Chlorophyll fluorescence induction in anaerobic Scenedesmus obliquus

Schreiber, Ulrich; Vidaver, William

doi:10.1016/0005-2728(74)90100-5

Cited by 63 publications

(56 citation statements)

References 21 publications

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“…Oxygen evolution and chlorophyll fluorescence measurements indicated an inhibition of PSII after anaerobic incubation of algae deprived of hydrogenase. In this respect, the data obtained for periods, when hydrogenase was not expressed (>20 min) [53]. Altogether, these results thus support the idea that H 2 photoproduction by hydrogenase is the process which enables algae to oxidize and thereby activate their photosynthetic electron transport chain after anaerobic incubation.…”

Section: Discussionsupporting

confidence: 75%

“…The effect of anaerobic pre-incubation in the dark on photosynthesis reactions had been already studied forty years ago in microalgal species naturally provided with or devoid of an hydrogenase [53][54][55][56]. Oxygen evolution and chlorophyll fluorescence measurements indicated an inhibition of PSII after anaerobic incubation of algae deprived of hydrogenase.…”

Section: Discussionmentioning

confidence: 99%

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A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield

Godaux

Emonds-Alt

Berne

et al. 2013

International Journal of Hydrogen Energy

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In Chlamydomonas reinhardtii, prolonged anaerobiosis leads to the expression of enzymes belonging to various fermentative pathways. Among them, oxygen-sensitive hydrogenases (HydA1/2) catalyze the synthesis of molecular hydrogen from protons and reduced ferredoxin in the stroma. In this work, by analyzing wild type and mutants affected in H2 production, we show that maximal PSII photosynthetic electron transfer during the first seconds of illumination after a prolonged darkanaerobiosis period is linearly related to hydrogenase capacity. Based on the specific chlorophyll fluorescence induction kinetics typical of hydrogenase-deficient mutants, we set up an in vivo fluorescence imaging screening protocol allowing to isolate mutants impaired in hydrogenase expression or activity, as well as mutants altered in related metabolic pathways required for energy production in anaerobiosis. Compared to previously described screens for mutants impaired in H2 production, our screening method is remarkably fast, sensitive and non invasive. Out of 3000 clones from a small-sized insertional mutant library, five mutants were isolated and the most affected one was analyzed and shown to be defective for the hydrogenase HydG assembly factor.Pierre Cardol, PhD, FNRS research associate Génétique des microorganismes -Institut de Botanique B22 Boulevard du Rectorat, 27 -Université de Liège-B-4000 Liège, Belgique Tel/Fax +32 4 3663840 e-mail: Pierre.cardol@ulg.ac.be Liège, 07 november 2012 Dear Editor, Please find here enclosed a revised version of our manuscript entitled 'A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield.' that had received a positive feedback from the first round of reviewing.We are grateful to you for having encouraged us to resubmit quickly a modified manuscript. We have addressed all the comments raised by the reviewers on our first submission. A point to point answer has been submitted along with the MS. Main changes are : (i) the addition of a new experimental set of data (hydrogen evolution measurements in all mutant strain and some control experiments) and (ii) all data that were previously not shown are now included in the manuscript in main tables or as supplemental figures.We hope that we have now improved our manuscript so you'll find it suitable for publication in International Journal of Hydrogen Energy. Sincerely yours,On behalf all coauthors, Pierre Cardol *Cover LetterReviewer #1:Major points:I. Please measure and show, respectively, the hydrogenase activity of the wild types or control strains (like respiratory mutants, pfl1-mutant) in your setup. Available literature shows that absolute values can differ significantly depending on exact experimental setup and strain. As the correlation between PSII quantum yield and hydrogenase activity is the major point of your study, this data is essential, and citing hydrogenase activities reported in literature is not sufficient.Answer : the...

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield

Godaux

Emonds-Alt

Berne

et al. 2013

International Journal of Hydrogen Energy

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“…For example, the initial OI rise is thought to represent the reduction of Q by PSII (2,8). The dip D has been proposed to be related to photooxidation by PSI of Q that was initially reduced by PSII (20,22). The DPS transient is related to electron flow on the reducing side of PSI, because it is eliminated by addition of methyl viologen which accepts electrons from PSI (1 1, 21).…”

Section: Methodsmentioning

confidence: 99%

Effects of Salinity on Primary Processes of Photosynthesis in the Red Alga Porphyra perforata

Satoh¹,

Smith²,

Fork³

1983

Plant Physiol.

