D27-LIKE1 isomerase has a preference towards trans/cis and cis/cis conversions of carotenoids in Arabidopsis.

Carotenoids contribute to a variety of physiological processes in plants, functioning also as biosynthesis precursors of ABA and strigolactones (SLs). SL biosynthesis starts with the enzymatic conversion of all-trans-ß-carotene to 9-cis-ß-carotene by the DWARF27 (D27) isomerase. In Arabidopsis, D27 has two closely related paralogs, D27-LIKE1 and D27-LIKE2, which were predicted to be ß-carotene-isomerases. In the present study, we characterised D27-LIKE1 and identified some key aspects of its physiological and enzymatic functions in Arabidopsis. d27-like1-1 mutant does not display any strigolactone-deficient traits and exhibits a substantially higher 9-cis-violaxanthin content, which is accompanied by a slightly higher ABA level. In vitro feeding assays with recombinant D27-LIKE1 revealed that the protein exhibits affinity to all ß-carotene isoforms but with an exclusive preference towards trans/cis conversions and the interconversion between 9-cis, 13-cis and 15-cis-ß-carotene forms, and accepts zeaxanthin and violaxanthin as substrates. Finally, we present evidence showing that D27-LIKE1 mRNA is phloem mobile and D27-LIKE1 is an ancient isomerase with a long evolutionary history. In summary, we demonstrate that D27-LIKE1 is a carotenoid isomerase with multi-substrate specificity and has a characteristic preference towards the catalysation of cis/cis interconversion of carotenoids. Therefore, D27-LIKE1 is a potential regulator of carotenoid cis pools and, eventually, SL and ABA biosynthesis pathways.

Water oxidation by photosystem II is the primary source of electrons for sustained H2 photoproduction in nutrient-replete green algae.

The unicellular green alga Chlamydomonas reinhardtii is capable of photosynthetic H2 production. H2 evolution occurs under anaerobic conditions and is difficult to sustain due to 1) competition between [FeFe]-hydrogenase (H2ase), the key enzyme responsible for H2 metabolism in algae, and the Calvin-Benson-Bassham (CBB) cycle for photosynthetic reductants and 2) inactivation of H2ase by O2 coevolved in photosynthesis. Recently, we achieved sustainable H2 photoproduction by shifting algae from continuous illumination to a train of short (1 s) light pulses, interrupted by longer (9 s) dark periods. This illumination regime prevents activation of the CBB cycle and redirects photosynthetic electrons to H2ase. Employing membrane-inlet mass spectrometry and [Formula: see text], we now present clear evidence that efficient H2 photoproduction in pulse-illuminated algae depends primarily on direct water biophotolysis, where water oxidation at the donor side of photosystem II (PSII) provides electrons for the reduction of protons by H2ase downstream of photosystem I. This occurs exclusively in the absence of CO2 fixation, while with the activation of the CBB cycle by longer (8 s) light pulses the H2 photoproduction ceases and instead a slow overall H2 uptake is observed. We also demonstrate that the loss of PSII activity in DCMU-treated algae or in PSII-deficient mutant cells can be partly compensated for by the indirect (PSII-independent) H2 photoproduction pathway, but only for a short (<1 h) period. Thus, PSII activity is indispensable for a sustained process, where it is responsible for more than 92% of the final H2 yield.

Analysis of the Association between Retinal Artery Occlusion and Acute Ischaemic Stroke/ST-Elevation Myocardial Infarction and Risk Factors in Hungarian Patients.

