Plant Sulfur Research Articles

Modern plants and sulfur isoscapes - A review, discussion, and construction of a pilot δ34S isoscape for mobility and provenance studies.

Sulfur isotopes are increasingly used as mobility indicators in humans and animals in biology, archaeology, and forensics. However, there has been a lack of modern sulfur isotope baseline "isoscape" studies using modern plants and animals, largely due to the possibility of contamination of the S isotope values by modern pollution. We collected plants from across a 900-km east-west transect of British Columbia Canada and measured their sulfur isotope values. We then used a random forest model to determine which variables best explained the isotope data patterning and produced a sulfur isoscape for the southern region of British Columbia. We see clear patterning in the plant sulfur isotope values that relate to geographical location and rainfall. Our model also shows that for this study area, it is unlikely that there is a significant influence of anthropogenic pollution on plant δ34S values. We also discuss the use of plants as a substrate for sulfur isoscapes and possible explanations for the often-observed difference between plant and animal δ34S values from the same region, related to differing sources of sulfur in plants compared to amino acids in human and animal tissues. We found that for areas of the world where sulfur pollution is likely less widespread, it is possible to produce a modern plant S isoscape that should be an accurate baseline for mobility studies. Using random forest modelling, we have produced a baseline sulfur isoscape map of southern British Columbia that can be used for ecology, forensic and archaeological studies.

Effects of soil and phylogeny on sulfur and phosphorus concentrations in wild plants on volcanic and non-volcanic soils in Japan

ABSTRACT Andosols are soils characterized by relatively high sulfur concentrations, but also by their low phosphorus availability for crops and vegetables. We assessed the effect of soil type on the concentrations of sulfur and phosphorus in plants using handheld X-ray fluorescence (XRF) analysis on herbarium specimens collected from Andosols and non-volcanic soils in Japan. The sulfur concentrations in plants from Andosols were higher than plants from non-volcanic soils, but there was no significant difference between their foliar phosphorus concentrations. Only three specimens out of 1203 herbarium specimens were below the sulfur concentration (1000 mg kg−1) needed for adequate growth of crops, but about half of specimens were below that for phosphorus (2000 mg kg−1). The sulfur concentrations were high in herbaceous plants, especially in plants from the Brassicaceae and Liliaceae families. Overall, the results show that the sulfur concentrations in wild plants from Japan were higher in Andosols, with a low risk for sulfur deficiency. In contrast, the effect of soil type on the phosphorus concentrations in plants was small, and this may be explained because most wild plants grow under phosphorus-limiting conditions. Finally, the analysis reveals a strong correlation between sulfur and phosphorus concentrations in plants, suggesting the existence of a mechanism that controls the sulfur and phosphorus concentration ratios.

Assessing critical plant sulfur concentration and nitrogen to sulfur ratio in spring canola production

AbstractAimsPlant S concentration (Sc) and nitrogen (N) to S ratio (N:S) in canola are important indicators for diagnosing S deficiency. A field study was conducted on sandy and clay loam soils at two sites in eastern Canada for three growing seasons to determine plant critical Sc and N:S ratios across various growth stages (GSs).MethodsFor each site year, factorial experiments consisting of combinations of four N levels (0, 80, 160, and 240 kg N ha–1) as urea (46–0–0) and four S levels (0, 20, 30, and 40 kg S ha–1) as potassium sulfate (0–0–50–18) were classified orthogonally to form 16 combinations. Muriate of potash (0–0–60) was also applied as needed to ensure all plots receiving the equal amount of potassium (K).ResultsOur study found that S fertilization increased plant Sc at each GS but reduced the whole‐plant N:S ratio, and the effect was stronger during the flowering stage. Both whole‐plant Sc and N:S ratios varied with GS, environment, and soil type and declined with plant aging. Our results showed that whole‐plant S analysis combined with visual signs of plant S deficiency (purple‐edged and cup‐shaped leaves with less green; stunted growth, slow blooming, and fewer flowers) appeared to be the best way to identify S problems in the field, and whole‐plant Sc and N:S ratios could confirm S deficiencies.ConclusionOur findings indicated that if the whole‐plant Sc in the rosette stage is <0.35% and the N:S ratio is >9.6, the plant may be S‐deficient, and timely supplementary S fertilization measures may be beneficial to canola crop yield.

Adaptive modifications in plant sulfur metabolism over evolutionary time.

