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Marine Environmental Research Jun 2024This study investigated the physiological responses of two tropical seagrass species, Halophila ovalis and Thalassia hemprichii, to heat stress under varying light...
This study investigated the physiological responses of two tropical seagrass species, Halophila ovalis and Thalassia hemprichii, to heat stress under varying light conditions in a controlled 5-day experiment. The experimental design included four treatments: control, saturating light, heat stress under sub-saturating light, and heat stress under saturating light (combined stress). We assessed various parameters, including chlorophyll fluorescence, levels of reactive oxygen species (ROS), antioxidant enzyme activities, and growth rates. In H. ovalis, heat stress resulted in a significant reduction in the maximum quantum yield of photosystem II (F/F) regardless of the light condition. However, the effects of heat stress on the effective quantum yield of photosystem II (ɸPSII) were more pronounced under saturating light conditions. In T. hemprichii, saturating irradiance exacerbated the heat stress effects on F/F and ɸPSII, although the overall photoinhibition was less severe than in H. ovalis. Heat stress led to ROS accumulation in H. ovalis and reduced the activity of superoxide dismutase (SOD) and ascorbate peroxidase in the sub-saturating light condition. Conversely, T. hemprichii exhibited elevated SOD activity under saturating light. Heat stress suppressed the growth of both seagrass species, regardless of the light environment. The Biomarker Response Index indicated that H. ovalis displayed severe effects in the heat stress treatment under both light conditions, while T. hemprichii exhibited moderate effects in sub-saturating light and major effects in saturating light conditions. However, the Effect Addition Index revealed an antagonistic interaction between heat stress and high light in both seagrass species. This study underscores the intricate responses of seagrasses, emphasizing the importance of considering both local and global stressors when assessing their vulnerability.
PubMed: 38852494
DOI: 10.1016/j.marenvres.2024.106589 -
Scientific Reports Jun 2024Water eutrophication has emerged as a pressing concern for massive algal blooms, and these harmful blooms can potentially generate harmful toxins, which can...
Water eutrophication has emerged as a pressing concern for massive algal blooms, and these harmful blooms can potentially generate harmful toxins, which can detrimentally impact the aquatic environment and human health. Consequently, it is imperative to identify a safe and efficient approach to combat algal blooms to safeguard the ecological safety of water. This study aimed to investigate the procedure for extracting total flavonoids from Z. bungeanum residue and assess its antioxidant properties. The most favorable parameters for extracting total flavonoids from Z. bungeanum residue were a liquid-solid ratio (LSR) of 20 mL/g, a solvent concentration of 60%, an extraction period of 55 min, and an ultrasonic temperature of 80 °C. Meanwhile, the photosynthetic inhibitory mechanism of Z. bungeanum residue extracts against M. aeruginosa was assessed with a particular focus on the concentration-dependent toxicity effect. Z. bungeanum residue extracts damaged the oxygen-evolving complex structure, influenced energy capture and distribution, and inhibited the electron transport of PSII in M. aeruginosa. Furthermore, the enhanced capacity for ROS detoxification enables treated cells to sustain their photosynthetic activity. The findings of this study hold considerable relevance for the ecological management community and offer potential avenues for the practical utilization of resources in controlling algal blooms.
Topics: Microcystis; Flavonoids; Photosynthesis; Zanthoxylum; Plant Extracts; Antioxidants; Allelopathy; Harmful Algal Bloom; Reactive Oxygen Species; Photosystem II Protein Complex
PubMed: 38851826
DOI: 10.1038/s41598-024-64129-x -
Plant Physiology and Biochemistry : PPB Jul 2024Role of redox homeostasis in fruit ripening of Capsicum annuum L. with oxidative metabolism was studied. The research aims the ability to reduce agents during...
