Cytokinins modulate a number of important developmental processes, including the last phase of leaf development, known as senescence, which is associated with chlorophyll breakdown, photosynthetic apparatus disintegration and oxidative damage. There is ample evidence that cytokinins can slow down all these senescence-accompanying changes. Here, we review relationships between the various mechanisms of action of these regulatory molecules. We highlight their connection to photosynthesis, the pivotal process that generates assimilates, however may also lead to oxidative damage. Thus, we also focus on cytokinin induction of protective responses against oxidative damage. Activation of antioxidative enzymes in senescing tissues is described as well as changes in the levels of naturally occurring antioxidative compounds, such as phenolic acids and flavonoids, in plant explants. The main goal of this review is to show how the biological activities of cytokinins may be related to their chemical structure. New links between molecular aspects of natural cytokinins and their synthetic derivatives with antisenescent properties are described. Structural motifs in cytokinin molecules that may explain why these molecules play such a significant regulatory role are outlined.

• Klíčová slova
• antioxidant, antioxidant enzymes, antisenescent, cytokinin, derivative, genes, photosynthesis, plant defence, structure and activity relationship,
• MeSH
• antioxidancia chemie   metabolismus   MeSH
• cytokininy chemie   metabolismus   MeSH
• flavonoidy analýza   MeSH
• fotosyntéza MeSH
• listy rostlin chemie   růst a vývoj   fyziologie   MeSH
• molekulární struktura MeSH
• rostliny chemie   MeSH
• vývoj rostlin MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• antioxidancia MeSH
• cytokininy MeSH
• flavonoidy MeSH

Amaranthus retroflexus L. (redroot pigweed) is one of the most problematic weeds in maize, sugar beet, vegetables, and soybean crop fields in Europe. Two pigweed amaranth biotypes (R1 and R2) from the Czech Republic resistant to photosystem II (PSII)-inhibiting herbicides were analyzed in this study. This study aimed to identify the genetic mechanisms that underlie the resistance observed in the biotypes. Additionally, we also intended to establish the use of chlorophyll fluorescence measurement as a rapid and reliable method for confirming herbicide resistance in this weed species. Both biotypes analyzed showed high resistance factors in a dose-response study and were thus confirmed to be resistant to PSII-inhibiting herbicides. A sequence analysis of the D1 protein revealed a well-known Ser-Gly substitution at amino acid position 264 in both biotypes. Molecular docking studies, along with the wild-type and mutant D1 protein's secondary structure analyses, revealed that the S264G mutation did not reduce herbicide affinity but instead indirectly affected the interaction between the target protein and the herbicides. The current study identified the S264G mutation as being responsible for conferring herbicide resistance in the pigweed amaranth biotypes. These findings can provide a strong basis for future studies that might use protein structure and mutation-based approaches to gain further insights into the detailed mechanisms of resistance in this weed species. In many individuals from both biotypes, resistance at a very early stage (BBCH10) of plants was demonstrated several hours after the application of the active ingredients by the chlorophyll fluorescence method. The effective PS II quantum yield parameter can be used as a rapid diagnostic tool for distinguishing between sensitive and resistant plants on an individual level. This method can be useful for identifying herbicide-resistant weed biotypes in the field, which can help farmers and weed management practitioners develop more effective weed control tactics.

• Klíčová slova
• D1 protein mutations, chlorophyll fluorescence, molecular docking,
• MeSH
• amarant * genetika   účinky léků   růst a vývoj   MeSH
• fotosystém II - proteinový komplex * genetika   metabolismus   MeSH
• herbicidy * farmakologie   MeSH
• mutace MeSH
• plevel genetika   účinky léků   MeSH
• rezistence k herbicidům * genetika   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• simulace molekulového dockingu MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH
• Názvy látek
• fotosystém II - proteinový komplex * MeSH
• herbicidy * MeSH
• rostlinné proteiny MeSH

There are two main types of bacterial photosynthesis: oxygenic (cyanobacteria) and anoxygenic (sulfur and non-sulfur phototrophs). Molecular mechanisms of photosynthesis in the phototrophic microorganisms can differ and depend on their location and pigments in the cells. This paper describes bacteria capable of molecular oxidizing hydrogen sulfide, specifically the families Chromatiaceae and Chlorobiaceae, also known as purple and green sulfur bacteria in the process of anoxygenic photosynthesis. Further, it analyzes certain important physiological processes, especially those which are characteristic for these bacterial families. Primarily, the molecular metabolism of sulfur, which oxidizes hydrogen sulfide to elementary molecular sulfur, as well as photosynthetic processes taking place inside of cells are presented. Particular attention is paid to the description of the molecular structure of the photosynthetic apparatus in these two families of phototrophs. Moreover, some of their molecular biotechnological perspectives are discussed.

