Photoinhibition and Recovery of Photosynthesis in psbA Gene-Inactivated Strains of Cyanobacterium Anacystis nidulans

The susceptibility of photosynthesis to photoinhibition and the rate of its recovery were studied in cyanobacterium Anacystis nidulans strain R2 and its two psbA gene-inactivated mutants R2S2C3 and R2K1. Changes in the fluorescence kinetics at 77K as well as the rate of O₂ evolution were measured when cells were exposed to high photosynthetic photon flux densities in the range of 0 to 2,000 micromoles per square meter per second. The R2S2C3 mutant has an active psbAI gene highly expressed under low and normal light intensities, whereas R2K1 possesses psbAII and psbAIII genes highly expressed under very high light intensities. The level of overall susceptibility of photosynthesis to photoinhibition was more pronounced in the wild type and the mutant R2S2C3 than in the mutant R2K1, especially at higher light intensities. In constrast, all three strains showed an increased but similar sensitivity to photoinhibition after addition of the translational inhibitor streptomycin; mutant R2K1 being slightly less sensitive at lower light intensities. The result is interpreted as demonstrating similar intrinsic susceptibility to photoinhibition of the two different forms of the D1 protein, form I and form II, encoded by the psbAI and psbAII/psbAIII genes, respectively. The increased resistance to photoinhibition of the R2K1 mutant was ascribed to an approximately 3 times higher rate of recovery than the wild type and the mutant R2S2C3. On the basis of our experiments we conclude that the susceptibilities to photoinhibition of the Anacystis nidulans psbA genes mutants studied are regulated mainly by modifying the rate of repair, i.e. the rate of turnover of the D1 protein.     

Distribution of Chlorophyll between the Two Photoreactions in Photosynthesis of the Blue-Green Alga Anacystis nidulans Grown at Two Different Light Intensities

Anacystis nidulans was grown in white light of two different intensities, 7 and 50 W ·m^?2. The in vivo pigmentations of the two cultures were compared. The ratio phycocyanin/chlorophyll a was 0.96 for cells grown at 7 W · m^?2 and 0.37 for cells grown at 50 W · m^?2. Phycocyanin-free photosynthetic lamellae (PSI-particles) were prepared, using French press treatment and fractionated centrifugation. Algae grown in the irradiance of 50 W · m^?2 showed a chlorophyll a/P700 ratio of 260, while algae grown at 7 W · m^?2 had a value of 140. Corresponding PSI-particles showed values of 122 and 109 respectively. Light-induced absorption difference spectra measured between 400–450nm indicated different ratios between cytochrome f and P700 in the two algal cultures. Enhancement studies of photosynthetic oxygen evolution were carried out. When a background beam of 691 nm was superimposed upon a signal beam of 625 nm, good enhancement was observed for both cultures. With the wavelengths 675 and 691 nm together a pronounced enhancement could be detected only in algae grown at the higher light level. Absorption spectra recorded on whole cells at 77°K revealed a small shift of the main red chlorophyll a absorption peak caused by light intensity. It is proposed that the reduction of the phycocyanin/chlorophyll a ratio in high light-grown cells is accompanied by an increased energy distribution by chlorophyll a into PSII.     

Reversible and Irreversible Inactivation of Photosynthesis in Relation to the Lipid Phases of Membranes in the Blue-Green Algae (Cyanobacteria) Anacystis nidulans and Anabaena variabilis

The Arrhenius plots of photosynthetic oxygen evolution in theblue-green algae Anacystis nidulans and Anabaena variabiliswere composed of two straight lines with break points whichwere very close to temperatures for the onset of phase separationof the thylakoid membranes. Irreversible inactivation of photosynthesisbegan to appear at the same temperature as the onset of phaseseparation of the cytoplasmic membranes in A. nidulans. Electrolytesbegan to leak from the cytoplasm into the outer medium, indicatingthat the permeability of the cytoplasmic membranes increasedwhen they entered the phase separation state. In A. variabilis,in which the cytoplasmic membranes had remained in the liquidcrystalline state above 0?C, no irreversible damage to photosynthesisnor leakage of electrolytes was observed between 0 and 20?C.These findings suggest that photosynthesis of the blue-greenalgae is reversibly suppressed when only the thylakoid membranesare in the phase separation state, and irreversibly inactivatedwhen the cytoplasmic membranes are in the phase separation state. (Received April 9, 1984; Accepted June 19, 1984)     

