Chlamydomonas Research Articles

Very high light resistant mutants of Chlamydomonas reinhardtii with impaired PSII function: D1 protein dynamics, functional PSII and PSI centers and intersystem electron transport capacities

Substitution of the Ala251 residue in the D1 reaction center protein of PSII with Leu resulted in a herbicide resistant phenotype with strongly decreased quantum efficiency, maximum rates of photosynthetic O2 evolution and photoautotrophic growth. Pool size of mutant D1 protein was similar to wildtype, even though D1 turnover was 25% faster in high light (HL, 600 µmol photons m-2 s-1), because synthesis was equally accelerated (Lardans et al., 1998, J. Biol. Chem. 272: 11082-11091). We have found that faster D1 turnover and impairment of PSII function persisted in very high light resistant (VHLR) mutants derived from L* when grown in HL and was further enhanced in very high light (VHL, 1500 µmol photons m-2 s-1). The D1 substitution decreased Fv/Fm, slowed forward electron transfer to QB 5 fold and eliminated detectable lateral electron transfer between PSII centers. In general, whole chain electron transport and redox kinetics at PSI were unaffected by the PSII mutation, but delivery of electrons from PSII and the intersystem carriers was less efficient than in wildtype. The A251L substitution diminished the amounts of functional PSII and PSI, determined from O2 flash yield and 800-830 nm absorbance changes, only when grown under low light (LL, 70 µmol photons m-2 s-1). Clearly, maximum PSII function is not a prerequisite for VHL resistance.

Isolation and characterization of regulatory mutants defective in CO2-signal transduction in Chlamydomonas reinhardtii

Isolation and characterization of regulatory mutants defective in CO2-signal transduction in Chlamydomonas reinhardtii

A chloroplast envelope-localized sulfate permease plays a role in the repair of photosystem II from photodamage

To elucidate the PSII repair mechanism from photodamage, we isolated DNA insertional transformants of Chlamydomonas reinhardtii aberrant in the repair process. One mutant, termed rep55.17, required acetate for growth and showed a light-intensity dependent

Regulation of phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase by NADP(H) in a bi-enzyme complex from Chlamydomonas reinhardtii.

Regulation of phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase by NADP(H) in a bi-enzyme complex from Chlamydomonas reinhardtii.

Polarizing microscopy of eyespot of Chlamydomonas: In situ observation of its location, orientation, and multiplication

Polarizing microscopy of eyespot of Chlamydomonas: In situ observation of its location, orientation, and multiplication

Photosystem I Measurements in Mutants B4 and F8 of Chlamydomonas

In the report “Oxygenic photoautotrophic growth without photosystem I” by J. W. Lee et al. ([19 July 1996, p. 364][1]) ([1][2]) and elsewhere ([2][3]), it is said that mutants of the green alga Chlamydomonas that lacked detectable levels of functional Photosystem I (PSI) were capable of photoreduction of atmospheric carbon dioxide, autotrophic growth, and sustained simultaneous photoevolution of H2 and O2. The absence of PSI in the mutant strains B4 and F8 used in our work ([1][2], [2][3]) was confirmed by physical, biochemical, and genetic techniques. Subsequent analyses in our own laboratories, however, as well as those of colleagues to whom we have sent the mutants, indicate that there is variability in the PSI content of the cultures that depends on growth conditions. While some strains retain undetectable amounts of P700, others contain variable (0 to 20%) amounts of wild-type P700. We stand by our original measurements, which showed a lack of detectable P700 in strains F8 and B4 at the time of these studies ([1][2], [2][3]). 1. [↵][4]1. J. W. Lee, 2. C. V. Tevault, 3. T. G. Owens, 4. E. Greenbaum , Science 273, 364 (1996); [OpenUrl][5][Abstract][6] ; see also 1. J. M. Olson , ibid. 275, 996 (1997); [OpenUrl][7] ; T. G. Owens, J. W. Lee, C. V. Tevault, E. Greenbaum, ibid. , p. 996. 2. [↵][8]1. E. Greenbaum, 2. J. W. Lee, 3. C. V. Tevault, 4. S. L. Blankinship, 5. L. J. Mets , Nature 376, 438 (1995). [OpenUrl][9][CrossRef][10][Web of Science][11] [1]: /lookup/doi/10.1126/science.273.5273.364 [2]: #ref-1 [3]: #ref-2 [4]: #xref-ref-1-1 View reference 1 in text [5]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.issn%253D0036-8075%26rft.aulast%253DLee%26rft.auinit1%253DJ.%2BW.%26rft.volume%253D273%26rft.issue%253D5273%26rft.spage%253D364%26rft.epage%253D367%26rft.atitle%253DOxygenic%2BPhotoautotrophic%2BGrowth%2BWithout%2BPhotosystem%2BI%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.273.5273.364%26rft_id%253Dinfo%253Apmid%252F8662525%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [6]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIyNzMvNTI3My8zNjQiO3M6NDoiYXRvbSI7czoyNDoiL3NjaS8yNzcvNTMyMy8xNjUuMy5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30= [7]: {openurl}?query=rft.jtitle%253Dibid.%26rft.volume%253D275%26rft.spage%253D996%26rft.atitle%253DIBID%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [8]: #xref-ref-2-1 View reference 2 in text [9]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D376%26rft.spage%253D438%26rft.atitle%253DNATURE%26rft_id%253Dinfo%253Adoi%252F10.1038%252F376438a0%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [10]: /lookup/external-ref?access_num=10.1038/376438a0&link_type=DOI [11]: /lookup/external-ref?access_num=A1995RM63900056&link_type=ISI