Sulfur (S) is an essential element for life on Earth. Plants are able to take up and utilize sulfate (SO42-), the most oxidized inorganic form of S compounds on Earth, through the reductive S assimilatory pathway that couples with photosynthetic energy conversion. Organic S compounds are subsequently synthesized in plants and made accessible to animals, primarily as the amino acid methionine. Thus, plant S metabolism clearly has nutritional importance in the global food chain. S metabolites may be part of redox regulation and drivers of essential metabolic pathways as cofactors and prosthetic groups, such as Fe-S centers, CoA, thiamine, and lipoic acid. The evolution of the S metabolic pathways and enzymes reflects the critical importance of functional innovation and diversifications. Here we review the major evolutionary alterations that took place in S metabolism across different scales and outline research directions that may take advantage of understanding the evolutionary adaptations.

CHF: A Disease Capturing Indians

At 30% of all fatalities worldwide, cardiovascular diseases (CVDs) are the major cause of mortality. The WHO estimates that 17.9 million people die from CVDs annually and that number will rise to 22.2 million by 2030. As individuals age, the mortality rate rises. In terms of gender, women die from CVD at a greater rate (51%) than do men (42%). The intricate clinical illness known as congestive heart failure (CHF) is marked by an inefficient heartbeat, which compromises the body's blood flow. Any condition affecting blood ejection from the ventricles into the systemic circulation or ventricular filling might lead to CHF. Daucus carota, Nerium oleander, Amaranthus viridis, Ginkgo biloba, Terminalia arjuna, Picrorhiza kurroa, Salvia miltiorrhiza, Tinospora cordifolia, Mucuna pruriens, Hydrocotyle asiatica, Bombax ceiba, and Andrographis paniculate are a few medicinal plants that are well-known for treating cardiovascular disease. These plants include flavonoids, polyphenols, plant sterol, plant sulphur compounds, and terpenoids, which are active phytochemicals. Given the rising incidence of CVD, a number of physiologically active substances with established biological effects have been identified discovered in a variety of plants; nonetheless, proper CVD preventive and treatment strategies are still needed. To fully comprehend the mechanism and phytochemicals found in particular plants that cure CVD, more study is required.

Keratinolytic activity of pigmenting and non-pigmenting soils strains of Trichophyton ajelloi

The aim of the study was to evaluate the keratinolytic activity of 37 Trichophyton ajelloi strains, both pigmenting and non–pigmenting, isolated from loamy soil and chernozem, and to identify strains with the highest efficiency of converting feather waste into easily assimilable forms of nitrogen and sulfur for plants. The study showed that among Trichophyton ajelloi strains isolated from loamy soil, pigmenting strains were more capable of biodegrading native feather keratin, while among the strains isolated from chernozem, non–pigmenting strains showed better abilities. The keratinolytic activity, as measured by feather weight loss after 42 days of culture, was on average higher in Trichophyton ajelloi strains isolated from loamy soil compared to those from chernozem. Extracellular keratinase activity, as well as release of soluble proteins and peptides in cultures of Trichophyton ajelloi strains isolated from loamy soil and chernozem increased throughout the experiment. Protease activity was high during the first 7 days of the experiment and increased again from day 28 of culture. The increase in the pH of the culture fluids was associated with the release of ammonium ions. The maximum release of ammonium and sulfate ions occurred on day 21 of culture. Three pigment–producing strains (No. III, XII, and XIV/XV) were among the most active in releasing large amounts of ammonium and sulfate ions. The biodegradation of feather waste by Trichophyton ajelloi strains can be used for the production of fertilizers suitable for the cultivation of plants, particularly those with high sulfur requirements.

Mechanistic Basis of Silicon Mediated Cold Stress Tolerance in Alfalfa (Medicago sativa L.)

