Further characterization of Anacystis shade phenotype as induced by sublethal ... On the contrary, sun phenotype is characterized by a low rate of antenna ...
Photosynthesis Research 26: 29-37, 1990. © 1990 Kluwer Academic Publishers. Printed in the Netherlands.
Regular paper
Shade adaptation in cyanobacteria Further characterization of Anacystis shade phenotype as induced by sublethal concentrations of DCMU-type inhibitors in strong light* Friederike Koenig Botanisches Institut, J.W. Goethe-Universitiit, D-6000 Frankfurt am Main, FRG Received 28 September 1989; accepted 18 April 1990
Key words: D1 protein, DCMU-type inhibitors, fluorescence excitation, light intensity adaptation, protein synthesis, thiosulphate oxidation Abstract
Growth of Anacystis in high light in the presence of sublethal concentrations of DCMU-type inhibitors leads to an increased synthesis of phycocyanin paralleled by a reduced rate of 35S methionine incorporation into the D1 protein compared to the high light controls, as is characteristic for naturally-induced shade phenotype. On the contrary, sun phenotype is characterized by a low rate of antenna synthesis, but a high rate of 35S methionine incorporation into the D1 protein. Room temperature excitation spectra of 684nm fluorescence emission clearly demonstrate the participation of the extraordinarily high concentration of phycocyanin in artificially shade-adapted cells in excitation energy transfer to chlorophyll. It could be shown that the development of shade-type appearance is not simply the consequence of an imbalance in electron transport, since an addition of thiosulphate to cultures growing in high light in the presence of DCMU-type inhibitors can only partially prevent or revert the change from sun to artificial- herbicide-induced- shade phenotype. This is regarded as evidence that the dynamic herbicide-binding D1 protein itself may play a role as a light meter in the process of natural shade adaptation, the rate of its degradation and resynthesis possibly giving the signal for the adaptive reorganization of the photosynthetic apparatus. The chain of signal transduction remains to be established.
Abbreviations: atrazine- 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine; c h l - chlorophyll; D 1 reaction center polypeptide carrying the secondary plastoquinone electron acceptor of PS II; DCMU 3-(3,4-dichlorophenyl)-l,l-dimethylurea; PAGE-polyacrylamide gel electrophoresis; PAR-photosynthetically active radiation; PC-phycocyanin; P C C - Pasteur Culture Collection; P S - photosystem; Q ~ - secondary plastoquinone electron acceptor of PS II; S A U G - Sammlung von Algenkulturen am Pflanzenphysiologischen Institut der Universtit~it Grttingen; S D S - sodium dodecyl sulphate Introduction
Shade type appearance can be induced in Anacystis not only by growth in low light but also * Dedicated to Professor Wilhelm Menke on the occasion of his 80th birthday.
in high light intensity in the presence of sublethal concentrations of DCMU-type inhibitors (Koenig 1987a,b). This inhibitor class was found to be the only one to slow down the turnover of the M r 32 000 QB binding protein which is lightdependent also in cyanobacteria (Goluobinoff et al. 1988). With the aim to understand the mech-
30 anism
of
cyanobacterial
shade
adaptation,
Anacystis cultures which were artificially shadeadapted by growth in high light intensity in the presence of 1 0 - 6 M atrazine were compared to cultures from deep shade. Both cell types are characterized by higher concentrations of both chlorophyll (chl) a and phycocyanin (PC) per cell and, in addition by a higher ratio of PC to chl compared to the corresponding sun-type. It was described earlier that shade phenotype induced by DCMU-type inhibitors in strong light may even contain a higher ratio of PC to chl than cells grown in very low light intensity (Koenig 1987a,b). The present investigation will answer the question whether the extraordinarily high PC concentration in artificially shade-adapted Anacystis does indeed function as an antenna capable of excitation energy transfer to chl or rather as a storage protein inactive in photosynthesis. Also, it will be tried to decide whether the induction of the shade-type in strong light in the presence of sublethal concentrations of DCMU-type inhibitors is simply due to an imbalance of electron transport or not. It will be investigated to which extent it can be prevented or reverted by donating electrons to the chain from thiosulphate, an electron donor known to feed in electrons at the cytochrome b6/f complex (Koenig 1990, Peschek 1978, Utkilen 1976). On the basis of the assumption that the dynamic M r 32000 QB and herbicide-binding protein, also called D1, might function as a meter in light intensity adaptation, the synthesis rate of this protein will be compared in strong light, in naturally shade adapted cells as well as in cultures grown in high light intensity under sublethal concentrations of DCMU-type inhibitors.