Chlamydomonas reinhardtii as the Photosynthetic Yeast

Chlamydomonas reinhardtii as the Photosynthetic Yeast

Flagellar, cellular and organismal polarity in Volvox carteri

ABSTRACT It has previously been shown that the flagellar apparatus of the mature Volvox carteri somatic cell lacks the 180° rotational symmetry typical of most unicellular green algae. This asymmetry has been postulated to be the result of rotation of each half of the flagellar apparatus. Here it is shown that V. carteri axonemes contain polarity markers that are similar to those found in Chlamydomonas, except that in V. carteri the number one doublets do not face each other as they do in Chlamydomonas but are oriented in parallel and at approximately right angles to the line that connects the flagella. Thus, the rotational orientations of the axonemes are consistent with the postulate that the flagella of V. carteri have rotated in opposite directions, as was predicted earlier from the positions of the basal fibers and microtubular rootlets. Moreover, high-speed cinephotomicrographic analysis shows that the V. carteri flagellar effective strokes are also oriented in approximately the same direction, and in parallel planes. These results suggest that the direction of the effective stroke in both Chlamydomonas and Volvox is fixed, and that rotation of the axoneme is the cause of the differences in flagellar motility observed between Chlamydomonas and Volvox. These differences are probably essential for effective organismal motility. Cellular polarity of V. carteri can be related to that of Chlamy domonas after taking into account the developmental reorientation of flagellar apparatus components. This reorientation also results in the movement of the eyespot from a position nearer one of the flagellar bases to a position approximately equidistant between them. By analogy to Chlamydomonas, the anti side of the V. car teri somatic cell faces the spheroid anterior, the syn side faces the spheroid posterior. The cis side of the cell is to the cell’s left (the right to an outside observer), although it cannot be described solely on the basis of eyespot position as it can in Chlamydomonas, while the trans side is to the cell’s right. It follows that if the direction of the effective flagellar stroke is specified by structural features, then effective organismal motility in V. carteri, will be accomplished only if the cells are held in the proper orientation with respect to one another. The simplest arrangement that will yield both progression and rotation in ovoid or spherical colonies composed of biflagellate isokont cells is one in which the cells are arranged with rotational symmetry about the anteriorposterior axis of the spheroid. Analysis of the polarity of somatic cells from throughout the spheroid shows that it is constructed with just such symmetry. This symmetry probably originates with the very first divisions.