AbstractCold stress (CS) impact on crops is one of the critical constraints for sustainable and smart agricultural production. CS adversely affects plants leading to growth retardation, necrosis, chlorosis, and significant yield loss. The objective of this study was to explore the mechanistic basis of silicon (Si) in enhancing CS tolerance in alfalfa plants. The fluorescence staining indicated that Si-reduced the intensity of CS-induced superoxide radical (O2•–) and hydrogen peroxide (H2O2) generation in plants that improved plant photosynthesis, cellular integrity, and alfalfa biomass production under CS. The exogenous supplementation of Si significantly restored the endogenous Si status accompanied by the upregulation of NIP (nodulin 26-like intrinsic protein) genes NIP2, NIP5;1, and NIP6;1 in alfalfa. The elemental concentration analysis revealed that exogenous silicon (E-Si) triggers the increase of calcium (Ca), magnesium (Mg), and sulfur (S) in plants subjected to Si-supplementation compared to the plants cultivated without Si under CS. The application of Si significantly increased the activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Furthermore, Si significantly enhanced the expression of CS-responsive candidate genes including ICE1, CBF1/DREB1C, CBF2/DREB1B, CBF3/DREB1A, COR15A, COR47, and KIN1 in alfalfa. These findings together provide mechanistic insights into Si-involving CS tolerance in alfalfa. This eco-friendly SC management strategy using Si treatment can be useful to plant breeders and farmers for developing CS-resilient smart alfalfa production through breeding program.

Plant & its Bioactive Components Uses in Cardio-Potential Diseases: A Sectional Study for Different Herbs

Thirty percent of all deaths that occur each year can be attributed to heart disease, stroke, and other forms of cardiovascular disease. The World Health Organisation (WHO) predicts that by the year 2030, the annual death toll from cardiovascular diseases will have increased to 22.2 million, up from the present annual total of 17.9 million. Mortality rates tend to go up in populations as they get older. The chance of dying from cardiovascular disease is significantly higher for females (51%) than it is for males (42%). The majority of people treat and prevent cardiovascular disease by using plant-based medications (also known as phytochemicals), either in addition to or in instead of pharmaceuticals that are readily available on the market. In this study, the efficacy of treating cardiovascular illness is evaluated using 92 different plants, including 15 terrestrial plants. A number of different medicinal herbs, including Daucus carota, Nerium oleander, Amaranthus Viridis, Ginkgo biloba, Terminalia arjuna, Picrorhiza kurroa, Salvia miltiorrhiza, Tinospora cordifolia, Mucuna pruriens, Hydrocotyle asiatica, Bombax ceiba, and Andrographis paniculate, are utilised to treat cardiovascular disease. There are a variety of active phytochemicals found in these plants, some of which include flavonoids, polyphenols, plant sterols, plant sulphur compounds, and terpenoids. Flavonoids, in general, are known to increase vasodilation by inhibiting the oxidation of low-density lipoprotein (LDL). Plant sterols reduce the amount of cholesterol in the blood, which in turn protects against cardiovascular disease. Plant sulphur compounds protect against cardiovascular disease in addition to their role in the activation of nuclear factor-erythroid factor 2-related factor 2 (Nrf2) and the inhibition of cholesterol formation. The incidence of cardiovascular disease can be reduced by increasing the synthesis of ATP in mitochondria, and terpenoids can diminish atherosclerotic lesion in the aortic valve. Even though several physiologically active compounds with acknowledged biological functions have been found in a wide variety of plants, the prevalence of cardiovascular disease continues to rise, making it imperative that effective CVD prevention and treatment strategies be developed. More research is required to understand both the mechanism and the individual phytochemicals in plants that treat CVD.
 GRAPHICAL ABSTRACT 

Salinity Induces Allometric Accumulation of Sulfur in Plants and Decouples Plant Nitrogen‐Sulfur Correlation in Alpine and Arid Wetlands

AbstractSalinization alters the elemental balance of wetlands and induces variations in plant survival strategies. Sulfur (S) plays vital roles in serving regulatory and catalytic functions in stress resistance of plants. Yet, how plant S and its relationships with nitrogen (N) vary across natural environmental gradients are not well documented. We collected 1,366 plant samples and 230 water and sediment samples from 230 wetlands in Tibetan Plateau and adjacent arid regions of western China, to analyze the effects of environmental variables on plant S accumulation and N‐S correlations. We found that plant S correlated with N in unimodal patterns. Salinity, rather than temperature or nutrient supply, promoted disproportionate accumulation of S but limited N uptake, inducing decoupling of N‐S correlation in plants. Toward high salinity, the faster increasing rates of total S than that of glutathione, the most abundant organic‐S compound in plant resistance, provided potential evidences explaining the decoupled plant N‐S correlation. A salinity of 3.9‰ was calculated to be a threshold at which substantial changes in plant N‐S correlation occurred. We designed a conceptual model to illustrate the mechanisms driving variations of N‐S correlation in plants and environments along salinity gradient. Furthermore, high salinity filtered out the salt‐sensitive species and reassembled the communities. In conclusion, increased salinity affected wetland plants by inducing S accumulation in plants and selecting salt‐tolerant species with high S concentrations at community level, providing evidences for plant adaptive mechanisms to salinity in arid regions.