• Klíčová slova
• anaerobes, anoxygenic bacteria, detoxification, hydrogen sulfide, molecular mechanisms of photosynthesis, water environment,
• MeSH
• anaerobióza MeSH
• Chlorobi klasifikace   genetika   fyziologie   MeSH
• Chromatiaceae klasifikace   genetika   fyziologie   MeSH
• fototrofní procesy genetika   MeSH
• fylogeneze MeSH
• síra metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• síra MeSH

Cyanobacteria hold great potential to revolutionize conventional industries and farming practices with their light-driven chemical production. To fully exploit their photosynthetic capacity and enhance product yield, it is crucial to investigate their intricate interplay with the environment including the light intensity and spectrum. Mathematical models provide valuable insights for optimizing strategies in this pursuit. In this study, we present an ordinary differential equation-based model for the cyanobacterium Synechocystis sp. PCC 6803 to assess its performance under various light sources, including monochromatic light. Our model can reproduce a variety of physiologically measured quantities, e.g. experimentally reported partitioning of electrons through four main pathways, O2 evolution, and the rate of carbon fixation for ambient and saturated CO2. By capturing the interactions between different components of a photosynthetic system, our model helps in understanding the underlying mechanisms driving system behavior. Our model qualitatively reproduces fluorescence emitted under various light regimes, replicating Pulse-amplitude modulation (PAM) fluorometry experiments with saturating pulses. Using our model, we test four hypothesized mechanisms of cyanobacterial state transitions for ensemble of parameter sets and found no physiological benefit of a model assuming phycobilisome detachment. Moreover, we evaluate metabolic control for biotechnological production under diverse light colors and irradiances. We suggest gene targets for overexpression under different illuminations to increase the yield. By offering a comprehensive computational model of cyanobacterial photosynthesis, our work enhances the basic understanding of light-dependent cyanobacterial behavior and sets the first wavelength-dependent framework to systematically test their producing capacity for biocatalysis.

• MeSH
• biologické modely * MeSH
• fotosyntéza * fyziologie   MeSH
• fykobilizomy metabolismus   MeSH
• koloběh uhlíku fyziologie   MeSH
• oxid uhličitý metabolismus   MeSH
• počítačová simulace MeSH
• světlo * MeSH
• Synechocystis * metabolismus   fyziologie   MeSH
• výpočetní biologie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fykobilizomy MeSH
• oxid uhličitý MeSH

Here, we report an effect of short acclimation to a wide span of temperatures on photosynthetic electron transfer, lipid and fatty acid composition in the snow alga Chlamydomonas cf. nivalis. The growth and oxygen evolution capacity were low at 2 °C yet progressively enhanced at 10 °C and were significantly higher at temperatures from 5 to 15 °C in comparison with the mesophilic control Chlamydomonas reinhardtii. In search of the molecular mechanisms responsible for the adaptation of photosynthesis to low temperatures, we have found unprecedented high rates of QA to QB electron transfer. The thermodynamics of the process revealed the existence of an increased structural flexibility that we explain with the amino acid changes in the D1 protein combined with the physico-chemical characteristics of the thylakoid membrane composed of > 80% negatively charged phosphatidylglycerol.

• Klíčová slova
• Chlamydomonas, electron transfer, phosphatidylglycerol, photosystem II, snow algae, temperature adaptation,
• MeSH
• chinony metabolismus   MeSH
• Chlamydomonas růst a vývoj   metabolismus   MeSH
• fotosyntéza * MeSH
• fotosystém II - proteinový komplex chemie   metabolismus   MeSH
• fyziologická adaptace MeSH
• intracelulární membrány metabolismus   MeSH
• konzervovaná sekvence MeSH
• kyslík metabolismus   MeSH
• lipidy MeSH
• metabolismus lipidů MeSH
• molekulární sekvence - údaje MeSH
• nízká teplota MeSH
• sekvence aminokyselin MeSH
• teplota MeSH
• termodynamika MeSH
• transport elektronů MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chinony MeSH
• fotosystém II - proteinový komplex MeSH
• kyslík MeSH
• lipidy MeSH

Photosystem II (PSII) is a multisubunit protein complex in cyanobacteria, algae and plants that use light energy for oxidation of water and reduction of plastoquinone. The conversion of excitation energy absorbed by chlorophylls into the energy of separated charges and subsequent water-plastoquinone oxidoreductase activity are inadvertently coupled with the formation of reactive oxygen species (ROS). Singlet oxygen is generated by the excitation energy transfer from triplet chlorophyll formed by the intersystem crossing from singlet chlorophyll and the charge recombination of separated charges in the PSII antenna complex and reaction center of PSII, respectively. Apart to the energy transfer, the electron transport associated with the reduction of plastoquinone and the oxidation of water is linked to the formation of superoxide anion radical, hydrogen peroxide and hydroxyl radical. To protect PSII pigments, proteins and lipids against the oxidative damage, PSII evolved a highly efficient antioxidant defense system comprising either a non-enzymatic (prenyllipids such as carotenoids and prenylquinols) or an enzymatic (superoxide dismutase and catalase) scavengers. It is pointed out here that both the formation and the scavenging of ROS are controlled by the energy level and the redox potential of the excitation energy transfer and the electron transport carries, respectively. The review is focused on the mechanistic aspects of ROS production and scavenging by PSII. This article is part of a Special Issue entitled: Photosystem II.

