Optimizing the electron transport chain to sustainably improve photosynthesis

Optimizing carbon and nitrogen metabolism in plants: From fundamental principles to practical applications

Carbon (C) and nitrogen (N) are fundamental elements essential for plant growth and development, serving as the structural and functional backbone of organic compounds and driving essential biological processes such as photosynthesis, carbohydrate metabolism, and N assimilation. The metabolism and transport of C involve the movement of sugars between shoots and roots through xylem and phloem transport systems, regulated by a sugar-signaling hub. Nitrogen uptake, transport, and metabolism are equally critical, with plants assimilating nitrate and ammonium through specialized transporters and enzymes in response to varying N levels to optimize growth and development. The coordination of C and N metabolism is key to plant productivity and the maintaining of agroecosystem stability. However, inefficient utilization of N fertilizers results in substantial environmental and economic challenges, emphasizing the urgent need to improve N use efficiency (NUE) in crops. Integrating efficient photosynthesis with N uptake offers opportunities for sustainable agricultural practices. This review discusses recent advances in understanding C and N transport, metabolism, and signaling in plants, with a particular emphasis on NUE-related genes in rice, and explores breeding strategies to enhance crop efficiency and agricultural sustainability.

Light and nutrient cues elicit metabolic reprogramming by targeting carbon fixation, redox balance, and ATP homeostasis in Agastache rugosa

MAIN CONCLUSION

The study uncovers how Agastache rugosa coordinates carbon fixation, redox balance, and ATP homeostasis via distinct metabolic strategies optimized for different light and nutrient conditions. This study explores the metabolic adaptations of Agastache rugosa (Fisch. & C.A.Mey.) Kuntze in varying light and nutrient conditions, focusing on the coordination between photosynthetic and respiratory pathways. Plants were grown under two light levels (high light, 0% shade; low-light, 50% shade) and four nutrient treatments (NPK1, 40 mg kg-1; NPK2, 80 mg kg-1; NPK3, 120 mg kg-1; NPK4, 160 mg kg-1) and key metabolic parameters were analyzed. High-light plants had peak carbonic anhydrase activity (5.17 ± 0.26 U g-1 FW) at NPK2, optimizing carbon fixation and redox balance with 20.6% and 12.8% higher NADP+/NADPH and NAD+/NADH ratios, each. Low-light plants upregulated PEPC (+110%), and PEPCK (+34%) at NPK4, displaying enhanced anaplerotic carbon fixation. Despite lower respiratory activity, (NADH-UQ, -50%; COX, -46%), plants under low-light had tenfold higher ATP at NPK3 through reduced consumption. Principal component and hierarchical cluster analyses (> 60% similarity) revealed distinct metabolic strategies between light treatments. Strong correlations among photosynthetic, respiratory, and redox parameters (r > 0.7, P < 0.001) indicated metabolic integration via shared regulatory networks. Our findings reveal the metabolic plasticity of A. rugosa, offering insights into plant adaptation with implications for cultivation. Moreover, multivariate analyses unveiled complex regulatory networks coordinating energy metabolism, highlighting the metabolic reprogramming employed by A. rugosa to maintain energetic and redox balance under dynamic environmental conditions.

A comparative study on ellagic acid's role in salt tolerance, growth, antioxidant system, photochemistry and nitrogen metabolism in wheat and chickpea

This study aims to evaluate the effectiveness of ellagic acid (EA) in mitigating stress induced by salt and enhancing the tolerance of wheat (a monocot) and chickpea (a dicot). The experiment included four treatment groups: a control (C), 12.5 μM EA application, 100 mM salt (NaCl-S) exposure, and a combined treatment with 12.5 μM EA and 100 mM salt (S + EA). Key physiological (e.g., photosynthetic efficiency: Fv/Fm, Fv/Fo, Fo/Fm), growth, and biochemical responses, including antioxidant enzyme activities (CAT, SOD, POX, APX, GST, GPX, NOX, GR, MDHAR, DHAR) and nitrogen metabolism enzymes (NR, GS, GOGAT, GDH), were evaluated to determine the role of exogenous EA in mitigating salt stress. The application of EA effectively mitigated salt stress in wheat and chickpea by enhancing the relative growth rate (RGR) and relative water content (RWC). EA reduced oxidative stress markers, lowering H2O2 levels by 16 % in wheat and 26 % in chickpea, and decreased TBARS content, particularly in wheat. Photosynthetic efficiency was stabilized, especially in wheat, as evidenced by improved OJIP parameters. Antioxidant enzyme activities (CAT, POX) increased in response to EA, with wheat showing greater activity under stress. EA partially restored nitrogen metabolism, with GS and GOGAT activities improving under combined EA and salt treatments, more prominently in wheat. EA enhanced redox homeostasis, with wheat showing a significant increase in tAsA/DHA (76 %) and GSH/GSSG (8 %) , while chickpea showed no change in tAsA/DHA and a decrease in GSH/GSSG under Salt + EA treatment. Overall, EA enhanced salt tolerance by strengthening antioxidant defenses, improving nitrogen assimilation, and stabilizing photosynthesis, with species-specific differences in response patterns.