Arbuscular Mycorrhiza Support Plant Sulfur Supply through Organosulfur Mobilizing Bacteria in the Hypho- and Rhizosphere.

This study aimed to elucidate the role of bacteria colonising mycorrhizal hyphae in organically bound sulfur mobilisation, the dominant soil sulfur source that is not directly plant available. The effect of an intact mycorrhizal symbiosis with access to stable isotope organo-34S enriched soils encased in 35 µm mesh cores was tested in microcosms with Agrostis stolonifera and Plantago lanceolata. Hyphae and associated soil were sampled from static mesh cores with mycorrhizal ingrowth and rotating mesh cores that exclude mycorrhizal ingrowth as well as corresponding rhizosphere soil, while plant shoots were analysed for 34S uptake. Static cores increased uptake of 34S at early stages of plant growth when sulfur demand appeared to be high and harboured significantly larger populations of sulfonate mobilising bacteria. Bacterial and fungal communities were significantly different in the hyphospheres of static cores when compared to rotating cores, not associated with plant hosts. Shifts in bacterial and fungal communities occurred not only in rotated cores but also in the rhizosphere. Arylsulfatase activity was significantly higher in the rhizosphere when cores stayed static, while atsA and asfA gene diversity was distinct in the microcosms with static and rotating cores. This study demonstrated that AM symbioses can promote organo-S mobilization and plant uptake through interactions with hyphospheric bacteria, enabling AM fungal ingrowth into static cores creating a positive feedback-loop, detectable in the microbial rhizosphere communities.

Transcriptome-wide modulation by Sargassum vulgare and Acanthophora spicifera extracts results in a prime-triggered plant signalling cascade in tomato and sweet pepper.

Seaweed extracts (SWEs) are becoming integrated into crop production systems due to their multiple beneficial effects including growth promotion and induction of defence mechanisms. However, the comprehensive molecular mechanisms of these effects are yet to be elucidated. The current study investigated the transcriptomic changes induced by SWEs derived from Sargassum vulgare and Acanthophora spicifera on tomato and sweet pepper plants. Tomato and sweet pepper plants were subjected to foliar treatment with alkaline extracts prepared from the above seaweeds. Transcriptome changes in the plants were assessed 72 h after treatments using RNA sequencing. The treated plants were also analysed for defence enzyme activities, nutrient composition and phytohormonal profiles. The results showed the significant enrichment of genes associated with several growth and defence processes including photosynthesis, carbon and nitrogen metabolism, plant hormone signal transduction, plant-pathogen interaction, secondary metabolite metabolism, MAPK signalling and amino acid biosynthesis. Activities of defence enzymes were also significantly increased in SWE-treated plants. Plant nutrient profiling showed significant increases in calcium, potassium, nitrogen, sulphur, boron, copper, iron, manganese, zinc and phosphorous levels in SWE-treated plants. Furthermore, the levels of auxins, cytokinins and gibberellins were also significantly increased in the treated plants. The severity of bacterial leaf spot and early blight incidence in plants treated with SWE was significantly reduced, in addition to other effects like an increase in chlorophyll content, plant growth, and fruit yield. The results demonstrated the complex effect of S. vulgare and A. spicifera extracts on the plants' transcriptome and provided evidence of a strong role of these extracts in increasing plant growth responses while priming the plants against pathogenic attack simultaneously. The current study contributes to the understanding of the molecular mechanisms of SWEs in plants and helps their usage as a viable organic input for sustainable crop production.

Variation Characteristics of Glucosinolate Contents in Leaf Mustard (Brassica juncea)

Mustard, which belongs to the family Brassicaceae, is an annual or biennial herb and is considered as one of the most important native vegetables in China. Glucosinolates are important secondary metabolites containing sulfur and nitrogen in plants, which form a network with other metabolic pathways that play important roles in plant growth, development, and interaction with the environment. We studied varied phenotypic and glucosinolate contents of 60 mustard resources collected from various areas of China. The results showed both agronomic traits and glucosinolates varied greatly among mustard resources. We detected nine glucosinolates in mustard resources and the contents of total glucosinolates ranged from 1.2023 to 30.7310 μmol/g. Through the correlation analysis, we preliminarily found a significant negative correlation between leaf color and glucosinolate contents but needed further validation. For mustard resource JC 18-56, we analyzed the glucosinolate contents in different organs of different growth stages. The results indicated a significant difference among organs in both glucosinolates concentration and composition. The contents of glucosinolatess in alabastrums at bolting stage were highest, up to 140.1257 μmol/g dry weight (DW). We found that the main glucosinolates in roots were 4-methoxyglucobrassicin, while in other organs the glucosinolates were sinigrin. The contents of glucosinolatess in different organs of mustard were as follows: alabastrums > seeds > flowers > siliques > leaves > flower stems > stems > roots. This study provides important references for the selection and cultivation of high-quality mustard varieties.

