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Biomolecules Mar 2024A Type I reaction center (RC) (Fe-S type, ferredoxin reducing) is found in several phyla containing anoxygenic phototrophic bacteria. These include the heliobacteria... (Review)
Review
A Type I reaction center (RC) (Fe-S type, ferredoxin reducing) is found in several phyla containing anoxygenic phototrophic bacteria. These include the heliobacteria (HB), the green sulfur bacteria (GSB), and the chloracidobacteria (CB), for which high-resolution homodimeric RC-photosystem (PS) structures have recently appeared. The 2.2-Å X-ray structure of the RC-PS of revealed that the core PshA apoprotein (PshA-1 and PshA-2 homodimeric pair) exhibits a structurally conserved PSI arrangement comprising five C-terminal transmembrane α-helices (TMHs) forming the RC domain and six N-terminal TMHs coordinating the light-harvesting (LH) pigments. The structure lacked quinone molecules, indicating that electrons were transferred directly from the A (8-OH-chlorophyll (Chl) ) acceptor to the F [4Fe-4S] component, serving as the terminal RC acceptor. A pair of additional TMHs designated as Psh X were also found that function as a low-energy antenna. The 2.5-Å resolution cryo-electron microscopy (cryo-EM) structure for the RC-PS of the green sulfur bacterium included a pair of Fenna-Matthews-Olson protein (FMO) antennae, which transfer excitations from the chlorosomes to the RC-PS (PscA-1 and PscA-2) core. A pair of cytochromes (PscC) molecules was also revealed, acting as electron donors to the RC bacteriochlorophyll (BChl) ' special pair, as well as PscB, housing the [4Fe-4S] cluster F and F, and the associated PscD protein. While the FMO components were missing from the 2.6-Å cryo-EM structure of the Zn- (BChl) ' special pair containing RC-PS of , a unique architecture was revealed that besides the (PscA) core, consisted of seven additional subunits including PscZ in place of PscD, the PscX and PscY cytochrome serial electron donors and four low mol. wt. subunits of unknown function. Overall, these diverse structures have revealed that (i) the HB RC-PS is the simplest light-energy transducing complex yet isolated and represents the closest known homolog to a common homodimeric RC-PS ancestor; (ii) the symmetrically localized Ca-binding sites found in each of the Type I homodimeric RC-PS structures likely gave rise to the analogously positioned MnCaO cluster of the PSII RC and the Tyr RC donor site; (iii) a close relationship between the GSB RC-PS and the PSII Chl proteins (CP)43 and CP47 was demonstrated by their strongly conserved LH-(B)Chl localizations; (iv) LH-BChls of the GSB-RC-PS are also localized in the conserved RC-associated positions of the PSII Chl and Chl sites; (v) glycosylated carotenoids of the GSB RC-PS are located in the homologous carotenoid-containing positions of PSII, reflecting an O-tolerance mechanism capable of sustaining early stages in the evolution of oxygenic photosynthesis. In addition to the close relationships found between the homodimeric RC-PS and PSII, duplication of the gene encoding the ancestral Type I RC apoprotein, followed by genetic divergence, may well account for the appearance of the heterodimeric Type I and Type II RCs of the extant oxygenic phototrophs. Accordingly, the long-held view that PSII arose from the anoxygenic Type II RC is now found to be contrary to the new evidence provided by Type I RC-PS homodimer structures, indicating that the evolutionary origins of anoxygenic Type II RCs, along with their distinct antenna rings are likely to have been preceded by the events that gave rise to their oxygenic counterparts.
Topics: Chlorobi; Photosynthetic Reaction Center Complex Proteins; Cryoelectron Microscopy; Bacteria; Apoproteins; Bacterial Proteins
PubMed: 38540731
DOI: 10.3390/biom14030311 -
Plant Physiology Nov 2020Blue light regulates multiple processes that optimize light capture and gas exchange in plants, including chloroplast movement, changes in stomatal conductance, and... (Comparative Study)
Comparative Study
Blue light regulates multiple processes that optimize light capture and gas exchange in plants, including chloroplast movement, changes in stomatal conductance, and altered organ positioning. In Arabidopsis (), these processes are primarily modulated by the blue light phototropin photoreceptors phot1 and phot2. Changes in leaf positioning and shape involve several signaling components that include NON-PHOTOTROPIC HYPOCOTYL3, PHYTOCHROME KINASE SUBSTRATE, ROOT PHOTOTROPISM2, and alterations in localized auxin streams. Direct phosphorylation of the auxin transporter ATP-BINDING CASSETTE subfamily B19 (ABCB19) by phot1 in phototropic seedlings suggests that phot1 may directly regulate ABCB19 to adjust auxin-dependent leaf responses. Here, mutants were analyzed for fluence and blue light-dependent changes in leaf positioning and morphology. displays upright petiole angles that remain unchanged in response to red and blue light. Similarly, mutants develop irregularly wavy rosette leaves that are less sensitive to blue light-mediated leaf flattening. Visualization of auxin distribution, measurement of auxin transport in protoplasts, and direct quantification of free auxin levels suggest these irregularities are caused by misregulation of ABCB19-mediated auxin distribution in addition to light-dependent auxin biosynthesis.
