Atmospheric Nitrogen Gas Research Articles

Effect of Cold Plasma Seed Treatment on Physiological and Biochemical Changes in Aged Mustard Seed Variety-RH0749

The low rate of seed germination is a major problem in modern agriculture. Cold-activated air plasma has been tested as a pre-treatment method to improve the rate and uniformity of the germination. In view of the widespread cultivation of mustard in India and other parts of the world, This study was conducted to determine alternative non-destructive seed treatment method based on cold plasma chemistry would offer a more viable alternative over traditional seed coating technologies Seed physiological characteristics as was modified in aged low vigour mustard seeds by coating the surface of the seeds with cold plasma process using a rotating plasma reactor during 2023-24 at CCS HAU, College of Agriculture Bawal. The source of atmospheric oxygen gas, nitrogen and heliun gas entering the plasma chamber during the reaction process determined the type of coating. Among the different treatments imposed, seed treatment with 300V at 10 Min significantly enhanced seed quality attributes viz., germination ( 92 %), root length ( 4.37 cm), shoot length ( 6.98 cm), mean seedling length (11.0 cm ), Seedling dry weight (2.67 mg) and SVI-I (1115), SVI-II (254), TDH (0.78 A480 nm) with lower electrical conductivity (14.20 dsm-1). The inhibitory effect noticed with a higher dose of plasma of 400v at 10 min suggested the need for judicious usage of these plasma frequencies in such applications. The first-ever report on the effect of new plasma state on seed germination and establishment of mustard revealed the positive influence that could be used as a seed treatment to enhance seed yield and quality.

Green synthesis and characterization of crystalline copper nanoparticles via sodium borohydride reduction towards enhanced gas sensing application

Copper nanoparticles were produced by a chemical reduction method from precursor copper sulphate using sodium borohydride as a reducing agent. Cu nanoparticles were created by the reduction of Cu2+ ions with NaBH4 in an alkaline solution. NaBH4 and CuSO4 have a molar ratio of 1.2 (6:5). CuSO4 has a concentration of 0.02 M, and 0.04 M NaBH4 was added dropwise to develop the precipitate. Further, characterizations were performed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR) and Ultraviolet and Visible Spectroscopy (UV–Vis). The synthesis of the pure copper nanoparticles with a cubic crystalline structure was established. The average crystallite size of copper particle size is about 56.73 nm. The values of resistivity of the Cu conductive films were measured 4.1 × 103 Ω cm, 8 0.8 × 10−2 Ω cm and 1.4 × 10−5 Ω cm at different atmospheric environments, including air, nitrogen gas, and hydrogen gas respectively.

Nitrogen-fixing organelle in a marine alga.

Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Biological nitrogen fixation, the reduction of abundant atmospheric nitrogen gas (N2) to biologically available ammonia, is a key metabolic process performed exclusively by prokaryotes. Candidatus Atelocyanobacterium thalassa, or UCYN-A, is a metabolically streamlined N2-fixing cyanobacterium previously reported to be an endosymbiont of a marine unicellular alga. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N2-fixing organelle, or "nitroplast."

Two distinct ferredoxins are essential for nitrogen fixation by the iron nitrogenase in Rhodobacter capsulatus.