Regulatory Coordination of Photophysical, Photochemical, and Biochemical Reactions in the Photosynthesis of Land Plants

Balance among the sequential photophysical, photochemical, and biochemical reactions of photosynthesis is needed for converting fleeting energy in light to stable energy in chemical bonds. Any imbalance acts as either a bottleneck for limiting photosynthetic efficiency or an agent for inducing structural and functional damage to photosynthetic apparatus. Not only must each reaction be carefully regulated, but regulatory processes must also be coordinated across the reactions. However, regulations of different stages of photosynthesis have rarely been studied jointly. Non-photochemical quenching (NPQ) and stomatal conductance (g s) are key regulators of photophysical and biochemical reactions, respectively. Existing evidence suggests that the redox state of plastoquinone regulates g s and that the photochemical reactions are partially regulated by the ultrastructural dynamics of thylakoids induced by osmotic water fluxes in chloroplasts of land plants. To examine how these regulations are coordinated and feedback to each other, we simultaneously measured NPQ and g s and inferred the redox state of plastoquinone and the light-induced thylakoid swelling/shrinking on numerous C3 and C4 species. For all species measured, NPQ and g s covary with the redox states of the electron transport chain, particularly plastoquinone, and increase as thylakoid swelling is inferred. NPQ has the maximal sensitivity at the light intensity at which thylakoid is inferred to be fully swollen. Our findings suggest that plant energy and water use strategies are intimately linked by evolution, and studying the regulations of different photosynthetic stages as a whole can lead to new insights of the functioning of photosynthetic machinery in dynamic environments.

Identification of the FBN gene family in tomato and functional analysis of SlFBN11 in the electron transport under low night temperature

FBNs are lipid-associated proteins that play a critical role in plant growth and stress response. However, the mechanisms of how FBNs proteins participate in the low night temperature response in tomato still unclear. Here we conducted a comprehensive genome-wide analysis of the FBN gene family in Solanum lycopersicum. In total, 14 SlFBN genes were identified, and information on their gene structures, protein motifs, phylogenetic relationships, and stress-related cis-regulatory elements (CREs) was provided. Among these, SlFBN11 was selected as a promising candidate for further functional characterization. The silencing of SlFBN11 destroys the redox balance of the PSI reaction center under low night temperature (LNT) stress, which led to increased ROS accumulation. Surprisingly, we found that the silencing of SlFNR2 also displayed an imbalance in electron transport of the PSI under LNT stress. Further experiments showed SlFBN11 can interact with SlFNR2 to positively response electron transport low night temperature. Collectively, the study provides a comprehensive analysis of the FBN genes family in Solanum lycopersicum and provides a theoretical basis for our understanding of the function of FBN genes in adaptation to LNT stresses.

Chloroplast ATP synthase: From structure to engineering

F-type ATP synthases are extensively researched protein complexes because of their widespread and central role in energy metabolism. Progress in structural biology, proteomics, and molecular biology has also greatly advanced our understanding of the catalytic mechanism, post-translational modifications, and biogenesis of chloroplast ATP synthases. Given their critical role in light-driven ATP generation, tailoring the activity of chloroplast ATP synthases and modeling approaches can be applied to modulate photosynthesis. In the future, advances in genetic manipulation and protein design tools will significantly expand the scope for testing new strategies in engineering light-driven nanomotors.

Hormetic Response of Photosystem II Function Induced by Nontoxic Calcium Hydroxide Nanoparticles

