Effects of Thiosulfate as a Sulfur Source on Plant Growth, Metabolites Accumulation and Gene Expression in Arabidopsis and Rice

Green synthesis of a dual-functional sulfur nanofertilizer to promote growth and enhance salt stress resilience in faba bean

BACKGROUND

Salinity is a major abiotic stress, and the use of saline water in the agricultural sector will incur greater demand under the current and future climate changing scenarios. The objective of this study was to develop a dual-functional nanofertilizer capable of releasing a micronutrient that nourishes plant growth while enhancing salt stress resilience in faba bean (Vicia faba L.).

RESULTS

Moringa oleifera leaf extract was used to synthesize sulfur nanoparticles (SNPs), which were applied as a foliar spray at different concentrations (0, 25, 50, and 100 mg/l) to mitigate the negative effects of salt stress (150 mM NaCl) on faba bean plants. The SNPs were characterized and found to be spherical in shape with an average size of 10.98 ± 2.91 nm. The results showed that salt stress had detrimental effects on the growth and photosynthetic performance (Fv/Fm) of faba bean compared with control, while foliar spraying with SNPs improved these parameters under salinity stress. SNPs application also increased the levels of osmolytes (soluble sugars, amino acids, proline, and glycine betaine) and nonenzymatic antioxidants, while reducing the levels of oxidative stress biomarkers (MDA and H2O2). Moreover, SNPs treatment under salinity stress stimulated the activity of antioxidant enzymes (ascorbate peroxidase (APX), and peroxidase (POD), polyphenol oxidase (PPO)) and upregulated the expression of stress-responsive genes: chlorophyll a-b binding protein of LHCII type 1-like (Lhcb1), ribulose bisphosphate carboxylase large chain-like (RbcL), cell wall invertase I (CWINV1), ornithine aminotransferase (OAT), and ethylene-responsive transcription factor 1 (ERF1), with the greatest upregulation observed at 50 mg/l SNPs.

CONCLUSION

Overall, foliar application of sulfur nanofertilizers in agriculture could improve productivity while minimizing the deleterious effects of salt stress on plants. Therefore, this study provides a strong foundation for future research focused on evaluating the replacement of conventional sulfur-containing fertilizers with their nanoforms to reduce the harmful effects of salinity stress and enhance the productivity of faba beans.

Simulated nitrogen load promoted mineralization of N2P1 compounds and accumulation of N4S2 compounds in soil dissolved organic matter in a typical subtropical estuarine marsh

Soil dissolved organic matter (DOM) is the most reactive pool in estuarine marshes, playing an important role in the biogeochemical processes of biogenetic elements. To investigate the impacts of enhanced nitrogen (N) load on DOM molecular composition and its interactions with microbes in typical Cyperus malaccensis mashes of the Min River estuary, a field N load experiment with four N levels (0, 37.50, 50 and 100 g exogenous N m-2 yr-1, respectively; applied monthly for a total of seven months) was performed. DOM molecular composition was characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), the microbial community compositions (MCC, including fungi and bacteria) were determined by high-throughput sequencing technique, and their relationships were presented by co-occurrence network analysis. The results indicated that enhanced N load had significant impacts on soil DOM molecular composition, with N/C and P/C of DOM decreasing but S/C increasing markedly. Meanwhile, enhanced N load decreased the percentages of N2P1 compounds (primarily lipids) but increased those of N4S2 compounds (mainly lignins and lipids). The relative abundances of lignins significantly increased with increasing N load levels, whereas the proportions of lipids decreased. The abundance of N2P1 and N4S2 compounds was primarily positively correlated with eutrophic and oligotrophic microorganisms, respectively. Therefore, mineralization of N2P1 compounds might act as a source to replenish inorganic P, while enrichment of N4S2 compounds may make great contribution to organic S accumulation. Overall, enhanced N load promoted P depletion and S enrichment via altering plant growth, litter decomposition and MCC.