added to the cultures in methanol to a final solvent concentration of 0.1%. On there being nothing else indicated, batch cultures were harvested after 6 d growth at 32°C in continuous white light at 1i0/xE m -2 s -a. White light was obtained as described earlier on (Feierabend 1986). Thiosulphate and sulphate were added as 1 M solutions of their sodium salts, adjusted to pH 7.5 by means of HCI. 1 c m 3 salt solution was added to 30 c m 3 batch cultures twice within 24 h. Cultures containing salt were shaken at 80 rpm.
Absorption and fluorescence measurements Absorption spectra were recorded by means of a scanning double beam spectro-photometer (Kontron, Uvikon 810). Fluorescence excitation spectra were measured at room temperature with a scanning fluorescence photometer (PerkinElmer, MPF-3). Excitation and emission slits were 4 nm each. The samples contained equal concentrations of chlorophyll (2.5/xg/cm3).
Determination of pigment contents and ratios Phycocyanin (PC) concentrations were determined as described earlier (Koenig 1987b, Myers et al. 1978) from the in vivo spectra of cells, using the equations and coefficients given by Myers et al. (1978). Chlorophyll (chl) contents were calculated either from the in vivo spectra as well (Myers et al. 1978) or from acetone extracts obtained after a short ultrasonic treatment of the cells. Molar ratios of PC to chl given in this paper represent the ratio of PC monomer to chl, the monomer containing 3 phycocyanobilin molecules. For comparison with values in the literature giving the ratio of chromophores, the values in the present paper have to be multiplied by a factor of 3.
Measurement of O2-evolution Material and methods
Culture conditions Anacystis nidulans (Synechococcus spec. PCC 6301, Synechococcus leopoliensis SAUG 1402-1) was grown in standard mineral media according to Allen (Carr et al. 1973). Inhibitors were
Light-dependent O2-evolution was monitored at the growth temperature of the cultures, by using a Clark-type electrode (Hansatech). White actinic light was provided by a slide projector. Immediately before the test, cells were transferred into fresh Allen's media (Carr et al. 1973).
31
Measurement of light intensity Photon flux density was measured by using a LI-COR LI-185 Quantum /Radiometer/Photometer equipped with a LI-190S quantum sensor.
Radioactive labelling (35S) of Anacystis proteins 30 c m 3 batch cultures in fresh Allen's media were labelled by the addition of 6.0/,~Ci 35S sulphate (specific radioactivity 1109 Ci/mmol) in the absence of unlabelled sulphate or 2.4/zCi 35S methionine (specific radioactivity 1117 Ci / mmol) in the presence of unlabelled sulphate. In the case of 35S sulphate used as a radioactive sulphur source, cells were grown in sulphate-free media for 90 min before addition of labelled sulphate. In experiments investigating the rate of synthesis of the D1 protein in differently grown cultures, growth in the presence of labelled sulphur source under otherwise original conditions of light and temperature was halted after 6, 12, 18, 24 and 30rain, respectively, by the addition of unlabelled sulphate or methionine (final concentration 1 mM) (Fig. 5). In pulse chase experiments, the pulse time was 30 min; the chase was 0, 1, 3, 5 and 9h, respectively (Fig. 1).
Polyacrylamide gel electrophoresis (PAGE) Equal numbers of cells from differently grown cultures (30 c m 3) w e r e harvested and resuspended in 0.7 c m 3 0.01 M sodium phosphate buffer (pH 7.0). The cell density was determined from the absorbance of the cultures at 800 nm, calibrated with a haemacytometer. By means of ultrasonic treatment, cells were disrupted, and samples were subsequently prepared for electrophoresis by adding both sodium dodecylsulphate (SDS) (final concentration 2.7% (w/v)) and 2-mercaptoethanol (final concentration 0.7% (v/v)). The heating of the samples (10min at 80°C) was followed by a 5 min centrifugation (13 200 x g). A separation of polypeptides was achieved using the discontinuous 'system II' described by Machold et al. (1979). After acid denaturation of the proteins by means of trichloroacetic acid gels were stained with Coomassie Brilliant Blue and, after destaining, were treated with 2,5-diphenyloxazol (Bonner and
Laskey 1974). Dried gels were exposed to X-ray film (Kodak X-Omat S) at -80°C. The molecular weight standards were myosin: (M r 200 000), phosphorylase b (M r 94 000), bovine serum albumin ( M r 67 000), ovalbumin (M r 43 000), carbonic anhydrase ( M r 3 0 0 0 0 ) , soybean trypsin inhibitor ( M r 20 100) and a-lactalbumin (14400). In order to evaluate the relative concentrations of the D1 protein and constituents of the antenna complex, X-ray films were scanned after exposure (Quick Scan R&D, Model 1053).
