Enhancing the light reactions of photosynthesis: Strategies, controversies, and perspectives

Comparative study of organosilicon and inorganic silicon in reducing cadmium accumulation in wheat: Insights into rhizosphere microbial communities and molecular regulation mechanisms

Silicon is widely used as a "quality element" and "stress resistance element" in crop production and the remediation of heavy metal-contamination soils. Compared to inorganic silicon, organosilicon has unique properties such as amphiphilicity, low surface energy and high biocompatibility. Our previous research has confirmed the effectiveness of organosilicon-modified fertilizers in inhibiting Cadmium (Cd) absorption in wheat. Therefore, it is of great importance to further explore the potential mechanisms and comprehensive benefits of organosilicon. In this study, the microbiological and molecular mechanisms by which organosilicon reduces Cd concentration in wheat compared to inorganic silicon were investigated in depth. The findings indicated that, in comparison with inorganic silicon, organosilicon exhibited a more remarkable efficacy. Specifically, it was more effective in reducing the Cd concentration in wheat grains, achieving a reduction range of 35-39 % as opposed to the 23-28 % reduction achieved by inorganic silicon. Moreover, it manifested a greater ability to mitigate health risks, with a reduction range of 33-42 % compared to the 25-30 % reduction of inorganic silicon. Furthermore, organosilicon contributed to a significant increase in wheat yield, with a growth range of 11-14 % in contrast to the 8-11 % increase from inorganic silicon. Additionally, it enhanced the quality of the grains, substantially improving the protein content and amino acid content. The comparative advantages of organosilicon over inorganic silicon would be firstly due to the reduction of the bioavailability of soil Cd by increasing the available silicon content in the soil and improving the soil microbial ecology (increasing the abundance of Bacillus, Pseudomonas, Massilia and Talaromyces and reducing the enrichment of Fusarium). Secondly, organosilicon achieved vacuolar compartmentalization of Cd by upregulating the expression of the ABC transporter gene (TaABCB7), thereby alleviating Cd toxicity and restricting Cd transport from leaves to grains. Meanwhile, organosilicon increased the wheat yield by optimizing the availability of soil nutrients and enhancing photosynthesis. These results demonstrate the immense potential of organosilicon in mitigating heavy metal contamination in crops.

Opportunities and Challenges of Microalgal Strain Development via Atmospheric and Room-Temperature Plasma (ARTP)

Enhancing microalgal strains for biofuels and bioproducts often relies on genetic modification, raising concerns over regulatory and public acceptance. As a non-GMO alternative, atmospheric and room-temperature plasma (ARTP) mutagenesis has emerged as a promising tool for strain development. This review explores ARTP potential, starting with operational principles and key parameters. Special emphasis is placed on lethality control and optimized screening conditions. Several widely-studied strains are covered, including Desmodesmus sp., Haematococcus lacustris, and Chlorella sorokiniana. Discussion then shifts into the microscopic world to explore differentially expressed genes (DEGs), tracing CO2 assimilation and metabolic pathways that drive accelerated growth. Four key areas are assessed in detail, spanning from photosynthetic carbon fixation, central carbon metabolism, alongside lipid and pigment biosynthesis. Major challenges are laid bare, from genetic stability all the way to reproducibility. Addressing challenges is essential to fully harness ARTP for microalgal biotechnology and extended application in sustainability.

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.

Horizontally acquired CSP genes contribute to wheat adaptation and improvement

Although horizontal gene transfer (HGT) often facilitates environmental adaptation of recipient organisms, whether and how they might affect crop evolution and domestication is unclear. Here we show that three genes encoding cold-shock proteins (CSPs) were transferred from bacteria to Triticeae, a tribe of the grass family that includes several major staple crops such as wheat, barley and rye. The acquired CSP genes in wheat (TaCSPs) are functionally conserved in their bacterial homologues by encoding a nucleic acid-binding protein. Experimental evidence indicates that TaCSP genes positively regulate drought response and improve photosynthetic efficiency under water-deficient conditions by directly targeting a type 1 metallothionein gene to increase reactive oxygen species scavenging, which in turn contributed to the geographic expansion of wheat. We identified an elite CSP haplotype in Aegilops tauschii, introduction of which to wheat significantly increased drought tolerance, photosynthetic efficiency and grain yields. These findings not only provide major insights into the role of HGT in crop adaptation and domestication, but also demonstrate that novel microbial genes introduced through HGT offer a stable and naturally optimized resource for transgenic crop breeding and improvement.

Biosynthesis of Bacteriochlorophylls and Bacteriochlorophyllides in Escherichia coli

Photosynthesis, the most important biological process on Earth, converts light energy into chemical energy with essential pigments like chlorophylls and bacteriochlorophylls. The ability to reconstruct photosynthesis in heterotrophic organisms could significantly impact solar energy utilization and biomass production. In this study, we focused on constructing light-dependent biosynthesis pathways for bacteriochlorophyll (BChl) a and bacteriochlorophyllide (BChlide) d and c in the model strain Escherichia coli. The production of the starting compound, Mg protoporphyrin monomethylester, was optimized by screening the ribosome binding sites for the expression of each of the five genes. By fusing a maltose-binding protein and apolipoprotein A-I domain with the membrane protein BchF, the yield of 3-hydroxyethyl-Chlide a was increased by five-fold. Anaerobic cultivation of the engineered E. coli strains facilitated the reduction of the C7=C8 double bond by chlorophyllide a oxidoreductase, a critical step in BChl a synthesis. We further enhanced BChl a production by adjusting the isopropyl-β-d-thiogalactopyranoside concentration to optimize enzyme production and introducing an exogenous superoxide dismutase to combat oxidative stress. Additionally, fusing BciC with a RIAD tag resulted in an eight-fold increase in the production of 3-vinyl BChlide d. This study lays the foundation for the reconstitution of BChl-based photosynthetic apparatus in heterotrophic model organisms, offering promising avenues for future research and applications in biotechnology.

