced, a significant extent of 3c e reoxidation arises when samples are used that were preilluminated at room temperature by one saturating flash followed by rapid freezing before performing the experiment, and (c) the extent of 3c e that is reoxidised at 258 K exhibits a characteristic binary oscillation as a function of the number of preillumination flashes given at room temperature. Based on these data it is inferred that Q f and 3c f are located at different equilibrium positions in the Q f site. As a consequence the formation of 3c f is coupled with significant structural changes that require sufficient flexibility of the protein matrix. This general feature corresponds with a recently proposed model for the acceptor side reactions of anoxygenic bacteria [Stowell, M.H

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“…quantum yield Flash-induced changes of the fluorescence quantum yield were monitored with a home-built equipment (Gleiter et al [17]). …”

Section: Measurements Of the Flash-induced Changes Of The Fluorescencementioning

confidence: 99%

Isolation and properties of PS II membrane fragments depleted of the non heme iron center

et al. 1996

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An Application of Thermoluminescence to Herbicide Studies

Cited by 23 publications

References 1 publication

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

Indirect evidence for structural changes coupled with Q^−⋅_B formation in photosystem II

Isolation and properties of PS II membrane fragments depleted of the non heme iron center

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An Application of Thermoluminescence to Herbicide Studies

Cited by 23 publications

References 1 publication

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

Adaptation to high light intensity in Synechococcus sp. strain PCC 7942: regulation of three psbA genes and two forms of the D1 protein

Indirect evidence for structural changes coupled with Q−⋅B formation in photosystem II

Isolation and properties of PS II membrane fragments depleted of the non heme iron center

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Indirect evidence for structural changes coupled with Q^−⋅_B formation in photosystem II