Murburn Model of Photosynthesis: Effect of Additives like Chloride and Bicarbonate

Oxygenic photosynthesis essentially involves photo-lysis (splitting of water to release oxygen), photo-reduction (formation of NADPH), and photo-phosphorylation (synthesis of ATP) reactions. These reactions use photoactive pigments such as chlorophylls and carotenoids. Z-scheme and Kok-Joliot cycle, the acclaimed and deterministic model of photosynthesis, are founded on the classical enzyme reaction mechanisms that depend solely on affinity-based interactions of enzymes with the substrates at defined active sites, for explaining electron/moiety transfers. In contrast, the new murburn model is built on stochastic collisions between diffusible reactive species (DRS) and other milieu components (including enzymes, substrates and ions). This novel perspective explains fast kinetics and action spectrum, and affords a spontaneously probable/evolvable biochemical system. The murburn perspective proposes that the photo-excitation of pigments in the chloroplast leads to effective charge separation and DRS-formation. DRS are stabilized/utilized by a pool of redox-active components via disordered/parallel bimolecular interactions at the thylakoid membrane interface. Herein, we provide details of how murburn model is a thermodynamically, kinetically, and mechanistically viable mechanism for the formation of ATP, NADPH and oxygen. The murburn model also provides more viable explanations for several classical experimental observations in photosynthesis (Emerson enhancement effect, Jagendorf/Racker experiments, etc.) and the non-specific effects of diverse additives (such as chloride and bicarbonate)

Comprehensive Analyses of the Enhancement of Oxygenesis in Photosynthesis by Bicarbonate and Effects of Diverse Additives: Z-scheme Explanation Versus Murburn Model

The Z-scheme electron transport chain (ETC) explanation for photosynthesis starts with the serial/sequential transfer of electrons sourced from water molecules bound at Photosystem II via a deterministic array of redox centers (of various stationary/mobile proteins), before "sinking" via the reduction of NADP+ bound at flavin-enzyme reductase. Several research groups’ finding that additives (like bicarbonate) enhance the light reaction had divided the research community because it violated the Z-scheme. The untenable aspects of the Z-scheme perception were demonstrated earlier and a murburn bioenergetics (a stochastic/parallel paradigm of ion-radical equilibriums) model was proposed to explain photophosphorylation and Emerson effect. Herein, we further support the murburn model with accurate thermodynamic calculations, which show that the cost of one-electron abstraction from bicarbonate [491 kJ/mol] is lower than water [527 kJ/mol]. Further, copious thioredoxin enables the capture of photoactivated electrons in milieu, which aid in the reduction of nicotinamide nucleotides. The diffusible reactive species (DRS) generated in milieu sponsor phosphorylations and oxygenic reactions. With structural analysis of Photosystems and interacting molecules, we chart out the equations of reactions that explain the loss of labeled O-atom traces in delocalized oxygenesis. Thus, this essay discredits the Z-scheme and explains key outstanding observations in the field

Research on computer vision application in industry field: focus on distribution network engineering

The operation of distribution networks is currently facing potential safety and quality defects that pose significant hazards. One solution to strengthen management, reduce manual workload, and improve efficiency and quality is by applying deep detection networks for dynamic defect detection in distribution network engineering. To start, defects in distribution network engineering are classified. Then, advanced deep detection networks and their applications in dynamic defect detection are researched and analyzed, along with a review of existing research. Key issues and their solutions for deep detection network application in dynamic defect detection in distribution network engineering are summarized. Finally, future research directions are explored to provide valuable references for future studies

Transmembrane peptide 4 and 5 of APJ are essential for its heterodimerization with OX1R