Enhancing crop yields to ensure food security by optimizing photosynthesis

The crop yields achieved through traditional plant breeding techniques appear to be nearing a plateau. Therefore, it is essential to accelerate advancements in photosynthesis, the fundamental process by which plants convert light energy into chemical energy, to further enhance crop yields. Research focused on improving photosynthesis holds significant promise for increasing sustainable agricultural productivity and addressing challenges related to global food security. This review examines the latest advancements and strategies aimed at boosting crop yields by enhancing photosynthetic efficiency. There has been a linear increase in yield over the years in historically released germplasm selected through traditional breeding methods, and this increase is accompanied by improved photosynthesis. We explore various aspects of the light reactions designed to enhance crop yield, including light harvest efficiency through smart canopy systems, expanding the absorbed light spectrum to include far-red light, optimizing non-photochemical quenching, and accelerating electron transport flux. At the same time, we investigate carbon reactions that can enhance crop yield, such as manipulating Rubisco activity, improving the Calvin-Benson-Bassham (CBB) cycle, introducing CO2 concentrating mechanisms (CCMs) in C3 plants, and optimizing carbon allocation. These strategies could significantly impact crop yield enhancement and help bridge the yield gap.

Effects of Far-Red Light and Ultraviolet Light-A on Growth, Photosynthesis, Transcriptome, and Metabolome of Mint (Mentha haplocalyx Briq.)

To investigate the effects of different light qualities on the growth, photosynthesis, transcriptome, and metabolome of mint, three treatments were designed: (1) 7R3B (70% red light and 30% blue light, CK); (2) 7R3B+ far-red light (FR); (3) 7R3B+ ultraviolet light A (UVA). The results showed that supplemental FR significantly promoted the growth and photosynthesis of mint, as evidenced by the increase in plant height, plant width, biomass, effective quantum yield of PSII photochemistry (Fv'/Fm'), maximal quantum yield of PSII (Fv/Fm), and performance index (PI). UVA and CK exhibited minimal differences. Transcriptomic and metabolomic analysis indicated that a total of 788 differentially expressed genes (DEGs) and 2291 differential accumulated metabolites (DAMs) were identified under FR treatment, mainly related to plant hormone signal transduction, phenylpropanoid biosynthesis, and flavonoid biosynthesis. FR also promoted the accumulation of phenylalanine, sinapyl alcohol, methylchavicol, and anethole in the phenylpropanoid biosynthesis pathway, and increased the levels of luteolin and leucocyanidin in the flavonoid biosynthesis pathway, which may perhaps be applied in practical production to promote the natural antibacterial and antioxidant properties of mint. An appropriate increase in FR radiation might alter transcript reprogramming and redirect metabolic flux in mint, subsequently regulating its growth and secondary metabolism. Our study uncovered the regulation of FR and UVA treatments on mint in terms of growth, physiology, transcriptome, and metabolome, providing reference for the cultivation of mint and other horticultural plants.

LcASR enhances tolerance to abiotic stress in Leymus chinensis and Arabidopsis thaliana by improving photosynthetic performance

As a crucial forage grass, Leymus chinensis plays significant roles in soil and water conservation owing to its robust stress resistance. However, the underlying molecular mechanisms of its stress tolerance remain unclear. In this study, a novel gene, designated as LcASR (Abiotic Stress Resistance in Leymus chinensis), imparting resilience to both high light and drought, was identified. Under normal growth conditions, heterologous overexpression of LcASR in Arabidopsis (HO lines) showed no significant difference in appearance compared to wild-type. Nevertheless, HO lines accumulate significantly higher chlorophyll content during the dark-to-light transition compared to the wild-type, indicating that the LcASR protein participates in chlorophyll synthesis during chloroplast development. Meanwhile, transgenic Arabidopsis and L. chinensis plants exhibited resistance to abiotic stresses such as high light and drought. Photosystem complexes analysis revealed that LHCII proteins remained stable within their respective complexes during high light stress. We hypothesize that LcASR may play a role in fine tuning of chlorophyll synthesis to enable plant adaptation to diverse stress conditions. Moreover, overexpression of LcASR in L. chinensis led to agronomically valuable traits such as deeper green color, higher biomass accumulation, prolonged withering period, and extended grazing durations. This study uncovers a novel gene in L. chinensis that enhances forage yield and provides valuable genetic resources for sheepgrass breeding.

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.

Fungus-derived opine enhances plant photosynthesis

INTRODUCTION

Plant-fungal interactions stimulate endophytic fungi to produce a plethora of metabolites that enhance plant growth and improve stress resistance. Opines, naturally occurring compounds formed through the condensation of amino acids with α-keto acids or sugars, have diverse biological functions and are mainly present in bacteria. Interestingly, investigations have revealed the presence of opine synthases (OSases) in fungal species as well, and their functions are yet to be studied.

OBJECTIVES

The objective of this study is to investigate the occurrence of OSases in fungal species, identify their products, and characterize the potential biological activity of the metabolites.

METHODS

We identified a putative class of OSases in fungi through sequence similarity network (SSN) analysis. The function of these enzymes was elucidated using methods including protein heterologous expression, in vitro biochemical characterization, in vivo gene knock-out, as well as product isolation and identification. Additionally, we conducted plant activity testing on the secondary metabolites through foliar spraying and performed transcriptomic analysis to uncover their functions.

RESULTS

A quarter of the PF18631 family members, which contain the C-terminal helical bundle domain of cucumopine synthase, are derived from endophytic fungi. Some of these enzymes catalyze the synthesis of tryptopine A (1-acetyl-3-carboxy-β-carboline) by condensing L-tryptophan and methylglyoxal. The tryptopine A can act as a growth regulator, promoting plant growth and transcriptionally reprogramming photosynthesis-related pathways, while enhancing the rate of plant photosynthesis by 25 %.

CONCLUSION

The findings of this study suggest that tryptopine A plays a crucial role as a signaling molecule in the establishment and maintenance of mutualistic associations between endophytic fungi and host plants, thereby enhancing our comprehension of fungal-plant symbiosis.

Nature-Inspired Artificial Aggregation-Induced Emission Antenna for Assembling with Algae to Promote Photosynthesis

Inspired by the structure of chlorophyll assembled on the thylakoid membrane through its long hydrophobic chain, we designed cationic aggregation-induced emission (AIE) amphiphiles with two long hydrophobic chains to assemble with the electronegative cytomembrane of algae for efficiently converting natural ultraviolet light into usable blue light to promote photosynthesis. The photosynthesis efficiency of algae depended on the carbon chain length of the AIE amphiphile due to the difference in assembly capacity with the algal membrane. The AIE amphiphile with two hydrophobic chains of 12 carbon atoms effectively intercalated into the cytomembrane of algae, serving as an artificial membrane-embedded antenna to significantly improve light utilization by algae. This resulted in increased electron generation and a 98.6% increase in the electron transfer rate. Consequently, oxygen and ATP production in light-dependent reactions were boosted by about 100% and 64.5%, respectively, and the lipid yield increased by 45.7% in dark reactions. In addition, the AIE amphiphile also demonstrated a low biotoxicity. These results highlight the potential of AIE amphiphiles as membrane-embedded artificial antennas for optimizing natural photosynthesis.

