Cysteine Desulfhydrase Research Articles

Structural analysis of the CJ0600 protein from Campylobacter jejuni

The Campylobacter jejuni bacterium, which causes foodborne enteritis in humans, expresses the uncharacterized protein CJ0600. Based on sequence analysis, CJ0600 has been proposed to function as a 1-aminocyclopropane-1-carboxylate (ACC) deaminase (AccDA) or cysteine desulfhydrase (CysDS). However, it has never been investigated whether CJ0600 exerts AccDA or CysDS activity or how CJ0600 mediates its enzymatic activity. To reveal the structural features necessary for the function of CJ0600, we determined the crystal structure of CJ0600 and characterized its enzymatic activity. CJ0600 contains two domains and features an interdomain pocket, which accommodates a pyridoxal 5′-phosphate (PLP) molecule as a Schiff base with its lysine residue (K35), as observed in its structural homologs, including AccDA, CysDS, and serine deaminase (SerDA). However, unlike its structural homologs, CJ0600 exists as a monomer and exhibits unique structural features throughout its structure. Moreover, CJ0600 contains unique active site residues that are not observed in AccDA, CysDS, or SerDA. Consistently, phylogenetic analysis indicates that CJ0600 and its orthologs are evolutionarily distinct from AccDA, CysDS, and SerDA. Indeed, CJ0600 showed no CysDS or SerDA activity and extremely weak AccDA activity. These observations suggest that CJ0600 functions as a unique PLP-dependent enzyme that has not been reported.

Regulation of arsenate stress by nitric oxide and hydrogen sulfide in Oryza sativa seedlings: Implication of sulfur assimilation, glutathione biosynthesis, and the ascorbate-glutathione cycle and its genes

Seed priming by nitric oxide (NO) and hydrogen sulphide (H2S) in combating against abiotic stress in plants is well documented. However, knowledge of fundamental mechanisms of their crosstalk is scrambled. Therefore, the reported study examined the probable role of NO and H2S in the mitigation of arsenate toxicity (As(V)) in rice seedlings and whether their potential signalling routes crossover. Results report that As(V) toxicity limited shoot and root length growth with more As accumulation in roots. As(V) further caused elevated reactive oxygen species levels, inhibited ascorbate-glutathione cycle enzymes and relative gene expression of its enzymes and thus, causing lipid and protein oxidation. These results correlate with reduced nitric oxide synthase-like and L–cysteine desulfhydrase activity along with endogenous NO and H2S. While, L-NAME or PAG augmented As(V) toxicity, and addition of SNP or NaHS effectively reversed their respective effects. Furthermore, SNP under PAG or NaHS under L-NAME were able to pacify As(V) stress, implicating that endogenous NO and H2S efficiently ameliorate As(V) toxicity but without their shared signaling in rice seedlings.

Persulfidation and phosphorylation of transcription factor SlWRKY6 differentially regulate tomato fruit ripening.

Cysteine desulfhydrase catalyses the generation of the signaling molecule hydrogen sulfide (H2S) in plants. In this study, we found that H2S can inhibit tomato (Solanum lycopersicum) fruit ripening and SlWRKY6 undergoes differential protein persulfidation in SlLCD1-overexpressing leaves. Then, further study indicated that SlWRKY6 could be persulfidated by H2S at Cys396. By construction of slwrky6 mutants and SlWRKY6-OE lines, we found that SlWRKY6 positively regulates leaf senescence and fruit ripening by activating the transcription of ripening-related genes STAYGREEN 1 (SlSGR1) and Senescence-Associated Gene 12 (SlSAG12). In addition, SlWRKY6 interacted with kinase SlMAPK4 and was phosphorylated at Ser33. Dual-luciferase transient expression assays and electrophoretic mobility shift assays indicated that SlWRKY6 persulfidation attenuated its transcriptional regulation of target genes SlSGR1 and SlSAG12, whereas SlWRKY6 phosphorylation by SlMAPK4 activated the transcription of target genes to promote fruit ripening. Moreover, we provided evidence that SlWRKY6 persulfidation attenuated its SlMAPK4-mediated phosphorylation to inhibit tomato fruit ripening. By transient expression of SlWRKY6, SlWRKY6C396A, SlWRKY6S33A, and SlWRKY6S33D in slwrky6 fruits, we found that SlWRKY6 persulfidation attenuated the expression of SlSGR1 and SlSAG12 thereby delaying tomato fruit ripening, while SlWRKY6 phosphorylation increased the expression of target genes. As tomato fruits ripened, endogenous H2S production decreased, while SlMAPK4 expression increased. Therefore, our findings reveal a model in which SlWRKY6 persulfidation due to higher endogenous H2S levels in un-ripened fruit inhibits its ability to activate SlSGR1 and SlSAG12 expression, while SlWRKY6 phosphorylation by SlMAPK4 activates its transcriptional activity, thereby promoting tomato fruit ripening.