Tris(methylthio)methane produced by Mortierella hyalina affects sulfur homeostasis in Arabidopsis

Microbial volatiles are important factors in symbiotic interactions with plants. Mortierella hyalina is a beneficial root-colonizing fungus with a garlic-like smell, and promotes growth of Arabidopsis seedlings. GC–MS analysis of the M. hyalina headspace and NMR analysis of the extracted essential oil identified the sulfur-containing volatile tris(methylthio)methane (TMTM) as the major compound. Incorporation of the sulfur from the fungal volatile into plant metabolism was shown by 34S labeling experiments. Under sulfur deficiency, TMTM down-regulated sulfur deficiency-responsive genes, prevented glucosinolate (GSL) and glutathione (GSH) diminishment, and sustained plant growth. However, excess TMTM led to accumulation of GSH and GSL and reduced plant growth. Since TMTM is not directly incorporated into cysteine, we propose that the volatile from M. hyalina influences the plant sulfur metabolism by interfering with the GSH metabolism, and alleviates sulfur imbalances under sulfur stress.

Prevention and Treatment of Cardiovascular Diseases with Plant Phytochemicals: A Review.

Cardiovascular diseases (CVDs) are the world's leading killers, accounting for 30% deaths. According to the WHO report, CVDs kill 17.9 million people per year, and there will be 22.2 million deaths from CVD in 2030. The death rates rise as people get older. Regarding gender, the death rate of women by CVD (51%) is higher than that of men (42%). To decrease and prevent CVD, most people rely on traditional medicine originating from the plant (phytochemicals) in addition to or in preference to commercially available drugs to recover from their illness. The CVD therapy efficacy of 92 plants, including 15 terrestrial plants, is examined. Some medicinal plants well known to treat CVD are, Daucus carota, Nerium oleander, Amaranthus Viridis, Ginkgo biloba, Terminalia arjuna, Picrorhiza kurroa, Salvia miltiorrhiza, Tinospora cordifolia, Mucuna pruriens, Hydrocotyle asiatica, Bombax ceiba, and Andrographis paniculate. The active phytochemicals found in these plants are flavonoids, polyphenols, plant sterol, plant sulphur compounds, and terpenoids. A general flavonoid mechanism of action is to prevent low-density lipoprotein oxidation, which promotes vasodilatation. Plant sterols prevent CVD by decreasing cholesterol absorption in the blood. Plant sulphur compound also prevent CVD by activation of nuclear factor-erythroid factor 2-related factor 2 (Nrf2) and inhibition of cholesterol synthesis. Quinone decreases the risk of CVD by increasing ATP production in mitochondria while terpenoids by decreasing atherosclerotic lesion in the aortic valve. Although several physiologically active compounds with recognized biological effects have been found in various plants because of the increased prevalence of CVD, appropriate CVD prevention and treatment measures are required. More research is needed to understand the mechanism and specific plants' phytochemicals responsible for treating CVD.