Regulation of anthocyanin synthesis in red lettuce in plant factory conditions: A review

Anthocyanins, natural pigments known for their vibrant hues and beneficial properties, undergo intricate genetic control. However, red vegetables grown in plant factories frequently exhibit reduced anthocyanin synthesis compared to those in open fields due to factors like inadequate light, temperature, humidity, and nutrient availability. Comprehending these factors is essential for optimizing plant factory environments to enhance anthocyanin synthesis. This review insights the impact of physiological and genetic factors on the production of anthocyanins in red lettuce grown under controlled conditions. Further, we aim to gain a better understanding of the mechanisms involved in both synthesis and degradation of anthocyanins. Moreover, this review summarizes the identified regulators of anthocyanin synthesis in lettuce, addressing the gap in knowledge on controlling anthocyanin production in plant factories, with potential implications for various crops beyond red lettuce.

Clomazone exposure-driven photosynthetic responses plasticity of Pontederia crassipes

Clomazone is known to contaminate aquatic environments and have a negative impact on macrophytes. However, recent reports suggests that Pontederia crassipes Mart. can withstand clomazone exposure while maintaining growth rates. We hypothesized that this maintenance of growth is supported by photosynthetic plasticity of old leaves (developed before herbicide application), while new leaves (developed after application) exhibit phytotoxic symptoms. To investigate, two experiments were conducted with doses ranging from 0.1 mg L-1 to 0.5 mg L-1 plus untreated controls. Various parameters were measured in old and new leaves over 7, 12, and 15 d post-application, including visual symptoms, chlorophyll index, photosynthetic pigments, chlorophyll fluorescence, gas exchange, glycolate oxidase activity, carbohydrate content, leaf epidermis anatomy, and growth parameters. Clomazone exposure induced chlorosis, particularly in new leaves across all doses. These visual symptoms were accompanied by stomatal closure, restricting gas exchange and CO2 fixation, leading to reduced photosynthetic rates and carbohydrate synthesis. However, clomazone did not affect old leaves, which maintained photosynthetic activity, sustaining essential metabolic processes of the plant, including reproductive functions. By ensuring high reproductive rates and metabolic continuity, old leaves supported the species' persistence despite clomazone presence.

Morphological and physiological plasticity of tomato in response to Azolla fern, a novel organic fertilizer of environmentally friendliness

Tomatoes are highly valued vegetable crops due to their excellent nutritional content. However, production remained low due to an incorrect combination of organic and inorganic soil nutrition. A pot experiment was conducted under shaded conditions with Azolla and inorganic nitrogen fertilization to determine the morphological and physiological plasticity of tomatoes. The study used a factorial combination of four levels of Azolla (0, 25, 50, and 75 g per pot) and four levels of nitrogen (0, 0.23, 0.46, and 0.69 g per pot) in a complete randomized design with three replications. We collected data on chlorophyll content (Chl a, Chl b, TChl), photosynthetic rate, water use efficiency, transpiration rate, stomata number, branch number (primary and secondary), plant height, leaf area, stomata conductance, relative water content, and number of leaves. Analysis of variance was employed to analyze the data, and the means were separated using the least significant differences test at a 5 % significance level. The results showed that primary and secondary branches, stomata number, transpiration rate, and water use efficiency were highly plastic due to the higher nitrogen levels and Azolla alone. The interaction effect of Azolla and nitrogen had a significant influence on chlorophyll content, photosynthesis rate, stomatal conductance, relative water content, number of leaves, plant height, and leaf area. It can be concluded that a balanced combination of organic and inorganic fertilizers remains essential for optimal tomato growth and physiology, emphasizing that the exclusive use of organic farming methods may not be the ideal solution.

Perspectives on improving photosynthesis to increase crop yield

Improving photosynthesis, the fundamental process by which plants convert light energy into chemical energy, is a key area of research with great potential for enhancing sustainable agricultural productivity and addressing global food security challenges. This perspective delves into the latest advancements and approaches aimed at optimizing photosynthetic efficiency. Our discussion encompasses the entire process, beginning with light harvesting and its regulation and progressing through the bottleneck of electron transfer. We then delve into the carbon reactions of photosynthesis, focusing on strategies targeting the enzymes of the Calvin-Benson-Bassham (CBB) cycle. Additionally, we explore methods to increase carbon dioxide (CO2) concentration near the Rubisco, the enzyme responsible for the first step of CBB cycle, drawing inspiration from various photosynthetic organisms, and conclude this section by examining ways to enhance CO2 delivery into leaves. Moving beyond individual processes, we discuss two approaches to identifying key targets for photosynthesis improvement: systems modeling and the study of natural variation. Finally, we revisit some of the strategies mentioned above to provide a holistic view of the improvements, analyzing their impact on nitrogen use efficiency and on canopy photosynthesis.

A pgr5 suppressor screen uncovers two distinct suppression mechanisms and links cytochrome b6f complex stability to PGR5

PROTON GRADIENT REGULATION5 (PGR5) is thought to promote cyclic electron flow, and its deficiency impairs photosynthetic control and increases photosensitivity of photosystem (PS) I, leading to seedling lethality under fluctuating light (FL). By screening for Arabidopsis (Arabidopsis thaliana) suppressor mutations that rescue the seedling lethality of pgr5 plants under FL, we identified a portfolio of mutations in 12 different genes. These mutations affect either PSII function, cytochrome b6f (cyt b6f) assembly, plastocyanin (PC) accumulation, the CHLOROPLAST FRUCTOSE-1,6-BISPHOSPHATASE1 (cFBP1), or its negative regulator ATYPICAL CYS HIS-RICH THIOREDOXIN2 (ACHT2). The characterization of the mutants indicates that the recovery of viability can in most cases be explained by the restoration of PSI donor side limitation, which is caused by reduced electron flow to PSI due to defects in PSII, cyt b6f, or PC. Inactivation of cFBP1 or its negative regulator ACHT2 results in increased levels of the NADH dehydrogenase-like complex. This increased activity may be responsible for suppressing the pgr5 phenotype under FL conditions. Plants that lack both PGR5 and DE-ETIOLATION-INDUCED PROTEIN1 (DEIP1)/NEW TINY ALBINO1 (NTA1), previously thought to be essential for cyt b6f assembly, are viable and accumulate cyt b6f. We suggest that PGR5 can have a negative effect on the cyt b6f complex and that DEIP1/NTA1 can ameliorate this negative effect.