Transfer of the Excitation Energy in Anacystis nidulans Grown to Obtain Different Pigment Ratios

The blue-green alga, Anacystis nidulans, was grown in lights of different colors and intensities, and its absorption and fluorescence properties were studied. Strong orange light, absorbed mainly by phycocyanin, causes reduction in the ratio of phycocyanin to chlorophyll a; strong red light, absorbed mainly by chlorophyll, causes an increase in this ratio. This confirms the earlier findings of Brody and Emerson (12) on Porphyridum, and of Jones and Myers (8) on Anacystis. Anacystis cultures grown in light of low intensity show, upon excitation of phycocyanin, emission peaks at 600 mmu and 680 mmu, due to the fluorescence of phycocyanin and chlorophyll a, respectively. Changes in the efficiency of energy transfer from phycocyanin to chlorophyll a are revealed by changes in the ratios of these two bands. A decrease in efficiency of energy transfer from phycocyanin to chlorophyll a seems to occur whenever the ratio of chlorophyll a to phycocyanin deviates from the normal. Algae grown in light of high intensity show, upon excitation of phycocyanin, only a fluorescence band at 660 mmu and no band at 680 mmu. This suggests reduced efficiency of energy transfer from phycocyanin to the strongly fluorescent form of chlorophyll a (chlorophyll a(2)) and perhaps increased transfer to the weakly fluorescent form of chlorophyll a (chlorophyll a(1)).     

Photoinhibition of Photosynthesis and its Recovery in Red Algae

In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phycodrys rubens, Phyllophora truncata, Polyneura hilliae) photoinhibition of photosynthesis has been investigated by means of both fluorescence and oxygen measurements. Measurements of absolute oxygen production show that photoinhibition causes a decline in the initial slope and in the rate of bending of the fluence rate-response curve (i.e. the photosynthetic efficiency at non-saturating fluence rates), as well as a decline in the photosynthetic capacity (Pm) at saturating fluence rates. Fluorescence data (Fv/Fm) were consistent with the results of oxygen measurements. Under excessive light photoinhibition protects photosynthesis against photo-damage in red algae. However, an increase in the initial fluorescence (Fo) after photoinhibitory treatment indicates that it could not prevent photodamage entirely. Action spectra of photoinhibition demonstrate that the main photoinhibition site in Polyneura hiliae is PS II, because far red light absorbed by PS I was ineffective. The strong increase of Fo in the blue wavelength range and the slight and partial recovery in weak blue light indicate that blue light especially causes photodamage. Recovery of photosynthesis requires dim white light conditions. Experiments with monochromatic light also show a wavelength dependence of recovery. Moreover, the recovery of photosynthesis after a photoinhibitory treatment is strongly temperature dependent, indicating participation of enzymatic processes. The comparison of fluorescence and oxygen measurement of the recovery shows different results in some species. The rate of oxygen production in red control light increased immediately after photoinhibited algae were exposed to weak light conditions. Surprisingly, the ratio of variable to maximum fluorescence (Fv/Fm) of Phyllophora truncata and the maximum fluorescence (Fm) of Polyneura hilliae show first a delay of the recovery under weak light conditions. Thus, in recovery experiments fluorescence and oxygen data are not quite consistent.     

Gene Loci in Maize Influencing Susceptibility to Chilling Dependent Photoinhibition of Photosynthesis