Speciation Features of Ferdinandcohnia quinoae sp. nov to Adapt to the Plant Host

The bacterial strain SECRCQ15T was isolated from seeds of Chenopodium quinoa in Spain. Phylogenetic, chemotaxonomic, and phenotypic analyses, as well as genome similarity indices, support the classification of the strain into a novel species of the genus Ferdinandcohnia, for which we propose the name Ferdinandcohnia quinoae sp. nov. To dig deep into the speciation features of the strain SECRCQ15T, we performed a comparative genomic analysis of the genome of this strain and those of the type strains of species from the genus Ferdinandcohnia. We found several genes related with plant growth-promoting mechanisms within the SECRCQ15T genome. We also found that singletons of F. quinoae SECRCQ15T are mainly related to the use of carbohydrates, which is a common trait of plant-associated bacteria. To further reveal speciation events in this strain, we revealed genes undergoing diversifying selection (e.g., genes encoding ribosomal proteins) and functions likely lost due to pseudogenization. Also, we found that this novel species contains 138 plant-associated gene-cluster functions that are unique within the genus Ferdinandcohnia. These features may explain both the ecological and taxonomical differentiation of this new taxon.

Multifarious characteristics of sulfur-oxidizing bacteria residing in rice rhizosphere

Sulfur-oxidizing bacteria (SOB) are versatile microorganisms known for their ability to oxidize various reduced sulfur compounds, namely, elemental sulfur (S0), hydrogen sulfide (H2S), tetrathionate (S4O62-), and trithionate (S3O62-) to sulfate (SO42-). In this study, out of twelve SOB isolates from rice rhizosphere, five were screened based on their sulfur oxidation potential, viz., SOB1, SOB2, SOB3, SOB4, and SOB5, and were identified as Ochrobactrum soli SOB1, Achromobacter xylosoxidans SOB2, Stenotrophomonas maltophilia SOB3, Brucella tritici SOB4, and Stenotrophomonas pavanii SOB5, respectively. All the isolates displayed chemolithotrophic nutritional mode by consuming thiosulfate and accumulating trithionate and tetrathionate in the growth medium which is ultimately oxidized to sulfate. The strains were authenticated with the production of thiosulfate oxidizing enzymes such as rhodanese and sulfite oxidase. Despite their tendency to oxidize reduced sulfur compounds, B. tritici SOB4 and S. pavanii SOB5 were also found to possess phosphate and zinc solubilization potential, acetic acid, and indole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. The presence of sulfanyl (R-SH) groups was noticed in the A. xylosoxidans SOB2. Elemental sulfur conversion into sulfate was noted in the S. maltophilia SOB3, and hydrogen sulfide conversion into sulfate was observed in the Ochromobacter soli SOB1. Sulfur oxidation potential coupled with beneficial properties of the isolates widen the knowledge on SOB.

A Synthetic Microbiome Based on Dominant Microbes in Wild Rice Rhizosphere to Promote Sulfur Utilization

Sulfur (S) is one of the main components of important biomolecules, which has been paid more attention in the anaerobic environment of rice cultivation. In this study, 12 accessions of rice materials, belonging to two Asian rice domestication systems and one African rice domestication system, were used by shotgun metagenomics sequencing to compare the structure and function involved in S cycle of rhizosphere microbiome between wild and cultivated rice. The sulfur cycle functional genes abundances were significantly different between wild and cultivated rice rhizosphere in the processes of sulfate reduction and other sulfur compounds conversion, implicating that wild rice had a stronger mutually-beneficial relationship with rhizosphere microbiome, enhancing sulfur utilization. To assess the effects of sulfate reduction synthetic microbiomes, Comamonadaceae and Rhodospirillaceae, two families containing the genes of two key steps in the dissimilatory sulfate reduction, aprA and dsrA respectively, were isolated from wild rice rhizosphere. Compared with the control group, the dissimilatory sulfate reduction in cultivated rice rhizosphere was significantly improved in the inoculated with different proportions groups. It confirmed that the synthetic microbiome can promote the S-cycling in rice, and suggested that may be feasible to construct the synthetic microbiome step by step based on functional genes to achieve the target functional pathway. In summary, this study reveals the response of rice rhizosphere microbial community structure and function to domestication, and provides a new idea for the construction of synthetic microbiome.

Vertical transfer and functional characterization of cotton seed core microbiome

Introduction

Microbiome within plant tissues is pivotal for co-evolution with host plants. This microbiome can colonize the plant, with potential transmission via seeds between parents and offspring, affecting seedling growth and host plant adaptability to the environment.

Methods

We employed 16S rRNA gene amplicon analysis to investigate the vertical distribution of core microbiome in cotton seeds across ecological niches [rhizosphere, root, stem, leaf, seed and seed-P (parental seed)] of the three cotton genotypes.

