TY - JOUR AU - Patil, Priyanka Pradeep AU - Kodru, Sandeesha AU - Szabó, Milán AU - Vass, Imre TI - Investigation of the effect of salt stress on photosynthetic electron transport pathways in the Synechocystis PCC 6803 cyanobacterium JF - PHYSIOLOGIA PLANTARUM J2 - PHYSIOL PLANTARUM VL - 177 PY - 2025 IS - 1 PG - 17 SN - 0031-9317 DO - 10.1111/ppl.70066 UR - https://m2.mtmt.hu/api/publication/35737494 ID - 35737494 N1 - Funding Agency and Grant Number: National Research, Development, and Innovation Office [K-132568] Funding text: This research was funded by the National Research, Development, and Innovation Office, grant number K-132568. AB - Cyanobacteria are important model organisms for studying the process of photosynthesis and the effects of environmental stress factors. This study aimed to identify the inhibitory sites of NaCl in the whole photosynthetic electron transport in Synechocysti s sp. PCC 6803 WT cells by using multiple biophysical tools. Exposure of cells to various NaCl concentrations (200 mM to 1 M) revealed the inhibition of Photosystem II (PSII) activity at the water oxidizing complex and between the Q A and Q B electron acceptors. In contrast to the inhibition of PSII, electron flow through Photosystem I (PSI) was accelerated, indicating enhanced cyclic electron flow. The oxygen‐evolving capacity of the cells was inhibited to a larger extent when only CO 2 was the final electron acceptor in the Calvin‐Benson‐Bassham (CBB) cycle than in the presence of the PSII electron acceptor DMBQ, suggesting important NaCl inhibitory site(s) downstream of PSI. Measurements of NADPH kinetics revealed NaCl‐induced inhibition of light‐induced production of NADPH as well as retardation of NADPH consumption both in the light and in the initial dark period after switching off the light. Chlorophyll fluorescence kinetics, measured in parallel with NADPH fluorescence, showed the enhancement of post‐illumination fluorescence rise up to 500 mM NaCl, which was however inhibited at higher NaCl concentrations. Our results show, for the first time, that NaCl inhibits the activity of the CBB cycle at least at two different sites, and confirm earlier results about the NaCl‐induced inhibition of the PSII donor and acceptor side and the enhancement of electron flow through PSI. LA - English DB - MTMT ER - TY - JOUR AU - Szabó, Milán AU - Szabó, Zoltán AU - Ábrahám, Ágnes AU - Nagy, Krisztina AU - Sass, László AU - Galajda, Péter AU - Vass, Imre TI - Assessment of the morphological features, physiological and photosynthetic activity of the different cell forms of Symbiodiniaceae using microfluidic methods JF - FRONTIERS IN PHOTOBIOLOGY J2 - FRONT PHOTOBIOL VL - 3 PY - 2025 SN - 2813-8228 DO - 10.3389/fphbi.2025.1645420 UR - https://m2.mtmt.hu/api/publication/36311585 ID - 36311585 AB - The dinoflagellate algae Symbiodiniaceae live in endosymbiosis with Anthozoa, which is essential for the existence of coral reefs. The cells of Symbiodiniaceae exist in two distinct forms: the flagellated, motile form and the non-flagellated, coccoid form, which play specific roles in the life cycle of these algae. The regulation and distribution of the different cell forms have been intensively studied in the past, however, the behavior and changes of the cell cycle are less characterized under conditions that mimic the coral tissue versus the free living environment, e.g., by manipulating the viscosity of the medium and thereby altering cell motility. In this work, we applied precisely controlled microfluidic tools to manipulate the viscosity of the medium, using the polysucrose Ficoll. We found that by the application of Ficoll the diurnal cycle of the different cell forms undergoes remarkable changes, the motility of the cells decreases, and the motile phase of the cell cycle becomes significantly shorter compared to the absence of Ficoll. The slowed motile cells are also amenable for single-cell analysis of the activity of PSII (F v /F m ). We therefore propose that the method developed here could serve as a sensitive monitoring system of the cell cycle changes and manipulation of cell motility mimicking the coral host environment, with concomitant single-cell photosynthetic activity analysis of Symbiodiniaceae. LA - English DB - MTMT ER - TY - JOUR AU - Zavřel, Tomáš AU - Segečová, Anna AU - Kovács, László AU - Lukeš, Martin AU - Novák, Zoltán AU - Pohland, Anne-Christin AU - Szabó, Milán AU - Somogyi, Boglárka AU - Prášil, Ondřej AU - Červený, Jan AU - Bernát, Gábor TI - A Comprehensive Study of Light Quality Acclimation in Synechocystis Sp. PCC 6803 JF - PLANT AND CELL PHYSIOLOGY J2 - PLANT CELL PHYSIOL VL - 65 PY - 2024 IS - 8 SP - 1285 EP - 1297 PG - 13 SN - 0032-0781 DO - 10.1093/pcp/pcae062 UR - https://m2.mtmt.hu/api/publication/35082092 ID - 35082092 N1 - Funding Agency and Grant Number: Ministry of Education, Youth and Sports of CR [LM2018123, CZ.02.1.01/0.0/0.0/16_026/0008413, LUAUS24131]; National Research, Development and Innovation Office of Hungary [K 140351, RRF-2.3.1-21-2022-00014] Funding text: The Ministry of Education, Youth and Sports of CR (LM2018123; CZ.02.1.01/0.0/0.0/16_026/0008413; LUAUS24131) and the National Research, Development and Innovation Office of Hungary, NKFIH (K 140351 and RRF-2.3.1-21-2022-00014). AB - Cyanobacteria play a key role in primary production in both oceans and fresh waters and hold great potential for sustainable production of a large number of commodities. During their life, cyanobacteria cells need to acclimate to a multitude of challenges, including shifts in intensity and quality of incident light. Despite our increasing understanding of metabolic regulation under various light regimes, detailed insight into fitness advantages and limitations under shifting light quality remains underexplored. Here, we study photo-physiological acclimation in the cyanobacterium Synechocystis sp. PCC 6803 throughout the photosynthetically active radiation (PAR) range. Using light emitting diodes (LEDs) with qualitatively different narrow spectra, we describe wavelength dependence of light capture, electron transport and energy transduction to main cellular pools. In addition, we describe processes that fine-tune light capture, such as state transitions, or the efficiency of energy transfer from phycobilisomes to photosystems (PS). We show that growth was the most limited under blue light due to inefficient light harvesting, and that many cellular processes are tightly linked to the redox state of the plastoquinone (PQ) pool, which was the most reduced under red light. The PSI-to-PSII ratio was low under blue photons, however, it was not the main growth-limiting factor, since it was even more reduced under violet and near far-red lights, where Synechocystis grew faster compared to blue light. Our results provide insight into the spectral dependence of phototrophic growth and can provide the foundation for future studies of molecular mechanisms underlying light acclimation in cyanobacteria, leading to light optimization in controlled cultivations. LA - English DB - MTMT ER - TY - CHAP AU - Szabó, Milán AU - Nagy, G. AU - Garab, Győző ED - Goessling, Johannes W. ED - Serôdio, João ED - Lavaud, Johann TI - Non-Invasive Biophysical Techniques to Monitor the Structural Plasticity of the Photosynthetic Machinery of Live Diatom Cells T2 - Diatom Photosynthesis PB - Wiley SN - 9781119842156 PY - 2024 SP - 245 EP - 266 PG - 22 DO - 10.1002/9781119842156.ch8 UR - https://m2.mtmt.hu/api/publication/35765728 ID - 35765728 N1 - Export Date: 24 March 2025 LA - English DB - MTMT ER - TY - JOUR AU - Bates, Harvey AU - Zavafer, Alonso AU - Szabó, Milán AU - Ralph, Peter J. TI - The slow-phase of chlorophyll fluorescence induction curve reflects the electron transport rates of Photosystem II in vivo in Chlorella vulgaris JF - JOURNAL OF APPLIED PHYCOLOGY J2 - J APPL PHYCOL VL - 35 PY - 2023 IS - 1 SP - 109 EP - 116 PG - 8 SN - 0921-8971 DO - 10.1007/s10811-022-02890-0 UR - https://m2.mtmt.hu/api/publication/33608945 ID - 33608945 N1 - Export Date: 12 April 2023 CODEN: JAPPE AB - Ideally methods and parameters to assess photosynthesis in the microalga Chlorella vulgaris must be rapid, non-invasive, accurate, and simple to implement. Methods such as the Quantum Yield of photosynthesis (phi(Po) or F-v/F-m) yield rapid results but do not reflect the actual electron turnover of PSII (ETRII). Alternatively, methods that calculate ETRII take several minutes to execute, require expensive