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.

EMS-induced missense mutation in TaCHLI-7D affects leaf color and yield-related traits in wheat

KEY MESSAGE

Mutations in TaCHLI impact chlorophyll levels and yield-related traits in wheat. Natural variations in TaCHLI-7A/B influence plant productivity, offering potential for molecular breeding. Chlorophyll is essential for plant growth and productivity. The CHLI subunit of the magnesium chelatase protein plays a key role inserting magnesium into protoporphyrin IX during chlorophyll biosynthesis. Here, we identify a novel wheat mutant chlorophyll (chl) that exhibits yellow-green leaves, reduced chlorophyll levels, and increased carotenoid content, leading to an overall decline in yield-related traits. Map-based cloning reveals that the chl phenotype is caused by a point mutation (Asp186Asn) in the TaCHLI-7D gene, which encodes subunit I of magnesium chelatase. Furthermore, the three TaCHLI mutants: chl-7b-1 (Pro82Ser), chl-7b-2 (Ala291Thr), and chl-7d-1 (Gly357Glu), also showed significant reductions in chlorophyll content and yield-related traits. However, TaCHLI-7D overexpression in rice significantly decreased thousand kernel weight, yield per plant, and germination. Additionally, natural variations in TaCHLI-7A/B are significantly associated with flag leaf, spike exsertion length, and yield per plant. Notably, the favorable haplotype, TaCHLI-7B-HapII, which displayed higher thousand kernel weight and yield per plant, is positively selected in wheat breeding. Our study provides insights on the regulatory molecular mechanisms underpinning leaf color and chlorophyll biosynthesis, and highlights TaCHLI functions, which provide useful molecular markers and genetic resources for wheat breeding.

Leaf Functional Traits and Their Influencing Factors in Six Typical Vegetation Communities

Leaf functional traits (LFTs) have become a popular topic in ecological research in recent years. Here, we measured eight LFTs, namely leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC), in six typical vegetation communities (sclerophyllous evergreen broad-leaved forests, temperate evergreen coniferous forests, cold-temperate evergreen coniferous forests, alpine deciduous broad-leaved shrubs, alpine meadows, and alpine scree sparse vegetation) in the Chayu River Basin, southeastern Qinghai-Tibet Plateau. Our aim was to explore their relationships with evolutionary history and environmental factors by combining the RLQ and the fourth-corner method, and the method of testing phylogenetic signal. The results showed that (i) there were significant differences in the eight LFTs among the six vegetation communities; (ii) the K values of the eight LFTs were less than 1; and (iii) except for LCC, all other LFTs were more sensitive to environmental changes. Among these traits, LA was the most affected by the environmental factors, followed by LNC. It showed that the LFTs in the study were minimally influenced by phylogenetic development but significantly by environmental changes. This study further verified the ecological adaptability of plants to changes in environmental factors and provides a scientific basis for predicting the distribution and diffusion direction of plants under global change conditions.

Unmasking Spatial Heterogeneity in Phytotoxicology Mechanisms Induced by Carbamazepine by Mass Spectrometry Imaging and Multiomics Analyses

Previous studies have highlighted the toxicity of pharmaceuticals and personal care products (PPCPs) in plants, yet understanding their spatial distribution within plant tissues and specific toxic effects remains limited. This study investigates the spatial-specific toxic effects of carbamazepine (CBZ), a prevalent PPCP, in plants. Utilizing desorption electrospray ionization mass spectrometry imaging (DESI-MSI), CBZ and its transformation products were observed predominantly at the leaf edges, with 2.3-fold higher concentrations than inner regions, which was confirmed by LC-MS. Transcriptomic and metabolic analyses revealed significant differences in gene expression and metabolite levels between the inner and outer leaf regions, emphasizing the spatial location's role in CBZ response. Notably, photosynthesis-related genes were markedly downregulated, and photosynthetic efficiency was reduced at leaf edges. Additionally, elevated oxidative stress at leaf edges was indicated by higher antioxidant enzyme activity, cell membrane impairment, and increased free fatty acids. Given the increased oxidative stress at the leaf margins, the study suggests using in situ Raman spectroscopy for early detection of CBZ-induced damage by monitoring reactive oxygen species levels. These findings provide crucial insights into the spatial toxicological mechanisms of CBZ in plants, forming a basis for future spatial toxicology research of PPCPs.

From leaf to multiscale models of photosynthesis: applications and challenges for crop improvement

To keep up with the growth of human population and to circumvent deleterious effects of global climate change, it is essential to enhance crop yield to achieve higher production. Here we review mathematical models of oxygenic photosynthesis that are extensively used, and discuss in depth a subset that accounts for diverse approaches providing solutions to our objective. These include models (1) to study different ways to enhance photosynthesis, such as fine-tuning antenna size, photoprotection and electron transport; (2) to bioengineer carbon metabolism; and (3) to evaluate the interactions between the process of photosynthesis and the seasonal crop dynamics, or those that have included statistical whole-genome prediction methods to quantify the impact of photosynthesis traits on the improvement of crop yield. We conclude by emphasizing that the results obtained in these studies clearly demonstrate that mathematical modelling is a key tool to examine different approaches to improve photosynthesis for better productivity, while effective multiscale crop models, especially those that also include remote sensing data, are indispensable to verify different strategies to obtain maximized crop yields.

How much could improving photosynthesis increase crop yields? A call for systems-level perspectives to guide engineering strategies

Global yield gaps can be reduced through breeding and improved agronomy. However, signs of yield plateaus from wheat and rice grown in intensively farmed systems indicate a need for new strategies if output is to continue to increase. Approaches to improve photosynthesis are suggested as a solution. Empirical evidence supporting this approach comes from small-scale free-CO2 air enrichment and transgenic studies. However, the likely achievable gains from improving photosynthesis are less understood. Models predict maximum increases in yield of 5.3-19.1% from genetic manipulation depending on crop, environment, and approach, but uncertainty remains in the presence of stress. This review seeks to provide context to the rationale for improving photosynthesis, highlight areas of uncertainty, and identify the steps required to create more accurate projections.

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.

