SummaryImproving the efficiency of crop photosynthesis has the potential to increase yields. Genetic manipulation showed photosynthesis can be improved by speeding up relaxation of photoprotective mechanisms during sun to shade transitions. However, it is unclear if natural variation in relaxation of non-photochemical quenching (NPQ) can be exploited in crop breeding programs. To address this issue, we measured six NPQ parameters in the 40 founder lines and common parent of a Soybean Nested Association Mapping (SoyNAM) panel over two field seasons in Illinois. NPQ parameters did not show consistently variable trends throughout development, and variation between sampling days suggests environmental impacts on NPQ which last more than 24 hours. 17 genotypes were found to show small but consistent differences in NPQ relaxation kinetics relative to a reference line providing a basis for future mapping studies. Finally, a soybean canopy model predicted available phenotypic variation could result in a 1.6% difference in carbon assimilation when comparing fastest and slowest relaxing NPQ values.Significance StatementEvidence suggests increasing the rate of relaxation of photoprotection can lead to improved biomass and yield. We compare photoprotection relaxation rates in 41 diverse soybean genotypes grown in the field, identifying lines with faster rates of relaxation, and predict a potential 1.6% difference in daily carbon assimilation which could contribute to improving soybean performance.

The effect of single dietary fibre (DF) on lowering uric acid (UA) level has been reported in the literature. However, the potential protective mechanism of DF against potassium oxybate-induced hyperuricaemia (HUA), as modelled by prophylactic administration, remains unclear. The data demonstrate that DF significantly decreased serum and cerebral tissue UA concentrations, inhibited xanthine oxidase expression and activity in the liver and reduced levels of creatinine and urea nitrogen in the serum. Additionally, it mitigated the deposition of amyloid-β in cerebral tissue. Correlation analysis showed that DF modulated the Toll-like receptor 4/NF-κB signalling pathway, attenuating oxidative stress and inflammatory responses in HUA mice. Additionally, DF helps to maintain the composition of the gut microbiota, reducing harmful Desulfovibrio and enriching beneficial Akkermansia and Ruminococcus populations. The results of the faecal metabolomics analysis indicate that DF facilitates the regulation of metabolic pathways involved in oxidative stress and inflammation. These pathways include pyrimidine metabolism, tryptophan metabolism, nucleotide metabolism and vitamin B6 metabolism. Additionally, the study found that DF has a preventive effect on anxiety-like behaviour induced by HUA. In summary, DF shows promise in mitigating HUA and cognitive deficits, primarily by modulating gut microbiota and metabolites.

Photosynthetic adaptations to light fluctuations do not occur instantaneously, leading to reduced carbon gain and lower productivity in agricultural crops. Enhancing the rapidity of photosynthetic responses to these fluctuations could potentially increase carbon assimilation by 13–32%, indicating a substantial opportunity for yield improvement of major crops. The most of crops can be categorized into C3 or C4 crops by their photosynthetic pathways. This review provides a comparative overview of the photosynthetic responses of both C3 and C4 crops to light fluctuations, highlighting the unique and shared challenges for these two photosynthetic pathways. In C3 crops, fast adjustments in non-photochemical quenching (NPQ), stomatal and mesophyll conductance, and Rubisco activation are essential for optimizing photosynthesis under variable light conditions. In contrast, C4 crops, including maize, sorghum, and sugarcane, benefit from their carbon concentration mechanism under high-light conditions but face challenges in coordinating the C4 and CBB (Calvin–Benson–Bassham) cycles. Strategies to enhance the activation of pyruvate phosphate dikinase (PPDK) and Rubisco, as well as to improve electron transport capacity and flexibility, could markedly boost their photosynthetic efficiency and productivity. Through a detailed understanding of the distinct mechanisms involved in C3 and C4 photosynthesis, this review underscores the need for tailored strategies to optimize the photosynthetic efficiency specific to each crop type. Exploring and leveraging these differences is crucial for propelling agricultural productivity forward.