Role of redox homeostasis in fruit ripening of Capsicum annuum L. with oxidative metabolism was studied. The research aims the ability to reduce agents during postharvest storage on fruit for delayed ripening with the regulation of oxidative stress. Thus, we applied 10 mM reduced glutathione (GSH) to fruit as pretreatment followed by 1 mM hydrogen peroxide (HO) as ripening-inducing treatment and observed during 7 days of storage at 25 °C. A decrease in total soluble solid and firmness under HO was increased while dehydration in tissue was decreased by GSH pretreatment. Glutathione regulated the turnover of organic acids to reducing sugars with higher activity of NADP malic enzyme that sustained the fruit coat photosynthesis through chlorophyll fluorescence, pigment composition, and photosystem II activity. Malondialdehyde accumulation was inversely correlated with GSH content and antioxidative enzyme activity that reduced loss of cell viability. Conclusively, regulation of oxidative stress with GSH may be effective in the extension of shelf life under postharvest storage.
Topics: Capsicum; Glutathione; Fruit; Oxidation-Reduction; Hydrogen Peroxide; Secondary Metabolism; Oxidative Stress; Food Storage; Malondialdehyde; Photosynthesis; Antioxidants
PubMed: 38850727
DOI: 10.1016/j.plaphy.2024.108789 -
BMC Plant Biology Jun 2024The phosphorylation of the Light-Harvesting Complex of photosystem II (LHCII) driven by STATE TRANSITION 7 (STN7) kinase is a part of one of the crucial regulatory...
BACKGROUND
The phosphorylation of the Light-Harvesting Complex of photosystem II (LHCII) driven by STATE TRANSITION 7 (STN7) kinase is a part of one of the crucial regulatory mechanisms of photosynthetic light reactions operating in fluctuating environmental conditions, light in particular. There are evidenced that STN7 can also be activated without light as well as in dark-chilling conditions. However, the biochemical mechanism standing behind this complex metabolic pathway has not been deciphered yet.
RESULTS
In this work, we showed that dark-chilling induces light-independent LHCII phosphorylation in runner bean (Phaseolus coccineus L.). In dark-chilling conditions, we registered an increased reduction of the PQ pool which led to activation of STN7 kinase, subsequent LHCII phosphorylation, and possible LHCII relocation inside the thylakoid membrane. We also presented the formation of a complex composed of phosphorylated LHCII and photosystem I typically formed upon light-induced phosphorylation. Moreover, we indicated that the observed steps were preceded by the activation of the oxidative pentose phosphate pathway (OPPP) enzymes and starch accumulation.
CONCLUSIONS
Our results suggest a direct connection between photosynthetic complexes reorganization and dark-chilling-induced activation of the thioredoxin system. The proposed possible pathway starts from the activation of OPPP enzymes and further NADPH-dependent thioredoxin reductase C (NTRC) activation. In the next steps, NTRC simultaneously activates ADP-glucose pyrophosphorylase and thylakoid membrane-located NAD(P)H dehydrogenase-like complex. These results in starch synthesis and electron transfer to the plastoquinone (PQ) pool, respectively. Reduced PQ pool activates STN7 kinase which phosphorylates LHCII. In this work, we present a new perspective on the mechanisms involving photosynthetic complexes while efficiently operating in the darkness. Although we describe the studied pathway in detail, taking into account also the time course of the following steps, the biological significance of this phenomenon remains puzzling.
Topics: Phaseolus; Phosphorylation; Light; Thylakoids; Photosystem I Protein Complex; Cold Temperature; Light-Harvesting Protein Complexes; Photosystem II Protein Complex; Plant Proteins; Starch; Pentose Phosphate Pathway; Enzyme Activation; Photosynthesis; Stress, Physiological; Protein Serine-Threonine Kinases
PubMed: 38849759
DOI: 10.1186/s12870-024-05169-3 -
Environmental Geochemistry and Health Jun 2024In our previous study, the decontamination efficiency of cesium-137 (Cs) by Napier grass (Pennisetum purpureum Schum.) in the field was shown to be variable and often...