Nitrogenases are the only enzymes able to fix gaseous nitrogen into bioavailable ammonia and hence are essential for sustaining life. Catalysis by nitrogenases requires both a large amount of ATP and electrons donated by strongly reducing ferredoxins or flavodoxins. Our knowledge about the mechanisms of electron transfer to nitrogenase enzymes is limited: The electron transport to the iron (Fe)-nitrogenase has hardly been investigated. Here, we characterized the electron transfer pathway to the Fe-nitrogenase in Rhodobacter capsulatus via proteome analyses, genetic deletions, complementation studies, and phylogenetics. Proteome analyses revealed an upregulation of four ferredoxins under nitrogen-fixing conditions reliant on the Fe-nitrogenase in a molybdenum nitrogenase knockout strain, compared to non-nitrogen-fixing conditions. Based on these findings, R. capsulatus strains with deletions of ferredoxin (fdx) and flavodoxin (fld, nifF) genes were constructed to investigate their roles in nitrogen fixation by the Fe-nitrogenase. R. capsulatus deletion strains were characterized by monitoring diazotrophic growth and Fe-nitrogenase activity in vivo. Only deletions of fdxC or fdxN resulted in slower growth and reduced Fe-nitrogenase activity, whereas the double deletion of both fdxC and fdxN abolished diazotrophic growth. Differences in the proteomes of ∆fdxC and ∆fdxN strains, in conjunction with differing plasmid complementation behaviors of fdxC and fdxN, indicate that the two Fds likely possess different roles and functions. These findings will guide future engineering of the electron transport systems to nitrogenase enzymes, with the aim of increased electron flux and product formation.IMPORTANCENitrogenases are essential for biological nitrogen fixation, converting atmospheric nitrogen gas to bioavailable ammonia. The production of ammonia by diazotrophic organisms, harboring nitrogenases, is essential for sustaining plant growth. Hence, there is a large scientific interest in understanding the cellular mechanisms for nitrogen fixation via nitrogenases. Nitrogenases rely on highly reduced electrons to power catalysis, although we lack knowledge as to which proteins shuttle the electrons to nitrogenases within cells. Here, we characterized the electron transport to the iron (Fe)-nitrogenase in the model diazotroph Rhodobacter capsulatus, showing that two distinct ferredoxins are very important for nitrogen fixation despite having different redox centers. In addition, our research expands upon the debate on whether ferredoxins have functional redundancy or perform distinct roles within cells. Here, we observe that both essential ferredoxins likely have distinct roles based on differential proteome shifts of deletion strains and different complementation behaviors.

LIBS plasma in atmospheric pressure argon, nitrogen and helium: Spatio-temporal distribution of plume emission and Hα linewidth

Laser Induced Breakdown Spectroscopy (LIBS) method is considered for assessing the retention of hydrogen isotopes in the ITER plasma-facing components during the maintenance breaks when the reactor is filled with near atmospheric pressure nitrogen or inert gas. At these conditions, the broadening of the spectral lines of hydrogen isotopes and the reduction of line intensities complicates the distinguishing of hydrogen isotopes. The aim of the present study was to investigate the effect of atmospheric pressure nitrogen, argon and helium ambient gas on the spatio-temporal distribution of the LIBS plasma plume emission and linewidths of Hα line, representing the hydrogen isotopes. Nd:YAG laser with 8 ns pulse width was used to ablate the molybdenum (Mo) target with hydrogen impurity. The development of the formed plasma plume was investigated by time and space-resolved emission spectra in the 20 nm range around the 656.28 nm Hα line. For all gases used in the experiments, the intensity and linewidth of Hα line decreased with the delay time between the laser pulse and the spectral registration. At the same linewidth values, the highest intensities were obtained in the helium atmosphere while the lowest intensity was obtained in nitrogen. According to spatially resolved spectral measurements, the Hα line was most intense near the Mo target while the Mo lines peaked farther away. In the case of the helium atmosphere, the plasma plume emission was observed at a longer distance from the target and it decayed faster than in argon and nitrogen atmospheres. According to these results, helium is the most beneficial ambient gas for hydrogen isotope detection by atmospheric pressure LIBS. The use of argon ambient gas may be required when LIBS is used for the simultaneous determination of fuel and He retention in the wall material.

EFFECT OF NITRATE CONTAMINATION IN GROUNDWATER- A WORLDWIDE CONCERN

Nitrate is a prevalent groundwater and surface water contaminant that is a major contributor to global groundwater contamination. Due to nitrogen fertiliser runoff from urban lawns and agricultural fields, nitrate levels in streams and rivers can reach dangerous levels. Many plant species, including the majority of edible ones, require it for growth; but, if it gets into water where it is not needed, it creates a problem. Both a serious environmental issue and a health risk result from this. Foods are preserved with sodium nitrite, particularly meats that have been cured. Additionally, nitrate may occasionally be added to serve as a container for nitrite. Almost 80% of air we breathe is composed of nitrogen, which is a significant component of the earth's atmosphere. All nitrates are primarily produced by atmospheric nitrogen gas. In a process known as nitrogen fixation, some plants transform this into organic nitrogen. Nitrate, which is dissolved nitrogen, is the most common type of ground water pollution. Numerous chemical and biological processes, such as nitrification and denitrification, affect the amount of nitrate in ground water. This review focuses on the extent of nitrate contamination and its impact on human population worldwide.

A haem-sequestering plant peptide promotes iron uptake in symbiotic bacteria.