Results

The findings demonstrated a significant decrease in microbiome diversity and network complexity from roots, stems, and leaves to seeds. The microenvironment exerted a more substantial influence on the microbiome structure of cotton than the genotypes. The core endophytic microorganisms in cotton seeds comprised 29 amplicon sequence variants (ASVs) affiliated with Acidimicrobiia, Alphaproteobacteria, Bacilli, Bacteroidia, Clostridia, Gammaproteobacteria, and unclassified_Proteobacteria. These vertically transmitted taxa are widely distributed in cotton plants. Through 16S rRNA gene-based function prediction analysis of the cotton microbiome, we preliminarily understood that there are potential differences in metabolic capabilities and phenotypic traits among microbiomes in different microhabitats.

Discussion

In conclusion, this study demonstrated the crucial role of the microenvironment in influencing the cotton microbiome and offered insights into the structures and functions of the cotton seed microbiome, facilitating future crop yield enhancement through core seed microbiome regulation.

Changes in Sulfur Metabolism in Mouse Brains following Radon Inhalation

Therapy using hot springs, including the high-level radioactive gas "radon", is traditionally conducted as an alternative treatment for various diseases. Oxidative-stress-related diseases are inhibited by the enhancement of antioxidative functions following radon inhalation. We have reported that radon inhalation increased the level of anti-oxidants, such as glutathione (G-SH), in the brain and had a protective antioxidative effect against transient global cerebral ischemic injury. However, no studies have yet revealed the changes in G-SH associated substances after radon inhalation. In this study, we comprehensively analyzed several metabolites, focusing on G-SH. Mice were exposed to radon at concentrations of 200, 2000, or 20,000 Bq/m³ for 1, 3, or 10 days. We detected 27 metabolites in the mouse brains. The result showed that the L-methionine levels increased, whereas the levels of urea, glutathione, and sulfite ion decreased under any condition. Although the ratio of G-SH to oxidized glutathione (GS-SG) decreased, glutathione monosulfide (G-S-SH) and cysteine monosulfide (Cys-S-SH) increased after radon inhalation. G-S-SH and Cys-S-SH can produce a biological defense against the imbalance of the redox state at very low-dose irradiation following radon inhalation because they are strong scavengers of reactive oxygen species. Additionally, we performed an overall assessment of high-dimensional data and showed some specific characteristics. We showed the changes in metabolites after radon inhalation using partial least squares-discriminant analysis and self-organizing maps. The results showed the health effects of radon, especially the state of sulfur-related metabolites in mouse brains under the exposure conditions for radon therapy.

A new therapy against ulcerative colitis via the intestine and brain using the Si-based agent

Ulcerative colitis (UC) is a non-specific inflammatory bowel disease that causes ulcers and erosions in the colonic mucosa and becomes chronic with cycles of amelioration and exacerbation. Because its exact etiology remains largely unclear, and the primary therapy is limited to symptomatic treatment, the development of new therapeutic agent for UC is highly desired. Because one of the disease pathogenesis is involvement of oxidative stress, it is likely that an appropriate antioxidant will be an effective therapeutic agent for UC. Our silicon (Si)-based agent, when ingested, allowed for stable and persistent generation of massive amounts of hydrogen in the gastrointestinal tract. We demonstrated the Si-based agent alleviated the mental symptom as well as the gastrointestinal symptoms, inflammation, and oxidation associated with dextran sodium sulfate-induced UC model through Hydrogen and antioxidant sulfur compounds. As the Si-based agent was effective in treating UC in the brain and large intestine of mice, it was considered to be capable of suppressing exacerbations and sustaining remission of UC.

miR395-regulated sulfate metabolism exploits pathogen sensitivity to sulfate to boost immunity in rice