In agronomically important C4 grasses, efficient CO2 delivery to Rubisco is facilitated by NADP-malic enzyme (C4NADP-ME), which decarboxylates malate in bundle sheath cells. However, understanding the molecular regulation of the C4NADP-ME gene in sugarcane (Saccharum spp.) is hindered by its complex genetic background. Enzymatic activity assays demonstrated that decarboxylation in sugarcane Saccharum spontaneum predominantly relies on the NADP-ME pathway, similar to sorghum (Sorghum bicolor) and maize (Zea mays). Comparative genomics analysis revealed the recruitment of 8 core C4 shuttle genes, including C4NADP-ME (SsC4NADP-ME2), in the C4 pathway of sugarcane. Contrasting to sorghum and maize, the expression of SsC4NADP-ME2 in sugarcane is regulated by different transcription factors (TFs). We propose a gene regulatory network for SsC4NADP-ME2, involving candidate TFs identified through gene coexpression analysis and yeast 1-hybrid experiment. Among these, ABA INSENSITIVE5 (ABI5) was validated as the predominant regulator of SsC4NADP-ME2 expression, binding to a G-box within its promoter region. Interestingly, the core element ACGT within the regulatory G-box was conserved in sugarcane, sorghum, maize, and rice (Oryza sativa), suggesting an ancient regulatory code utilized in C4 photosynthesis. This study offers insights into SsC4NADP-ME2 regulation, crucial for optimizing sugarcane as a bioenergy crop.

Photosynthesis and crop growth are inseparable processes that govern plant carbon assimilation and allocation. An accurate model description of these processes can bridge dynamics at the leaf and canopy levels, assisting in identifying potential photosynthetic improvements that can be converted into increased yield. Integrating multiscale biophysical processes and achieving computational effectiveness for seasonal simulations, however, are challenging. Here, we present a fully coupled modelling framework that integrates a metabolic model of C3 photosynthesis (ePhotosynthesis) and a semi-mechanistic crop growth model (BioCro). We replaced the leaf-level Farquhar photosynthesis model in BioCro with the ePhotosynthesis model that mechanistically describes the photosystem electron transport processes and the C3 carbon metabolism including the Calvin-Benson-Bassham cycle and the photorespiratory pathway. The coupled BioCro-ePhotosynthesis model was calibrated to represent a soybean cultivar and developed to be operationally fast for seasonal simulations. As an example of model application, we conducted a global sensitivity analysis of 26 enzymes under an average daytime intercepted radiation of 400 mu mol m-2 s-1, identifying 2 enzymes, phosphoglycerate kinase (PGK) and phosphoribulokinase (PRK), which had the largest impact on the leaf-level assimilation. Increasing PGK and PRK by 2-fold was predicted to increase the leaf-level assimilation by 8.3 % and the final seed yield by 6.75 % +/- 0.5 % over 4 years of observed field climate data. The coupled BioCro-ePhotosynthesis model provides a seamless and efficient integration between the leaf-level metabolism and the field-level yield over a full growing season. The coupled model could be further applied to investigate non-steady-state photosynthetic processes such as non-photochemical quenching.

C-glycosylated flavones (CGFs) are the main flavonoids in duckweed (Lemna turionifera), known for their diverse pharmacological activities and nutritional values. However, the molecular mechanisms underlying flavonoid metabolism in duckweed remain poorly understood. This study identified a P1-Like R2R3-MYB transcription factor, LtP1L, as a crucial regulator of CGF biosynthesis and transport in L. turionifera. Over-expression of LtP1L led to a six-fold increase in CGF levels, whereas the CRISPR-mediated knockdown of LtP1L caused a drastic 74.3 % decrease in CGF contents compared with the wild type. LtP1L specifically activated the expression of genes encoding key enzymes involved in the biosynthesis of CGFs, including flavanone 3'-hydroxylases (F3'H), flavanone 2-hydroxylases (F2H), and C-glycosyltransferase (CGT). Meanwhile, LtP1L activated genes associated with phenylalanine and phenylpropanoid biosynthesis pathways, such as 3-deoxy-7-phosphoheptulonate synthase (DHS), phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate: CoA ligase (4CL), redirecting carbon metabolic flux towards flavonoid pathway at the early stages of phenylalanine synthesis. In addition, LtP1L directly bound to a novel AC-like cis-element in the promoter of a tonoplast-localized ATP-binding cassette (ABC) transporter LtABCC4 and activated its expression. Furthermore, the preference of LtABCC4 for isoorientin over orientin during vacuolar transport was evidenced by the significant reduction of isoorientin compared to orientin in the Ltabcc4crispr lines. Altogether, LtP1L acts as a crucial transcriptional orchestrator in coordinating the biosynthesis and intracellular transport of CGFs in duckweed.