• MeSH
• fotosystém II - proteinový komplex chemie   metabolismus   MeSH
• molekulární modely MeSH
• oxidace-redukce MeSH
• přenos energie MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• scavengery volných radikálů metabolismus   MeSH
• transport elektronů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• fotosystém II - proteinový komplex MeSH
• reaktivní formy kyslíku MeSH
• scavengery volných radikálů MeSH

Grass pea (Lathyrus sativus) is a leguminous plant of outstanding tolerance to abiotic stress. The aim of the presented study was to describe the mechanism of grass pea (Lathyrus sativus L.) photosynthetic apparatus acclimatisation strategies to salinity stress. The seedlings were cultivated in a hydroponic system in media containing various concentrations of NaCl (0, 50, and 100 mM), imitating none, moderate, and severe salinity, respectively, for three weeks. In order to characterise the function and structure of the photosynthetic apparatus, Chl a fluorescence, gas exchange measurements, proteome analysis, and Fourier-transform infrared spectroscopy (FT-IR) analysis were done inter alia. Significant differences in the response of the leaf and stem photosynthetic apparatus to severe salt stress were observed. Leaves became the place of harmful ion (Na+) accumulation, and the efficiency of their carboxylation decreased sharply. In turn, in stems, the reconstruction of the photosynthetic apparatus (antenna and photosystem complexes) activated alternative electron transport pathways, leading to effective ATP synthesis, which is required for the efficient translocation of Na+ to leaves. These changes enabled efficient stem carboxylation and made them the main source of assimilates. The observed changes indicate the high plasticity of grass pea photosynthetic apparatus, providing an effective mechanism of tolerance to salinity stress.

• Klíčová slova
• Lathyrus sativus, ROS, cyclic electron transport, linear electron transport, photosynthetic apparatus, photosystem I, photosystem II, salt stress,
• MeSH
• aklimatizace * MeSH
• fotosyntéza * MeSH
• fyziologický stres MeSH
• Lathyrus fyziologie   MeSH
• salinita * MeSH
• semenáček fyziologie   MeSH
• solný stres MeSH
• stonky rostlin fyziologie   MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH

Banana is one of the most important food and fruit crops in the world and its growth is ceasing at 10-17 °C. However, the mechanisms determining the tolerance of banana to mild (>15 °C) and moderate chilling (10-15 °C) are elusive. Furthermore, the biochemical controls over the photosynthesis in tropical plant species at low temperatures above 10 °C is not well understood. The purpose of this research was to reveal the response of chilling-sensitive banana to mild (16 °C) and moderate chilling stress (10 °C) at the molecular (transcripts, proteins) and physiological levels. The results showed different transcriptome responses between mild and moderate chilling stresses, especially in pathways of plant hormone signal transduction, ABC transporters, ubiquinone, and other terpenoid-quinone biosynthesis. Interestingly, functions related to carbon fixation were assigned preferentially to upregulated genes/proteins, while photosynthesis and photosynthesis-antenna proteins were downregulated at 10 °C, as revealed by both digital gene expression and proteomic analysis. These results were confirmed by qPCR and immunofluorescence labeling methods. Conclusion: Banana responded to the mild chilling stress dramatically at the molecular level. To compensate for the decreased photosynthesis efficiency caused by mild and moderate chilling stresses, banana accelerated its carbon fixation, mainly through upregulation of phosphoenolpyruvate carboxylases.

• Klíčová slova
• banana (Musa spp. AAA), carbon fixation, immunofluorescence labeling, mild chilling, phosphoenolpyruvate carboxylases, photosynthesis,
• MeSH
• banánovník genetika   metabolismus   MeSH
• fosfoenolpyruvátkarboxylasa genetika   metabolismus   MeSH
• fotosyntéza * MeSH
• reakce na chladový šok * MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• transkriptom * MeSH
• upregulace MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fosfoenolpyruvátkarboxylasa MeSH
• rostlinné proteiny MeSH