instrumentation, and manual input. In this work, we describe a method to estimate ETRII in real-time via predictive statistic modelling. This method utilises the Kautsky induction curve and a low-cost chlorophyll a fluorometer. Our model optimises the fit of linear regressions between the normalized fluorescence intensity after F-m (named S-ETR) and ETRII measurements using traditional methods. This allows for an estimation of ETRII in real-time through Kautsky induction curves alone. S-ETR can then be used as a faster alternative to quenching analysis to determine bioenergetics performance during steady state and can be assessed with any chlorophyll fluorometer capable of measuring the Kautsky induction curve. The S-ETR parameter allows for a high-throughput and high-resolution assessment of photosynthesis while being non-invasive, having lower production costs, and with lower technical requirements. Furthermore, the biophysical bases of the method are discussed. LA - English DB - MTMT ER - TY - JOUR AU - Mohammad Aslam, Sabit AU - Vass, Imre AU - Szabó, Milán TI - Characterization of the Flash-Induced Fluorescence Wave Phenomenon in the Coral Endosymbiont Algae, Symbiodiniaceae JF - INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES J2 - INT J MOL SCI VL - 24 PY - 2023 IS - 10 PG - 14 SN - 1661-6596 DO - 10.3390/ijms24108712 UR - https://m2.mtmt.hu/api/publication/34043896 ID - 34043896 N1 - Funding Agency and Grant Number: National Research, Development and Innovation Office (NKFIH) [FK128977]; Biological Research Centre, Szeged, Hungary Funding text: This research was funded by The National Research, Development and Innovation Office (NKFIH), grant number FK128977, and the APC was funded by Biological Research Centre, Szeged, Hungary. AB - The dinoflagellate algae, Symbiodiniaceae, are significant symbiotic partners of corals due to their photosynthetic capacity. The photosynthetic processes of the microalgae consist of linear electron transport, which provides the energetic balance of ATP and NADPH production for CO2 fixation, and alternative electron transport pathways, including cyclic electron flow, which ensures the elevated ATP requirements under stress conditions. Flash-induced chlorophyll fluorescence relaxation is a non-invasive tool to assess the various electron transport pathways. A special case of fluorescence relaxation, the so-called wave phenomenon, was found to be associated with the activity of NAD(P)H dehydrogenase (NDH) in microalgae. We showed previously that the wave phenomenon existed in Symbiodiniaceae under acute heat stress and microaerobic conditions, however, the electron transport processes related to the wave phenomenon remained unknown. In this work, using various inhibitors, we show that (i) the linear electron transport has a crucial role in the formation of the wave, (ii) the inhibition of the donor side of Photosystem II did not induce the wave, whereas inhibition of the Calvin-Benson cycle accelerated it, (iii) the wave phenomenon was related to the operation of type II NDH (NDH-2). We therefore propose that the wave phenomenon is an important marker of the regulation of electron transport in Symbiodiniaceae. LA - English DB - MTMT ER - TY - JOUR AU - Patil, Priyanka Pradeep AU - Nagy, Krisztina AU - Ábrahám, Ágnes AU - Vass, Imre AU - Szabó, Milán TI - Monitoring the photosynthetic activity at single-cell level in Haematococcus lacustris JF - PHOTOSYNTHETICA J2 - PHOTOSYNTHETICA VL - 61 PY - 2023 IS - SI SP - 473 EP - 482 PG - 10 SN - 0300-3604 DO - 10.32615/ps.2023.042 UR - https://m2.mtmt.hu/api/publication/34473960 ID - 34473960 N1 - Funding Agency and Grant Number: National Research, Development, and Innovation Office [NKFIH FK 128977]; [GINOP-2.3.2-15-2016-00026] Funding text: This work was supported by the National Research, Development, and Innovation Office (grant NKFIH FK 128977) and the grant GINOP-2.3.2-15-2016-00026. We thank Dr. Peter Galajda (BRC, Szeged) for fruitful discussions and for providing the microfluidic infrastructure. AB - Haematococcus lacustris is an important species of green algae because it produces the high-value carotenoid astaxanthin. Astaxanthin production is enhanced by various stress conditions causing the transformation