Background and Objectives: We aimed to analyse data on retinal artery occlusion (RAO) patients to explore correlations with acute ischaemic stroke (AIS), ST-elevation myocardial infarction (STEMI), and cardio/cerebrovascular comorbidities. Patients and Methods: Our retrospective cohort study included 169 RAO and 169 age- and gender-matched control patients. We examined the association of AIS, STEMI, and related comorbidities such as hypertension (HT), type 1 and type 2 diabetes (T1DM and T2DM, respectively), hyperlipidaemia, and ischaemic heart disease (IHD) with RAO. We also recorded atrial fibrillation in our RAO patients. Results: Our results demonstrated that RAO patients developed both AIS and STEMI at a significantly higher rate compared to controls (p < 0.001 for both). We also found that RAO patients had a significantly higher prevalence of HT and hyperlipidaemia (p1 = 0.005, p2 < 0.001) compared to controls. Multiple risk factors together significantly increased the odds of developing AIS and STEMI. Conclusions: Our results suggest that through identifying and treating the risk factors for RAO patients, we can reduce the risk of AIS, STEMI, and RAO of the fellow eye. Considering that ophthalmologists are often the first detectors of these cardiovascularly burdened patients, collaboration with colleagues from internal medicine, cardiology, and neurology is essential to achieve secondary prevention.

Ascorbate inactivates the oxygen-evolving complex in prolonged darkness.

Ascorbate (Asc, vitamin C) is an essential metabolite participating in multiple physiological processes of plants, including environmental stress management and development. In this study, we acquired knowledge on the role of Asc in dark-induced leaf senescence using Arabidopsis thaliana as a model organism. One of the earliest effects of prolonged darkness is the inactivation of oxygen-evolving complexes (OEC) as demonstrated here by fast chlorophyll a fluorescence and thermoluminescence measurements. We found that inactivation of OEC due to prolonged darkness was attenuated in the Asc-deficient vtc2-4 mutant. On the other hand, the severe photosynthetic phenotype of a psbo1 knockout mutant, lacking the major extrinsic OEC subunit PSBO1, was further aggravated upon a 24-h dark treatment. The psbr mutant, devoid of the PSBR subunit of OEC, performed only slightly disturbed photosynthetic activity under normal growth conditions, whereas it showed a strongly diminished B thermoluminescence band upon dark treatment. We have also generated a double psbo1 vtc2 mutant, and it showed a slightly milder photosynthetic phenotype than the single psbo1 mutant. Our results, therefore, suggest that Asc leads to the inactivation of OEC in prolonged darkness by over-reducing the Mn-complex that is probably enabled by a dark-induced dissociation of the extrinsic OEC subunits. Our study is an example that Asc may negatively affect certain cellular processes and thus its concentration and localization need to be highly controlled.

The mechanism of photosystem-II inactivation during sulphur deprivation-induced H2 production in Chlamydomonas reinhardtii.

Sulphur limitation may restrain cell growth and viability. In the green alga Chlamydomonas reinhardtii, sulphur limitation may induce H2 production lasting for several days, which can be exploited as a renewable energy source. Sulphur limitation causes a large number of physiological changes, including the inactivation of photosystem II (PSII), leading to the establishment of hypoxia, essential for the increase in hydrogenase expression and activity. The inactivation of PSII has long been assumed to be caused by the sulphur-limited turnover of its reaction center protein PsbA. Here we reinvestigated this issue in detail and show that: (i) upon transferring Chlamydomonas cells to sulphur-free media, the cellular sulphur content decreases only by about 25%; (ii) as demonstrated by lincomycin treatments, PsbA has a significant turnover, and other photosynthetic subunits, namely RbcL and CP43, are degraded more rapidly than PsbA. On the other hand, sulphur limitation imposes oxidative stress early on, most probably involving the formation of singlet oxygen in PSII, which leads to an increase in the expression of GDP-L-galactose phosphorylase, playing an essential role in ascorbate biosynthesis. When accumulated to the millimolar concentration range, ascorbate may inactivate the oxygen-evolving complex and provide electrons to PSII, albeit at a low rate. In the absence of a functional donor side and sufficient electron transport, PSII reaction centers are inactivated and degraded. We therefore demonstrate that the inactivation of PSII is a complex and multistep process, which may serve to mitigate the damaging effects of sulphur limitation.

Effects of selenate and red Se-nanoparticles on the photosynthetic apparatus of Nicotiana tabacum.