An equilibrium model for electron transfer in photosystem II acceptor complex: an application to Chlamydomonas reinhardtii cells of D1 mutants and those treated with formate

La decomposition des emissions de fluorescence de la chlorophylle a des systemes photosynthetiques apres un flash unique saturant est d'habitude analysee par trois ou quatre exponentielles, qui sont en relation avec les differents modes de reoxidation du [Q⁻A]. Ce modele est appele le modele independant de decomposition. Dans la presente publication nous avons teste ces decompositions des emissions de fluorescence chez 'Chlamydomonas reinhardtii' (type sauvage et cinq mutants) d'une maniere differente que nous appellerons le modele d'equilibre, car nous tenons compte des reactions d'equilibres apparents entre le Q⁻AQB et QAQ⁻B et, en plus, d'un flux d'electrons quittant le complexe QAQB. Ce modele suppose que les constantes de vitesse de liaison et de degagement de la plastoquinone s'aneantissent et n'influencent pas les resultats. Cette analyse nous permet la prediction du temps de vie moyen pour le transport d'electrons en avant (τab) du Q⁻A vers le QB et le Q⁻B, la constante d'equilibre apparente (kab/kba), le temps de vie moyen (τPQ) d'electrons quittant le PS II, essentiellement vers le pool de la plastoquinone (PQ) ainsi que le rapport entre les centres rapides et lents du photosysteme II. Nous presenterons en plus une comparaison de ces resultats avec ceux obtenus par le modele independant (Govindjee et al. 1992). Du fait que dans la presente publication les trois parametres independants (τab, τba et τPQ) sont obtenus a partir d'une seule mesure de decomposition des emissions de fluorescence de la chl a, nous presentons nos resultats pour qu'ils puissent etre verifies par d'autres mesures et methodes. Si l'on suppose que le parametre de transfert d'energie (p) entre les systemes est de 0.5, les mutants Dl Ar-207 (F255Y), Br-202 (L175F)et Dr-18 (V219I) montrent un transfert d'energie en avant (QAQB⁽⁻⁾ → Q⁻AQ⁻B⁽⁼⁾ pratiquement inchange (temps de vie moyen τab = 600 - 950 μs) et, en plus, un rapport des centres reactionnels du PS II rapides et lents pratiquement egale de 0.1 a 0.2 en comparaison avec le type sauvage. Par contre, chez les mutants Ar-204 (G256D) et DCMU-4 (S264A), on observe un temps de vie moyen du transport d'electrons en avant augmente plusieurs fois (τab ≈ 2'000 μs), des constantes d'equilibre apparentes du Q⁻AQB = QAQ⁻B modifiees (la plus faible chez S264A et G256D, intermediaire chez V219I et la plus elevee chez F255Y), et des rapports exceptionnellement eleves (0.6 - 0.8) de centres reactionnels rapides et lents du PS II. L'adjonction de formiate a 100 ou 200 mM provoque une augmentation du temps de vie du transport d'electrons en avant (Q⁻A vers QB) chez le type sauvage de 640 a 990 μs ainsi qu'aux cinq mutants testes. Le plus grand changement est observe chez S264A (de 1.4 a ~30 ms), le plus petit chez L275F (de 950 μs a 1.4 ms). Le traitement au formiate (appauvrissement en bicarbonate) conduit a une augmentation du temps de vie pour le transport d'electrons vers le pool de la PQ de 1.5 a 5 fois selon le mutant, une diminution des constantes d'equilibre apparentes de la reaction Q⁻AQB = QAQ⁻B d'un facteur de 2 a 6 ainsi qu'a une augmentation remarquable en centres lents. Tous ces effets sont reversibles par le bicarbonate.

Isozymal Relationships between Zoospores & Vegetative Cells of Chlamydomonas Euryale

قورنت الأبواغ الحيوانية وخلالا التكاثر الخضري للكلاميدومونس أييوريال من خلال تفريدها كهربائيا على الجل من حيث بروتيناتها الذوابة الكلية ونظم التشابه الإنزيمي لإنزيمات الفاستيراز ، والفوسفاتاز القلوي ، مالات وهيدروجيناز ، جلوتامات ديهيدروجيناز ، ليوسين أمينوببتيداز ، بيرأ كسيداز ، تيروسيناز ، جلوتامات أكسالوأسيتات ترانس أميناز ، أميلاز ، لبيان مدى وجود اختلاف ، وعولجت النتائج طبقا لأقرب تطابق حسابي . دلت النتائج على وجود تطابق 100% لنوعي الخلايا في التشابه الإنزيمي للأميلاز فقط ، بينما بالنسبة للبروتينات الذوابة الكلية وأنزيمات الألفاستيراز، والمالات وديهيدروجيناز ، والجلوتامات وديهيدروجيناز ، والتيروسيناز والليوسين أمينوبيتيداز ، والبير كسيداز فكانت النتيجة بين 50-80% . بينما كانت النتيجة صفرا % بالنسبة للفوسفاتاز القلوي والجلوتامات أكسالو أسيتات ترانس أميناز وكان مدى التشابه المبني على البروتينات الكلية الذوابة وتسعة أنظمة للتشابه الإنزيمي 50%. وقد نوقشت الأسباب للنتائج المحتملة غير المتوقعة مع إبداء التوصيات .