of green vegetative cells to red cells with high amounts of astaxanthin, which plays various photoprotective and antioxidant roles. Although intensive research has been conducted to reveal the regulation of astaxanthin production, the photosynthetic capacity of the various cell forms is unresolved at the single-cell level. In this work, we characterized the photosynthetic and morphological changes of Haematococcus cells, using a combination of microfluidic tools and microscopic chlorophyll fluorescence imaging. We found marked but reversible changes in the variable chlorophyll fluorescence signatures upon the transformation of green cells to red cells, and we propose that the photosynthetic activity as revealed by single-cell chlorophyll fluorescence kinetics serves as a useful phenotypic marker of the different cell forms of Haematococcus. LA - English DB - MTMT ER - TY - JOUR AU - Iwasaki, Kenji AU - Szabó, Milán AU - Tamburic, Bojan AU - Evenhuis, Christian AU - Zavafer, Alonso AU - Kuzhiumparambil, Unnikrishnan AU - Ralph, Peter TI - Investigating the impact of light quality on macromolecular of Chaetoceros muelleri JF - FUNCTIONAL PLANT BIOLOGY J2 - FUNCT PLANT BIOL VL - 49 PY - 2022 IS - 5-6 Special Issue SP - 554 EP - 564 PG - 11 SN - 1445-4408 DO - 10.1071/FP21131 UR - https://m2.mtmt.hu/api/publication/32473846 ID - 32473846 N1 - Funding Agency and Grant Number: Climate Change Cluster (C3) of the University of Technology Sydney (Australia) Funding text: This work was supported by funding from the Climate Change Cluster (C3) of the University of Technology Sydney (Australia). AB - Diatoms (Bacillariophyceae) are important to primary productivity of aquatic ecosystems. This algal group is also a valuable source of high value compounds that are utilised as aquaculture feed. The productivity of diatoms is strongly driven by light and CO2 availability, and macro- and micronutrient concentrations. The light dependency of biomass productivity and metabolite composition is well researched in diatoms, but information on the impact of light quality, particularly the productivity return on energy invested when using different monochromatic light sources, remains scarce. In this work, the productivity return on energy invested of improving growth rate, photosynthetic activity, and metabolite productivity of the diatom Chaetoceros muelleri under defined wavelengths (blue, red, and green) as well as while light is analysed. By adjusting the different light qualities to equal photosynthetically utilisable radiation, it was found that the growth rate and photosynthetic oxygen evolution was unchanged under white, blue, and green light, but it was lower under red light. Blue light improved the productivity return on energy invested for biomass, total protein, total lipid, total carbohydrate, and in fatty acids production, which would suggest that blue light should be used for aquaculture feed production. LA - English DB - MTMT ER - TY - JOUR AU - Patil, Priyanka Pradeep AU - Mohammad Aslam, Sabit AU - Vass, Imre AU - Szabó, Milán TI - Characterization of the wave phenomenon of flash-induced chlorophyll fluorescence in Chlamydomonas reinhardtii JF - PHOTOSYNTHESIS RESEARCH J2 - PHOTOSYNTH RES VL - 152 PY - 2022 SP - 235 EP - 244 PG - 10 SN - 0166-8595 DO - 10.1007/s11120-022-00900-3 UR - https://m2.mtmt.hu/api/publication/32677799 ID - 32677799 N1 - Funding Agency and Grant Number: ELKH Biological Research Center; National Research, Development and Innovation OfficeNational Research, Development & Innovation Office (NRDIO) - Hungary [NKFIH FK128977]; Hungarian Academy of Sciences, MTA Premium Postdoctoral Research Program [PREMIUM-2017-38] Funding text: Open access funding provided by ELKH Biological Research Center. The work was supported by the National Research, Development and Innovation Office (NKFIH FK128977) and the Hungarian Academy of Sciences, MTA Premium Postdoctoral Research Program (Grant ID: PREMIUM-2017-38). AB - Flash-induced chlorophyll fluorescence relaxation is a powerful tool to monitor the reoxidation reactions of the reduced primary quinone acceptor, QA− by QB and the plastoquinone (PQ) pool, as well as the charge recombination reactions between the donor and acceptor side