Chemicals Chemicals used were reagent grade wherever possible. SDS was purchased from Pierce, and atrazine from SERVA.
Results
Growth of Anacystis in high light intensity in the presence of 10 -6 M atrazine induces a shade-type appearance, as characterized by pigment content and photosynthetic activity (Figs. 1 and 2). From pulse chase experiments it can be inferred t h a t - parallel to a slow decrease in D1 protein synthesis- the addition of atrazine to cells precultured and growing in strong white light leads to an increased PC synthesis (Fig. 1), in turn resulting in a higher level of antenna pigment protein. The latter can be concluded from both the Coomassie-stained polypeptide patterns of the respective gels (data not shown) and the absorption spectra (Koenig 1987a,b). The corresponding gels also show that the ratio of PS I to PS II is increased both in cells grown in deep shade (5/zE m -2 s -1) and in the presence of 10-6M atrazine at high light intensity (100/xE m -2 s-l). This well complies with earlier published data for naturally shade-adapted Anacystis (Kawamura et al. 1979). Light saturation of O2-evolution (recorded in white light) was found to be similar both in naturally and artificially shade-adapted Anacystis, whereby artificially shade-adapted cells had a slightly higher maximum speed than naturally shade-adapted ones, when calculated on the basis of chl (Fig. 2). Artificially shade-adapted cells thus took an intermediate position between
32
0h
3 2 kDn
3h
~
f
f f
t
antenna
32 k0a
Fig. I. Decrease of 35S labelled M r 32 000 Qa binding protein from the thylakoid membranes and parallel synthesis of labelled phycocyanin antenna in the presence of 10-~M atrazine at 110/.LE m -2 s -1 and 32°C during 9 h of chase. 35S labelled polypeptide profiles of SDS-PAGE separated Anacystis proteins were compared on the basis of identical cell number. Cells precultured at 110/zE m -2 s -1 and 32°C in the absence of any inhibitor were exposed to 35S sulphate for 30 min. Atrazine was added together with 35S sulphate and was present during chase. Growth of parallel cultures was stopped after 0, 1, 3, 5 and 9 h of chase. Equal results were obtained with labelled sulphate and methionine, respectively. Arrows mark the D1 protein (32kDa) and subunits of phycocyanin (antenna).
cells naturally adapted to high light and low light, respectively. Room temperature excitation spectra of 684 nm fluorescence emission deafly show that the high concentration of PC relative to chl in
artificially shade-adapted cells (Koenig 1987a,b) is capable of transferring energy to chl. The ratio of the 684nm emission, excited by 625 and 440 nm light, respectively, was determined to be 2.802 in naturally shade-adapted cells (grown at 5/~E m -2 s -1) and 4.061 in cells grown in high light (110/xE m - 2 s -~) in the presence of 10-6M atrazine. For high light controls, a ratio of 0.774 was recorded. Apparently, carotenoids transfer energy to chl in this system (Fig. 3). The induction of shade type by sublethal concentrations of atrazine in strong light cannot be fully prevented or reverted by electron donation from thiosulphate to PSI (Fig. 4, upper part). The addition of thiosulphate only induces a small change in the PC/chl ratio in favor of chl, a change which can hardly be distinguished from the one induced by the addition of comparable concentrations of sulphate (control). A thiosulphate concentration capable of completely reverting or even preventing the shade adaptation induced by the DCMU-type inhibitor (PC/chl 0.3 to PC/chl 0.1) was not found. The proton concentration of the media was generally shifted by Anacytis from an initial pH 7.8 down to pH 10.5 during preculture. The subsequent addition of thiosulphate and sulphate had comparable effects on the pH of the cultures; they resulted in parallel increases in proton concentration in the media (Fig. 4, lower part). Thus, the small difference between the effects of thiosulphate and sulphate on the PC/ chl ratio (Fig. 4, upper part) is not due to a difference in the proton concentration of the media. The comparison of 35S methionine incorporation into the D1 protein under different growth conditions indicated that the rates of D1 synthesis were similar in cells grown in shade (Fig. 5C) and cells grown in high light intensity in the presence of a sublethal concentration (10 -6 M) of atrazine (Fig. 5D). Both cultures (Fig. 5C and D) showed markedly reduced rates of D1 (32 kDa) synthesis compared to the high light controls (Fig. 5B). The synthesis of D1 was also reduced compared to the high light controls (Fig. 5B) when 10 -6 M atrazine was present only during the labelling experiment of cells precultured in high light intensity in the absence of herbicide (Fig. 5A). Atrazine further reduced the rate of
33
~00 = t'"u
~
c~ E
•
110,uEm-2s -1 no additions
300
O //
E
~
•
110uEm-2s -1
•
200
I0-6M ofrozine
¢-
-,--°
f / ~ - - o
"~ o > ~u I
......