Zno nanoparticles: improving photosynthesis, shoot development, and phyllosphere microbiome composition in tea plants

BACKGROUND

Nanotechnology holds revolutionary potential in the field of agriculture, with zinc oxide nanoparticles (ZnO NPs) demonstrating advantages in promoting crop growth. Enhanced photosynthetic efficiency is closely linked to improved vigor and superior quality in tea plants, complemented by the beneficial role of phyllosphere microorganisms in maintaining plant health. However, the effects of ZnO NPs on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms have not been fully investigated.

RESULTS

This study investigated the photosynthetic physiological parameters of tea plants under the influence of ZnO NPs, the content of key photosynthetic enzymes such as RubisCO, chlorophyll content, chlorophyll fluorescence parameters, transcriptomic and extensive targeted metabolomic profiles of leaves and new shoots, mineral element composition in these tissues, and the epiphytic and endophytic microbial communities within the phyllosphere. The results indicated that ZnO NPs could enhance the photosynthesis of tea plants, upregulate the expression of some genes related to photosynthesis, increase the accumulation of photosynthetic products, promote the development of new shoots, and alter the content of various mineral elements in the leaves and new shoots of tea plants. Furthermore, the application of ZnO NPs was observed to favorably influence the microbial community structure within the phyllosphere of tea plants. This shift in microbial community dynamics suggests a potential for ZnO NPs to contribute to plant health and productivity by modulating the phyllosphere microbiome.

CONCLUSION

This study demonstrates that ZnO NPs have a positive impact on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms, which can improve the growth condition of tea plants. These findings provide new scientific evidence for the application of ZnO NPs in sustainable agricultural development and contribute to advancing research in nanobiotechnology aimed at enhancing crop yield and quality.

Optimal photosynthesis requires a balanced diet of ions

This article is a Commentary on Kunz et al. (2024), 243: 543–559.

Chloroplast ion homeostasis - what do we know and where should we go?

Plant yields heavily depend on proper macro- and micronutrient supply from the soil. In the leaf cells, nutrient ions fulfill specific roles in biochemical reactions, especially photosynthesis housed in the chloroplast. Here, a well-balanced ion homeostasis is maintained by a number of ion transport proteins embedded in the envelope and thylakoid membranes. Ten years ago, the first alkali metal transporters from the K+ EFFLUX ANTIPORTER family were discovered in the model plant Arabidopsis. Since then, our knowledge about the physiological importance of these carriers and their substrates has greatly expanded. New insights into the role of alkali ions in plastid gene expression and photoprotective mechanisms, both prerequisites for plant productivity in natural environments, were gained. The discovery of a Cl- channel in the thylakoid and several additional plastid alkali and alkali metal transport proteins have advanced the field further. Nevertheless, scientists still have long ways to go before a complete systemic understanding of the chloroplast's ion transportome will emerge. In this Tansley review, we highlight and discuss the achievements of the last decade. More importantly, we make recommendations on what areas to prioritize, so the field can reach the next milestones. One area, laid bare by our similarity-based comparisons among phototrophs is our lack of knowledge what ion transporters are used by cyanobacteria to buffer photosynthesis fluctuations.

Modulation of Photosystem II Function in Celery via Foliar-Applied Salicylic Acid during Gradual Water Deficit Stress

Water deficit is the major stress factor magnified by climate change that causes the most reductions in plant productivity. Knowledge of photosystem II (PSII) response mechanisms underlying crop vulnerability to drought is critical to better understanding the consequences of climate change on crop plants. Salicylic acid (SA) application under drought stress may stimulate PSII function, although the exact mechanism remains essentially unclear. To reveal the PSII response mechanism of celery plants sprayed with water (WA) or SA, we employed chlorophyll fluorescence imaging analysis at 48 h, 96 h, and 192 h after watering. The results showed that up to 96 h after watering, the stroma lamellae of SA-sprayed leaves appeared dilated, and the efficiency of PSII declined, compared to WA-sprayed plants, which displayed a better PSII function. However, 192 h after watering, the stroma lamellae of SA-sprayed leaves was restored, while SA boosted chlorophyll synthesis, and by ameliorating the osmotic potential of celery plants, it resulted in higher relative leaf water content compared to WA-sprayed plants. SA, by acting as an antioxidant under drought stress, suppressed phototoxicity, thereby offering PSII photoprotection, together with enhanced effective quantum yield of PSII photochemistry (ΦPSII) and decreased quantity of singlet oxygen (1O2) generation compared to WA-sprayed plants. The PSII photoprotection mechanism induced by SA under drought stress was triggered by non-photochemical quenching (NPQ), which is a strategy to protect the chloroplast from photo-oxidative damage by dissipating the excess light energy as heat. This photoprotective mechanism, triggered by NPQ under drought stress, was adequate in keeping, especially in high-light conditions, an equal fraction of open PSII reaction centers (qp) as of non-stress conditions. Thus, under water deficit stress, SA activates a regulatory network of stress and light energy partitioning signaling that can mitigate, to an extent, the water deficit stress on PSII functioning.

Review on Microreactors for Photo-Electrocatalysis Artificial Photosynthesis Regeneration of Coenzymes

In recent years, with the outbreak of the global energy crisis, renewable solar energy has become a focal point of research. However, the utilization efficiency of natural photosynthesis (NPS) is only about 1%. Inspired by NPS, artificial photosynthesis (APS) was developed and utilized in applications such as the regeneration of coenzymes. APS for coenzyme regeneration can overcome the problem of high energy consumption in comparison to electrocatalytic methods. Microreactors represent a promising technology. Compared with the conventional system, it has the advantages of a large specific surface area, the fast diffusion of small molecules, and high efficiency. Introducing microreactors can lead to more efficient, economical, and environmentally friendly coenzyme regeneration in artificial photosynthesis. This review begins with a brief introduction of APS and microreactors, and then summarizes research on traditional electrocatalytic coenzyme regeneration, as well as photocatalytic and photo-electrocatalysis coenzyme regeneration by APS, all based on microreactors, and compares them with the corresponding conventional system. Finally, it looks forward to the promising prospects of this technology.

Differential photosynthetic plasticity of Amazonian tree species in response to light environments

To investigate how and to what extent there are differences in the photosynthetic plasticity of trees in response to different light environments, six species from three successional groups (late successional, mid-successional, and pioneers) were exposed to three different light environments [deep shade - DS (5% full sunlight - FS), moderate shade - MS (35% FS) and full sunlight - FS]. Maximum net photosynthesis (Amax), leaf N partitioning, stomatal, mesophile, and biochemical limitations (SL, ML, and BL, respectively), carboxylation velocity (Vcmax), and electron transport (Jmax) rates, and the state of photosynthetic induction (IS) were evaluated. Higher values of Amax, Vcmax, and Jmax in FS were observed for pioneer species, which invested the largest amount of leaf N in Rubisco. The lower IS for pioneer species reveals its reduced ability to take advantage of sunflecks. In general, the main photosynthetic limitations are diffusive, with SL and ML having equal importance under FS, and ML decreasing along with irradiance. The leaf traits, which are more determinant of the photosynthetic process, respond independently in relation to the successional group, especially with low light availability. An effective partitioning of leaf N between photosynthetic and structural components played a crucial role in the acclimation process and determined the increase or decrease of photosynthesis in response to the light conditions.