Variation in tolerance in chilling-dependent photoinhibition has been associated with a wide range of traits in comparative physiological studies. A sweet corn (Zea mays L.) population of 214 F_2:3 families previously mapped to near-saturation with 93 RFLP DNA markers were subjected to low temperature and high-light events prior to measurement of the maximum dark-adapted quantum efficiency of PS II (F_v/F_m), to identify loci associated with variation in chilling-dependent photoinhibition. In the first assay with ten families varying in seedling growth and germination, significant differences were observed among families in their response to and recovery from exposure to high light at low temperature. All the 214 F_2:3 families from this population were then evaluated for tolerance of chilling-dependent photoinhibition in a controlled environment and then in three replicated trials in the field, each following naturally occurring chilling events during spring. The measured effects on F_v/F_m were analyzed with software that mapped segregating loci that regulate trait expression and linked to genetic markers (PLABQTL). QTL 3.096 (i.e. 96 cM on chromosome three) was consistently identified in both controlled environment and in the mean of the three field trails. Another QTL at 8.025, described the greatest percentage of total phenotypic variance (ca. 10%) for the mean reduction in F_v/F_m of all three periods of measurement in the field. A third QTL (4.136) showed a highly significant association in the third field trial. These three QTLs were closely associated with genes that have been mechanistically related to photoinhibition tolerance and repair. The results suggest that the ratio of F_v/F_m is an approach that may be used in establishing marker-assisted breeding for improved tolerance to chilling of maize in the light and in turn better early-season growth in cool temperate climates.     

Thermal Properties of Membrane Lipids from two Cyanobacteria, Anacystis nidulans and Synechococcus sp.

The composition and positional distribution of fatty acids inmonogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidylglyceroland sulphoquinovosyldiacylglycerol from two cyanobacteria, Anacystisnidulans and Synechococcus sp. grown at 25°C have been determinedand compared with measurements of the phase separation temperaturesof the lipids. Only monogalactosyldiacylglycerol in Anacystisand sulphoquinovosyldiacylglycerol in Synechococcus showed phaseseparation temperatures above 0°C. The phase transitiontemperature of a sample of sulphoquinovosyldiacylglycerol containingover 90% of the dihexadecanoyl molecular species has been determinedto be 43°C for the Na⁺ salt and 38°C for the Mg⁺⁺ salt. ^*Deceased. September 14, 1986. (Received June 25, 1986; Accepted August 25, 1986)     

Membrane Development in the Cyanobacterium, Anacystis nidulans, during Recovery from Iron Starvation

Deprivation of iron from the growth medium results in physiological as well as structural changes in the unicellular cyanobacterium Anacystis nidulans R2. Important among these changes are alterations in the composition and function of the photosynthetic membranes. Room-temperature absorption spectra of iron-starved cyanobacterial cells show a chlorophyll absorption peak at 672 nanometers, 7 nanometers blue-shifted from its normal position at 679 nanometers. Iron-starved cells have decreased amounts of chlorophyll and phycobilins. Their fluorescence spectra (77K) have one prominent chlorophyll emission peak at 684 nanometers as compared to three peaks at 687, 696, and 717 nanometers from normal cells. Chlorophyll-protein analysis of iron-deprived cells indicated the absence of high molecular weight bands. Addition of iron to iron-starved cells induced a restoration process in which new components were initially synthesized and integrated into preexisting membranes; at later times, new membranes were assembled and cell division commenced. Synthesis of chlorophyll and phycocyanins started almost immediately after the addition of iron. The absorption peak slowly returned to its normal wavelength within 24 to 28 hours. The fluorescence emission spectrum at 77K changed over a period of 14 to 24 hours during which the 696- and 717-nanometer peaks grew to their normal levels, and the 684 nanometer peak moved to 687 nanometers and its relative intensity decreased to its normal level. Analysis of chlorophyll-protein complexes on polyacrylamide gels showed that high molecular weight chlorophyll-protein bands were formed during this time, and that low molecular weight bands (related to photosystem II) disappeared. The origin of the fluorescence emission at 687 and 696 nanometers is discussed in relation to the specific chlorophyll-protein complexes formed during iron reconstitution.     