/
o_. . . . . . . . . . . . . . . . .
Q. . . . .
~-__ lO~Em-2s-1
-
no addahons
100
O
0
I
I
I
I
200
/.00
600
800
I
pEm-2s -1
1000
Fig. 2. Light saturation of O2-evolution (Nmoles O2/mg chlh) in Anacystis grown under different culture conditions. Temperature during growth and experiment was 32°C.
300 I
~00 I
500 I
600 I
nm
10 -6 PI a t r a z i n e
E
r-.,d" OO
110 ~ E m-2 s-1
t-" O
oq
E¢u
>0
i--
700 I
no ndditions 5 pE m -2 s -1
,=
,=
no addifions
o
=.
110 pE m-2 s-1
to._
I
I
I
I
I
300
/.00
500
600
700
nm
Fig. 3. Excitation spectra of 684 nm fluorescence emission of Anacystis cultures grown at 32°C under different conditions of light intensity and composition of the media. The spectra were recorded at room temperature. The samples contained 2.5/.Lg chl/cm 3.
34 0,t~ o
sutphc#e
-i.~. °'3~
t III I I
10-6 M of Pazine
~'
I
t
I
0,2
.~-E
thiosulphafe
i_J 0,1
confroL ~ no oddifions
O" 10, 5 -
control 10-6 M atrazine .o sutphofe on thiosutphafe
"tt~
sulphate
8,5
,
,
0,5
1,0
,
,
1,5 2,0 ld salt added
Fig. 4. Influence of thiosulphate and sulphate on pigmentation (upper part) and pH (lower part) of cultures grown at 32°C and 110/xE m -2 s -1 in the presence of 10 -6 M atrazine. While there is a small difference between the impact of an addition of sulphate (Q) and thiosulphate (,t) on pigmentation, the effects of the addition of sulphate (©) and thiosulphate (A) on the pH of the media are identical. Mean errors of 6 independent experiments are indicated.
D1 synthesis when present during the labelling of artificially shade-adapted Anacystis (Fig. 5E). The synthesis rate of the two low molecular weight components (Fig. 5, marked by arrows) as judged from their concentration in the cells after 12 min exposure to 35S methionine-is inversely related to the rate of D1 synthesis. Unlike the situation shown in Fig. 1, the two low molecular weight components highly labelled under conditions of low D1 synthesis and vice versa, are not subunits of phycocyanin. Phycocyanin synthesis is comparably slow, much slower than D1 synthesis. Its synthesis rate, however, could be demonstrated to be inversely related to the synthesis rate of the D1 protein (data not shown), just like the rate of synthesis of the heavily labelled low molecular weight components (Fig. 5). The two low molecular weight components were not labelled in the case
32kOo
Fig. 5. Radioactivity in Anacystis proteins after 12 min exposure to 35S methionine. Different culture conditions were A, B, C, D, E: Temperature °C
Light intensity /zE m -2 s -1
Atrazine during preculture
Atrazine during labelling experiment
A B C D E
110 110 5 110 110
-
10 -6 M 10 -6 M
32 32 32 32 32
10 -6 10 -6
M M
Polypeptide patterns of equal numbers of cells are compared with respect to 35S labelled bands, showing a clear dependence of 3SS incorporation into the M~ 32000 QB binding protein (32 kDa) on the culture conditions.
of cells precultured under high light conditions in the absence of any inhibitor and exposed to 10 -6 M atrazine during pulse labelling by growth in the presence of 3SS sulphate and during chase (Fig. 1). They remain to be identified.