Effect of hydrogen sulfide (H2S) on the growth and development of tobacco seedlings in absence of stress

BackgroundHydrogen sulfide (H2S) is a novel signaling molecule involved in the growth and development of plants and their response to stress. However, the involvement of H2S in promoting the growth and development of tobacco plants is still unclear.ResultsIn this study, we explored the effect of pre-soaking or irrigating the roots of tobacco plants with 0.0, 2.0, 4.0, 6.0, and 8.0 mM of sodium hydrosulfide (NaHS) on endogenous H2S production, antioxidant enzymatic and cysteine desulfhydrase activities, seed germination, agronomic traits, photosynthetic pigments contents, and root vigor. The results revealed that exogenous NaHS treatment could significantly promote endogenous H2S production by inducing gene expression of D/L-CD and the activities of D/L-CD enzymes. Additionally, a significant increase in the agronomic traits and the contents of photosynthetic pigments, and no significant difference in carotenoid content among tobacco plants treated with 0.0 to 8.0 mM of NaHS was observed. Additionally, a significant increase in the germination speed, dry weight, and vigor of tobacco seeds, whereas no significant effect on the percentage of seed germination was observed on NaHS treatment. Furthermore, NaHS treatment could significantly increase the activity of superoxide dismutase (SOD) and peroxidase (POD) enzymes, which reduces damage due to oxidative stress by maintaining reactive oxygen species homeostasis.ConclusionsThese results would aid in enhancing our understanding of the involvement of H2S, a novel signaling molecule to promote the growth and development of tobacco plants.

Gene Expression in Cadmium Sulfide Biological-Nanoparticle Hybrids

Through millions of years of evolution, bacteria have developed unique and complex ways to survive, allowing them to inhabit ecosystems all over the Earth, including places with high metal ion concentrations. Bacteria have developed many survival mechanisms to evade metal ion toxicity. Survival mechanisms to evade metal toxicity include the ability to transform metal ions into nanoparticles. When metal ions bind to other constituents to form nanoparticles, the metal ion concentrations in the environment can be lowered, in turn lessening the likelihood of cells encountering toxic concentrations of metals. These nanoparticles can be expelled by the bacteria into the environment, remain inside the bacteria, or attached to the cell surface. Bacteria and metal nanoparticles have many useful functions on their own. Furthermore, these functions can be combined when the two come together. Cells that produce metal nanoparticles that remain attached to their surface are referred to as biological-nanoparticle hybrids (bionanohybrids), as shown in the scanning electron image in Fig. 1. Surface-associated nanoparticles (SANs) can enhance biological functions, enabling a variety of new applications related to bioremediation, energy production and storage, and agricultural and medical advances. Bionanohybrid research also creates new opportunities to investigate microbial communities, synthetic biology, and the origins of life. Metal-sulfide SANs are of particular interest due to their semi-conductor abilities and examples of their generation by multiple bacterial species. This includes bacteria inhabiting metal-rich extreme environments like the Mariana Trench, to bacteria found in the human gut (such as E. coli). While these bacteria are very different, they do share in common the cysteine desulfhydrase enzyme—which plays a crucial role in the formation of metal-sulfide bionanohybrids. Cysteine desulfhydrase converts the amino acid cysteine into sulfide that then reacts with environmental metal cations to create metal sulfide nanoparticles (Raouf Hosseini and Nasiri Sarvi 2015). Under the right conditions (e.g., optimal ratios of metal and cysteine to cell density and growth phase), the resulting nanoparticles remain attached to the surface of the cell, as shown in Fig. 1 (Barnes et al. 2022). Despite the emergence of bionanohybrid applications, very little is known about how the bionanohybrid lifestyle impacts cells. This project aims to uncover some of the fundamental questions regarding bionanohybrid gene expression by analyzing the RNA transcripts from E. coli K-12 cells with different degrees of cadmium sulfide (CdS) SAN coverage. Gene expression studies may reveal fundamental differences between bionanohybrids and uncoated bacteria, potentially informing development of industrially advantageous bacteria strains that can produce more SANs. Gel electrophoresis and/or density gradient centrifugation will be used to separate cells that are uncoated, lightly coated, medium coated, and heavily coated proir to RNA isolation and purification. Scanning electron microscopy will confirm SAN coverage in these different fractions. RNA sequencing will indicate if there are any differences in gene expression between uncoated cells and bionanoybrids, as well as examine if SAN cell coverage has any relationship to gene expression. This research promises to open doors to new applications related to bionanohybrids while expanding our knowledge of microbial biology.