MicroRNAs (miRNAs) play important roles in plant physiological activities. However, their roles and molecular mechanisms in boosting plant immunity, especially through the modulation of macronutrient metabolism in response to pathogens, are largely unknown. Here, we report that an evolutionarily conserved miRNA, miR395, promotes resistance to Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), two destructive bacterial pathogens, by regulating sulfate accumulation and distribution in rice. Specifically, miR395 targets and suppresses the expression of the ATP sulfurylase gene OsAPS1, which functions in sulfate assimilation, and two sulfate transporter genes, OsSULTR2;1 and OsSULTR2;2, which function in sulfate translocation, to promote sulfate accumulation, resulting in broad-spectrum resistance to bacterial pathogens in miR395-overexpressing plants. Genetic analysis revealed that miR395-triggered resistance is involved in both pathogen-associated molecular pattern-triggered immunity and R gene-mediated resistance. Moreover, we found that accumulated sulfate but not S-metabolites inhibits proliferation of pathogenic bacteria, revealing a sulfate-mediated antibacterial defense mechanism that differs from sulfur-induced resistance. Furthermore, compared with other bacteria, Xoo and Xoc, which lack the sulfate transporter CysZ, are sensitive to high levels of extracellular sulfate. Accordingly, miR395-regulated sulfate accumulation impaired the virulence of Xoo and Xoc by decreasing extracellular polysaccharide production and biofilm formation. Taken together, these results suggest that rice miR395 modulates sulfate metabolism to exploit pathogen sensitivity to sulfate and thereby promotes broad-spectrum resistance.

Impact of spaceflight and artificial gravity on sulfur metabolism in mouse liver: sulfur metabolomic and transcriptomic analysis

Spaceflight induces hepatic damage, partially owing to oxidative stress caused by the space environment such as microgravity and space radiation. We examined the roles of anti-oxidative sulfur-containing compounds on hepatic damage after spaceflight. We analyzed the livers of mice on board the International Space Station for 30 days. During spaceflight, half of the mice were exposed to artificial earth gravity (1 g) using centrifugation cages. Sulfur-metabolomics of the livers of mice after spaceflight revealed a decrease in sulfur antioxidants (ergothioneine, glutathione, cysteine, taurine, thiamine, etc.) and their intermediates (cysteine sulfonic acid, hercynine, N-acethylserine, serine, etc.) compared to the controls on the ground. Furthermore, RNA-sequencing showed upregulation of gene sets related to oxidative stress and sulfur metabolism, and downregulation of gene sets related to glutathione reducibility in the livers of mice after spaceflight, compared to controls on the ground. These changes were partially mitigated by exposure to 1 g centrifugation. For the first time, we observed a decrease in sulfur antioxidants based on a comprehensive analysis of the livers of mice after spaceflight. Our data suggest that a decrease in sulfur-containing compounds owing to both microgravity and other spaceflight environments (radiation and stressors) contributes to liver damage after spaceflight.

Development of quantitative analytical method for volatile thiol compound with LC-ESI-MS as nonvolatile derivative by integrating a thiol-specific derivatization

Generally, volatile thiols are hard to be measured with ESI (electrospray ionization)-type LC-MS due to the volatility. Therefore, we here evaluated the pretreatment of their S-bimanyl derivatization by monobromobimane to enable the detection as nonvolatile derivative. Consequently, we successfully developed the convenient and efficient method through the quantitative analysis of 2-furanmethanethiol (volatile thiol odorant of coffee aroma) in coffee bean.

Sulfur nanoparticles mediated improvement of salt tolerance in wheat relates to decreasing oxidative stress and regulating metabolic activity

Salinity is a critical issue impairing the growth and productivity of most crop species through the mediated ionic and osmotic imbalances. As a way forward, the current study was tailored to elucidate the capacity of sulfur nanoparticles (SNPs) to amend salinity consequences on growth and physio-biochemical attributes of wheat. In a controlled experiment, wheat seeds were primed for 12 h with either 100 μM SNPs or deionized water then sown in plastic pots containing 5 kg clay-sand mixture (2:1 w/w). A week later, pots received NaCl (100 or 200 mM) as a sole treatment or in combination with SNPs and after three weeks the data of morph-bio-physiological traits were recorded. Salinity decreased growth rate, pigmentation, protein, amino acids, cysteine, ascorbate, flavonoids and phenolics content in wheat leaves. Plants pre-treated with 100 μM SNPs showed improved growth rate, pigmentation, nitrogen metabolism as well as non-enzymatic antioxidant contents as compared with salinized treatments. Neither salt nor SNP treatments affected photosynthetic performance rate (Fv/fm), however both treatments induced glutathione content. SNP treatment retrieved the undue excessive activities of catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD) and polyphenol oxidase (PPO) besides the increased level of proline caused by salt stress. Likewise, 100 μM SNPs rebalanced the declined nitrogen, phosphorus and potassium contents and decreased sodium uptake caused by salinity. On the whole, priming with 100 μM SNPs improved photosynthetic pigments, nitrogen metabolism, antioxidant status and ionic relations contributing to the enhancement of growth attributes in wheat under salinity.