Symbiotic partnerships with rhizobial bacteria enable legumes to grow without nitrogen fertilizer because rhizobia convert atmospheric nitrogen gas into ammonia via nitrogenase. After Sinorhizobium meliloti penetrate the root nodules that they have elicited in Medicago truncatula, the plant produces a family of about 700 nodule cysteine-rich (NCR) peptides that guide the differentiation of endocytosed bacteria into nitrogen-fixing bacteroids. The sequences of the NCR peptides are related to the defensin class of antimicrobial peptides, but have been adapted to play symbiotic roles. Using a variety of spectroscopic, biophysical and biochemical techniques, we show here that the most extensively characterized NCR peptide, 24 amino acid NCR247, binds haem with nanomolar affinity. Bound haem molecules and their iron are initially made biologically inaccessible through the formation of hexamers (6 haem/6 NCR247) and then higher-order complexes. We present evidence that NCR247 is crucial for effective nitrogen-fixing symbiosis. We propose that by sequestering haem and its bound iron, NCR247 creates a physiological state of haem deprivation. This in turn induces an iron-starvation response in rhizobia that results in iron import, which itself is required for nitrogenase activity. Using the same methods as for L-NCR247, we show that the D-enantiomer of NCR247 can bind and sequester haem in an equivalent manner. The special abilities of NCR247 and its D-enantiomer to sequester haem suggest a broad range of potential applications related to human health.

Functional analysis of the nitrogenase protective protein CowN

Nitrogenase is the only enzyme that can catalyze ATP‐dependent nitrogen fixation in bacteria, an important biological process that reduces atmospheric nitrogen gas into ammonia. The bacterium Gluconacetobacter diazotrophicus expresses nitrogenase and is agriculturally relevant since it provides ammonia to commercial crops such as sugarcane and pineapple. The environmental gas carbon monoxide tightly inhibits nitrogenase. To prevent this inhibition, diazotrophs have evolved a small protein, CowN, which interacts with nitroganse and lowers the affinity of CO binding. In doing so, CowN allows nitrogenase to stay active despite the presence of CO Although we know that CowN protects nitrogenase from CO, we do not know how it achieves its protective effect. Both CowN’s mechanism and structure remain undetermined. This poster presents a structure‐function analysis of CowN. The C‐terminus of CowN contains a conserved Cys (C90 in G. diazotrophicus) and a semi‐conserved second S‐containing residue, either Cys or Met. Due to this conservation, we hypothesize that the C‐terminus of CowN is crucial to its function. To test this hypothesis, we made a series of C‐terminal mutations, expecting that mutations to C90 would abolish activity. Surprisingly, we discovered that the conserved Cys is not required for CowN function. A C90S mutant was almost fully active, suggesting that either a thiol or a hydroxyl group at the CowN C‐terminus is sufficient for activity. In contrast, mutations to the second S‐containing residue, M91 in G. diazotrophcius, and to both C90 and M91 fully abolish CowN activity and destabilize the structure. Together, the results confirm our hypothesis that CowN’s C‐terminus is required for activity, however, they also reveal that the presence of the conserved Cys is not necessary for function. Future work will aim to solve the CowN structure and to elucidate the role of residue C90.

Reaction Mechanisms, Kinetics, and Improved Catalysts for Ammonia Synthesis from Hierarchical High Throughput Catalyst Design.