Increasing evidence indicates some G protein-coupled receptors function as a heterodimer, which provide a novel target for therapeutics investigation. However, study on the receptor-receptor interaction interface, a potent target on interfering dimer formation, are still limited. Here, using bioluminescence resonance energy transfer (BRET) combined with co-immunoprecipitation (Co-IP), we found a new constitutive GPCR heterodimer, apelin receptor (APJ)-orexin receptor type 1 (OX1R). Both APJ and OX1R co-internalized when constantly subjected to cognate agonist (apelin-13 or orexin-A) specific to either protomer. Combined with BRET and immunostaining, the in vitro synthesized transmembrane peptides (TMs) interfering experiments suggests that TM4 and 5 of APJ act as the interaction interface of the APJ-OX1R heterodimer, and co-internalization could be disrupted by these peptides as well. Our study not only provide new evidence on GPCR heterodimerization, but address a novel heterodimerization interface, which can be severed as a potential pharmacological target

Plant Physiology under Abiotic Stresses: Deepening the Connotation and Expanding the Denotation

Abiotic stress factors influence many aspects of plant physiology. The works collected in the Special Issue deepen plant physiology’s connotation (such as plant electrophysiology) under abiotic stress and expand the denotation (such as environmental pollutants as abiotic stress factors). At the same time, the achievements of the selected papers published in the Special Issue also exhibit their potential application value in the production of horticultural plants

The Increase in the Karstification–Photosynthesis Coupled Carbon Sink and Its Implication for Carbon Neutrality

Two of the most important CO2 sequestration processes on Earth are plant photosynthesis and rock chemical dissolution. Photosynthesis is undoubtedly the most important biochemical reaction and carbon sink processes on Earth. Karst geological action does not produce net carbon sinks. Photosynthesis and karstification in nature are coupled. Karstification–photosynthesis coupling can stabilize and increase the capacity of karstic and photosynthetic carbon sinks. Bidirectional isotope tracer culture technology can quantify the utilization of different inorganic carbon sources by plants. Bicarbonate utilization by plants is a driver of karstification–photosynthesis coupling, which depends on plant species and the environment. Carbonic anhydrase, as a pivot of karstification–photosynthesis coupling, can promote inorganic carbon assimilation in plants and the dissolution of carbonate rocks. Karst-adaptable plants can efficiently promote root-derived bicarbonate and atmospheric carbon dioxide use by plants, finally achieving the conjugate promotion of karstic carbon sinks and photosynthetic carbon sinks. Strengthening karstification–photosynthesis coupling and developing karst-adaptable plants will greatly improve the capacity of carbon sinks in karst ecosystems and better serve the “Carbon peak and Carbon neutralization” goals of China

Plant Physiology under Abiotic Stresses: Deepening the Connotation and Expanding the Denotation

Abiotic stress factors influence many aspects of plant physiology. The works collected in the Special Issue deepen plant physiology’s connotation (such as plant electrophysiology) under abiotic stress and expand the denotation (such as environmental pollutants as abiotic stress factors). At the same time, the achievements of the selected papers published in the Special Issue also exhibit their potential application value in the production of horticultural plants

Differential Responses of Nitrate/Ammonium Use to Bicarbonate Supply in Two <i>Brassicaceae</i> Species under Simulated Karst Habitat

In the karst habitats with nitrate-abundant and ammonium-rare soil, the bicarbonate supply plays a crucial role in both inorganic carbon and nitrogen assimilation in various plant species. Consequently, two carbon sources, carbon dioxide (CO2) and bicarbonate (HCO3−), and two nitrogen sources, namely nitrate (NO3−) and ammonium (NH4+) are available for plants. However, variations in the absorption and utilization of nitrate, ammonium, and inorganic carbon during bicarbonate supply in different plants are not well-depicted. In this study, we evaluated the nitrate/ammonium use efficiency and their contributions to the total nitrogen assimilation/utilization capacity at different bicarbonate levels using a bidirectional stable nitrogen isotope tracer approach. The inorganic carbon assimilation, such as the photosynthesis, carbon/nitrogen enzymatic activities, carbon/nitrogen content, nitrogen assimilation/utilization capacity, and nitrate/ammonium contributions to plant growth, were also evaluated to decipher the responses of both carbon and nitrogen metabolism to bicarbonate supply in karst habitats. With the increasing bicarbonate level, Orychophragmus violaceus (Ov) was found to be more available for nitrate to total nitrogen assimilation and utilization than Bn (Brassica napus). Further, it enhanced the contributions of nitrate and nitrogen accumulation/utilization capacity and inorganic carbon assimilation, increasing photosynthesis, carbon/nitrogen enzymatic activities, and carbon accumulation, and promoted the growth in Ov. Though the highest bicarbonate level was conducive to ammonium utilization and water use efficiency in both Ov and Bn, it inhibited total inorganic carbon and nitrogen assimilation, leading to growth suppression in Bn compared to Ov. Moreover, considering the optimistic responses of both carbon and nitrogen assimilation to the high bicarbonate supply in nitrate-abundant, as well as ammonium-rare, environments, we conclude that Ov was more adaptable to the karst habitats. This study provides a novel approach to elucidate the responses of nitrate/ammonium utilization and inorganic carbon assimilation to bicarbonate. Furthermore, the current study reveals the complex interactions among different carbon–nitrogen metabolism pathways in various plants and their adaptations to karst habitats