35 Discus~on
When shade character is induced b6Y the growth of Anacystis in the presence of 10- M atrazine, phycobiliproteins are synthesized very soon after the inhibitor has been added. A pulse chase experiment with atrazine present during chase clearly shows that the well known decrease of label in the D1 protein (Goluobinoff et al. 1988, Koenig 1987c) is paralleled by a gradual increase of 35S incorporation into phycobiliproteins (Fig. 1). It is important to note that from the great number of inhibitors of photosynthetic electron transport, only DCMU-type inhibitors could be seen to induce this shade character. The growth of Anacystis in the presence of phenolic inhibitors never resulted in shade adaptation (Koenig 1987a,b), even though these compounds inhibit photosynthetic electron transport and may bind to the D1 protein also in this organism. Phenolic inhibitors have recently been shown to bind to position 249 in the D1 protein in spinach (Oettmeier et al. 1989). However, binding of phenolic inhibitors never protects the D1 protein from proteolytic degradation (Trebst 1988). Concerning pigmentation, the ratio of PS I to PS II as well as photosynthetic capacity (Figs. 1 and 2), the artificially-developed shade type (Koenig 1987a,b) corresponds well to the one induced by growth of Anacystis in deep shade (Kawamura et al. 1979, Oquist 1974). From the room temperature excitation spectra of 684nm fluorescence emission it can be concluded that the extraordinarily high concentration of phycobiliproteins in relation to chl in artificially shade-adapted Anacystis functions as an antenna for chl and not simply as a storage protein inactive in photosynthesis (Fig. 3) (Hatfield et ah 1989). No information is available at present on whether the high PC concentration is due to an increase in the number of phycobilisomes or only in the length of the rods within the phycobilisomes of a constant number. With respect to Vinex, light saturation curves of O2-evolution in Anacystis naturally adapted to high and low light, respectively, are found to correspond well to results published earlier (Samuelsson et ah 1987). Astonishingly, photosynthetic capacity (Vmax) is found to be higher in artificially shade-adapted cells than in cells
grown in shade despite the fact, that the excess PC appears to be active in photosynthesis as concluded from the excitation spectra of 684 nm fluorescence emission (Fig. 3). Moreover, the conclusion can be drawn that the observed shade effect is not merely the consequence of an imbalance of PSI and PS II electron transport (Fujita et al. 1987) or a shift in the ratio of ATP to N A D P H (Melis et al. 1985). Obviously, the degree of shade type appearance due to inhibitor-binding to the D1 protein is widely independent of electron transport, at least through the cytochrome b6/f complex. The latter can be concluded from the observation that thiosulphate is not able to fully prevent or revert the adaptive reorganization induced by DCMU-type inhibitors in strong light (Fig. 4, upper part). Thiosulphate is an electron donor to PSI in Anacystis (Koenig 1990, Peschek 1978, Utkilen 1976) known to be able to shift the PC/chl ratio in Anacystis grown in shade to lower rates, in direction of sun type concerning the antenna pigment system (Koenig 1990). It is worth bearing in mind, however, that growth of Anacystis in low light in the presence of thiosulphate, but in the absence of any inhibitor, induces high light conditions only in the antenna pigment system; a high ratio of PS I to PS II reaction centers- as is characteristic for shade-adapted c e l l s - i s maintained under these conditions (Koenig 1990). For Anacystis R2 it has been shown recently (Brusslan and Haselkorn 1989) that the turnover of D1 can be uncoupled even from electron transport through PS II, a result which stands in contradiction to earlier observations with Spirodela which were originally interpreted as pointing to a strict correlation, at least of the breakdown of D1 with electron transport (Mattoo et al. 1984). Later on an independence of electron t r a n s p o r t - a t least of PS I I - c o u l d be detected also in this organism as demonstrated by D1 degradation in far red light (Gaba et al. 1987). The present investigation shows that syntheses- both of D1 and PC in Anacystis PCC 6301- are strongly correlated with conditions of light intensity and inhibitor binding, PC synthesis being inversely correlated to D1 synthesis. Rate of D1 synthesis is high in strong light (Fig. 5B)