Overexpression of cassava melatonin receptor PMTR1 plays dual roles in development under light and dark conditions in Arabidopsis

KEY MESSAGE

MePMTR1 is involved in plant development and production as well as photosynthesis in plant. Melatonin is widely involved in plant growth and development as well as stress responses. Compared with the extending studies of melatonin in stress responses, the direct link between melatonin and plant development in the whole stages remains unclear. With the identification of phytomelatonin receptor PMTR1 in plants, melatonin signalling is becoming much clearer. However, the function of MePMTR1 in tropical crop cassava remains elusive. In this study, we found that overexpression of MePMTR1 showed larger biomass than wild type (WT), including higher number and area of leaves, weight, and accompanying with higher photosynthetic efficiency. Consistently, exogenous melatonin accelerated photosynthetic rate in Arabidopsis. In addition, MePMTR1-overexpressed plants exhibited more resistance to dark-induced senescence compared with WT, demonstrated by higher chlorophyll, lower hydrogen peroxide and superoxide content. In summary, this study illustrated that melatonin and its receptor regulate growth, development and senescence in plants, highlighting the potential application of melatonin and its receptor in improving crop yield and photosynthesis.

Psb28 protein is indispensable for stable accumulation of PSII core complexes in Arabidopsis

Enhancing the efficiency of photosynthesis represents a promising strategy to improve crop yields, with keeping the steady state of PSII being key to determining the photosynthetic performance. However, the mechanisms whereby the stability of PSII is maintained in oxygenic organisms remain to be explored. Here, we report that the Psb28 protein functions in regulating the homeostasis of PSII under different light conditions in Arabidopsis thaliana. The psb28 mutant is much smaller than the wild-type plants under normal growth light, which is due to its significantly reduced PSII activity. Similar defects were seen under low light and became more pronounced under photoinhibitory light. Notably, the amounts of PSII core complexes and core subunits are specifically decreased in psb28, whereas the abundance of other representative components of photosynthetic complexes remains largely unaltered. Although the PSII activity of psb28 was severely reduced when subjected to high light, its recovery from photoinactivation was not affected. By contrast, the degradation of PSII core protein subunits is dramatically accelerated in the presence of lincomycin. These results indicate that psb28 is defective in the photoprotection of PSII, which is consistent with the observation that the overall NPQ is much lower in psb28 compared to the wild type. Moreover, the Psb28 protein is associated with PSII core complexes and interacts mainly with the CP47 subunit of PSII core. Taken together, these findings reveal an important role for Psb28 in the protection and stabilization of PSII core in response to changes in light environments.

Mechanistic Insights on Salicylic Acid-Induced Enhancement of Photosystem II Function in Basil Plants under Non-Stress or Mild Drought Stress

Photosystem II (PSII) functions were investigated in basil (Ocimum basilicum L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS) conditions. Under MiDS, SA-sprayed leaves retained significantly higher (+36%) chlorophyll content compared to NS, SA-sprayed leaves. PSII efficiency in SA-sprayed leaves under NS conditions, evaluated at both low light (LL, 200 μmol photons m-2 s-1) and high light (HL, 900 μmol photons m-2 s-1), increased significantly with a parallel significant decrease in the excitation pressure at PSII (1-qL) and the excess excitation energy (EXC). This enhancement of PSII efficiency under NS conditions was induced by the mechanism of non-photochemical quenching (NPQ) that reduced singlet oxygen (1O2) production, as indicated by the reduced quantum yield of non-regulated energy loss in PSII (ΦNO). Under MiDS, the thylakoid structure of water-sprayed leaves appeared slightly dilated, and the efficiency of PSII declined, compared to NS conditions. In contrast, the thylakoid structure of SA-sprayed leaves did not change under MiDS, while PSII functionality was retained, similar to NS plants at HL. This was due to the photoprotective heat dissipation by NPQ, which was sufficient to retain the same percentage of open PSII reaction centers (qp), as in NS conditions and HL. We suggest that the redox status of the plastoquinone pool (qp) under MiDS and HL initiated the acclimation response to MiDS in SA-sprayed leaves, which retained the same electron transport rate (ETR) with control plants. Foliar spray of SA could be considered as a method to improve PSII efficiency in basil plants under NS conditions, at both LL and HL, while under MiDS and HL conditions, basil plants could retain PSII efficiency similar to control plants.

Potential molecular mechanism of photosynthesis regulation by PeMPK7 in poplar under para-hydroxybenzoic acid stress

Due to continuous plantation of poplar, its growth and biomass accumulation may be negatively affected by the accumulation of allelochemicals such as para-hydroxybenzoic acid (pHBA) in soil. As photosynthesis is the most fundamental process in plants, it can be negatively impacted by pHBA stress. Therefore, it is crucial to improve photosynthetic capacity under pHBA stress to facilitate poplar plant growth. The mitogen-activated protein kinase (MAPK) cascade pathway is widely involved in environmental stress responses in plants. However, the regulation mechanisms of photosynthesis-related pathways by MAPK pathway genes under pHBA stress are still unclear. In this study, through transcriptome analysis and weighted gene co-expression network analysis, we observed that PeMPK7 overexpression in poplar can regulate the expression of photosynthesis-related genes and transcription factor genes, namely, WRKY1, WRKY33, and ERF3, during the early stage of pHBA stress. In addition, PeMPK7 can improve photosynthesis in poplar under long-term pHBA stress. Moreover, yeast two-hybrid and pull-down assays confirmed the interaction between PeMPK7 and PeMKK7/10. Based on these results, a schematic diagram of the pathways involved in the regulation of photosynthesis by PeMPK7 was constructed. This study provided novel insights into the molecular mechanisms of regulation of pHBA stress via MAPK cascade pathway.