Stability and biomineralization of cadmium sulfide nanoparticles biosynthesized by the bacterium Rhodopseudomonas palustris under light

Cadmium (Cd) pollution is regarded as a potent problem due to its hazard risks to the environment, making it crucial to be removed. Compared to the physicochemical techniques (e.g., adsorption, ion exchange, etc.), bioremediation is a promising alternative technology for Cd removal, due to its cost-effectiveness, and eco-friendliness. Among them, microbial-induced cadmium sulfide mineralization (Bio-CdS NPs) is a process of great significance for environmental protection. In this study, microbial cysteine desulfhydrase coupled with cysteine acted as a strategy for Bio-CdS NPs by Rhodopseudomonas palustris. The synthesis, activity, and stability of Bio-CdS NPs-R. palustris hybrid was explored under different light conditions. Results show that low light (LL) intensity could promote cysteine desulfhydrase activities to accelerate hybrid synthesis, and facilitated bacterial growth by the photo-induced electrons of Bio-CdS NPs. Additionally, the enhanced cysteine desulfhydrase activity effectively alleviated high Cd-stress. However, the hybrid rapidly dissolved under changed environmental factors, including light intensity and oxygen. The factors affecting the dissolution were ranked as follows: darkness/microaerobic ≈ darkness/aerobic < LL/microaerobic < high light (HL)/microaerobic < LL/aerobic < HL/aerobic. The research provides a deeper understanding of Bio-CdS NPs-bacteria hybird synthesis and its stability in Cd-polluted water, allowing advanced bioremediation treatment of heavy metal pollution in water.

The Effect of Dietary Cysteine Level on Cysteine Metabolism in Rats

Male, Sprague-Dawley rats were fed l-amino acid diets that contained 0.4% l methionine and either 0, 0.2% (control), or 2.6% l-cysteine (free base) for 5 or 20 days. Hepatic cysteine dioxygenase activity in rats fed 2.6% cysteine was 5 and 3-times as great as in pair-fed control rats at 5 and 20 days, respectively. Cysteine sulfinate decarboxylase activity in liver of rats fed 2.6% cysteine for 20 days was about 40% of the pair-fed control level. The activity of cysteine sulfinate aminotransferase and the rate of cysteine desulfhydration were not influenced by dietary cysteine content. Rats that had been fed these diets for 5 days were intubated with 5 g of diet that contained either 0.2% or 2.6% l-[35S]cysteine. The 24-hour urinary excretion of total 35S, 35SO4, and [35S]taurine by rats that had been fed 2.6% cysteine for 5 days and intubated with 0.2% l-[35S]cysteine was 1.4-, 1.8-, and 2.4-fold, respectively, that of pair-fed control rats. About 2.1, 1.8, and 9.1 times as much 35S, 35SO/4, and [35S]taurine, respectively, were excreted by rats fed 2.6% cysteine for 5 days and intubated with 2.6% l-[35S]cysteine as was excreted by pair-fed control rats. Urinary excretion of these metabolites was not different between rats fed 0 and 0.2% cysteine. These results indicate that the cysteine sulfinate pathway plays a major regulatory role in the metabolism of excess cysteine.cysteine cysteine desulfhydrase cysteine dioxygenase cysteine sulfinate decarboxylase taurine sulfate

Production of indole and hydrogen sulfide by the oxygen-tolerant mutant strain Clostridium sp. Aeroto-AUH-JLC108 contributes to form a hypoxic microenvironment.