Selenium (Se) is a natural trace element, which shifts its action in a relatively narrow concentration range from nutritional role to toxicity. Although it has been well established that in plants chloroplasts are among the primary targets, the mechanism of toxicity on photosynthesis is not well understood. Here, we compared selenate and red-allotrope elemental selenium nanoparticles (red nanoSe) in in vitro tobacco cultures to investigate their effects on the structure and functions of the photosynthetic machinery. Selenate at 10 mg/L concentration retarded plant growth; it also led to a decreased chlorophyll content, accompanied with an increase in the carotenoid-to-chlorophyll ratio. Structural examinations of the photosynthetic machinery, using electron microscopy, small-angle neutron scattering and circular dichroism spectroscopy, revealed significant perturbation in the macro-organization of the pigment-protein complexes and sizeable shrinkage in the repeat distance of granum thylakoid membranes. As shown by chlorophyll a fluorescence transient measurements, these changes in the ultrastructure were associated with a significantly diminished photosystem II activity and a reduced performance of the photosynthetic electron transport, and an enhanced capability of non-photochemical quenching. These changes in the structure and function of the photosynthetic apparatus explain, at least in part, the retarded growth of plantlets in the presence of 10 mg/L selenate. In contrast, red nanoSe, even at 100 mg/L and selenate at 1 mg/L, exerted no negative effect on the growth of plantlets and affected only marginally the thylakoid membrane ultrastructure and the photosynthetic functions.

Alport Patients without Classic Ocular Symptoms Have Smaller Lens Diameter.

BACKGROUND The aim of this study was to present ophthalmological findings regarding Alport syndrome and report refractometry data and to present possible early signs of the syndrome. MATERIAL AND METHODS Seven patients suffering from Alport syndrome were referred to the Department of Ophthalmology at the University of Debrecen between January 1st, 2014, and December 31st, 2015. All patients underwent slit lamp evaluation and dilated fundus biomicroscopy, with special attention paid to lenticonus and retinal changes. IOL Master, Pentacam HR, and ultrasound biomicroscopy were performed to assess keratometry, corneal thickness, anterior chamber depth, lens size, and axial length data. RESULTS One patient out of seven had ocular symptoms. Posterior polymorphous corneal dystrophy (PPMD) and dot-and-fleck retinopathy were seen. Meanwhile, although keratoconus was not proven, remarkable astigmatism with high myopia was detected. The other six patients were found to have a significantly smaller lens diameter (an average of 7.82±0.66 mm, p=0.035) compared to normal controls (an average of 8.65±0.46 mm). Lenses also tended to be thicker in Alport patients (3.48±0.19 mm) compared to controls (3.4±0.2 mm), although the difference was not significant (p=0.394). The power of the lens also showed a significant difference (p=0.026), with Alport patients having lower lens power. CONCLUSIONS Alport syndrome patients without classical ophthalmological findings have smaller crystalline lens diameter and lower lens power. These signs may support the diagnosis of Alport syndrome. Ophthalmologists should not only seek for the known classic signs, but also the parameters of the crystalline lens, especially if genetic testing is not available.

Regulation of ascorbate biosynthesis in green algae has evolved to enable rapid stress-induced response via the VTC2 gene encoding GDP-l-galactose phosphorylase.

Ascorbate (vitamin C) plays essential roles in stress resistance, development, signaling, hormone biosynthesis and regulation of gene expression; however, little is known about its biosynthesis in algae. In order to provide experimental proof for the operation of the Smirnoff-Wheeler pathway described for higher plants and to gain more information on the regulation of ascorbate biosynthesis in Chlamydomonas reinhardtii, we targeted the VTC2 gene encoding GDP-l-galactose phosphorylase using artificial microRNAs. Ascorbate concentrations in VTC2 amiRNA lines were reduced to 10% showing that GDP-l-galactose phosphorylase plays a pivotal role in ascorbate biosynthesis. The VTC2 amiRNA lines also grow more slowly, have lower chlorophyll content, and are more susceptible to stress than the control strains. We also demonstrate that: expression of the VTC2 gene is rapidly induced by H2 O2 and 1 O2 resulting in a manifold increase in ascorbate content; in contrast to plants, there is no circadian regulation of ascorbate biosynthesis; photosynthesis is not required per se for ascorbate biosynthesis; and Chlamydomonas VTC2 lacks negative feedback regulation by ascorbate in the physiological concentration range. Our work demonstrates that ascorbate biosynthesis is also highly regulated in Chlamydomonas albeit via mechanisms distinct from those previously described in land plants.