We have developed a Triangular Spatial Relationship (TSR)-based computational method for protein structure comparison and motif discovery that is both sequence and structure alignment-free. A protein 3D structure is modeled by all possible triangles that are constructed with every three Cα atoms of amino acids as vertices. Every triangle is represented using an integer (a key). The keys are calculated by a rule-based formula which is a function of a representative length, a representative angle, and the vertex labels associated with amino acids. A 3D structure is thereby represented by a vector of integers (TSR keys). Global or local structure comparisons are achieved by computing all keys or a set of keys, respectively. Many enzymatic reactions and notable marketed drugs are highly stereospecific. Thus, in this paper, we propose a modified key calculation formula by including a mechanism for discriminating mirror-image keys to capture stereo geometry. We assign a positive or a negative sign to the integers representing mirror-image keys. Applying the new key calculation function provides the ability to further discriminate mirror-image keys that were previously considered identical. As the result, applying the mirror-image discrimination capability (i) significantly increases the number of distinct keys; (ii) decreases the number of common keys; (iii) decreases structural similarity; (iv) increases the opportunity to identify specific keys for each type of the receptors. The specific keys identified in this study for the cases of without (not applying) and with (applying) mirror-image discrimination can be considered as the structure signatures that exclusively belong to a certain type of receptors. Applying mirror-image discrimination introduces stereospecificity to keys for allowing more precise modeling of ligand - target interactions. The development of mirror-image TSR keys of Cα atom, in conjunction with the integration of Cα TSR keys with all-atom TSR keys for amino acids and drugs, will lead to a new and promising computational method for aiding drug design and discovery.

Peach (Prunus persica L.), as a traditional kind of fruits in China, was extremely dependent on large application of nitrogen (N) fertilizer to maintain high fruit yield and commercial income, resulting in raising environmental damage risk. Therefore, a three-year field trail was conducted to clarify the environmental N loss under conventional management, investigate the positive effects of optimal N management, legume cover and 3,4-dimethylpyrazole phosphate (DMPP) on N input/output and the net ecosystem economic benefits (NEEB). There are four treatments in this study: conventional fertilizer management with 521.1 kg N ha-1 yr-1 input (CU); optimal N management including 406.4 kg N ha-1 yr-1 input and deep fertilization (OP); DMPP was added to OP at rate of 1 % (w/w) (OPD); legume (white clover) was covered to OPD (OPDG). Results showed 102.9 kg N ha-1 was removed by annual fruit and residues (including pruned branches, pruned and fallen leaves), while 70.2 kg N ha-1 was lost to the environment by ammonia (NH3), nitrous oxide (N2O) and N runoff loss under the conventional fertilizer management. While, the optimal N management mitigated NH3 volatilization about 49.3 %, further added DMPP abated N2O emission by 61.4 %, besides covered white clover lowered N runoff loss by 64.5 %. The NEEB results revealed that optimal N management combined with added DMPP and covered white clover could minimize the production cost, reduce environmental damage cost by 35.9 %, increase fruit yield by 10.3 % and achieved the maximum NEEB with improvement of 27.1 %, in comparison of the conventional fertilizer management. Generally, conventional peach cultivation constituted overwhelming N loss to raise potential environmental risk. While, extending mode of optimized N management combined with DMPP and legume cover could not only realize high fruit revenue, but also abate environmental N losses, thereby should be considered as effective strategy for sustainable fruit cropping systems.

There is a limited understanding of the carbon assimilation capacity of nonfoliar green tissues and its impact on yield and seed quality since most photosynthesis research focuses on leaf photosynthesis. In this study, we investigate the photosynthetic efficiency of soybean (Glycine max) pods and seeds in a field setting and evaluate its effect on mature seed weight and composition. We demonstrate that soybean pod and seed photosynthesis contributes 13% to 14% of the mature seed weight. Carbon assimilation by soybean pod and seed photosynthesis can compensate for 81% of carbon loss through the respiration of the same tissues, and our model predicts that soybean pod and seed photosynthesis contributes up to 9% of the total daily carbon gain of the canopy. Chlorophyll fluorescence (CF) shows that the operating efficiency of photosystem II in immature soybean seeds peaks at the 10 to 100 mg seed weight stage, while that of immature pods peaks at the 75 to 100 mg stage. This study provides quantitative information about the efficiency of soybean pod and seed photosynthesis during tissue development and its impact on yield.