In this study, the oxygen-tolerant mutant strain Clostridium sp. Aeroto-AUH-JLC108 was found to produce indole when grown aerobically. The tnaA gene coding for tryptophanase responsible for the production of indole was cloned. The tnaA gene from Aeroto-AUH-JLC108 is 1677bp and has one point mutation (C36G) compared to the original anaerobic strain AUH-JLC108. Phylogenetic analyses based on the amino acid sequence showed significant homology to that of TnaA from Flavonifractor. Furthermore, we found that the tnaA gene also exhibited cysteine desulfhydrase activity. The production of hydrogen sulfide (H2S) was accompanied by decrease in the amount of the dissolved oxygen in the culture medium. Similarly, the amount of indole produced by strain Aeroto-AUH-JLC108 obviously decreased the oxidation-reduction potential (ORP) in BHI liquid medium. The results demonstrated that production of indole and H2S helped to form a hypoxic microenvironment for strain Aeroto-AUH-JLC108 when grown aerobically.

Identification and functional characterization of a cystathionine β-lyase (CBL) enzyme for H2S production in Arabidopsis thaliana

Sulfide or sulfur metabolism plays an important role in the growth and development of plants. Cystathionine β-lyase (CBL) is an important enzyme in methionine synthesis, but a comprehensive understanding of CBL functions is limited. As the third gasotransmitter, hydrogen sulfide (H2S) plays important physiological roles in plants. In this study, we found that the endogenous H2S content in Arabidopsis thaliana cbl mutants was lower than that in the wild type. Under PEG-based osmotic stress conditions, the H2S contents of CBL-overexpression (OE-CBL) plants increased significantly compared with the wild type. Additionally, the OE-CBL plants increased their tolerance to osmotic stress by increasing the transcription levels of drought-related genes and their relative water-loss rates. Compared with cbl and wild type, OE-CBL plants resisted drought stress by significantly closing their stomata, resulting in improved survival rates. Root tip-bending experiments showed that CBL overexpression relieved osmotic, heavy metal and cold stresses in Arabidopsis. The recombinant CBL activity in vitro revealed that CBL produced H2S using L-cysteine as a substrate. Thus, CBL had a very strong cysteine desulfhydrase activity that could produce endogenous H2S using L-cysteine as a substrate, and it played an important role in plant abiotic stress resistance.

Roles of a Cysteine Desulfhydrase LCD1 in Regulating Leaf Senescence in Tomato.

Hydrogen sulfide (H2S), a novel gasotransmitter in both mammals and plants, plays important roles in plant development and stress responses. Leaf senescence represents the final stage of leaf development. The role of H2S-producing enzyme L-cysteine desulfhydrase in regulating tomato leaf senescence is still unknown. In the present study, the effect of an L-cysteine desulfhydrase LCD1 on leaf senescence in tomato was explored by physiological analysis. LCD1 mutation caused earlier leaf senescence, whereas LCD1 overexpression significantly delayed leaf senescence compared with the wild type in 10-week tomato seedlings. Moreover, LCD1 overexpression was found to delay dark-induced senescence in detached tomato leaves, and the lcd1 mutant showed accelerated senescence. An increasing trend of H2S production was observed in leaves during storage in darkness, while LCD1 deletion reduced H2S production and LCD1 overexpression produced more H2S compared with the wild-type control. Further investigations showed that LCD1 overexpression delayed dark-triggered chlorophyll degradation and reactive oxygen species (ROS) accumulation in detached tomato leaves, and the increase in the expression of chlorophyll degradation genes NYC1, PAO, PPH, SGR1, and senescence-associated genes (SAGs) during senescence was attenuated by LCD1 overexpression, whereas lcd1 mutants showed enhanced senescence-related parameters. Moreover, a correlation analysis indicated that chlorophyll content was negatively correlated with H2O2 and malondialdehyde (MDA) content, and also negatively correlated with the expression of chlorophyll degradation-related genes and SAGs. Therefore, these findings increase our understanding of the physiological functions of the H2S-generating enzyme LCD1 in regulating leaf senescence in tomato.