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The effects of salinity on the primary processes of photosynthesis were studied in the red alga Porphyra perforate. The results show that there are at least three sites in the photosynthetic apparatus of this alga that were affected by increased salinity. The first site, photoactivation and dark-inactivation of electron flow on the reducing side of photosystem I, was completely inhibited at high salinity. The second site, electron flow on the oxidizing side (water side) of photosystem II, was inhibited as was the re-oxidation of Q in the presence of 343,4-dichlorophenyl)-1,1-dimethylurea. The third site affected by high salinity was the transfer of light energy probably from pigment system II to I. High salinity reduced the amount of light energy that reached the reaction centers of photosystem II.These effects are discussed in relation to the mechanisms available to this plant to avoid photoinhibition when it is exposed to stresses such as high light and high salinity which are conditions that are commonly found in the intertidal habitat.The intertidal red alga Porphyra perforate lives where, at low tide, the plants are routinely exposed to air-drying. As a result of evaporative water loss, the salt concentration of extracellular water can increase up to about 10 times above normal levels. During desiccation at low tide this alga can lose up to 90% of its fresh weight (23). This air-drying has the effect of slowly increasing external salt concentrations in the small amount of water remaining around the algal tissues. The osmotic stress of airdrying can be experimentally induced by increasing external salt concentrations around algal tissues. This method has the advantage of allowing greater control over tissue dehydration than is possible using air-drying. Upon dehydration either by high salt or by air-drying, the photosynthesis of Porphyra is similarly inhibited (23). Furthermore, this alga is often exposed to high light intensities in combination with tissue dehydration in the field. It is well known that photoinhibition of photosynthesis can take place during experimental conditions under which photosynthesis is inhibited and there is an excess amount of light energy (5,13,15,16,18 6,8). It was observed that below a water content of 20 to 25%, the fluorescence time course became similar to that in the presence of DCMU. When the water content was less than 20%, the variable part of fluorescence (F, became small, whereas at 5% the F, was totally eliminated but F0 was little affected (24). From these and other results, Wiltens et al. (24) suggested that electron flow between the two photosystems was inhibited by low water content. The decrease of F, under conditions of very low water content was attributed to an accelerated back reaction of PSII because of the inhibition of the re-reduction of P680 with electrons normally derived from water. By contrast, Fork and Oquist (4) showed that there still remained relatively large amounts of F, in dark dried Porphyra. It is natural to assume that water oxidati...

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“…This slow reactivation shows a pronounced lag, the duration of which increases with the length of the anaerobic incubation. O 2 evolved by PSII possibly feeds back to reoxidize the PQ pool either directly (chlororespiration) or via PSI photochemistry (Mehler reaction) or via the malate shunt, therefore further stimulating the reactivation of PSII photochemistry (67). The synthesis of hydrogenase under anaerobic conditions, likely providing extra electron acceptors at the level of PSI and ferredoxin, also stimulates O 2 evolution and photochemical quenching of chlorophyll fluorescence (68).…”

Section: Interaction Between Carbon Metabolism and Electron Transportmentioning

confidence: 99%

Central Carbon Metabolism and Electron Transport in Chlamydomonas reinhardtii: Metabolic Constraints for Carbon Partitioning between Oil and Starch

2013

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eThe metabolism of microalgae is so flexible that it is not an easy task to give a comprehensive description of the interplay between the various metabolic pathways. There are, however, constraints that govern central carbon metabolism in Chlamydomonas reinhardtii that are revealed by the compartmentalization and regulation of the pathways and their relation to key cellular processes such as cell motility, division, carbon uptake and partitioning, external and internal rhythms, and nutrient stress. Both photosynthetic and mitochondrial electron transfer provide energy for metabolic processes and how energy transfer impacts metabolism and vice versa is a means of exploring the regulation and function of these pathways. A key example is the specific chloroplast localization of glycolysis/gluconeogenesis and how it impacts the redox poise and ATP budget of the plastid in the dark. To compare starch and lipids as carbon reserves, their value can be calculated in terms of NAD(P)H and ATP. As microalgae are now considered a potential renewable feedstock, we examine current work on the subject and also explore the possibility of rerouting metabolism toward lipid production. Photosynthetic algae fix atmospheric carbon (CO 2 ) by using light energy to drive a series of chemical and redox reactions. This fixed carbon is transformed into reserve molecules that can be broken down at a later time to provide the cell with ATP, reducing power, and carbon skeletons. Starch, a polymer of glucose, is synthesized and degraded as a normal process in a light-dark cell cycle. Starch is also accumulated to prepare for gametogenesis, but it is not a prerequisite. The type and quantity of the reserve depend on environmental and cellular factors: stresses such as nutrient deprivation, salinity, temperature, and high light can be stimuli for starch accumulation and also for triacylglycerol (TAG) synthesis leading to lipid body accumulation in algae. Under nonstress conditions, starch would appear to be a preferential source of reserve in green algae as it is in plant leaves, whereas under stress conditions and in plant oil seeds, storage neutral lipids will accumulate to high levels.Photosynthesis is a tightly controlled process, from the capture of light energy to the conversion of this energy into ATP and reducing power (NADPH). ATP and NADPH feed the Calvin cycle, which is responsible for CO 2 fixation. In the absence of exogenous carbon supply, photosynthesis is the only source of energy, and CO 2 fixation provides carbon skeletons for all reactions in the cell. Tight control of the photosynthetic reactions is required to fit the downstream metabolic reactions in the chloroplast.We deliberately oriented our presentation and our choice of references toward Chlamydomonas reinhardtii, a unicellular green alga that has garnered much attention from the scientific community, primarily because it is haploid and the genetics have been extensively developed, but it has also proven to be a robust model system for the study of photosynthesis. No...

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Chlorophyll fluorescence induction in anaerobic Scenedesmus obliquus

Cited by 63 publications

References 21 publications

A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield

A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield

Effects of Salinity on Primary Processes of Photosynthesis in the Red Alga Porphyra perforata

Central Carbon Metabolism and Electron Transport in Chlamydomonas reinhardtii: Metabolic Constraints for Carbon Partitioning between Oil and Starch

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