Iron Deficiency in the Blue-Green Alga Anacystis nidulans: Changes in Pigmentation and Photosynthesis

Phycocyanin-free photosynthetic lamellae (PSI-particles) were prepared from Anacystis nidulans, grown in complete and iron-deficient media. French press treatment and fractionated centrifugation were used. Absorption studies of the particles revealed an iron deficiency-induced shift of the main red chlorophyll a absorption peak from 679 to 673 nm as reported before for whole cells. The shift may reflect a changed distribution between different chlorophyll a forms. Action spectra for photo-oxidation of mammalian cytochrome c with photosynthetic lamellae revealed an iron deficiency-induced shift, corresponding to that found in the absorption spectra. As photo-oxidation of cytochrome c is mediated by PSI, it is believed that chlorophyll a also after the shift towards shorter wavelengths, is active in PSI. A decreased photosynthetic capacity of PSI, due to iron deficiency, was shown by time course studies of photosynthetic oxygen evolution, by photo-oxidation studies of P700 and mammalian cytochrome c, by photo-reduction studies of NADP and by combined studies of light-induced and chemical oxidation of P700. The ration chlorophyll a/700 was also determined for whole cells, lyophilized cells and PSI-particles. Iron deficiency caused an increased ratio in all studied fractions. The results of this work imply that energy is transferred with less efficiency within the photosynthetic units of PSI in iron-deficient A. nidulans than in iron-supplied algae.     

Responses of Two CAM Species to Different Irradiances during Growth and Susceptibility to Photoinhibition by High Light

Two CAM species, Kalanchoë daigremontiana Hamet et Perrier and Hoya carnosa (L.) R. Br., were grown under a range of five photon flux area densitites (PFD) and then characterized. Significant acclimation to shade was indicated by progressive decreases in leaf thickness, rates of respiratory O₂ uptake, light compensation point, maximum rates of photosynthetic O₂ evolution, nocturnal acid accumulation, and δ¹³C values, and increases in chlorophyll concentration and absolute levels of room temperature (25°C) and 77K fluorescence. Quantum yields (as measured by O₂ exchange) and the ratio of variable 77K fluorescence over the maximum yield (F_v/F_m) were relatively constant across the treatments. The only significant deviation from the above characteristics was in H. carnosa grown under full glasshouse PFD, where it apparently experienced photoinhibition. Following a photoinhibitory treatment, K. daigremontiana exhibited increases in the light compensation point and progressively greater reductions in the quantum yield, maximum photosynthetic rate, F_v/F_m, and the variable component of room temperature fluorescence with increasing shade during growth. Thus although Crassulacean acid metabolism plants can adjust to shaded conditions, they are susceptible to photoinhibition when exposed to higher PFD than that experienced during growth.     

光强在低温弱光胁迫后番茄叶片光合作用恢复中的作用

为了研究光强在低温弱光胁迫后番茄叶片光合作用恢复中的作用,以番茄品种浙粉202为材料,研究了低温弱光后恢复期全光照与遮荫对光合作用和叶绿素荧光参数的影响。结果表明：低温弱光（8℃/12℃,PFD 80 μmol·m^-2·s^-1）导致番茄叶片P_n、Φ_PSⅡ、qP和F_v′/F_m′的下降,但诱导了NPQ的上升,未引起F_v/F_m的变化;全光照（100%光照）下恢复1 使得植株叶片P_n、F_v/F_m、Φ_PSⅡ、qP、NPQ和F_v′/F_m′均大幅下降,随后光合和荧光参数可缓慢恢复至对照水平;遮荫（40%光照）恢复植株F_v/F_m、Φ_PSⅡ和F_v′/F_m′仅在第一天稍有下降,而P_n和qP还略有上升,NPQ虽有所降低但仍显著高于对照水平,随后光合和荧光参数均可迅速恢复到对照水平。说明低温弱光虽抑制了光合作用的进行,但并未引起光抑制的发生;全光照恢复加剧了叶片光抑制的发生,而遮荫恢复可通过叶片PSⅡ光化学活性的快速恢复和天线色素热耗散能力的增强以保护光合机构免受伤害,有利于光合作用的迅速恢复。     

Light dark modulation of glycogen phosphorylase activity in the blue-green alga, Anacystis nidulans