Topics: ATP-Binding Cassette Transporters; Arabidopsis; Gene Expression Regulation, Plant; Genes, Plant; Genetic Variation; Genotype; Hypocotyl; Light; Phototropism; Phytochrome; Plant Leaves
PubMed: 32855213
DOI: 10.1104/pp.20.00223 -
BioRxiv : the Preprint Server For... Feb 2024Optimal imaging strategies remain underdeveloped to maximize information for fluorescence microscopy while minimizing the harm to fragile living systems. Taking hint...
Optimal imaging strategies remain underdeveloped to maximize information for fluorescence microscopy while minimizing the harm to fragile living systems. Taking hint from the supercontinuum generation in ultrafast laser physics, we generated supercontinuum fluorescence from untreated unlabeled live samples before nonlinear photodamage onset. Our imaging achieved high-content cell phenotyping and tissue histology, identified bovine embryo polarization, quantified aging-related stress across cell types and species, demystified embryogenesis before and after implantation, sensed drug cytotoxicity in real-time, scanned brain area for targeted patching, optimized machine learning to track small moving organisms, induced two-photon phototropism of leaf chloroplasts under two-photon photosynthesis, unraveled microscopic origin of autumn colors, and interrogated intestinal microbiome. The results enable a facility-type microscope to freely explore vital molecular biology across life sciences.
PubMed: 38328159
DOI: 10.1101/2024.01.26.577383 -
Scientific Reports Feb 2021The sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical...
The sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the "fibril reorientation and slippage" hypothesis, global biophysical equations, and local statistical biophysical models are discussed.
Topics: Biological Phenomena; Biophysics; Cell Wall; Gravitropism; Light; Models, Biological; Phototropism; Phycomyces
PubMed: 33574466
DOI: 10.1038/s41598-021-83254-5 -
Toxins Sep 2020[D-Leu]MC-LR and MC-LR, two microcystins differing in one amino acid, constitute a sanitary and environmental problem owing to their frequent and concomitant presence in... (Comparative Study)
Comparative Study
[D-Leu]MC-LR and MC-LR: A Small-Large Difference: Significantly Different Effects on L. (Fabaceae) Growth and Phototropic Response after Single Contact during Imbibition with Each of These Microcystin Variants.
[D-Leu]MC-LR and MC-LR, two microcystins differing in one amino acid, constitute a sanitary and environmental problem owing to their frequent and concomitant presence in water bodies of the Americas and their association with human intoxication during recreational exposure to cyanobacterial bloom. Present in reservoirs used for irrigation as well, they can generate problems in the development of crops such as , of nutritional and economic interest to the region. Although numerous works address the toxic effects of MC-LR, information on the toxicity of [D-Leu]MC-LR is limited. Our objective was to study the toxic effects of [D-Leu]MC-LR and MC-LR (3.5 µg/ml) on after a single contact at the imbibition stage. Our findings indicate that 10 days post treatment, [D-Leu]MC-LR generates morphological and physiological alterations more pronounced than those caused by MC-LR. In addition to the alterations produced by [D-Leu]MC-LR in the development of seedlings and the structure of the leaves, roots and stems, we also found alterations in leaf stomatal density and conductivity, a longer delay in the phototropic response and a decrease in the maximum curvature angles achieved with respect to that observed for MC-LR. Our findings indicate that these alterations are linked to the greater inhibition of phosphatase activity generated by [D-Leu]MC-LR, rather than to oxidative damage. We observed that 30 days after treatment with MC-LR, plants presented better development and recovery than those treated with [D-Leu]MC-LR. Further studies are required on [D-Leu]MC-LR and MC-LR toxicity and their underlying mechanisms of action.
Topics: Lipid Peroxidation; Marine Toxins; Microcystins; Oxidative Stress; Phaseolus; Phosphoprotein Phosphatases; Phototrophic Processes; Plant Development; Plant Proteins; Time Factors
PubMed: 32932764
DOI: 10.3390/toxins12090585 -
PloS One 2021Photo-induced behavioral responses (photobehaviors) are crucial to the survival of motile phototrophic organisms in changing light conditions. Volvocine green algae are...