The Haber-Bosch (HB) process is the primary chemical synthesis technique for industrial production of ammonia (NH3) for manufacturing nitrate-based fertilizer and as a potential hydrogen carrier. The HB process alone is responsible for over 2% of all global energy usage to produce more than 160 million tons of NH3 annually. Iron catalysts are utilized to accelerate the reaction, but high temperatures and pressures of atmospheric nitrogen gas (N2) and hydrogen gas (H2) are required. A great deal of research has aimed at increased performance over the last century, but the rate of progress has been slow. This Account focuses on determining the atomic-level reaction mechanism for HB synthesis of NH3 on the Fe catalysts used in industry and how to use this knowledge to suggest greatly improved catalysts via a novel paradigm of catalyst rational design.We determined the full reaction mechanism on the two most active surfaces for the HB process, Fe(111) and Fe(211)R. We used density functional theory (DFT) to predict the free-energy barriers for all 12 important reactions and the 34 most important 2 × 2 surface configurations. Then we incorporated the mechanism into kinetic Monte Carlo (kMC) simulations run for several hours of real time to predict turnover frequencies (TOFs). The predicted TOFs are within experimental error, indicating that the predicted barriers are within 0.04 eV of experiment.With this level of accuracy, we are poised to use DFT to improve the catalyst. Rather than forming bulk alloys with uniform concentration, we aimed at finding additives that strongly prefer near-surface sites so that minor amounts of the additive might lead to dramatic improvements. However, even for a single additive, the combinations of surface species and reactions multiplies significantly, with ∼48 reaction steps to examine and nearly 100 surface configurations per 2 × 2 site. To make it practical to examine tens of dopant candidates, we developed the hierarchical high-throughput catalysis screening (HHTCS) approach, which we applied to both the Fe(111) and Fe(211) surfaces. For HHTCS, we identified the most important 4 reaction steps out of 12 for the two surfaces to examine >50 dopant cases, where we required performance at each step no worse than for pure Fe. With HHTCS, the computational cost is about 1% of that for doing the full reaction mechanism, allowing us to do ≈50 cases in about 1/2 the time it took to do pure Fe(111). The new leads identified with HHTCS are then validated with full mechanistic studies.For Fe(111), we predict three high-performance dopants that strongly prefer the second layer: Co with a rate 8 times higher, Ni with a rate 16 times higher, and Si with a rate 43 times higher, at 400 °C and 20 atm. We also found four dopants that strongly prefer the top layer and improve performance: Pt or Rh 3 times faster and Pd or Cu 2 times faster. For Fe(211), the best dopant was found to be second-layer Co with a rate 3 times faster than that for the undoped surface.The DFT/kMC data were used to predict reshaping of the catalyst particles under reaction conditions and how to tune dopant content so as to maximize catalytic area and thus activity. Finally, we show how to validate our mechanistic modeling via a comparison between theoretical and experimental operando spectroscopic signatures.

Characterization of Terrihabitans soli gen. nov., sp. nov., a Novel 0.2 μm-Filterable Soil Bacterium Belonging to a Widely Distributed Lineage of Hyphomicrobiales (Rhizobiales)

We previously showed that novel filterable bacteria remain in “sterile” (<0.2 μm filtered) terrestrial environmental samples from Japan, China, and Arctic Norway. Here, we characterized the novel filterable strain IZ6T, a representative strain of a widely distributed lineage. Phylogenetic analysis showed that this strain was affiliated with the Rhizobiales (now proposed as Hyphomicrobiales) of Alphaproteobacteria, but distinct from any other type strains. Strain IZ6T shared the following chemotaxonomic features with the closest (but distantly) related type strain, Flaviflagellibacter deserti SYSU D60017T: ubiquinone-10 as the major quinone; phosphatidylethanolamine, phosphatidylcholine, and phosphatidylglycerol as major polar lipids; and slightly high G+C content of 62.2 mol%. However, the cellular fatty acid composition differed between them, and the unsaturated fatty acid (C18:1ω7c/C18:1ω6c) was predominantly found in our strain. Moreover, unlike methyrotrophs and nitrogen-fixers of the neighboring genera of Hyphomicrobiales (Rhizobiales), strain IZ6T cannot utilize a one-carbon compound (e.g., methanol) and fix atmospheric nitrogen gas. These findings were consistent with the genome-inferred physiological potential. Based on the phylogenetic, physiological, and chemotaxonomic traits, we propose that strain IZ6T represents a novel genus and species with the name Terrihabitans soli gen. nov., sp. nov. (=NBRC 106741T = NCIMB 15058T). The findings will provide deeper insight into the eco-physiology of filterable microorganisms.

Systemic control of nodule formation by plant nitrogen demand requires autoregulation-dependent and independent mechanisms.

In legumes interacting with rhizobia, the formation of symbiotic organs involved in the acquisition of atmospheric nitrogen gas (N2) is dependent on the plant nitrogen (N) demand. We used Medicago truncatula plants cultivated in split-root systems to discriminate between responses to local and systemic N signaling. We evidenced a strong control of nodule formation by systemic N signaling but obtained no clear evidence of a local control by mineral nitrogen. Systemic signaling of the plant N demand controls numerous transcripts involved in root transcriptome reprogramming associated with early rhizobia interaction and nodule formation. SUPER NUMERIC NODULES (SUNN) has an important role in this control, but we found that major systemic N signaling responses remained active in the sunn mutant. Genes involved in the activation of nitrogen fixation are regulated by systemic N signaling in the mutant, explaining why its hypernodulation phenotype is not associated with higher nitrogen fixation of the whole plant. We show that the control of transcriptome reprogramming of nodule formation by systemic N signaling requires other pathway(s) that parallel the SUNN/CLE (CLAVATA3/EMBRYO SURROUNDING REGION-LIKE PEPTIDES) pathway.