Ascorbate accumulation during sulphur deprivation and its effects on photosystem II activity and H2 production of the green alga Chlamydomonas reinhardtii.

In nature, H2 production in Chlamydomonas reinhardtii serves as a safety valve during the induction of photosynthesis in anoxia, and it prevents the over-reduction of the photosynthetic electron transport chain. Sulphur deprivation of C. reinhardtii also triggers a complex metabolic response resulting in the induction of various stress-related genes, down-regulation of photosynthesis, the establishment of anaerobiosis and expression of active hydrogenase. Photosystem II (PSII) plays dual role in H2 production because it supplies electrons but the evolved O2 inhibits the hydrogenase. Here, we show that upon sulphur deprivation, the ascorbate content in C. reinhardtii increases about 50-fold, reaching the mM range; at this concentration, ascorbate inactivates the Mn-cluster of PSII, and afterwards, it can donate electrons to tyrozin Z(+) at a slow rate. This stage is followed by donor-side-induced photoinhibition, leading to the loss of charge separation activity in PSII and reaction centre degradation. The time point at which maximum ascorbate concentration is reached in the cell is critical for the establishment of anaerobiosis and initiation of H2 production. We also show that ascorbate influenced H2 evolution via altering the photosynthetic electron transport rather than hydrogenase activity and starch degradation.

[Adult-onset rare diseases]. / Felnottkorban kiteljesedo ritka kórképek.

The present paper is focusing on rare diseases manifesting in late childhood or adulthood. A part of these syndromes are not of genetic origin, such as relatively or absolutely rare infections, autoimmune diseases, tumours, or diseases due to rare environmental toxic agents. In addition, even a large proportion of genetic disorders may develop in adulthood or may have adult forms as well, affecting are almost each medical specialization. Examples are storage disorders (e.g. adult form of Tay-Sachs disease, Gaucher-disease), enzyme deficiencies (e.g. ornithin-transcarbamylase deficiency of the urea cycle disorders), rare thrombophilias (e.g. homozygous factor V. Leiden mutation, antithrombin deficiency), or some rare monogenic disorders such as Huntington-chorea and many others. It is now generally accepted that at least half of the 6-8000 "rare diseases" belong either to the scope of adult-care (e.g. internal medicine, neurology), or to "age-neutral" specialities such as ophtalmology, dermatology etc.).

Increased level of platelet P-selectin in nonarteritic anterior ischemic optic neuropathy.

PURPOSE: P-selectin receptor is expressed in platelets and endothelial cells in a cell-activation-dependent manner. Platelet P-selectin (CD62) levels may become elevated in a number of vasoocclusive diseases, including arteriosclerosis, atherothrombosis, and diabetes mellitus (DM). Nonarteritic anterior ischemic optic neuropathy (NAION) is associated with a sudden loss of vision due to the vascular insufficiency of ciliary arteries supplying the optic nerve. In this study, our aim was to investigate the presence of increased platelet reactivity in the development of NAION. METHODS: Twenty-one NAION patients, 39 healthy control subjects, and 44 patients suffering from diabetes mellitus (DM) were examined in our case-control, pilot study. Platelet activation was investigated by flow cytometric analysis of the mean fluorescence intensity (MFI) of CD62 on platelets. These results were compared among the different study groups. RESULTS: NAION patients showed considerably although not significantly (p = 0.2017) higher P-selectin MFI values (71.98 ± 40.30) versus healthy subjects (55.48 ± 20.95), insulin-dependent DM patients (50.02 ± 13.08), and non-insulin-dependent DM subjects (54.72 ± 24.74). However, logistic regression analysis resulted in a statistically significant adjusted effect on the odds of NAION when CD62 MFI values were logarithmically transformed (OR: 3.86, 95 % CI: 1.10 to 13.53, p = 0.0346). CONCLUSION: Elevated platelet CD62 positivity may be related to NAION, suggesting a possible role of enlarged platelet activity in the generation of this type of ischemic optic neuropathy.

Tear fluid proteomics multimarkers for diabetic retinopathy screening.