36 and is slowed down both by low light (Fig. 5C) and inhibitor binding in strong light (Fig. 5C). Lower incorporation of radioactivity into the D1 protein in shade and through inhibitor binding in strong light is not primarily due to a shortage in methionine in the cells, as other polypeptides are readily synthesized under these conditions. Light-dependent synthesis and breakdown of the D1 protein in the presence of thiosulphate remain to be investigated. Future experiments will also reveal which of the two forms of D1 (Curtis and Haselkorn 1984, Golden et al. 1986, Morden and Golden 1989) will be preferentially synthesized under the conditions of natural and artificial shade adaptation, respectively. For Anacystis R2, it was recently shown that form I increases with decreasing light intensity, while form II prevails under conditions of strong light (Schaefer and Golden 1989). On the basis of the present results, especially the strict correlation of D1 synthesis with conditions of light intensity and inhibitor binding, and the inverse correlation of PC synthesis with that of D1, the active participation of the dynamic herbicide-binding D1 protein as a meter in light intensity adaptation is postulated. At present it is not clear, which of the dynamic aspects of this protein might constitute the signal initiating the adaptation process. It could arise from different rates of degradation and resynthesis. The basis for the dynamics of this protein stays an open question. The signal transduction chain remains to be established. For this purpose it may be helpful to uncouple D1 and PC syntheses. For Spinacia different components of the photosynthetic apparatus were assigned control functions in electron transport under different conditions (Heber et al. 1988). For Spirodela a special role of the D1 turnover was discussed but so far not proven in context with natural and artificial shade adaptation (Mattoo and Edelman 1985).
Acknowledgements The author wishes to thank the Deutsche Forschungsgemeinschaft for the grant which made this work possible and Prof Dr J. Feierabend for his encouragement and support.
Valuable technical assistance given by M. Jenninger and D. Sch6nborn is also acknowledged.
References Bonner WM and Laskey RA (1974) A film detection method for tritium labelled proteins and nucleic acids in polyacrylamide gels. Eur J Biochem 46:83-88 Brusslan J and Haselkorn R (1989) Resistance to the photosystem II herbicide diuron is dominant to sensitivity in the cyanobacterium Synechococcus sp. PCC 7942. EMBO J 8: 1237-1245 Carr NG, Komarek J and Whitton BA (1973) Notes on isolation and laboratory culture. In: Carr NG and Whitton BA (eds) The Biology of Blue-Green Algae. Botanical monographs, Vol 9, pp 525-530, appendix B. University of California Press, Berkeley and Los Angeles Curtis SE and Haselkorn R (1984) Isolation, sequence and expression of two members of the 32 kD thylakoid membrane protein gene family from the cyanobacterium Anabaena 7120. Plant Mol Biol 3:249-258 Feierabend J (1986) Investigation on the site of synthesis of chloroplastic enzymes of nitrogen metabolism by the use of heat-treated 70S ribosome-deficient rye leaves. Physiol Plant 67:145-150 Fujita Y, Murakami A and Ohki K (1987) Regulation of photosystem composition in the cyanobacterial photosynthetic system: the regulation occurs in response to the redox state of the electron pool located between the two photosystems. Plant Cell Physiol 28:283-292 Gaba V, Marder JB, Greenberg BM, Mattoo AK and Edelman M (1987) Degradation of the 32 kD herbicide binding protein in far red light. Plant Physiol 84:348-352 Golden SS, Brusslan and Haselkorn R (1986) Expression of a family of psbA genes encoding a photosystem II polypeptide in the cyanobacterium Anacystis nidulans R2. EMBO J 