Impact of Azotobacter in Different Doses of Dichlorvos

Azotobacter is free living, non–symbiotic, heterotrophic bacteria capable of fixing an average of 20kg N / hector year. Azotobacter species are Gram negative, free–living, aerobic soil dwelling, oval or spherical bacteria that form thick–walled cysts (means of asexual reproduction under favorable condition). Out of six species of Azotobacter, some of them are motile by means of peritrichous flagella while others are not. They are typically polymorphic and their size ranges from 2–10µm long and 1–2µm wide. A. chroococcum is the first aerobic free– living nitrogen fixer. These bacteria utilize atmospheric nitrogen gas for their cell protein synthesis. Dichlorvos is an organophosphate widely used as an insecticide to control household pests, in public health, and protecting stored products from insects. In present study of dichlorvos in Azotobacter through different doses are effected of seed germination and observed the toxicity and harmful effect of dichlorvos solution.

Microbes aiding plant growth: Probiotics in plants.

Micro-organisms, including viruses, bacteria and fungi are generally perceived as pathogens, causing different diseases in plants and animals including human beings. However, there are many microbes known which not only help in the growth of their host organisms but are essential for their survival. Plants have symbiotic relationship with many microbes which are essential for the survival for both the host and micro-organisms. Nitrogen fixing bacteria which associate with the roots of leguminous plants can fix atmospheric Nitrogen gas into ammonia which is essential for plant growth. These bacteria, generally known as Plant Growth Promoting Rhizobcteria (PGPR) derive their food from the host leguminous plants, mutually benefitting each other. Some common examples of PGPR genera exhibiting plant growth promoting activity are: Pseudomonas, Azospirillum, Azotobacter, Bacillus, Burkholdaria, Enterobacter, Rhizobium, Erwinia, Mycobacterium, Mesorhizobium, Flavobacterium, etc. Viruses and fungi are also known to have such relationships with plants, eg. Vesicular Arbuscular Mycorrhiza (VAM).

Iron-Only and Vanadium Nitrogenases: Fail-Safe Enzymes or Something More?

The enzyme molybdenum nitrogenase converts atmospheric nitrogen gas to ammonia and is of critical importance for the cycling of nitrogen in the biosphere and for the sustainability of life. Alternative vanadium and iron-only nitrogenases that are homologous to molybdenum nitrogenases are also found in archaea and bacteria, but they have a different transition metal, either vanadium or iron, at their active sites. So far alternative nitrogenases have only been found in microbes that also have molybdenum nitrogenase. They are less widespread than molybdenum nitrogenase in bacteria and archaea, and they are less efficient. The presumption has been that alternative nitrogenases are fail-safe enzymes that are used in situations where molybdenum is limiting. Recent work indicates that vanadium nitrogenase may play a role in the global biological nitrogen cycle and iron-only nitrogenase may contribute products that shape microbial community interactions in nature.

Optical Investigations of N2 Atmospheric Pressure Plasma Jets

In this study, firstly, N 2 atmospheric pressure plasma jet (APPJ) system was presented. Nitrogen gas discharges are produced as jet using an AC power supply which can be adjusted between 6-18 kV and the frequency value of 13-20 kHz at atmospheric pressure. The change of length of produced atmospheric pressure nitrogen plasma jet, according to gas flow rate has been investigated and the produced jet length was approximately 2 cm for 5 L/min when the applied voltage was 18 kV and the frequency was 15 kHz. Nitrogen plasma jet produced at atmospheric pressure was examined with optical emission spectroscopy (OES) and the correlation between gas flow rate and emission spectra were investigated. Furthermore, electron temperature and electron density of atmospheric pressure nitrogen gas plasma jet were estimated under different flow rates of N 2 gas.

Fluxomic Analysis Reveals Central Carbon Metabolism Adaptation for Diazotroph Azotobacter vinelandii Ammonium Excretion

Diazotrophic bacteria are an attractive biological alternative to synthetic nitrogen fertilizers due to their remarkable capacity to fix atmospheric nitrogen gas to ammonium via nitrogenase enzymes. However, how diazotrophic bacteria tailor central carbon catabolism to accommodate the energy requirement for nitrogenase activity is largely unknown. In this study, we used Azotobacter vinelandii DJ and an ammonium excreting mutant, AV3 (ΔNifL), to investigate central carbon metabolism fluxes and central cell bioenergetics in response to ammonium availability and nitrogenase activity. Enabled by the powerful and reliable methodology of 13C-metabolic flux analysis, we show that the respiratory TCA cycle is upregulated in association with increased nitrogenase activity and causes a monotonic decrease in specific growth rate. Whereas the activity of the glycolytic Entner–Doudoroff pathway is positively correlated with the cell growth rate. These new observations are formulated into a 13C-metabolic flux model which further improves the understanding and interpretation of intracellular bioenergetics. This analysis leads to the conclusion that, under aerobic conditions, respiratory TCA metabolism is responsible for the supply of additional ATP and reducing equivalents required for elevated nitrogenase activity. This study provides a quantitative relationship between central carbon and nitrogen metabolism in an aerobic diazotroph for the first time.