Appraisal of H2S metabolism in Arabidopsis thaliana: In silico analysis at the subcellular level

Hydrogen sulfide (H₂S) has become a new signal molecule in higher plants which seems to be involved in almost all physiological processes from seed germination, root and plant growth until flowering and fruit ripening. Moreover, H₂S also participates in the mechanism of response against adverse environmental stresses. However, its basic biochemistry in plant cells can be considered in a nascent stage. Using the available information of the model plant Arabidopsis thaliana, the goal of the present study is to provide a broad overview of H₂S metabolism and to display an in silico analysis of the 26 enzymatic components involved in the metabolism of H₂S and their subcellular compartmentation (cytosol, chloroplast and mitochondrion) thus providing a wide picture of the cross-talk inside the organelles and amongst them and, consequently, to get a better understanding of the cellular and tissue implications of H₂S. This information will be also relevant for other crop species, especially those whose whole genome is not yet available.

Ergothioneine, a metabolite of the gut bacterium Lactobacillus reuteri, protects against stress-induced sleep disturbances

The relationships between depression and gut microbiota, particularly those involving the immune system, have become a major focus of recent research. Here, we analyzed changes in gut microbiota and their sulfur metabolites in the feces of a depression rat model using the modified 14-day social defeat stress (SDS) paradigm. Our results showed that SDS increased fecal Lactobacillus reuteri in correlation with ergothioneine levels at around day 11, which continued for at least 1 month following SDS administration. In vitro study further revealed that L. reuteri is capable of producing ergothioneine. Although the known anti-inflammatory and anti-oxidative actions of ergothioneine suggested that the increased fecal ergothioneine levels may be related to intestinal anti-inflammatory defense mechanisms, no change was observed in the plasma ergothioneine levels during the same observation period, indicating that the defense mechanisms may not be sufficiently reflected in the body. As ergothioneine is a natural ingredient that is absorbed mainly from the upper gastrointestinal tract, we hypothesized that oral ergothioneine may exert antidepressant effects. As expected, oral administration of ergothioneine prior to and during the SDS paradigm had a preventative effect on SDS-induced depressive behaviors, such as social avoidance and depression-like sleep abnormalities, particularly those of rapid eye movement sleep. These findings indicate that ergothioneine, a metabolite of L. reuteri, may be a common substance in the microbiota-gut-brain axis that prevents stress-induced sleep disturbances, especially those associated with depression.

Development of high-throughput quantitative analytical method for L-cysteine-containing dipeptides by LC-MS/MS toward its fermentative production

l-Cysteine (Cys) is metabolically fundamental sulfur compound and important components in various cellular factors. Interestingly, free-form Cys itself as a simple monomeric amino acid was recently shown to function in a novel antioxidative system (cysteine/cystine shuttle system) in Escherichia coli. However, as for Cys-containing dipeptides, the biological functions, effects, and even contents have still remained largely elusive. The potential functions should be a part of cellular redox system and important in basic and applied biology. For its progress, establishment of reliable quantitation method is the first. However, such accurate analysis is unexpectedly difficult even in Cys, because thiol compounds convert through disulfide-exchange and air oxidation during sample preparation. Addressing this problem, in this study, thiol molecules like Cys-containing dipeptides were derivatized by using monobromobimane (thiol-specific alkylating reagent) and detected as S-bimanyl derivatives by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). Sample separation was processed with a C18 column (2.1 mm × 150 mm, 1.7 μm) and with water-acetonitrile gradient mobile phase containing 0.1% (v/v) formic acid at flow rate of 0.25 ml/min. The mass spectrometer was operated in the multiple reaction monitoring in positive/negative mode with electrospray ionization. The derivatization could indeed avoid the unfavorable reactions, namely, developed the method reflecting their correct contents on sampling. Furthermore, the method was successfully applied to monitoring Cys-containing dipeptides in E. coli Cys producer overexpressing bacD gene. This is the first report of the quantitative analysis of Cys-containing dipeptides, which should be useful for further study of fermentative production of Cys-containing dipeptides.