In our previous study, the decontamination efficiency of cesium-137 (Cs) by Napier grass (Pennisetum purpureum Schum.) in the field was shown to be variable and often influenced by natural environmental factors. To elucidate the factors influencing this variable Cs-decontamination efficiency, we investigated the influences of soil type and drought stress on Cs accumulation using cesium-133 (Cs) in Napier grass grown in plastic containers. The experiment was performed using two soil types (Soil A and B) and three different soil moisture conditions: well-watered control (CL), slight drought stress (SD), and moderate drought stress (MD). Overall, our results indicate that soil type and drought have a significant impact on plant growth and Cs accumulation in Napier grass. Plant height (PH), tiller number (TN), leaf width (W), and dry matter weight of aboveground parts (DW) and root parts (DW) in Soil B were greater than those in Soil A. Drought stress negatively affected chlorophyll fluorescence parameters (maximal quantum efficiency of photosystem (PS) II photochemistry and potential activity of PS II), PH, TN, W, DW, DW, and total Cs content (TCs), but it had a positive effect on Cs concentration. The Cs concentration in the aboveground parts (Cs) was increased by MD approximately 1.62-fold in Soil A and 1.11-fold in Soil B compared to each CL counterpart. The TCs in the aboveground parts (TCs) decreased due to drought by approximately 19.9%-39.0% in Soil A and 49.9%-62.7% in Soil B; however, there was no significant effect on TCs due to soil type. The results of this study indicate that soil moisture is a key factor in maintaining Napier grass Cs-decontamination efficiency.
Topics: Cesium Radioisotopes; Droughts; Soil Pollutants, Radioactive; Pennisetum; Soil
PubMed: 38849625
DOI: 10.1007/s10653-024-02023-1 -
The Plant Cell Jun 2024The photosynthetic apparatus is formed by thylakoid membrane-embedded multiprotein complexes that carry out linear electron transport in oxygenic photosynthesis. The...
The photosynthetic apparatus is formed by thylakoid membrane-embedded multiprotein complexes that carry out linear electron transport in oxygenic photosynthesis. The machinery is largely conserved from cyanobacteria to land plants, and structure and function of the protein complexes involved are relatively well studied. By contrast, how the machinery is assembled in thylakoid membranes remains poorly understood. The complexes participating in photosynthetic electron transfer are composed of many proteins, pigments and redox-active cofactors, whose temporally and spatially highly coordinated incorporation is essential to build functional mature complexes. Several proteins, jointly referred to as assembly factors, engage in the biogenesis of these complexes to bring the components together in a step-wise manner, in the right order and time. In this review, we focus on the biogenesis of the terminal protein supercomplex of the photosynthetic electron transport chain, photosystem I (PSI), in vascular plants. We summarize our current knowledge of the assembly process and the factors involved, and describe the challenges associated with resolving the assembly pathway in molecular detail.
PubMed: 38848316
DOI: 10.1093/plcell/koae169 -
Journal of the American Chemical Society Jun 2024Redox-inactive metal ions are essential in modulating the reactivity of various oxygen-containing metal complexes and metalloenzymes, including photosystem II (PSII)....
Redox-inactive metal ions are essential in modulating the reactivity of various oxygen-containing metal complexes and metalloenzymes, including photosystem II (PSII). The heart of this unique membrane-protein complex comprises the MnCaO cluster, in which the Ca ion acts as a critical cofactor in the splitting of water in PSII. However, there is still a lack of studies involving Ca-based reactive oxygen species (ROS) systems, and the exact nature of the interaction between the Ca center and ROS in PSII still generates intense debate. Here, harnessing a novel Ca-TEMPO complex supported by the β-diketiminate ligand to control the activation of O, we report the isolation and structural characterization of hitherto elusive Ca peroxides, a homometallic Ca hydroperoxide and a heterometallic Ca/K peroxide. Our studies indicate that the presence of K cations is a key factor controlling the outcome of the oxygenation reaction of the model Ca-TEMPO complex. Combining experimental observations with computational investigations, we also propose a mechanistic rationalization for the reaction outcomes. The designed approach demonstrates metal-TEMPO complexes as a versatile platform for O activation and advances the understanding of Ca/ROS systems.
PubMed: 38847558
DOI: 10.1021/jacs.4c00906 -
Seasonal variation in the relationship between leaf chlorophyll content and photosynthetic capacity.Plant, Cell & Environment Jun 2024Accurate estimation of photosynthesis is crucial for ecosystem carbon cycle modelling. Previous studies have established an empirical relationship between photosynthetic...