BACKGROUND: The aim of the project was to develop a novel method for diabetic retinopathy screening based on the examination of tear fluid biomarker changes. In order to evaluate the usability of protein biomarkers for pre-screening purposes several different approaches were used, including machine learning algorithms. METHODS: All persons involved in the study had diabetes. Diabetic retinopathy (DR) was diagnosed by capturing 7-field fundus images, evaluated by two independent ophthalmologists. 165 eyes were examined (from 119 patients), 55 were diagnosed healthy and 110 images showed signs of DR. Tear samples were taken from all eyes and state-of-the-art nano-HPLC coupled ESI-MS/MS mass spectrometry protein identification was performed on all samples. Applicability of protein biomarkers was evaluated by six different optimally parameterized machine learning algorithms: Support Vector Machine, Recursive Partitioning, Random Forest, Naive Bayes, Logistic Regression, K-Nearest Neighbor. RESULTS: Out of the six investigated machine learning algorithms the result of Recursive Partitioning proved to be the most accurate. The performance of the system realizing the above algorithm reached 74% sensitivity and 48% specificity. CONCLUSIONS: Protein biomarkers selected and classified with machine learning algorithms alone are at present not recommended for screening purposes because of low specificity and sensitivity values. This tool can be potentially used to improve the results of image processing methods as a complementary tool in automatic or semiautomatic systems.

A PSII photosynthetic control is activated in anoxic cultures of green algae following illumination.

Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O2 which diminishes the expression and the activity of the hydrogenase enzyme catalyzing H2 production. Here we report a third, hitherto unknown challenge: We found that under anoxia, a slow-down switch is activated in photosystem II (PSII), diminishing the maximal photosynthetic productivity by three-fold. Using purified PSII and applying in vivo spectroscopic and mass spectrometric techniques on Chlamydomonas reinhardtii cultures, we show that this switch is activated under anoxia, within 10 s of illumination. Furthermore, we show that the recovery to the initial rate takes place following 15 min of dark anoxia, and propose a mechanism in which, modulation in electron transfer at the acceptor site of PSII diminishes its output. Such insights into the mechanism broaden our understanding of anoxic photosynthesis and its regulation in green algae and inspire new strategies to improve bio-energy yields.

Clinical Investigation of Hereditary and Acquired Thrombophilic Factors in Patients with Venous and Arterial Thromboembolism.

Background: The clinical relevance of thrombophilic laboratory factors, especially the "mild" ones, and the need for their screening is not generally recommended in venous (VTE) and/or arterial (ATE) thromboembolism. Methods: Our aim was to investigate possible associations between comorbidities and 16 inherited/acquired "severe" and "mild" laboratory thrombophilic factors (detailed in introduction) in patients (n=348) with VTE/ATE without a serious trigger (high-risk surgical intervention, active cancer and/or chemo-radiotherapy). Cases with VTE/ATE were enrolled when the thrombotic event occurred under the age of 40, in case of positive family history, recurrent thromboembolism, idiopathic event or unusual location. Patients without a detailed thrombophilia screening or who suffered from both ATE/VTE were excluded to find potential distinct thrombosis type specific thrombophilic risks. The possible role of "mild" factor accumulation was also investigated in VTE (n=266). Results: Elevation of factor VIII clotting activity was associated with VTE rather than ATE. Varicose veins together with postthrombotic syndrome were strongly related to several "mild" factors. Besides "severe" we found that the "mild" thrombophilic factors were also strongly associated with VTE/ATE. Comorbidities/conditions such as diabetes and smoking were generally associated with hyperlipidemia; moreover, both had a correlation with lipoprotein (a) in VTE. We also revealed an important contribution of "mild" factors in increasing trends of several types and localizations of VTE. Conclusion: In summary, besides the "severe" thrombophilic factors, the "mild" ones also seem to play a non-negligible role in the manifestation of thrombosis, especially in combination. Therefore, an extended screening might be useful in the personalized recommendation of antithrombotic prophylaxis.

The physiological role of ascorbate as photosystem II electron donor: protection against photoinactivation in heat-stressed leaves.