Effects of sodium hydrosulfide and rhizobia on the growth rate, nutrient stoichiometry, and nutrient resorption of soybean (Glycine max L.)#

AbstractBackground and aimsNaHS, a donor of hydrogen sulfide (H2S), which is emerging as a potential signaling molecule, may regulate various physiological processes in plants. However, how soybean (Glycine max L.) responds to NaHS and rhizobia (Sinorhizobium fredii) inoculation remains unclear.MethodsWe explored the effects of NaHS and rhizobia on the growth rate, nodules, nitrogenase activities (NA), chlorophyll content, soluble protein content, photosynthesis (Pn), chlorophyll fluorescent parameters, endogenous H2S accumulation, l/d‐cysteine desulfhydrase (GmLCD and GmDCD) gene expression, nitrogen (N), phosphorus (P), potassium (K) contents, and nutrient resorption.ResultsThe results showed that rhizobia significantly increased the shoot, root, total dry weight, and growth rate, and NaHS promoted nodule numbers and NA in soybean. Moreover, chlorophyll content, soluble protein content, Pn, endogenous H2S accumulation, and GmLCD and GmDCD gene expression levels were promoted by NaHS and rhizobia. In addition, during all growth stages of soybean, the levels of N, P, and K and the N:P ratio in different tissues were affected by NaHS and rhizobia. Additionally, NaHS and rhizobia also significantly enhanced N resorption efficiency (NRE) and K resorption efficiency (KRE), but decreased P resorption efficiency (PRE).ConclusionTherefore, NaHS and rhizobia regulated the growth rate, nutrient stoichiometry, and nutrient resorption efficiency of soybean. These findings provide information that will be useful for predicting how NaHS and rhizobia lead to variations in nutrient uptake and nutrient conservation strategies.

Implication of nitric oxide and hydrogen sulfide signalling in alleviating arsenate stress in rice seedlings

Nitric oxide (NO) and hydrogen sulfide (H2S) since their discovery have proven to be game changing molecules in alleviating abiotic stress. They individually play role in plant stress management while the pathways of stress regulation through their crosstalk remain elusive. The current study focuses on investigating the interplay of NO and H2S signalling in the amelioration of arsenate As(V) toxicity in rice seedlings and managing its growth, photosynthesis, sucrose and proline metabolism. Results show that As(V) exposure declined fresh weight (biomass) due to induced cell death in root tips. Moreover, a diminished RuBisCO activity, decline in starch content with high proline dehydrogenase activity and increased total soluble sugars content was observed which further intensified in the presence of Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME, an inhibitor of nitric oxide synthase-like activity), and DL-propargylglycine (PAG, an inhibitor of cysteine desulfhydrase activity). These results correlate with lower endogenous level of NO and H2S. Addition of L-NAME increased As(V) toxicity. Interestingly, addition of SNP reverses effect of L-NAME suggesting that endogenous NO has a role in mitigating As(V) toxicity. Similarly, exogenous H2S also significantly alleviated As(V) stress, while PAG further stimulated As(V) toxicity. Furthermore, application of H2S in the presence of L – NAME and NO in the presence of PAG could still mitigate As(V) toxicity, suggesting that endogenous NO and H2S could independently mitigate As(V) stress.

Stomatal regulation: Role of H2S-induced persulfidation in ABA signaling

Stomatal regulation: Role of H2S-induced persulfidation in ABA signaling

Calcium-crosslinked alginate-encapsulated bacteria for remediating of cadmium-polluted water and production of CdS nanoparticles