CONTROL OF PHOTOSYNTHETIC REDUCTANT: THE ROLE OF LIGHT AND TEMPERATURE ON SUSTAINED HYDROGEN PHOTOEVOLUTION BY Chlamydomonas sp. IN AN ANOXIC, CARBON DIOXIDE‐CONTAINING ATMOSPHERE*

Abstract–Sustained hydrogen photoevolution from Chlamy domonas reinhardtii and C. Moewusii was measured under an anoxic, CO2‐containing atmosphere. It has been discovered that light intensity and temperature influence the partitioning of reductant between the hydrogen photoevolution pathway and the Calvin cycle. Under low incident light intensity (1‐3 W m‐2) or low temperature (approx. 0°C), the flow of photosynthetic reductant to the Calvin cycle was reduced, and reductant was partitioned to the hydrogen pathway as evidenced by sustained H2 photoevolution. Under saturating light (25 W m‐2) and moderate temperature (20±5°C), the Calvin cycle became the absolute sink for reductant with the exception of a burst of H2 occurring at light on. This burst of H2 corresponded to the expression of about 450 electrons for each photosynthetic electron transport chain. These results suggest that the hydrogen pathway and the Calvin cycle compete for reductant under anoxic conditions and that partioning between the two pathways can, to a certain extent, be controlled by the appropriate choice of experimental conditions.

A consecutive cryo lm/cryo sem technique and its use in the study of freezing injury in chlamydomonas reinhardtii CW15 +

A consecutive cryo lm/cryo sem technique and its use in the study of freezing injury in chlamydomonas reinhardtii CW15 +

SINGLE PHOTONS ARE SUFFICIENT TO TRIGGER MOVEMENT RESPONSES IN Chlamydomonas reinhardtii

Abstract— The unicellular green alga Chlamy domonas reinhardtii shows two distinct movement responses upon changes in green light irradiance: These are direction changes and stop responses. The dependence of both responses on the intensity of applied flashes was measured and analysed with the help of Poisson statistics. In dark‐adapted cells both responses were ‘single‐photon’ events. Preillumination of cells or background irradiation decreased the sensitivity for the stop response, now requiring two or more photons to trigger it. In the blind, carotenoid‐negative mutant FN 68 the light‐sensitivity for a stop‐response was reconstituted by addition of all trans retinal. This result indicated that not only the receptor for phototaxis but also that for the stop response is a retinal protein. In addition, stimulus‐response curves from the literature were analysed by Poisson statistics.

The Transport and Metabolism of Urea inChara australis

The Transport and Metabolism of Urea in<i>Chara australis</i>

A mutant of Chlamydomonas reinhardtii altered in the transfort of ammonium and methylammonium

A mutant of Chlamydomonas reinhardtii altered in the transfort of ammonium and methylammonium

Hydrogen production by a mixed culture of a green alga, Chlamydomonas reinhardtii and a photosynthetic bacterium, Rhodospirillum rubrum.

An about, 4-fold H2 evolution rate and a 5-fold H2 molar yield (mol H2/mol glucose) were obtained with a mixed culture of Chlamy domonas reinhardtii and Rhodosprillum rubrum, compared with in the case of an algal culture of C. reinhardtii alone. This increasing effect was due to the consumption of formate formed by C. reinhardtii; R. rubrum evolved hydrogen from formate via the formate hydrogen-lyase system under dark anaerobic (N2) conditions. Maximum H2 evolution by the mixed culture was observed with a ratio of 8 :2 (alga: bacterium) at a total cell concentration of above 0.6 mg dry wt/ml. Sustained H2 production with an alternating light/dark cycle in a membrane reactor, in which this alga and bacterium were cultured in separate compartments, was performed for one week.