Previously, we showed that ascorbate (Asc), by donating electrons to photosystem II (PSII), supports a sustained electron transport activity in leaves in which the oxygen-evolving complexes were inactivated with a heat pulse (49°C, 40 s). Here, by using wild-type, Asc-overproducing, and -deficient Arabidopsis (Arabidopsis thaliana) mutants (miox4 and vtc2-3, respectively), we investigated the physiological role of Asc as PSII electron donor in heat-stressed leaves (40°C, 15 min), lacking active oxygen-evolving complexes. Chlorophyll-a fluorescence transients show that in leaves excited with trains of saturating single-turnover flashes spaced 200 ms apart, allowing continual electron donation from Asc to PSII, the reaction centers remained functional even after thousands of turnovers. Higher flash frequencies or continuous illumination (300 µmol photons m(-2) s(-1)) gradually inactivated them, a process that appeared to be initiated by a dramatic deceleration of the electron transfer from Tyr(Z) to P680(+), followed by the complete loss of charge separation activity. These processes occurred with half-times of 1.2 and 10 min, 2.8 and 23 min, and 4.1 and 51 min in vtc2-3, the wild type, and miox4, respectively, indicating that the rate of inactivation strongly depended on the Asc content of the leaves. The recovery of PSII activity, following the degradation of PSII proteins (D1, CP43, and PsbO), in moderate light (100 µmol photons m(-2) s(-1), comparable to growth light), was also retarded in the Asc-deficient mutant. These data show that high Asc content of leaves contributes significantly to the ability of plants to withstand heat-stress conditions.

Microfluidic Platforms Designed for Morphological and Photosynthetic Investigations of Chlamydomonas reinhardtii on a Single-Cell Level.

Chlamydomonas reinhardtii is a model organism of increasing biotechnological importance, yet, the evaluation of its life cycle processes and photosynthesis on a single-cell level is largely unresolved. To facilitate the study of the relationship between morphology and photochemistry, we established microfluidics in combination with chlorophyll a fluorescence induction measurements. We developed two types of microfluidic platforms for single-cell investigations: (i) The traps of the "Tulip" device are suitable for capturing and immobilizing single cells, enabling the assessment of their photosynthesis for several hours without binding to a solid support surface. Using this "Tulip" platform, we performed high-quality non-photochemical quenching measurements and confirmed our earlier results on bulk cultures that non-photochemical quenching is higher in ascorbate-deficient mutants (Crvtc2-1) than in the wild-type. (ii) The traps of the "Pot" device were designed for capturing single cells and allowing the growth of the daughter cells within the traps. Using our most performant "Pot" device, we could demonstrate that the FV/FM parameter, an indicator of photosynthetic efficiency, varies considerably during the cell cycle. Our microfluidic devices, therefore, represent versatile platforms for the simultaneous morphological and photosynthetic investigations of C. reinhardtii on a single-cell level.

Bilateral central retinal vein occlusion caused by malignant hypertension in a young patient.

Central retinal vein occlusion (CRVO) occurring simultaneously in both eyes is a rare condition, in such cases usually associated with severe systemic disease. Overall, only 10% of all CRVO patients are younger than 40 years. A relatively young patient reported with simultaneous bilateral CRVO associated with chronic kidney disease and malignant hypertension. A case of a 35-year-old male patient presented with the complaint of decreased vision in both eyes. Ophthalmic examination revealed bilateral CRVO. Chronic kidney disease leading to malignant hypertension and hyperviscosity was diagnosed as the underlying cause. Clinical support and medical therapy effectively controlled the hypertension, leading to improvement of both the systemic and ocular changes. To the best of our knowledge, this is the first case report of simultaneous bilateral CRVO in a young patient associated with chronic renal failure and malignant hypertension. Primary care providers, either ophthalmologists or physicians, need to consider both common and atypical risk factors for retinal vein occlusion, in order to prevent further ocular morbidity and systemic complications.

Analysis of intravitreal bevacizumab treatment for macular oedema due to retinal vein occlusion.