In pursuit of high fruit yield, overwhelming amount of nitrogen (N) fertilizer was applied in orchard, resulting in lower fertilizer N uptake and higher environmental loss. Unlike cereal crops, fruit trees have long time nutrient storage from juvenile growth to adult stage. It is crucial to clarify whether the source of N distribution in each tree organ at different growth stages is dominated by stored N remobilization or applied fertilizer-N uptake, which would help to propose suitable fertilization timings and optimal N management in fruit cropping systems. Here, we conducted a 15N isotope enrichment trial in commercial peach orchard to assess the applied synthesized fertilizer-N contribution in peach organs N uptake, environmental N loss and residual N in the soil. Ammonium sulfate ((NH4)2SO4, 10.12 atom % 15N) as the N source was applied with four split applications at 382.5 kg N ha-1 during one plant growth cycle. Results show N deriving from fertilizer (NDFF) accounted for 24.5% in leaves and 38.4% in fruits, respectively, while the maximum 15N enrichment found in harvest fruits. After harvest, nearly 28.8% of applied fertilizer-N was absorbed by peach tree, of which 15.9% was stored in perennial branches, stem and root system. Meanwhile, 9.5% of labeled fertilizer-N lost to the environment through surface runoff, ammonia (NH3) volatilization and nitrous oxide (N2O) emission. After harvest, the 0-160 cm soil profile retained 29.6% of labelled fertilizer-N, only one-third of which in 0-60 cm soil lays was potentially reutilized by peach trees. The unaccounted N, including N leaching and N loss from the N removal progress, was 32.1% of the 15N labelled fertilizer-N. Generally, more applied fertilizer-N moved to the environment in high N input peach orchard, it is necessary to optimize fertilizer N management to realize green production in fruit cropping systems.

Terrestrial CAM plants typically occur in hot semiarid regions, yet can show high crop productivity under favorable conditions. To achieve a more mechanistic understanding of CAM plant productivity, a biochemical model of diel metabolism was developed and integrated with 3-D shoot morphology to predict the energetics of light interception and photosynthetic carbon assimilation. Using Agave tequilana as an example, this biochemical model faithfully simulated the four diel phases of CO2 and metabolite dynamics during the CAM rhythm. After capturing the 3-D form over an 8-yr production cycle, a ray-tracing method allowed the prediction of the light microclimate across all photosynthetic surfaces. Integration with the biochemical model thereby enabled the simulation of plant and stand carbon uptake over daily and annual courses. The theoretical maximum energy conversion efficiency of Agave spp. is calculated at 0.045-0.049, up to 7% higher than for C3 photosynthesis. Actual light interception, and biochemical and anatomical limitations, reduced this to 0.0069, or 15.6 Mg ha-1  yr-1 dry mass annualized over an 8-yr cropping cycle, consistent with observation. This is comparable to the productivity of many C3 crops, demonstrating the potential of CAM plants in climates where little else may be grown while indicating strategies that could raise their productivity.

Potato (Solanum tuberosum) is a significant non-grain food crop in terms of global production. However, its yield potential might be raised by identifying means to release bottlenecks within photosynthetic metabolism, from the capture of solar energy to the synthesis of carbohydrates. Recently, engineered increases in photosynthetic rates in other crops have been directly related to increased yield - how might such increases be achieved in potato? To answer this question, we derived the photosynthetic parameters V-cmax and J(max) to calibrate a kinetic model of leaf metabolism (e-Photosynthesis) for potato. This model was then used to simulate the impact of manipulating the expression of genes and their protein products on carbon assimilation rates in silico through optimizing resource investment among 23 photosynthetic enzymes, predicting increases in photosynthetic CO2 uptake of up to 67%. However, this number of manipulations would not be practical with current technologies. Given a limited practical number of manipulations, the optimization indicated that an increase in amounts of three enzymes - Rubisco, FBP aldolase, and SBPase - would increase net assimilation. Increasing these alone to the levels predicted necessary for optimization increased photosynthetic rate by 28% in potato.