Carotenoids are naturally occurring pigments that absorb light in the spectral region in which the sun irradiates maximally. These molecules transfer this energy to chlorophylls, initiating the primary photochemical events of photosynthesis. Carotenoids also regulate the flow of energy within the photosynthetic apparatus and protect it from photoinduced damage caused by excess light absorption. To carry out these functions in nature, carotenoids are bound in discrete pigment-protein complexes in the proximity of chlorophylls. A few three-dimensional structures of these carotenoid complexes have been determined by X-ray crystallography. Thus, the stage is set for attempting to correlate the structural information with the spectroscopic properties of carotenoids to understand the molecular mechanism(s) of their function in photosynthetic systems. In this Account, we summarize current spectroscopic data describing the excited state energies and ultrafast dynamics of purified carotenoids in solution and bound in light-harvesting complexes from purple bacteria, marine algae, and green plants. Many of these complexes can be modified using mutagenesis or pigment exchange which facilitates the elucidation of correlations between structure and function. We describe the structural and electronic factors controlling the function of carotenoids as energy donors. We also discuss unresolved issues related to the nature of spectroscopically dark excited states, which could play a role in light harvesting. To illustrate the interplay between structural determinations and spectroscopic investigations that exemplifies work in the field, we describe the spectroscopic properties of four light-harvesting complexes whose structures have been determined to atomic resolution. The first, the LH2 complex from the purple bacterium Rhodopseudomonas acidophila, contains the carotenoid rhodopin glucoside. The second is the LHCII trimeric complex from higher plants which uses the carotenoids lutein, neoxanthin, and violaxanthin to transfer energy to chlorophyll. The third, the peridinin-chlorophyll-protein (PCP) from the dinoflagellate Amphidinium carterae, is the only known complex in which the bound carotenoid (peridinin) pigments outnumber the chlorophylls. The last is xanthorhodopsin from the eubacterium Salinibacter ruber. This complex contains the carotenoid salinixanthin, which transfers energy to a retinal chromophore. The carotenoids in these pigment-protein complexes transfer energy with high efficiency by optimizing both the distance and orientation of the carotenoid donor and chlorophyll acceptor molecules. Importantly, the versatility and robustness of carotenoids in these light-harvesting pigment-protein complexes have led to their incorporation in the design and synthesis of nanoscale antenna systems. In these bioinspired systems, researchers are seeking to improve the light capture and use of energy from the solar emission spectrum.

• MeSH
• chlorofyl chemie   metabolismus   MeSH
• Dinoflagellata chemie   metabolismus   MeSH
• Eukaryota metabolismus   MeSH
• fotosyntéza * fyziologie   MeSH
• glukosidy MeSH
• glykosidy MeSH
• karotenoidy * chemie   metabolismus   MeSH
• lutein chemie   metabolismus   MeSH
• přenos energie MeSH
• Rhodopseudomonas metabolismus   MeSH
• světlo MeSH
• světlosběrné proteinové komplexy * chemie   metabolismus   MeSH
• tylakoidy metabolismus   MeSH
• xanthofyly metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• chlorofyl MeSH
• glukosidy MeSH
• glykosidy MeSH
• karotenoidy * MeSH
• lutein MeSH
• neoxanthin MeSH Prohlížeč
• peridinin MeSH Prohlížeč
• rhodopin glucoside MeSH Prohlížeč
• salinixanthin MeSH Prohlížeč
• světlosběrné proteinové komplexy * MeSH
• violaxanthin MeSH Prohlížeč
• xanthofyly MeSH

Antenna proteins play a major role in the regulation of light-harvesting in photosynthesis. However, less is known about a possible link between their sizes (oligomerization state) and fluorescence intensity (number of photons emitted). Here, we used a microscopy-based method, Fluorescence Correlation Spectroscopy (FCS), to analyze different antenna proteins at the particle level. The direct comparison indicated that Chromera Light Harvesting (CLH) antenna particles (isolated from Chromera velia) behaved as the monomeric Light Harvesting Complex II (LHCII) (from higher plants), in terms of their radius (based on the diffusion time) and fluorescence yields. FCS data thus indicated a monomeric oligomerization state of algal CLH antenna (at our experimental conditions) that was later confirmed also by biochemical experiments. Additionally, our data provide a proof of concept that the FCS method is well suited to measure proteins sizes (oligomerization state) and fluorescence intensities (photon counts) of antenna proteins per single particle (monomers and oligomers). We proved that antenna monomers (CLH and LHCIIm) are more "quenched" than the corresponding trimers. The FCS measurement thus represents a useful experimental approach that allows studying the role of antenna oligomerization in the mechanism of photoprotection.

• Klíčová slova
• Chromera velia, antenna proteins, fluorescence correlation spectroscopy, light-harvesting, microscopy, photosynthesis, protein diffusion, protein oligomerization,
• MeSH
• bílkoviny řas chemie   metabolismus   MeSH
• fluorescence * MeSH
• fluorescenční spektrometrie MeSH
• fotosyntéza * MeSH
• kinetika MeSH
• multimerizace proteinu MeSH
• transport proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bílkoviny řas MeSH