5:2789-2798 Goluobinoff P, Brusslan J, Golden SS, Haselkorn R and Edelman M (1988) Characterization of the photosystem II 32 kDa protein in Synechococcus PCC7942. Plant Mol Biol 11:441-447 Hatfield PM, Guikema JA, St. John JB and Gendel SM (1989) Characterization of the adaptation response of Anacystis nidulans to growth in the presence of sublethal doses of herbicide. Current Microbiol 18:369-374 Heber U, Neimanis S and Dietz K-J (1988) Fractional control of photosynthesis by the QB protein, the cytochrome f i b 6 complex and other components of the photosynthetic apparatus. Planta 173:267-274 Kawamura M, Mimuro M and Fujita Y (1979) Quantitative relationship between two reaction centers in the photosynthetic system of blue-green algae. Plant Cell Physiol 20: 697-705 Koenig F (1987a) Involvement of the QB binding protein (M r 32 000) in the adaptation of the photosynthetic apparatus to light intensity. In: Biggins J (ed) Progress in Photosynthesis Research, Vol 4, pp 95-98. Martinus Nijhoff Publishers, Dordrecht
37 Koenig F (1987b) A role of the QB binding protein in the mechanism of cyanobacterial adaptation to light intensity? Z Naturforsch 42c: 727-737 Koenig F (1987c) General occurrence of a pool of the M~ 32000 QB binding polypeptide-D-1 p r o t e i n - i n photosynthetic membranes? Biol Chem Hoppe-Seyler 368: 1260, abstract Koenig F (1990) Growth of Anacystis in the presence of thiosulphate and its consequences for the architecture of the photosynthetic apparatus. Botanica Acta 103:54-61 Machold O, Simpson DJ and Lindberg MOller B (1979) Chlorophyll proteins of thylakoids from wild-type and mutants of barley (Hordeum vulgare). Carlsberg Res Commun 44:235-254 Machold-O, Simpson DJ and Lindberg MOller B (1979) Chlorophyll proteins of thylakoids from wild-type and mutants of barley (Hordeum vulgare). Carlsberg Res Commun 44:235-254 Mattoo AK, Hoffman-Falk H, Marder JB and Edelman M (1984) Regulation of protein metabolism: Coupling of photosynthetic electron transport to in vivo degradation of the rapidly metabolized 32-kilodalton protein of the chloroplast membranes. Proc Natl Acad Sci USA 81: 13801384 Mattoo AK and Edelman M (1985) Photoregulation and metabolism of a thylakoidal herbicide-receptor protein. In: St. John JB, Berlin E and Jackson PC (eds) Frontiers of Membrane Research in Agriculture, pp 24-34. Rowman & Allanheld, Totowa Melis A, Manodori A, Glick RE, Ghirardi ML, McCauley SW and Neale PJ (1985) The mechanism of photosynthetic membrane adaptation to environmental stress conditions: a hypothesis on the role of electron transport capacity and of ATP/NADPH pool in the regulation of the thylakoid
membrane organization and function. Physiol V6g 23: 757767 Morden CW and Golden SS (1989) psbA genes indicate common ancestry of prochlorophytes and chloroplasts. Nature 337:382-385 Myers J, Graham J-R and Wang R T (1978) On spectral control of pigmentation in Anacystis nidulans (Cyanophyceae) J Phycol 14:513-518 Oettmeier W, Masson K and H6hfeld J (1989) (125j) Azidoioxynil labels Wa1249 of the photosystem II D-1 reaction center protein. Z Naturforsch 44c: 444-449 0quist G (1974) Distribution of chlorophyll between the two photoreactions in photosynthesis of the blue-green alga Anacystis nidulans grown at two different light intensities. Physiol Plant 30:38-44 Peschek GA (1978) Reduced sulfur and nitrogen compounds and molecular hydrogen as electron donors for anaerobic CO 2 photoreduction in Anacystis nidulans. Arch Microbiol 119:313-322 Samuelsson G, L6nneborg A, Gustafsson P and Oquist G (1987) The susceptibility of photosynthesis to photoinhibition and the capacity of recovery in high and low light grown cyanobacteria, Anacystis nidulans. Plant Physiol 83: 438-441 Schaefer MR and Golden SS (1989) Light availability influences the ratio of two forms of D1 in cyanobacterial thylakoids. J Biol Chem 264:7412-7417 Trebst A, Depka B, Kraft B and Johanningmeier (1988) The QB site modulates the conformation of the photosystem II reaction center polypeptides. Photosynth Res 18:163-177 Utkilen HC (1976) Thiosulphate as electron donor in the blue-green alga Anacystis nidulans. J Gen Microbiol 95: 177-180