Photo-induced behavioral responses (photobehaviors) are crucial to the survival of motile phototrophic organisms in changing light conditions. Volvocine green algae are excellent model organisms for studying the regulatory mechanisms of photobehavior. We recently reported that unicellular Chlamydomonas reinhardtii and multicellular Volvox rousseletii exhibit similar photobehaviors, such as phototactic and photoshock responses, via different ciliary regulations. To clarify how the regulatory systems have changed during the evolution of multicellularity, we investigated the photobehaviors of four-celled Tetrabaena socialis. Surprisingly, unlike C. reinhardtii and V. rousseletii, T. socialis did not exhibit immediate photobehaviors after light illumination. Electrophysiological analysis revealed that the T. socialis eyespot does not function as a photoreceptor. Instead, T. socialis exhibited slow accumulation toward the light source in a photosynthesis-dependent manner. Our assessment of photosynthetic activities showed that T. socialis chloroplasts possess higher photoprotection abilities against strong light than C. reinhardtii. These data suggest that C. reinhardtii and T. socialis employ different strategies to avoid high-light stress (moving away rapidly and gaining photoprotection, respectively) despite their close phylogenetic relationship.
Topics: Chlorophyta; Photic Stimulation; Phototropism; Volvox
PubMed: 34699573
DOI: 10.1371/journal.pone.0259138 -
International Journal of Molecular... Mar 2021Plants are exposed to numerous biotic and abiotic stresses, and light is one of the most important factors that influences the plant morphology. This study was carried...
Plants are exposed to numerous biotic and abiotic stresses, and light is one of the most important factors that influences the plant morphology. This study was carried out to examine how the lighting direction affected the plant morphology by investigating the growth parameters, epidermal cell elongation, stomatal properties, and physiological changes. Seedlings of two head lettuce ( L.) cultivars, Caesar Green and Polla, were subjected to a 12 h photoperiod with a 300 μmol·m·s photosynthetic photon flux density (PPFD) provided by light emitting diodes (LEDs) from three directions: the top, side, and bottom, relative to the plants. Compared with the top and side lighting, the bottom lighting increased the leaf angle and canopy by stimulating the epidermal cell elongation in leaf midrib, reduced the leaf number and root biomass, and induced large stomata with a low density, which is associated with reduced stomatal conductance and carbohydrate contents. However, the proline content and quantum yield exhibited no significant differences with the different lighting directions in both cultivars, which implies that the plants were under normal physiological conditions. In a conclusion, the lighting direction had a profound effect on the morphological characteristics of lettuce, where the plants adapted to the changing lighting environments.
Topics: Carbohydrate Metabolism; Chlorophyll; Gene Expression Regulation, Plant; Lactuca; Lighting; Photosynthesis; Plant Development; Plant Epidermis; Plant Leaves; Plant Physiological Phenomena; Plant Stomata; Quantitative Trait, Heritable
PubMed: 33808879
DOI: 10.3390/ijms22063157 -
The Plant Journal : For Cell and... May 2021Phototropins, the UVA-blue light photoreceptors, endow plants to detect the direction of light and optimize photosynthesis by regulating positioning of chloroplasts and...
Phototropins, the UVA-blue light photoreceptors, endow plants to detect the direction of light and optimize photosynthesis by regulating positioning of chloroplasts and stomatal gas exchange. Little is known about their functions in other developmental responses. A tomato Non-phototropic seedling1 (Nps1) mutant, bearing an Arg495His substitution in the vicinity of LOV2 domain in phototropin1, dominant-negatively blocks phototropin1 responses. The fruits of Nps1 mutant were enriched in carotenoids, particularly lycopene, compared with its parent, Ailsa Craig. On the contrary, CRISPR/CAS9-edited loss of function phototropin1 mutants displayed subdued carotenoids compared with the parent. The enrichment of carotenoids in Nps1 fruits is genetically linked with the mutation and exerted in a dominant-negative fashion. Nps1 also altered volatile profiles with high levels of lycopene-derived 6-methyl 5-hepten2-one. The transcript levels of several MEP and carotenogenesis pathway genes were upregulated in Nps1. Nps1 fruits showed altered hormonal profiles with subdued ethylene emission and reduced respiration. Proteome profiles showed a causal link between higher carotenogenesis and increased levels of protein protection machinery, which may stabilize proteins contributing to MEP and carotenogenesis pathways. The enhancement of carotenoid content by Nps1 in a dominant-negative fashion offers a potential tool for high lycopene-bearing hybrid tomatoes.