Pollution with the heavy metal cadmium (Cd2+) is a global problem. Cadmium adversely affects living organisms, highlighting the need to develop new methods for removal of this pollutant from the environment. In this study, we used a novel biomaterial based on calcium-crosslinked alginate-encapsulated bacteria to precipitate Cd2+ in polluted water. Our results show that calcium-crosslinked alginate-encapsulated bacteria effectively removed Cd2+ ions from cadmium-polluted water. Approximately 100% of Cd2+ ions were removed by 10 g (wet weight) of this biomaterial when the loading concentration of Cd2+ reached 1 mM in a volume of 50 ml water. During this process, a CdS nanoparticle, showing good crystallinity in the quantum range, was simultaneously produced. To validate the activity and stability of this biomaterial, we measured cysteine desulfhydrase activity in the stored biomaterial and whether this biomaterial could be recycled. The encapsulated bacteria maintained catalytic activity for at least 2 weeks. The capsules were easily regenerated and possessed good recyclability. Our results indicated that calcium-crosslinked alginate-encapsulated bacteria are suitable for depletion of Cd2+ in polluted water and for production of CdS nanoparticles. These calcium-crosslinked alginate-encapsulated bacteria are safe for biological manipulation and can be widely used to produce CdS nanoparticles during bioremediation of Cd2+-polluted water. KEY POINTS: • Calcium-crosslinked alginate-encapsulated bacteria can effectively precipitate Cd2+ in water coupled with production of CdS quantum dots. • The encapsulated bacteria maintained catalytic activity for at least 2 weeks. • The capsules were easily regenerated and possessed good recyclability.

A nuclear-localized cysteine desulfhydrase plays a role in fruit ripening in tomato

Hydrogen sulfide (H2S) is a gaseous signaling molecule that plays multiple roles in plant development. However, whether endogenous H2S plays a role in fruit ripening in tomato is still unknown. In this study, we show that the H2S-producing enzyme l-cysteine desulfhydrase SlLCD1 localizes to the nucleus. By constructing mutated forms of SlLCD1, we show that the amino acid residue K24 of SlLCD1 is the key amino acid that determines nuclear localization. Silencing of SlLCD1 by TRV-SlLCD1 accelerated fruit ripening and reduced H2S production compared with the control. A SlLCD1 gene-edited mutant obtained through CRISPR/Cas9 modification displayed a slightly dwarfed phenotype and accelerated fruit ripening. This mutant also showed increased cysteine content and produced less H2S, suggesting a role of SlLCD1 in H2S generation. Chlorophyll degradation and carotenoid accumulation were enhanced in the SlLCD1 mutant. Other ripening-related genes that play roles in chlorophyll degradation, carotenoid biosynthesis, cell wall degradation, ethylene biosynthesis, and the ethylene signaling pathway were enhanced at the transcriptional level in the lcd1 mutant. Total RNA was sequenced from unripe tomato fruit treated with exogenous H2S, and transcriptome analysis showed that ripening-related gene expression was suppressed. Based on the results for a SlLCD1 gene-edited mutant and exogenous H2S application, we propose that the nuclear-localized cysteine desulfhydrase SlLCD1 is required for endogenous H2S generation and participates in the regulation of tomato fruit ripening.

Abstract 3342: The colorectal cancer associated microbe Odoribacter splanchnicus produces genotoxic hydrogen sulfide via cysteine metabolism

Abstract The proinflammatory and genotoxic properties of hydrogen sulfide (H2S) have been implicated as an environmental trigger of colonic disease. Recent evidence links sulfidogenic bacteria capable of metabolizing organic sulfur substrates, like dietary sulfur amino acids and taurine conjugated bile acids, with increased colorectal cancer (CRC) and colitis risk as a consequence of a “western” type diet. Our previous work demonstrates that the sulfidogenic bacterium, Odoribacter splanchnicus, is a significant indicator of CRC in African Americans who are at higher risk of CRC incidence and death than other races and ethnicities in the United States. This observation has been corroborated by several recent studies that observed O. splanchnicus to be associated with CRC and colitis-induced CRC. While previous work has reported that O. splanchnicus may be sulfidogenic, its method of H2S production has yet to be characterized. Production of H2S by O. splanchnicus was confirmed in vitro using sulfide indole and motility media, and varying sulfur substrates. A predictive metabolic analysis of 74 O. splanchnicus metagenomes taken from publicly available CRC cohorts did not reveal complete pathways commonly associated with H2S production, however genes for a polar amino acid transporter were revealed. Therefore, a genomic analysis was performed revealing that O. splanchnicus harbors the sulfidogenic genes tryptophanase (tnaA) and cystathionine-β-synthase. The enzyme TnaA has been previously shown in Eschericia coli to produce indole or H2S from tryptophan or cysteine, respectively. However, the E. coli amino acid sequence shares only 44.85% identity with that from O. splanchnicus, thus heterologous protein expression of recombinant tnaA was performed to determine enzyme functionality. Enzyme kinetics and pH optimum were obtained using the spectrophotometric BiCl3 assay, which turns black in presence of H2S. Functional analysis of recombinant purified TnaA revealed bifunctionality of the enzyme with positive tryptophanase and cysteine desulfhydrase activity with differing substrates. Cysteine desulfhydrase activity resulted in consumption of L-cysteine with subsequent production of H2S and pyruvate. Thus, TnaA is a functional enzyme that warrants further evaluation as possibly relating to sulfidogenic O. splanchnicus being linked to CRC and colitis-associated CRC. Citation Format: Patricia G. Wolf, Vladimir Kolosslov, Zhichao Zhou, Lindsey Ly, Heidi Doden, Saravanan Devendran, Adam M. Breister, Luke Lucio, Paige Polak, Sarah Matatov, Karthik Anantharaman, Jason M. Ridlon, Rex Gaskins. The colorectal cancer associated microbe Odoribacter splanchnicus produces genotoxic hydrogen sulfide via cysteine metabolism [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3342.