Protein phosphorylation and dephosphorylation play an essential role in regulating their functions. Three phosphorylation sites of Slr0599, a eukaryotic type Ser/Thr kinase, of cyanobacterium Synechocystis sp. PCC6803, were identified by a mass spectrometry study. Slr0599 was suggested to function in nitrogen metabolism and/or carbon transport. In the process of generating Slr0599 phosphorylation-site mutations, a slr0599 knockout strain (slr0599KO) was generated. slr0599KO has similar pigment contents including chlorophylls and carotenoids as the wild type Synechocystis sp. PCC6803 wild type. They have similar low-temperature fluorescence emission spectra, demonstrating the deletion of Slr0599 does not affect the assembly and functions of photosystem I and II. The deletion of Slr0599 does not affect the growth rate and photosynthetic activity of the mutated strain when it is cultured in a medium with different nitrogen concentrations. The physiological characterization demonstrated a modest growth defect under photoautotrophic or high-salt stress conditions. The 3D structure of Slr0599 has not been determined experimentally. Therefore, we built a model structure of Slr0599 using the CAMK1 structure as a template because Slr0599 and CAMK1 share relatively high sequence similarity. To optimize the model structure, we performed molecular dynamics simulations. The potential energy profile shows a decreasing trend in the beginning and a stable trend in the late phase of the simulations. The global structure analyses demonstrate the stable H bonding from the second to the last 5-ns simulations that generally agrees with the potential energy profile. The local structure studies allow to identify the top two stable H bond pairs and reveal that the Asp-Phe-Gly (DFG) motif of Slr0599 has a similar geometry as that of representative kinases and phosphatases using the TSR-based method. The two phosphorylation sites: Ser229 and Thr304 were shown to be at the protein surface. Collectively, this study provides evidence of a potential role of Slr0599 in modulating cell growth and builds a foundation for more detailed analysis of its structure and function relations.

Virus-induced gene silencing (VIGS) is a powerful tool for transient gene functional analysis in plants, especially for monocot species (e.g., grasses) that are recalcitrant to transformation. Despite various VIGS systems that have been developed in different plant species, none was previously available for the bioenergy crop Miscanthus. Here, we report the establishment of an efficient and robust VIGS system mediated by Tobacco Rattle Virus (TRV) in Miscanthus. We first investigated the impact of various factors that may affect gene silencing efficiency using the Miscanthus sinensis Phytoene Desaturase (MsPDS) gene as a visual indicator of photobleaching. Then, we optimized the TRV-elicited VIGS procedure using an orthogonal experimental design with four factors (sprout size, Agrobacterium concentration, vacuum infiltration time, and co-incubation time) each at three levels. The following led to the highest silencing efficiency (similar to 76%): inoculation of germinating seedlings (1.0-2.0 mm), Agrobacterium tumefaciens culture grown to optical density at 600 nm (OD600) of 0.4, vacuum infiltration for 90 min, and co-incubation for 5 h. The VIGS system established was applicable for both M. sinensis and M. lutarioriparius, with comparable gene silencing efficiency. We verified the efficacy of the VIGS system via the functional characterization of the role of a MYB transcription factor, MsMYB112, in salt stress tolerance. Expression of MsMYB112 was successfully knocked down using the VIGS system, and this led to compromised salt tolerance in the silenced Miscanthus plants. The TRV-based VIGS system established may, therefore, substantially facilitate functional genomic studies in Miscanthus.

Abstract Compared to the large number of studies focused on the factors controlling C3 photosynthesis efficiency, there are relatively fewer studies of the factors controlling photosynthetic efficiency in C4 leaves. Here, we used a dynamic systems model of C4 photosynthesis based on maize (Zea mays) to identify features associated with high photosynthetic efficiency in NADP-malic enzyme (NADP-ME) type C4 photosynthesis. We found that two additional factors related to coordination between C4 shuttle metabolism and C3 metabolism are required for efficient C4 photosynthesis: (1) accumulating a high concentration of phosphoenolpyruvate through maintaining a large PGA concentration in the mesophyll cell chloroplast and (2) maintaining a suitable oxidized status in bundle sheath cell chloroplasts. These identified mechanisms are in line with the current cellular location of enzymes/proteins involved in the starch synthesis, the Calvin–Benson cycle and photosystem II of NADP-ME type C4 photosynthesis. These findings suggested potential strategies for improving C4 photosynthesis and engineering C4 rice.