Sulfate Fertilization Preserves Tomato Fruit Nutritional Quality

Sulfur is an essential mineral in human nutrition, involved in vital biochemical processes. Sulfur deficient soil is becoming a severe issue, resulting from increased agricultural production and decreased sulfur emissions. Tomato cultivation using sulfur-poor soils and desalinated water is becoming widespread, and might result in plant and fruit sulfur deficiency. In the current work, we aimed at evaluating the effect of sulfur fertilization (0.1–4 mM) on fruit sulfur concentrations, under both low (4 mM) and high (11 mM) nitrogen fertilization, to assess fruit sulfur biofortification, alongside the effect on fruit mineral composition, and on tomato plants. The experiment was performed on a semi-commercial scale, during two seasons, with a real-life fertilization range. We evaluated fruit elemental composition, in addition to young (diagnostic) leaves, as an indication to nutritional status. Our results show no harmful effect of low sulfur treatment on plant growth and high yield. Increased fertilization-sulfur exclusively induced sulfur accumulation in the fruit, while increasing fertilization-nitrogen subsequently increased fruit nitrogen. Sulfur treatments resulted in a consistent negative effect on fruit molybdenum and calcium, as well as a positive effect on fruit sodium levels. At the same time, other fruit minerals, including phosphorus, potassium, magnesium, iron, zinc, manganese, and copper, remained unaltered by sulfur treatments. Leaf response trends generally adhered to those of fruit. Taken together, our findings suggest that sulfur fertilization can biofortify tomato with sulfur while retaining fruit mineral composition and nutritional quality, excluding a decrease in Molybdenum levels, to assure food security and maintain fruit and vegetables as a significant source of sulfur and other minerals. Possibilities of practical application of this work’s results include optimization of fertilization levels in crop cultivation under sulfur deficiency for yield and nutritional quality, alongside the biofortification of tomatoes with sulfur and nitrogen with no adverse effect to other fruit minerals.

Sulfur fertilization strategy affects grass yield, nitrogen uptake, and nitrate leaching: A field lysimeter study#

AbstractBackgroundGlobally and at the European Union level there are mounting concerns regarding nitrogen (N) losses from agricultural systems and pressure to reduce N losses to water and air. Suboptimal plant sulfur (S) availability can reduce plant N efficiency and thereby increase N loss potential. Climate change action demands lower sulfur dioxide emissions thus S deposition levels are at an all‐time low.AimsThe objectives of the current study were to (1) determine the potential for adequate S nutrition to increase grassland yield and N efficiency, (2) determine if alleviating S deficiency reduces nitrate leaching, and (3) evaluate a number of strategies for applying S including the use of cattle slurry.MethodsThis work was completed using a free‐draining sandy loam grassland lysimeter facility. There were six treatments using calcium ammonium nitrate (CAN), CAN + calcium sulfate (CAN+S), ammonium sulfate + CAN (AS+CAN), and slurry (Slurry+CAN and Slurry+CAN+S, respectively) to deliver S strategies. The yield, plant N and S uptake, and nitrate and sulfate leachate were measured to compare treatments.ResultsApplication of mineral S fertilizer increased yields significantly (up to 2,907 kg ha–1) and increased apparent fertilizer nitrogen recovery from 39% to 47–49%. Alleviating S deficiency also significantly decreased nitrate leaching to levels not differing significantly from the control. There was a reduction of 46% in nitrate leaching with the addition of mineral S (CAN+S and AS+CAN) compared to N only. The nitrate concentration standard for drinking water was not breached for treatments that included S (6.6–11 mg NO3–‐N L–1), whereas it was breached for those without S (23–40 mg NO3–‐N L–1). The S applied in the slurry treatment was not adequate (9 kg S ha–1) to meet plant requirements.ConclusionThis study provides evidence that optimization of S nutrition has the potential to deliver large agronomic and environmental benefits along with potential as a nitrate leaching migration strategy on S‐deficient soils.

Measurement of flux through sulfate assimilation using [35S]sulfate.

Sulfur metabolism provides a number of compounds that are essential for plant survival and fitness and that affect the yield and quality of crops. Sulfur metabolism is a dynamic process, responding to a number of external cues. Because of this dynamics and rapid turnover, steady-state levels of sulfur-containing compounds do not always fully reflect plant responses to such cues. Therefore, measurements of the flux through sulfate assimilation may give a more precise estimate of the effects of environmental stimuli or metabolic disturbances on sulfur metabolism. The flux can be determined after feeding plants with sulfate labelled with an isotopic tracer. Here we describe a protocol for using [35S]sulfate to measure flux through sulfate assimilation in Arabidopsis. The protocol can be adapted for any plant species and growth conditions, and does not require any special equipment beyond a standard high performance liquid chromatograph. We hope that the protocol will support our colleagues in a more frequent use of flux measurements to answer new biological questions in plant sulfur metabolism.