The Increase in the Karstification–Photosynthesis Coupled Carbon Sink and Its Implication for Carbon Neutrality

Two of the most important CO2 sequestration processes on Earth are plant photosynthesis and rock chemical dissolution. Photosynthesis is undoubtedly the most important biochemical reaction and carbon sink processes on Earth. Karst geological action does not produce net carbon sinks. Photosynthesis and karstification in nature are coupled. Karstification–photosynthesis coupling can stabilize and increase the capacity of karstic and photosynthetic carbon sinks. Bidirectional isotope tracer culture technology can quantify the utilization of different inorganic carbon sources by plants. Bicarbonate utilization by plants is a driver of karstification–photosynthesis coupling, which depends on plant species and the environment. Carbonic anhydrase, as a pivot of karstification–photosynthesis coupling, can promote inorganic carbon assimilation in plants and the dissolution of carbonate rocks. Karst-adaptable plants can efficiently promote root-derived bicarbonate and atmospheric carbon dioxide use by plants, finally achieving the conjugate promotion of karstic carbon sinks and photosynthetic carbon sinks. Strengthening karstification–photosynthesis coupling and developing karst-adaptable plants will greatly improve the capacity of carbon sinks in karst ecosystems and better serve the “Carbon peak and Carbon neutralization” goals of China

Effect of Bicarbonate Stress on Carbonic Anhydrase Gene Expressions from Orychophragmus violaceus and Brassica juncea seedlings

Three beta-type genes coding for carbonic anhydrase and CA activities from Orychophragmus violaceus L. and Brassica juncea L. leaves in response to NaHCO3-induced bicarbonate stress were examined. Three full-length cDNA CDS sequences were designated as OvCA1, OvCA3, and OvCA4 in Orychophragmus violaceus, and as BjCA1, BjCA3, and BjCA4 in Brassica juncea; these genes encoding beta-CAs were identified and characterized. In particular, OvCA1 and BjCA1 encode two putative chloroplast isoforms. OvCA3 and BjCA3 encode two putative cytosolic isoforms. OvCA4 and BjCA4 encode two putative plasma membrane isoforms. Quantitative real-time RT-PCR analysis revealed that OvCA1 and OvCA4 expressions in Orychophragmus violaceus, BjCA1, and BjCA4 expressions in Brassica juncea changed synchronously with CA activities as bicarbonate stress was intensified. Bicarbonate stress synchronously stimulated OvCA1 and OvCA4 expressions along with CA activities in Orychophragmus violaceus at slight stress level; but it decreased CA activity, BjCA1 and BjCA4 expressions, and stimulated BjCA3 expression in Brassica juncea. Orychoophragmus violaceus could better adapt to slight bicarbonate stress than Brassica juncea due to the former exhibiting higher OvCA3 expression levels and CA activities than the latter. The responses of CA1 and CA4 in Orychophragmus violaceus and CA3 in Brassica juncea to bicarbonate stress partly regulate HCO3- to water and CO 2 supplied to plants. Diverse CA gene expressions can partially account for different adaptation strategies of the two plant species subjected to different bicarbonate stress levels