components of Photosystem II (PSII). Under certain conditions, when the PQ pool is highly reduced (e.g. in microaerobic conditions), a wave phenomenon appears in the fluorescence relaxation kinetics, which reflects the transient reoxidation and re-reduction of QA− by various electron transfer processes, which in cyanobacteria is mediated by NAD(P)H dehydrogenase (NDH-1). The wave phenomenon was also observed and assigned to the operation of type 2 NAD(P)H dehydrogenase (NDH-2) in the green alga Chlamydomonas reinhardtii under hydrogen-producing conditions, which required a long incubation of algae under sulphur deprivation (Krishna et al. J Exp Bot 70 (21):6321–6336, 2019). However, the conditions that induce the wave remained largely uncharacterized so far in microalgae. In this work, we investigated the wave phenomenon in Chlamydomonas reinhardtii under conditions that lead to a decrease of PSII activity by applying hydroxylamine treatment, which impacts the donor side of PSII in combination with a strongly reducing environment of the PQ pool (microaerobic conditions). A similar wave phenomenon could be induced by photoinhibitory conditions (illumination with strong light in the presence of the protein synthesis inhibitor lincomycin). These results indicate that the fluorescence wave phenomenon is activated in green algae when the PSII activity decreases relative to Photosystem I (PS I) activity and the PQ pool is strongly reduced. Therefore, the fluorescence wave could be used as a sensitive indicator of altered intersystem electron transfer processes, e.g. under stress conditions. LA - English DB - MTMT ER - TY - JOUR AU - Patil, Priyanka Pradeep AU - Vass, Imre AU - Szabó, Milán TI - Characterization of the Wave Phenomenon in Flash-Induced Fluorescence Relaxation and Its Application to Study Cyclic Electron Pathways in Microalgae JF - INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES J2 - INT J MOL SCI VL - 23 PY - 2022 IS - 9 SN - 1661-6596 DO - 10.3390/ijms23094927 UR - https://m2.mtmt.hu/api/publication/32799849 ID - 32799849 N1 - Funding Agency and Grant Number: National Research, Development and Innovation Office [FK128977]; Hungarian Academy of Sciences, MTA Premium Postdoctoral Research Program [PREMIUM-2017-38] Funding text: This research was funded by the National Research, Development and Innovation Office, grant number FK128977 and the Hungarian Academy of Sciences, MTA Premium Postdoctoral Research Program, grant number PREMIUM-2017-38. The APC was funded by National Research, Development and Innovation Office, grant number FK128977. AB - Photosynthesis is a series of redox reactions, in which several electron transport processes operate to provide the energetic balance of light harvesting. In addition to linear electron flow, which ensures the basic functions of photosynthetic productivity and carbon fixation, alternative electron transport pathways operate, such as the cyclic electron flow (CEF), which play a role in the fine tuning of photosynthesis and balancing the ATP/NADPH ratio under stress conditions. In this work, we characterized the electron transport processes in microalgae species that have high relevance in applied research and industry (e.g., Chlorella sorokiniana, Haematococcus pluvialis, Dunaliella salina, Nannochloropsis sp.) by using flash-induced fluorescence relaxation kinetics. We found that a wave phenomenon appeared in the fluorescence relaxation profiles of microalgae to different extents; it was remarkable in the red cells of H. pluvialis, D. salina and C. sorokiniana, but it was absent in green cells of H. pluvialis and N. limnetica. Furthermore, in microalgae, unlike in cyanobacteria, the appearance of the wave required the partial decrease in the activity of Photosystem II, because the relatively high Photosystem II/Photosystem I ratio in microalgae prevented the enhanced oxidation of the plastoquinone pool. The wave phenomenon was shown to be related to the antimycin A-sensitive pathway of CEF in C. sorokiniana but not in other species. Therefore, the fluorescence wave phenomenon appears to be a species-specific indicator of the redox reactions of the plastoquinone pool and certain pathways of cyclic electron flow. LA - English DB - MTMT ER -