In recent years, inorganic nanoparticles, including calcium hydroxide nanoparticles [Ca Ca(OH)2 NPs], have attracted significant interest for their ability to impact plant photosynthesis and boost agricultural productivity. In this study, the effects of 15 and 30 mg L-1 oleylamine-coated calcium hydroxide nanoparticles [Ca(OH)2@OAm NPs] on photosystem II (PSII) photochemistry were investigated on tomato plants at their growth irradiance (GI) (580 μmol photons m-2 s-1) and at high irradiance (HI) (1000 μmol photons m-2 s-1). Ca(OH)2@OAm NPs synthesized via a microwave-assisted method revealed a crystallite size of 25 nm with 34% w/w of oleylamine coater, a hydrodynamic size of 145 nm, and a ζ-potential of 4 mV. Compared with the control plants (sprayed with distilled water), PSII efficiency in tomato plants sprayed with Ca(OH)2@OAm NPs declined as soon as 90 min after the spray, accompanied by a higher excess excitation energy at PSII. Nevertheless, after 72 h, the effective quantum yield of PSII electron transport (ΦPSII) in tomato plants sprayed with Ca(OH)2@OAm NPs enhanced due to both an increase in the fraction of open PSII reaction centers (qp) and to the enhancement in the excitation capture efficiency (Fv'/Fm') of these centers. However, the decrease at the same time in non-photochemical quenching (NPQ) resulted in an increased generation of reactive oxygen species (ROS). It can be concluded that Ca(OH)2@OAm NPs, by effectively regulating the non-photochemical quenching (NPQ) mechanism, enhanced the electron transport rate (ETR) and decreased the excess excitation energy in tomato leaves. The delay in the enhancement of PSII photochemistry by the calcium hydroxide NPs was less at the GI than at the HI. The enhancement of PSII function by calcium hydroxide NPs is suggested to be triggered by the NPQ mechanism that intensifies ROS generation, which is considered to be beneficial. Calcium hydroxide nanoparticles, in less than 72 h, activated a ROS regulatory network of light energy partitioning signaling that enhanced PSII function. Therefore, synthesized Ca(OH)2@OAm NPs could potentially be used as photosynthetic biostimulants to enhance crop yields, pending further testing on other plant species.

Molecular design of microalgae as sustainable cell factories

Microalgae are regarded as sustainable and potent chassis for biotechnology. Their capacity for efficient photosynthesis fuels dynamic growth independent from organic carbon sources and converts atmospheric CO2 directly into various valuable hydrocarbon-based metabolites. However, approaches to gene expression and metabolic regulation have been inferior to those in more established heterotrophs (e.g., prokaryotes or yeast) since the genetic tools and insights in expression regulation have been distinctly less advanced. In recent years, however, these tools and their efficiency have dramatically improved. Various examples have demonstrated new trends in microalgal biotechnology and the potential of microalgae for the transition towards a sustainable bioeconomy.

Comprehensive overview of how to fade into succinate dehydrogenase dysregulation in cancer cells by naringenin-loaded chitosan nanoparticles

Mitochondrial respiration complexes play a crucial function. As a result, dysfunction or change is intimately associated with many different diseases, among them cancer. The epigenetic, evolutionary, and metabolic effects of mitochondrial complex IΙ are the primary concerns of our review. Provides novel insight into the vital role of naringenin (NAR) as an intriguing flavonoid phytochemical in cancer treatment. NAR is a significant phytochemical that is a member of the flavanone group of polyphenols and is mostly present in citrus fruits, such as grapefruits, as well as other fruits and vegetables, like tomatoes and cherries, as well as foods produced from medicinal herbs. The evidence that is now available indicates that NAR, an herbal remedy, has significant pharmacological qualities and anti-cancer effects. Through a variety of mechanisms, including the induction of apoptosis, cell cycle arrest, restriction of angiogenesis, and modulation of several signaling pathways, NAR prevents the growth of cancer. However, the hydrophobic and crystalline structure of NAR is primarily responsible for its instability, limited oral bioavailability, and water solubility. Furthermore, there is no targeting and a high rate of breakdown in an acidic environment. These shortcomings are barriers to its efficient medical application. Improvement targeting NAR to mitochondrial complex ΙΙ by loading it on chitosan nanoparticles is a promising strategy.

Determinants of photochemical characteristics of the photosynthetic electron transport chain of maize

Introduction

The photosynthetic electron transport chain (ETC) is the bridge that links energy harvesting during the photophysical reactions at one end and energy consumption during the biochemical reactions at the other. Its functioning is thus fundamental for the proper balance between energy supply and demand in photosynthesis. Currently, there is a lack of understanding regarding how the structural properties of the ETC are affected by nutrient availability and plant developmental stages, which is a major roadblock to comprehensive modeling of photosynthesis.

Methods

Redox parameters reflect the structural controls of ETC on the photochemical reactions and electron transport. We conducted joint measurements of chlorophyll fluorescence (ChlF) and gas exchange under systematically varying environmental conditions and growth stages of maize and sampled foliar nutrient contents. We utilized the recently developed steady-state photochemical model to infer redox parameters of electron transport from these measurements.

Results and discussion

We found that the inferred values of these photochemical redox parameters varied with leaf macronutrient content. These variations may be caused either directly by these nutrients being components of protein complexes on the ETC or indirectly by their impacts on the structural integrity of the thylakoid and feedback from the biochemical reactions. Also, the redox parameters varied with plant morphology and developmental stage, reflecting seasonal changes in the structural properties of the ETC. Our findings will facilitate the parameterization and simulation of complete models of photosynthesis.