Accurate estimation of photosynthesis is crucial for ecosystem carbon cycle modelling. Previous studies have established an empirical relationship between photosynthetic capacity (maximum carboxylation rate, V; maximum electron transport rate, J) and leaf chlorophyll (Chl) content to infer global photosynthetic capacity. However, the basis for the Chl-V relationship remains unclear, which is further evidenced by the temporal variations in the Chl-V relationship. Using multiple years of observations of four deciduous tree species, we found that V and J acclimate to photosynthetically active radiation faster (4-8 weeks) than Chl (10-12 weeks). This mismatch in temporal scales causes seasonality in the V-Chl relationship. To account for the mismatch, we used a Chl fluorescence parameter (quantum yield of Photosystem II, Φ(II)) to tighten the relationship and found Φ(II) × Chl correlated with V and J (r = 0.74 and 0.72 respectively) better than only Chl (r = 0.7 and 0.6 respectively). It indicates that Φ(II) accounts for the short-term adjustment of leaf photosynthetic capacity to light, which was not captured by Chl. Our study advances our understanding of the ecophysiological basis for the empirical V-Chl relationship and how to better infer V from Chl and fluorescence, which guides large-scale photosynthesis simulations using remote sensing.
PubMed: 38847340
DOI: 10.1111/pce.14997 -
Journal of Photochemistry and... May 2024The deprotonation of O6 within the S state marks the final deprotonation event before the formation of oxygen‑oxygen bond interactions and eventual production and...
The deprotonation of O6 within the S state marks the final deprotonation event before the formation of oxygen‑oxygen bond interactions and eventual production and release of dioxygen. Gaining a thorough understanding of this event, from the proton acceptors involved, to the exfiltration pathways available, is key in determining the nature of the resulting oxygen species, influencing the mechanism through which the first oxygen‑oxygen bond forms. Computational analysis, using BS-DFT methodologies, showed that proton abstraction by the local Glu189 residue provides consistent evidence against this being a viable mechanistic pathway due to the lack of a stable product structure. In contrast, abstraction via W3 shows an increasingly stable oxo-oxo product state between r[O5O6] = 2.1 Å & 1.9 Å. The resulting oxo-oxo state is stabilised through donation of β electron character from O6 to Mn1 and α electron character from O6 to O5. This donation from the O6 lone pair is shown to be a key factor in stabilising the oxo-oxo state, in addition to showing the initiation of first O5-O6 bond.
PubMed: 38843709
DOI: 10.1016/j.jphotobiol.2024.112946 -
International Journal of Biological... Jun 2024Fructose 1,6-bisphosphate aldolase (FBA) is a pivotal enzyme, which plays a critical role in fixing CO through the process of in the Calvin cycle. In this study, a...
Fructose 1,6-bisphosphate aldolase (FBA) is a pivotal enzyme, which plays a critical role in fixing CO through the process of in the Calvin cycle. In this study, a comprehensive exploration of the FBA family genes in moso bamboo (Phyllostachys edulis) was conducted by the bioinformatics and biological analyses. A total of nine FBA genes (PeFBA1-PeFBA9) were identified in the moso bamboo genome. The expression patterns of PeFBAs across diverse tissues of moso bamboo suggested that they have multifaceted functionality. Notably, PeFBA8 might play an important role in regulating photosynthetic carbon metabolism. Co-expression and cis-element analyses demonstrated that PeFBA8 was regulated by a photosynthetic regulatory transcription factor (PeGLK1), which was confirmed by yeast one-hybrid and dual-luciferase assays. In-planta gene editing analysis revealed that the edited PeFBA8 mutants displayed compromised photosynthetic functionality, characterized by reduced electron transport rate and impaired photosystem I, leading to decreased photosynthesis rate overall, compared to the unedited control. The recombinant protein of PeFBA8 from prokaryotic expression exhibited enzymatic catalytic function. The findings suggest that the expression of PeFBA8 can affect photosynthetic efficiency of moso bamboo leaves, which underlines the potential of leveraging PeFBA8's regulatory mechanism to breed bamboo varieties with enhanced carbon fixation capability.
PubMed: 38838894
DOI: 10.1016/j.ijbiomac.2024.132885