Genome-wide identification of GA2ox genes family and analysis of PbrGA2ox1-mediated enhanced chlorophyll accumulation by promoting chloroplast development in pear

BACKGROUND

Chlorophyll (Chl) is an agronomic trait associated with photosynthesis and yield. Gibberellin 2-oxidases (GA2oxs) have previously been shown to be involved in Chl accumulation. However, whether and how the PbrGA2ox proteins (PbrGA2oxs) mediate Chl accumulation in pear (Pyrus spp.) is scarce.

RESULTS

Here, we aimed to elucidate the role of the pear GA2ox gene family in Chl accumulation and the related underlying mechanisms. We isolated 13 PbrGA2ox genes (PbrGA2oxs) from the pear database and identified PbrGA2ox1 as a potential regulator of Chl accumulation. We found that transiently overexpressing PbrGA2ox1 in chlorotic pear leaves led to Chl accumulation, and PbrGA2ox1 silencing in normal pear leaves led to Chl degradation, as evident by the regreening and chlorosis phenomenon, respectively. Meanwhile, PbrGA2ox1-overexpressing (OE) tobacco plants discernably exhibited Chl built-up, as evidenced by significantly higher Pn and Fv/Fm. In addition, RNA sequencing (RNA-seq), physiological and biochemical investigations revealed an increase in abscisic acid (ABA), methyl jasmonate (MeJA), and salicylic acid (SA) concentrations and signaling pathways; a marked elevation in reducing and soluble sugar contents; and a marginal decline in the starch and sucrose levels in OE plants. Interestingly, PbrGA2ox1 overexpression did not prominently affect Chl synthesis. However, it indeed facilitated chloroplast development by increasing chloroplast number per cell and compacting the thylakoid granum stacks. These findings might jointly contribute to Chl accumulation in OE plants.

CONCLUSION

Overall, our results suggested that GA2oxs accelerate Chl accumulation by stimulating chloroplast development and proved the potential of PbrGA2ox1 as a candidate gene for genetically breeding biofortified pear plants with a higher yield.

Advances in light system engineering across the phototrophic spectrum

Current work in photosynthetic engineering is progressing along the lines of cyanobacterial, microalgal, and plant research. These are interconnected through the fundamental mechanisms of photosynthesis and advances in one field can often be leveraged to improve another. It is worthwhile for researchers specializing in one or more of these systems to be aware of the work being done across the entire research space as parallel advances of techniques and experimental approaches can often be applied across the field of photosynthesis research. This review focuses on research published in recent years related to the light reactions of photosynthesis in cyanobacteria, eukaryotic algae, and plants. Highlighted are attempts to improve photosynthetic efficiency, and subsequent biomass production. Also discussed are studies on cross-field heterologous expression, and related work on augmented and novel light capture systems. This is reviewed in the context of translatability in research across diverse photosynthetic organisms.

Organic Semiconducting Polymers for Augmenting Biosynthesis and Bioconversion

Solar-driven biosynthesis and bioconversion are essential for achieving sustainable resources and renewable energy. These processes harness solar energy to produce biomass, chemicals, and fuels. While they offer promising avenues, some challenges and limitations should be investigated and addressed for their improvement and widespread adoption. These include the low utilization of light energy, the inadequate selectivity of products, and the limited utilization of inorganic carbon/nitrogen sources. Organic semiconducting polymers offer a promising solution to these challenges by collaborating with natural microorganisms and developing artificial photosynthetic biohybrid systems. In this Perspective, we highlight the latest advancements in the use of appropriate organic semiconducting polymers to construct artificial photosynthetic biohybrid systems. We focus on how these systems can enhance the natural photosynthetic efficiency of photosynthetic organisms, create artificial photosynthesis capability of nonphotosynthetic organisms, and customize the value-added chemicals of photosynthetic synthesis. By examining the structure-activity relationships and emphasizing the mechanism of electron transfer based on organic semiconducting polymers in artificial photosynthetic biohybrid systems, we aim to shed light on the potential of this novel strategy for artificial photosynthetic biohybrid systems. Notably, these coupling strategies between organic semiconducting polymers and organisms during artificial photosynthetic biohybrid systems will pave the way for a more sustainable future with solar fuels and chemicals.

Field-work reveals a novel function for MAX2 in a native tobacco's high-light adaptions

Laboratory studies have revealed that strigolatone (SL) and karrikin (KAR) signalling mediate responses to abiotic and biotic stresses, and reshape branching architecture that could increase reproductive performance and crop yields. To understand the ecological function of SL and KAR signalling, transgenic lines of wild tobacco Nicotiana attenuata, silenced in SL/KAR biosynthesis/signalling were grown in the glasshouse and in two field plots in the Great Basin Desert in Utah over four field seasons. Of the lines silenced in SL and KAR signalling components (irMAX2, irD14, irKAI2 and irD14 × irKAI2 plants), which exhibited the expected increases in shoot branching, only irMAX2 plants showed a strong leaf-bleaching phenotype when grown in the field. In the field, irMAX2 plants had lower sugar and higher leaf amino acid contents, lower lifetime fitness and were more susceptible to herbivore attack compared to wild-type plants. These irMAX2 phenotypes were not observed in glasshouse-grown plants. Transcriptomic analysis revealed dramatic responses to high-light intensity in irMAX2 leaves in the field: lutein contents decreased, and transcriptional responses to high-intensity light, singlet oxygen and hydrogen peroxide increased. PAR and UV-B manipulations in the field revealed that the irMAX2 bleaching phenotype is reversed by decreasing PAR, but not UV-B fluence. We propose that NaMAX2 functions in high-light adaptation and fitness optimisation by regulating high-light responses independently of its roles in the SL and KAR signalling pathways. The work provides another example of the value of studying the function of genes in the complex environments in which plants evolved, namely nature.

Responding to light signals: a comprehensive update on photomorphogenesis in cyanobacteria

Cyanobacteria are ancestors of chloroplast and perform oxygen-evolving photosynthesis similar to higher plants and algae. However, an obligatory requirement of photons for their growth results in the exposure of cyanobacteria to varying light conditions. Therefore, the light environment could act as a signal to drive the developmental processes, in addition to photosynthesis, in cyanobacteria. These Gram-negative prokaryotes exhibit characteristic light-dependent developmental processes that maximize their fitness and resource utilization. The development occurring in response to radiance (photomorphogenesis) involves fine-tuning cellular physiology, morphology and metabolism. The best-studied example of cyanobacterial photomorphogenesis is chromatic acclimation (CA), which allows a selected number of cyanobacteria to tailor their light-harvesting antenna called phycobilisome (PBS). The tailoring of PBS under existing wavelengths and abundance of light gives an advantage to cyanobacteria over another photoautotroph. In this work, we will provide a comprehensive update on light-sensing, molecular signaling and signal cascades found in cyanobacteria. We also include recent developments made in other aspects of CA, such as mechanistic insights into changes in the size and shape of cells, filaments and carboxysomes.