Mitigation of chromium (VI) toxicity by additional sulfur in some vegetable crops involves glutathione and hydrogen sulfide

Toxic metals cause substantial reduction in crop yields every year. Therefore, worldwide scientific efforts are being made to reduce such losses in crop productivity by using certain chemical protectants such as nutrients like sulfur (S), hydrogen sulfide (H2S), glutathione (GSH), etc. Therefore in this study, we have tested potential of additional S, along with probable involvement of H2S and GSH in mitigating hexavalent chromium (CrVI) toxicity in tomato, pea and brinjal seedlings. Chromium (VI) decreased shoot and root length, endogenous H2S, and cell viability due to greater Cr accumulation that led to cell death in roots. Chromium (VI) enhanced oxidative stress markers i.e. superoxide radical, hydrogen peroxide, lipid peroxidation and protein oxidation due to down-regulation in ascorbate-glutathione cycle. However, additional S reversed toxic effect of Cr(VI). Chromium (VI) slightly stimulated enzymes of glutathione biosynthesis. Besides this, the results also showed that addition of buthionine sulphoximine (BSO, synthetic inhibitor of glutathione biosynthesis) interestingly further enhanced Cr(VI) toxicity even in the presence of additional S. But this effect of BSO was reversed by the addition of GSH. Interestingly, hydroxylamine (HA, synthetic inhibitor of cysteine desulfhydrase) had also further increased Cr(VI) toxicity even in the presence of additional S but sodium hydrosulfide (NaHS, an H2S donor) reversed this effect. Furthermore, ameliorative behaviour of NaHS against Cr(VI) toxicity was reversed by the hypotaurine (HT, a H2S scavenger). All together results suggested that additional S involved GSH and H2S in mitigating Cr(VI) toxicity in studied vegetables, in which GSH acted downstream of H2S signal.

Bacterial Synthesis of Ternary CdSAg Quantum Dots through Cation Exchange: Tuning the Composition and Properties of Biological Nanoparticles for Bioimaging and Photovoltaic Applications.