PURPOSE: Our aim was to analyse the clinical effect of intravitreal bevacizumab treatment for macular oedema due to central/branch retinal vein occlusion (CRVO/BRVO). The end points were final best-corrected visual acuity (BCVA), BCVA improvement, final central 1-mm macular subfield thickness (CST) and change in CST. METHODS: Our study included 34 CRVO and 25 BRVO patients. Patients received intravitreal bevacizumab (IVB) treatment at our department. Our control group consisted of 50 CRVO and 30 BRVO patients, who had not received this treatment because their disease developed before the anti-VEGF treatment became available. For statistical analysis, two-sample t-test, Pearson's correlation, and ANOVA were used. The level of significance was defined at p < 0.05. RESULTS: With the two-sample t-test we found significant improvement of BCVA in the IVB-treated group (CRVO: 0.171 ± 0.270, p1 = 3.25×10-4; BRVO: 0.215 ± 0.282, p2 = 5.52×10-4). The difference in BCVA improvement was also significant compared to the control group (CRVO: p1 = 3.46×10-4; BRVO: p2 = 0.003). Significant decrease was observed in the CST in the treated group (CRVO: -345.114 ± 280.577, p1 = 6.94×10-9; BRVO: -151.875 ± 174.341, p2 = 1.67×10-4). In case of BRVO patients the final BCVA was significantly better in the treated group (0.617 ± 0.334) compared to the control group (0.406 ± 0.357), p = 0.016. CONCLUSION: IVB treatment results in significantly better final visual acuity and leads to significantly increased BCVA improvement compared to patients with RVO-induced macular oedema receiving no treatment.

Thin cell layer cultures of Chlamydomonas reinhardtii L159I-N230Y, pgrl1 and pgr5 mutants perform enhanced hydrogen production at sunlight intensity.

Photobiological hydrogen (H2) production is a promising renewable energy source. HydA hydrogenases of green algae are efficient but O2-sensitive and compete for electrons with CO2-fixation. Recently, we established a photoautotrophic H2 production system based on anaerobic induction, where the Calvin-Benson cycle is inactive and O2 scavenged by an absorbent. Here, we employed thin layer cultures, resulting in a three-fold increase in H2 production relative to bulk CC-124 cultures (50 µg chlorophyll/ml, 350 µmol photons m-2 s-1). Productivity was maintained when increasing the light intensity to 1000 µmol photons m-2s-1 and the cell density to 150 µg chlorophyll/ml. Remarkably, the L159I-N230Y photosystem II mutant and the pgrl1 photosystem I cyclic electron transport mutant produced 50% more H2 than CC-124, while the pgr5 mutant generated 250% more (1.2 ml H2/ml culture in six days). The photosynthetic apparatus of the pgr5 mutant and its in vitro HydA activity remained remarkably stable.

Elimination of the flavodiiron electron sink facilitates long-term H2 photoproduction in green algae.

BACKGROUND: The development of renewable and sustainable biofuels to cover the future energy demand is one of the most challenging issues of our time. Biohydrogen, produced by photosynthetic microorganisms, has the potential to become a green biofuel and energy carrier for the future sustainable world, since it provides energy without CO2 emission. The recent development of two alternative protocols to induce hydrogen photoproduction in green algae enables the function of the O2-sensitive [FeFe]-hydrogenases, located at the acceptor side of photosystem I, to produce H2 for several days. These protocols prevent carbon fixation and redirect electrons toward H2 production. In the present work, we employed these protocols to a knockout Chlamydomonas reinhardtii mutant lacking flavodiiron proteins (FDPs), thus removing another possible electron competitor with H2 production. RESULTS: The deletion of the FDP electron sink resulted in the enhancement of H2 photoproduction relative to wild-type C. reinhardtii. Additionally, the lack of FDPs leads to a more effective obstruction of carbon fixation even under elongated light pulses. CONCLUSIONS: We demonstrated that the rather simple adjustment of cultivation conditions together with genetic manipulation of alternative electron pathways of photosynthesis results in efficient re-routing of electrons toward H2 photoproduction. Furthermore, the introduction of a short recovery phase by regular switching from H2 photoproduction to biomass accumulation phase allows to maintain cell fitness and use photosynthetic cells as long-term H2-producing biocatalysts.