Optimizing the electron transport chain to sustainably improve photosynthesis

Genetically improving photosynthesis is a key strategy to boosting crop production to meet the rising demand for food and fuel by a rapidly growing global population in a warming climate. Many components of the photosynthetic apparatus have been targeted for genetic modification for improving photosynthesis. Successful translation of these modifications into increased plant productivity in fluctuating environments will depend on whether the electron transport chain (ETC) can support the increased electron transport rate without risking overreduction and photodamage. At present atmospheric conditions, the ETC appears suboptimal and will likely need to be modified to support proposed photosynthetic improvements and to maintain energy balance. Here, I derive photochemical equations to quantify the transport capacity and the corresponding reduction level based on the kinetics of redox reactions along the ETC. Using these theoretical equations and measurements from diverse C3/C4 species across environments, I identify several strategies that can simultaneously increase the transport capacity and decrease the reduction level of the ETC. These strategies include increasing the abundances of reaction centers, cytochrome b6f complexes, and mobile electron carriers, improving their redox kinetics, and decreasing the fraction of secondary quinone-nonreducing photosystem II reaction centers. I also shed light on several previously unexplained experimental findings regarding the physiological impacts of the abundances of the cytochrome b6f complex and plastoquinone. The model developed, and the insights generated from it facilitate the development of sustainable photosynthetic systems for greater crop yields.

Coordination of carbon assimilation, allocation, and utilization for systemic improvement of cereal yield

The growth of yield outputs is dwindling after the first green revolution, which cannot meet the demand for the projected population increase by the mid-century, especially with the constant threat from extreme climates. Cereal yield requires carbon (C) assimilation in the source for subsequent allocation and utilization in the sink. However, whether the source or sink limits yield improvement, a crucial question for strategic orientation in future breeding and cultivation, is still under debate. To narrow the knowledge gap and capture the progress, we focus on maize, rice, and wheat by briefly reviewing recent advances in yield improvement by modulation of i) leaf photosynthesis; ii) primary C allocation, phloem loading, and unloading; iii) C utilization and grain storage; and iv) systemic sugar signals (e.g., trehalose 6-phosphate). We highlight strategies for optimizing C allocation and utilization to coordinate the source-sink relationships and promote yields. Finally, based on the understanding of these physiological mechanisms, we envisage a future scenery of "smart crop" consisting of flexible coordination of plant C economy, with the goal of yield improvement and resilience in the field population of cereals crops.

Studying the effect of light intensity on the photosynthetic mechanism of pepper leaf yellowing mutants by proteomics and phosphoproteomics

The leaf is an important plant organ and is closely related to agricultural yield. Photosynthesis plays a critical role in promoting plant growth and development. Understanding the mechanism of leaf photosynthesis regulation will help improve crop yield. In this study, the pepper yellowing mutant was used as the experimental material, and the photosynthetic changes of pepper leaves (yl1 and 6421) under different light intensities were analyzed by chlorophyll fluorimeter and photosynthesis meter. Changes in proteins and enrichment of phosphopeptides in pepper leaves were determined. The results showed that different light intensities had significant effects on the chlorophyll fluorescence and photosynthetic parameters of pepper leaves. The differentially expressed proteins (DEPs) and differentially expressed phosphorylated proteins (DEPPs) were mainly involved in photosynthesis, photosynthesis-antenna proteins, and carbon fixation in photosynthetic organisms. In yl1 leaves, the phosphorylation levels of photosynthesis and photosynthesis-antenna proteins LHCA2, LHCA3, PsbC, PsbO, and PsbP were lower under low light treatment, but significantly higher under high light intensity compared with wild-type leaves. In addition, many proteins involved in the carbon assimilation pathway, including TKT, Rubisco, and PGK, were phosphorylated, and this modification level was significantly higher in yl1 than in the wild type under high light intensity. These results provide a new perspective for studying the photosynthesis mechanism of pepper under different light intensities.

Improving Nitrogen Use Efficiency in Rice for Sustainable Agriculture: Strategies and Future Perspectives

Nitrogen (N) is an important nutrient for the growth and development of rice. The application of N fertilizer has become one of the inevitable ways to increase rice yield due to insufficient soil N content. However, in order to achieve stable and high yield, farmers usually increase N fertilizer input without hesitation, resulting in a series of problems such as environmental pollution, energy waste and low production efficiency. For sustainable agriculture, improving the nitrogen use efficiency (NUE) to decrease N fertilizer input is imperative. In the present review, we firstly demonstrate the role of N in mediating root architecture, photosynthesis, metabolic balance, and yield components in rice. Furthermore, we further summarize the current agronomic practices for enhancing rice NUE, including balanced fertilization, the use of nitrification inhibitors and slow-release N fertilizers, the split application of N fertilizer, root zone fertilization, and so on. Finally, we discuss the recent advances of N efficiency-related genes with potential breeding value. These genes will contribute to improving the N uptake, maintain the N metabolism balance, and enhance the NUE, thereby breeding new varieties against low N tolerance to improve the rice yield and quality. Moreover, N-efficient varieties also need combine with precise N fertilizer management and advanced cultivation techniques to realize the maximum exploitation of their biological potential.

The era of cultivating smart rice with high light efficiency and heat tolerance has come of age

How to improve the yield of crops has always been the focus of breeding research. Due to the population growth and global climate change, the demand for food has increased sharply, which has brought great challenges to agricultural production. In order to make up for the limitation of global cultivated land area, it is necessary to further improve the output of crops. Photosynthesis is the main source of plant assimilate accumulation, which has a profound impact on the formation of its yield. This review focuses on the cultivation of high light efficiency plants, introduces the main technical means and research progress in improving the photosynthetic efficiency of plants, and discusses the main problems and difficulties faced by the cultivation of high light efficiency plants. At the same time, in view of the frequent occurrence of high-temperature disasters caused by global warming, which seriously threatened plant normal production, we reviewed the response mechanism of plants to heat stress, introduced the methods and strategies of how to cultivate heat tolerant crops, especially rice, and briefly reviewed the progress of heat tolerant research at present. Given big progress in these area, the era of cultivating smart rice with high light efficiency and heat tolerance has come of age.