Coordinated bacterial and plant sulfur metabolism in Enterobacter sp. SA187–induced plant salt stress tolerance

Enterobacter sp. SA187 is a root endophytic bacterium that maintains growth and yield of plants under abiotic stress conditions. In this work, we compared the metabolic wirings of Arabidopsis and SA187 in the free-living and endophytic interaction states. The interaction of SA187 with Arabidopsis induced massive changes in bacterial gene expression for chemotaxis, flagellar biosynthesis, quorum sensing, and biofilm formation. Besides modification of the bacterial carbon and energy metabolism, various nutrient and metabolite transporters and the entire sulfur pathway were up-regulated. Under salt stress, Arabidopsis resembled plants under sulfate starvation but not when colonized by SA187, which reprogramed the sulfur regulon of Arabidopsis. In accordance, salt hypersensitivity of multiple Arabidopsis sulfur metabolism mutants was partially or completely rescued by SA187 as much as by the addition of sulfate, L-cysteine, or L-methionine. Many components of the sulfur metabolism that are localized in the chloroplast were partially rescued by SA187. Finally, salt-induced accumulation of reactive oxygen species as well as the hypersensitivity of LSU mutants were suppressed by SA187. LSUs encode a central regulator linking sulfur metabolism to chloroplast superoxide dismutase activity. The coordinated regulation of the sulfur metabolic pathways in both the beneficial microorganism and the host plant is required for salt stress tolerance in Arabidopsis and might be a common mechanism utilized by different beneficial microbes to mitigate the harmful effects of different abiotic stresses on plants.

Identification and removal of sulfhydryl groups from wastewaters

Thiols represent a source of environmental pollution especially wastewater. This work proposed to study the elaboration of cellulose acetate polymer-based membranes for their application in the removal of a sulfhydryl groups of real biological treated wastewaters. The addition of nanoparticles to membranes improves the water purification capacity by promoting a good separation of sulfur, more particularly by ZnO-NPs. We used ultrafiltration membrane-assisted ZnO and TiO2 NPs application on real effluents from different biological treatment plants. We identified the hydrosulfite (thiol) group in wastewater and we used membrane processes ultrafiltration technique for sulfur removal. We evaluated the degradation of sulfur in biological treatment plants in Tunisia: The urban wastewater treatment plant or the conventional plant of Rades Malienne is a secondary biological wastewater treatment plant noted STEP1. The rural wastewater treatment plant based vertical flow planted with Phragmites australis from the Grombalia region noted STEP2 and rural wastewater treatment plant based horizontal flow planted with Phragmites australis from the Grombalia region noted STEP3. STEP1 is found to be more loaded with sulfur. Application of AC-ZnO membrane gives 99.07% and 99.55% of sulfur removal from wastewater of STEP1 and STEP3. STEP3 is 50 times less charged on sulfur than STEP1. We suggested that when the sulfur content is high, this leads to an increase in mineral elements. This could be explained by the interactions between thiols and the major elements that cause mineral pollution.

Interaction Between Sulfur and Iron in Plants.

It is well known that S interacts with some macronutrients, such as N, P, and K, as well as with some micronutrients, such as Fe, Mo, Cu, Zn, and B. From our current understanding, such interactions could be related to the fact that: (i) S shares similar chemical properties with other elements (e.g., Mo and Se) determining competition for the acquisition/transport process (SULTR transporter family proteins); (ii) S-requiring metabolic processes need the presence of other nutrients or regulate plant responses to other nutritional deficiencies (S-containing metabolites are the precursor for the synthesis of ethylene and phytosiderophores); (iii) S directly interacts with other elements (e.g., Fe) by forming complexes and chemical bonds, such as Fe-S clusters; and (iv) S is a constituent of organic molecules, which play crucial roles in plants (glutathione, transporters, etc.). This review summarizes the current state of knowledge of the interplay between Fe and S in plants. It has been demonstrated that plant capability to take up and accumulate Fe strongly depends on S availability in the growth medium in both monocots and dicot plants. Moreover, providing S above the average nutritional need enhances the Fe content in wheat grains, this beneficial effect being particularly pronounced under severe Fe limitation. On the other hand, Fe shortage induces a significant increase in the demand for S, resulting in enhanced S uptake and assimilation rate, similar to what happens under S deficiency. The critical evaluation of the recent studies on the modulation of Fe/S interaction by integrating old and new insights gained on this topic will help to identify the main knowledge gaps. Indeed, it remains a challenge to determine how the interplay between S and Fe is regulated and how plants are able to sense environmental nutrient fluctuations and then to adapt their uptake, translocation, assimilation, and signaling. A better knowledge of the mechanisms of Fe/S interaction might considerably help in improving crop performance within a context of limited nutrient resources and a more sustainable agriculture.