Experimental Study on Decomposition and Evaporation Characteristics of N,N,N′,N′-Tetramethylethylenediamine and 1,2,4-Triazole

N,N,N′,N′-Tetramethylethylenediamine (TMEDA) is one of the candidate substances of hydrazine for hypergolic bipropellant applications. In this study, two experimental analyses were performed to investigate the characteristics of TMEDA and TMEDA mixed with 1,2,4-triazole. First of all, thermogravimetric analysis was performed to analyze thermal decomposition process of the candidate materials. During heating, TMEDA started to evaporate at a temperature below its boiling point and 1,2,4-triazole evaporated subsequently. In addition, evaporation behaviors of TMEDA droplets with two concentrations of 1,2,4-triazole (10% and 20% by weight) were studied at various temperatures. A single droplet experimentation was accomplished in a high-pressure chamber using a heating system under atmospheric nitrogen gas condition. Its droplet behavior was recorded with a high-speed camera and the data were post-processed using Visual Basic software to trace the droplet diameter variation. Bubbling and puffing were observed in the case of the TMEDA containing 1,2,4-triazole above 400 °C. As a result, the rate of evaporation was substantially enhanced by increasing the concentration of 1,2,4-triazole at same temperature. However, the evaporation rates after TMEDA evaporation were the same irrespective of the concentration of 1,2,4-triazole.

Apparatus for Dissociation of Atmospheric Nitrogen and other Linear Gas Molecules

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Chlorosis as a Developmental Program in Cyanobacteria: The Proteomic Fundament for Survival and Awakening

Cyanobacteria that do not fix atmospheric nitrogen gas survive prolonged periods of nitrogen starvation in a chlorotic, dormant state where cell growth and metabolism are arrested. Upon nutrient availability, these dormant cells return to vegetative growth within 2-3 days. This resuscitation process is highly orchestrated and relies on the stepwise reinstallation and activation of essential cellular structures and functions. We have been investigating the transition to chlorosis and the return to vegetative growth as a simple model of a cellular developmental process and a fundamental survival strategy in biology. In the present study, we used quantitative proteomics and phosphoproteomics to describe the proteomic landscape of a dormant cyanobacterium and its dynamics during the transition to vegetative growth. We identified intriguing alterations in the set of ribosomal proteins, in RuBisCO components, in the abundance of central regulators and predicted metabolic enzymes. We found O-phosphorylation as an abundant protein modification in the chlorotic state, specifically of metabolic enzymes and proteins involved in photosynthesis. Nondegraded phycobiliproteins were hyperphosphorylated in the chlorotic state. We provide evidence that hyperphosphorylation of the terminal rod linker CpcD increases the lifespan of phycobiliproteins during chlorosis.

Legume nodulation: The host controls the party.

Global demand to increase food production and simultaneously reduce synthetic nitrogen fertilizer inputs in agriculture are underpinning the need to intensify the use of legume crops. The symbiotic relationship that legume plants establish with nitrogen-fixing rhizobia bacteria is central to their advantage. This plant-microbe interaction results in newly developed root organs, called nodules, where the rhizobia convert atmospheric nitrogen gas into forms of nitrogen the plant can use. However, the process of developing and maintaining nodules is resource intensive; hence, the plant tightly controls the number of nodules forming. A variety of molecular mechanisms are used to regulate nodule numbers under both favourable and stressful growing conditions, enabling the plant to conserve resources and optimize development in response to a range of circumstances. Using genetic and genomic approaches, many components acting in the regulation of nodulation have now been identified. Discovering and functionally characterizing these components can provide genetic targets and polymorphic markers that aid in the selection of superior legume cultivars and rhizobia strains that benefit agricultural sustainability and food security. This review addresses recent findings in nodulation control, presents detailed models of the molecular mechanisms driving these processes, and identifies gaps in these processes that are not yet fully explained.