In this study, we introduce a biological method for the production of ternary Quantum Dots (QDs): complex nanostructures with tunable optical and structural properties that utilizes post-synthesis modifications through cation exchange. This versatile in-situ cation exchange method being reported for the first time shows great potential for extending the scope of microbial synthesis. By using this bacterial-based method, we easily synthesize and purify CdS, CdSAg, and Ag2S nanocrystals of a size below 15 nm and with variable morphologies that exhibit fluorescence emissions covering a broad spectral range (from 400 to 800 nm). Energy-dispersive X-ray spectroscopy (EDS) results indicate the partial replacement of Cd2+ by Ag+ when AgNO3 concentration is increased. This replacement produces CdSAg ternary QDs hetero-structures with high stability, fluorescence in the NIR-I (700 - 800 nm), and 36.13% quantum yield. Furthermore, this reaction can be extended for the production of soluble Ag2S nanoparticles (NPs) without any traces of Cd. QDs biosynthesized through this cation exchange process display very low toxicity when tested in bacterial or human cell lines. Biosynthesized ternary hetero-structures were used as red fluorescent dyes to label HeLa cells in confocal microscopy studies, which validates its use in bioimaging applications in the near infrared region. In addition, the application of biologically-produced cadmium NPs in solar cells is reported for the first time. The three biosynthesized QDs were successfully used as photosensitizers, where the CdSAg QDs show the best photovoltaic parameters. Altogether, obtained results validate the use of bacterial cells for the controlled production of nanomaterials with properties that allow their application in diverse technologies. We developed a simple biological process for obtaining tunable Quantum Dots (QDs) with different metal compositions through a cation exchange process. Nanoparticles (NPs) are produced in the extracellular space of bacterial cells exposed to cysteine and CdCl2 in a reaction that depends on S2− generation mediated by cysteine desulfhydrase enzymes and uses cellular biomolecules to stabilize the nanoparticle. Using this extracellular approach, water-soluble fluorescent CdS, CdSAg, and Ag2S Quantum Dots with a tunable emission ranging from 400 to 800 nm were generated. This is the first study reporting the use of microorganisms to produce tunable ternary QDs and the first time that a cation exchange process mediated by cells is described. Obtained results validate the use of biological synthesis to produce NPs with new characteristics and opens a completely new research field related to the use of microorganisms to synthesize complex NPs that are difficult to obtain with regular chemical methods.

WRKY13 Enhances Cadmium Tolerance by Promoting D-CYSTEINE DESULFHYDRASE and Hydrogen Sulfide Production.

Hydrogen sulfide (H2S), a plant gasotransmitter, functions in the plant response to cadmium (Cd) stress, implying a role for cysteine desulfhydrase in producing H2S in this process. Whether d -CYSTEINE DESULFHYDRASE (DCD) acts in the plant Cd response remains to be identified, and if it does, how DCD is regulated in this process is also unknown. Here, we report that DCD-mediated H2S production enhances plant Cd tolerance in Arabidopsis (Arabidopsis thaliana). When subjected to Cd stress, a dcd mutant accumulated more Cd and reactive oxygen species and showed increased Cd sensitivity, whereas transgenic lines overexpressing DCD had decreased Cd and reactive oxygen species levels and were more tolerant to Cd stress compared with wild-type plants. Furthermore, the expression of DCD was stimulated by Cd stress, and this up-regulation was mediated by a Cd-induced transcription factor, WRKY13, which bound to the DCD promoter. Consistently, the higher Cd sensitivity of the wrky13-3 mutant was rescued by the overexpression of DCD Together, our results demonstrate that Cd-induced WRKY13 activates DCD expression to increase the production of H2S, leading to higher Cd tolerance in plants.

Persulfidation-based Modification of Cysteine Desulfhydrase and the NADPH Oxidase RBOHD Controls Guard Cell Abscisic Acid Signaling.

Hydrogen sulfide (H2S) is a gaseous signaling molecule that regulates diverse cellular signaling pathways through persulfidation, which involves the post-translational modification of specific Cys residues to form persulfides. However, the mechanisms that underlie this important redox-based modification remain poorly understood in higher plants. We have, therefore, analyzed how protein persulfidation acts as a specific and reversible signaling mechanism during the abscisic acid (ABA) response in Arabidopsis (Arabidopsis thaliana). Here we show that ABA stimulates the persulfidation of l-CYSTEINE DESULFHYDRASE1, an important endogenous H2S enzyme, at Cys44 and Cys205 in a redox-dependent manner. Moreover, sustainable H2S accumulation drives persulfidation of the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG PROTEIN D (RBOHD) at Cys825 and Cys890, enhancing its ability to produce reactive oxygen species. Physiologically, s-persulfidation-induced RBOHD activity is relevant to ABA-induced stomatal closure. Together, these processes form a negative feedback loop that fine-tunes guard cell redox homeostasis and ABA signaling. These findings not only expand our current knowledge of H2S function in the context of guard cell ABA signaling, but also demonstrate the presence of a rapid signal integration mechanism involving specific and reversible redox-based post-translational modifications that occur in response to changing environmental conditions.