Photosynthesis is an important remaining opportunity for further improvement in the genetic yield potential of our major crops. Measurement, analysis, and improvement of leaf CO2 assimilation (A) have focused largely on photosynthetic rates under light-saturated steady-state conditions. However, in modern crop canopies of several leaf layers, light is rarely constant, and the majority of leaves experience marked light fluctuations throughout the day. It takes several minutes for photosynthesis to regain efficiency in both sun-shade and shade-sun transitions, costing a calculated 10-40% of potential crop CO2 assimilation. Transgenic manipulations to accelerate the adjustment in sun-shade transitions have already shown a substantial productivity increase in field trials. Here, we explore means to further accelerate these adjustments and minimize these losses through transgenic manipulation, gene editing, and exploitation of natural variation. Measurement andanalysis of photosynthesis in sun-shade and shade-sun transitions are explained. Factors limiting speeds of adjustment and how they could be modified to effect improved efficiency are reviewed, specifically nonphotochemical quenching (NPQ), Rubisco activation, and stomatal responses.

While flux balance analysis (FBA) provides a framework for predicting steady-state leaf metabolic network fluxes, it does not readily capture the response to environmental variables without being coupled to other modelling formulations. To address this, we coupled an FBA model of 903 reactions of soybean (Glycine max) leaf metabolism with e-photosynthesis, a dynamic model that captures the kinetics of 126 reactions of photosynthesis and associated chloroplast carbon metabolism. Successful coupling was achieved in an iterative formulation in which fluxes from e-photosynthesis were used to constrain the FBA model and then, in turn, fluxes computed from the FBA model used to update parameters in e-photosynthesis. This process was repeated until common fluxes in the two models converged. Coupling did not hamper the ability of the kinetic module to accurately predict the carbon assimilation rate, photosystem II electron flux, and starch accumulation of field-grown soybean at two CO2 concentrations. The coupled model also allowed accurate predictions of additional parameters such as nocturnal respiration, as well as analysis of the effect of light intensity and elevated CO2 on leaf metabolism. Predictions included an unexpected decrease in the rate of export of sucrose from the leaf at high light, due to altered starch-sucrose partitioning, and altered daytime flux modes in the tricarboxylic acid cycle at elevated CO2. Mitochondrial fluxes were notably different between growing and mature leaves, with greater anaplerotic, tricarboxylic acid cycle and mitochondrial ATP synthase fluxes predicted in the former, primarily to provide carbon skeletons and energy for protein synthesis.

Summary Use of a complete dynamic model of NADP‐malic enzyme C 4 photosynthesis indicated that, during transitions from dark or shade to high light, induction of the C 4 pathway was more rapid than that of C 3 , resulting in a predicted transient increase in bundle‐sheath CO 2 leakiness ( ϕ ). Previously, ϕ has been measured at steady state; here we developed a new method, coupling a tunable diode laser absorption spectroscope with a gas‐exchange system to track ϕ in sorghum and maize through the nonsteady‐state condition of photosynthetic induction. In both species, ϕ showed a transient increase to > 0.35 before declining to a steady state of 0.2 by 1500 s after illumination. Average ϕ was 60% higher than at steady state over the first 600 s of induction and 30% higher over the first 1500 s. The transient increase in ϕ , which was consistent with model prediction, indicated that capacity to assimilate CO 2 into the C 3 cycle in the bundle sheath failed to keep pace with the rate of dicarboxylate delivery by the C 4 cycle. Because nonsteady‐state light conditions are the norm in field canopies, the results suggest that ϕ in these major crops in the field is significantly higher and energy conversion efficiency lower than previous measured values under steady‐state conditions.

Cyanobacteria are a group of oxygenic photosynthetic bacteria with great potentials in biotechnological applications and advantages as models for photosynthesis research. The subcellular localizations of the majority of proteins in any cyanobacteria remain undetermined, representing a major challenge in using cyanobacteria for both basic and industrial researches. Here, using label-free quantitative proteomics, we map 2027 proteins of Synechocystis sp. PCC6803, a model cyanobacterium, to different subcellular compartments and generate a proteome atlas with such information. The atlas leads to numerous unexpected but important findings, including the predominant localization of the histidine kinases Hik33 and Hik27 on the thylakoid but not the plasma membrane. Such information completely changes the concept regarding how the two kinases are activated. Together, the atlas provides subcellular localization information for nearly 60% proteome of a model cyanobacterium, and will serve as an important resource for the cyanobacterial research community.

Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures. Several additional putative bottlenecks for photosynthetic performance under drought, heat, or chilling stress or during photosynthetic induction await further experimental verification. Based on source-sink interactions in maize, sugarcane, and sorghum, alleviating these photosynthetic bottlenecks during establishment and growth of the harvestable parts are likely to improve yield. The expected benefits are also shown to be augmented by the increasing trend in planting density, which increases the impact of photosynthetic source limitation on crop yields.