29] Purification and characterization of Chlamydomonas flagellar dyneins

29] Purification and characterization of Chlamydomonas flagellar dyneins

Photosynthesis Involvement in the Mechanism of Action of Diphenyl Ether Herbicides

Photosynthesis is not required for the toxicity of diphenyl ether herbicides, nor are chloroplast thylakoids the primary site of diphenyl ether herbicide activity. Isolated spinach (Spinacia oleracea L.) chloroplast fragments produced malonyl dialdehyde, indicating lipid peroxidation, when paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were added to the medium, but no malonyl dialdehyde was produced when chloroplast fragments were treated with the methyl ester of acifluorfen (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid), oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], or MC15608 (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-chlorobenzoate). In most cases the toxicity of acifluorfen-methyl, oxyfluorfen, or MC15608 to the unicellular green alga Chlamydomonas eugametos (Moewus) did not decrease after simultaneous treatment with diuron. However, diuron significantly reduced cell death after paraquat treatment at all but the highest paraquat concentration tested (0.1 millimolar). These data indicate electron transport of photosynthesis is not serving the same function for diphenyl ether herbicides as for paraquat. Additional evidence for differential action of paraquat was obtained from the superoxide scavenger copper penicillamine (copper complex of 2-amino-3-mercapto-3-methylbutanoic acid). Copper penicillamine eliminated paraquat toxicity in cucumber (Cucumis sativus L.) cotyledons but did not reduce diphenyl ether herbicide toxicity.

LIGHT-INDUCED TURNOVER OF THYLAKOID POLYPEPTIDES IN CHLAMYDOMONAS REINHARDI

The turnover rate of the 32–34 kD and the light-harvesting complex (LHC) polypeptides of the photosynthetic membranes has been measured by radioactive pulse labeling and chase experiments in Chlamydomonas reinhardi cell cultures during logarithmic growth in the light. Loss of radioactivity from the various polypeptides was similar when 35 SO 4 or 14 C-acetate were used as radioactive tracers. However, the rate of 35 SO 4 incorporation into the 32–34 kD polypeptides, as compared to that of the LHC polypeptides, was higher than that of 14 C-acetate. The half-life of the LHC polypeptides was similar to the generation time and it can therefore be concluded that these polypeptides do not turn over significantly in dividing cells. The half-life of the 32–34 kD polypeptides was 3.5 h, or about one-third to one-quarter of the generation time. The radioactive labeling of the 32–34 kD polypeptides was considerably faster than expected from the rate of decay, and a plateau was reached after about two hours, while labeling of the LHC polypeptides continued. No loss of radioactivity from the 32–34 kD polypeptides could be detected during the first 3–4 h of chase immediately after pulse labeling. These results might suggest that the newly synthesized, membrane-bound 32–34 kD polypeptides appear first in the form of a small “transient pool” and are not immediately integrated in active photosystem II units where the light-induced turnover occurs. Turnover of the 32–34 kD polypeptides is markedly slower in dark-growing cells and is partially inhibited when cytoplasmic protein synthesis is inhibited. Inhibition of chloroplast protein synthesis during cell growth does not significantly affect the turnover of the 32–34 kD polypeptides.

GLOEOCOCCUS TETIMSPORUS SP. NOV. (TETRASPORALES, PALM ELL ACEAE), FROM COLORADO MOUNTAIN LAKES1

ABSTRACTA new species, Gloeococcus tetrasporus sp. nov., collected from mountain lakes, is described from unialgal culture. Vegetative cells are ellipsoid and Chlamydomo nas–like, occur in tetrad complexes within the general colonial matrix, and exhibit slow, limited motility within the confines of the individual gelatinous matrices. The colonial matrix is amorphous and structureless, without a definite bounding layer. Colonies may reach several centimeters in size. Vegetative cells have a parietal cup–shaped chloroplast with a central–basal pyrenoid and a small, linear stigma, two contractile vacuoles, and two short flagella. Cell division is by eleutheroschisis in nonflagellate cells. After two divisions, four daughter cells arc formed within the expanded parent wall that will become incorporated into the colonial matrix. Zoospores are formed either from transformed vegetative cells or after cytokinesis. Zoospore flagella are two to three times the length of vegetative cell flagella. Rapid flagellar movement ruptures the sheath and liberates the zoospores. When zoospores settle, they secrete new sheaths, and divide twice to initiate new colonies. Sexual reproduction and formation of resistant spores were not observed.