Topics: CRISPR-Associated Protein 9; CRISPR-Cas Systems; Carotenoids; Fruit; Gene Editing; Loss of Function Mutation; Solanum lycopersicum; Metabolic Networks and Pathways; Mutation; Phototropins
PubMed: 33608974
DOI: 10.1111/tpj.15206 -
Physical Chemistry Chemical Physics :... Jun 2021Photosensory receptors containing the flavin-binding light-oxygen-voltage (LOV) domain are modular proteins that fulfil a variety of biological functions ranging from...
Photosensory receptors containing the flavin-binding light-oxygen-voltage (LOV) domain are modular proteins that fulfil a variety of biological functions ranging from gene expression to phototropism. The LOV photocycle is initiated by blue-light and involves a cascade of intermediate species, including an electronically excited triplet state, that leads to covalent bond formation between the flavin mononucleotide (FMN) chromophore and a nearby cysteine residue. Subsequent conformational changes in the polypeptide chain arise due to the remodelling of the hydrogen bond network in the cofactor binding pocket, whereby a conserved glutamine residue plays a key role in coupling FMN photochemistry with LOV photobiology. Although the dark-to-light transition of LOV photosensors has been previously addressed by spectroscopy and computational approaches, the mechanistic basis of the underlying reactions is still not well understood. Here we present a detailed computational study of three distinct LOV domains: EL222 from Erythrobacter litoralis, AsLOV2 from the second LOV domain of Avena sativa phototropin 1, and RsLOV from Rhodobacter sphaeroides LOV protein. Extended protein-chromophore models containing all known crucial residues involved in the initial steps (femtosecond-to-microsecond) of the photocycle were employed. Energies and rotational barriers were calculated for possible rotamers and tautomers of the critical glutamine side chain, which allowed us to postulate the most energetically favoured glutamine orientation for each LOV domain along the assumed reaction path. In turn, for each evolving species, infrared difference spectra were constructed and compared to experimental EL222 and AsLOV2 transient infrared spectra, the former from original work presented here and the latter from the literature. The good agreement between theory and experiment permitted the assignment of the majority of observed bands, notably the ∼1635 cm-1 transient of the adduct state to the carbonyl of the glutamine side chain after rotation. Moreover, both the energetic and spectroscopic approaches converge in suggesting a facile glutamine flip at the adduct intermediate for EL222 and more so for AsLOV2, while for RsLOV the glutamine keeps its initial configuration. Additionally, the computed infrared shifts of the glutamine and interacting residues could guide experimental research addressing early events of signal transduction in LOV proteins.
Topics: Amino Acid Sequence; Avena; Cysteine; Flavin Mononucleotide; Glutamine; Hydrogen Bonding; Isomerism; Models, Molecular; Normal Distribution; Photochemical Processes; Phototropins; Protein Binding; Protein Conformation; Spectrophotometry, Infrared; Sphingomonadaceae; Structure-Activity Relationship; Thermodynamics
PubMed: 34142688
DOI: 10.1039/d1cp00447f -
Plants (Basel, Switzerland) Aug 2023Nowadays, not only the roots, but also leaves and flowers of ginseng are increasingly popular ingredients in supplements for healthcare products and traditional...
Nowadays, not only the roots, but also leaves and flowers of ginseng are increasingly popular ingredients in supplements for healthcare products and traditional medicine. The cultivation of the shade-loving crop, ginseng, is very demanding in terms of the light environment. Along with the intensity and duration, light direction is another important factor in regulating plant morphophysiology. In the current study, three lighting directions-top (T), side (S), or top + side (TS)-with an intensity of 30 ± 5 μmol·m·s photosynthetic photon flux density (PPFD) were employed. Generally, compared with the single T lighting, the composite lighting direction, TS, was more effective in shaping the ginseng with improved characteristics, including shortened, thick shoots; enlarged, thick leaves; more leaf trichomes; earlier flower bud formation; and enhanced photosynthesis. The single S light resulted in the worst growth parameters and strongly inhibited the flower bud formation, leading to the latest flower bud observation. Additionally, the S lighting acted as a positive factor in increasing the leaf thickness and number of trichomes on the leaf adaxial surface. However, the participation of the T lighting weakened these traits. Overall, the TS lighting was the optimal direction for improving the growth and development traits in ginseng. This preliminary research may provide new ideas and orientations in ginseng cultivation lodging resistance and improving the supply of ginseng roots, leaves, and flowers to the market.
PubMed: 37571002
DOI: 10.3390/plants12152849