Abstract The photoautotrophic procaryote, Anacystis nidulans, accumulates glycogen as a carbon reserve during illumination and nitrogen limitation. Glycogen phosphorylase participates in the mobilization of the polysaccharide in a dark period and was found to be a point of regulatory control of glycogen degradation. Specific enzyme activity of non-dividing cells increased twofold upon transfer from light to dark and decreased again upon re-illumination. This dark stimulation of enzyme activity was not inhibited by either rifampicin or chloramphenicol, whereas a light-induced decrease was abolished by DCMU, an inhibitor of photosynthetic electron transport. Deactivation of glycogen phosphorylase could be simulated by dithiothreitol in vitro. A spheroplast lysate either with or without chromatophores and a partially purified glycogen-enzyme complex responded to dithiothreitol. These results are compatible with an interpretation in terms of redox changes taking place with the enzyme in an activation/deactivation cycle. The inactive form maintained in a reduced state by photosynthetic electron transport is thought to be converted into an active form in the dark.     

Photosynthetic Light Reactions in Chemically Fixed Anacystis nidulans, Chlorella pyrenoidosa, and Porphyridium cruentum

The photochemical activities of various species of unicellular algae (Anacystis nidulans, Chlorella pyrenoidosa, and Porphyridium cruentum) were studied following chemical fixation. Fixation with formaldehyde and glutaraldehyde yielded cells which retained their ability to perform photosystem I and photosystem II reactions. The photochemical efficiencies of some fixed algae are as great as those of unfixed spinach chloroplasts. Fixed algae containing accessory pigments appear to be useful models for further studies of the light reactions of photosynthesis.     

Changes in Pigment Composition and Photosynthesis Induced by Iron-Deficiency in the Blue-Green Alga Anacystis nidulans

Absorption spectra and photosynthetic action spectra have been determined for living Anacystis grown in complete and iron-deficient inorganic media. The absorption studies have shown a spectral shift from 679 nm to 673 nm in the chlorophyll a absorption peak when the algae had to grow without iron. The shift is believed to reflect a changed ratio between at least two chlorophyll a forms denoted Ca670 and Ca680 in this work. Action spectra determinations have revealed a similar shift from 677 nm to 672 nm in the photosynthetic activity peak of chlorophyll a when Anacystis was transferred to a medium without iron. It is proposed that both Ca670 and Ca680 participate in light absorption for photo-system I.     

Ultraviolet Light Inactivation and Photoreactivation of AS-1 Cyanophage in Anacystis nidulans

Black light effected photorecovery of AS-1 cyanophage and wild-type cells. However, only partial photoreactivation of AS-1 was observed in a partially photoreactivable mutant of Anacystis nidulans.     

The Potential for Photoinhibition of Pinus sylvestris L. Seedlings Exposed to High Light and Low Soil Temperature

The effect of high light and root chilling on gas exchange,chlorophyll fluorescence, and bulk shoot water potential (_shoot)was examined for Pinus sylvestris seedlings. Transferring plantsfrom low light (200 µmol m^–2s^–1, PAR) anda soil temperature of 15 °C to high light (850 µmolm^–2 s^–1) and 1 °C caused >90% decrease innet photosynthesis and leaf conductance measured at 350 mm³dm^-3 CO₂, and a decrease in the ratio of variable to maximumfluorescence (F_v/F_m) from 0.83 to 0.63. The decrease in Fv/Fmwas, however, only marginally greater than when seedlings weretransferred from low to high light but kept at a soil temperatureof 15 °C. Thus, photoinhibition was a minor component ofthe substantial decrease observed for net photosynthesis at1 °C soil temperature. The decrease in net photosynthesisand _shoot at 1 °C was associated with an increase in calculatedintracellular CO₂ concentration, suggesting that non-stomatalfactors related to water stress were involved in inhibitingcarbon assimilation. Measurements at saturating external CO₂concentration, however, indicate that stomatal closure was thedominant factor limiting net photosynthesis at low soil temperature.This interpretation was confirmed with additional experimentsusing Pinus taeda and Picea engelmannii seedlings. Decreasesin gas-exchange variables at 5 °C soil temperature werenot associated with changes in _shoot Thus, hormonal factors,localized decreases in _needles or changes in xylem flux maymediate the response to moderate root chilling.     

The biosynthesis of phycocyanobilin in Anacystis nidulans

Aminolevulinic acid, the common precursor of linear and cyclic tetrapyrroles, can arise either by condensation of succinate and glycine or from the ent