Inhibition of the mitochondrial respiratory components (Complex I and Complex III) as stimuli to induce oxidative damage in Oryza sativa L. under thiocyanate exposure

GhiPLATZ17 and GhiPLATZ22, zinc-dependent DNA-binding transcription factors, promote salt tolerance in upland cotton

KEY MESSAGE

The utilization of transcriptome analysis, functional validation, VIGS, and DAB techniques have provided evidence that GhiPLATZ17 and GhiPLATZ22 play a pivotal role in improving the salt tolerance of upland cotton. PLATZ (Plant AT-rich sequences and zinc-binding proteins) are known to be key regulators in plant growth, development, and response to salt stress. In this study, we comprehensively analyzed the PLATZ family in ten cotton species in response to salinity stress. Gossypium herbaceum boasts 25 distinct PLATZ genes, paralleled by 24 in G. raimondii, 25 in G. arboreum, 46 in G. hirsutum, 48 in G. barbadense, 43 in G. tomentosum, 67 in G. mustelinum, 60 in G. darwinii, 46 in G. ekmanianum, and a total of 53 PLATZ genes attributed to G. stephensii. The PLATZ gene family shed light on the hybridization and allopolyploidy events that occurred during the evolutionary history of allotetraploid cotton. Ka/Ks analysis suggested that the PLATZ gene family underwent intense purifying selection during cotton evolution. Analysis of synteny and gene collinearity revealed a complex pattern of segmental and dispersed duplication events to expand PLATZ genes in cotton. Cis-acting elements and gene expressions revealed that GhiPLATZ exhibited salt stress resistance. Transcriptome analysis, functional validation, virus-induced gene silencing (VIGS), and diaminobenzidine staining (DAB) demonstrated that GhiPLATZ17 and GhiPLATZ22 enhance salt tolerance in upland cotton. The study can potentially advance our understanding of identifying salt-resistant genes in cotton.

Elucidating the intricacies of the H2S signaling pathway in gasotransmitters: Highlighting the regulation of plant thiocyanate detoxification pathways

In recent decades, there has been increasing interest in elucidating the role of sulfur-containing compounds in plant metabolism, particularly emphasizing their function as signaling molecules. Among these, thiocyanate (SCN-), a compound imbued with sulfur and nitrogen, has emerged as a significant environmental contaminant frequently detected in irrigation water. This compound is known for its potential to adversely impact plant growth and agricultural yield. Although adopting exogenous SCN- as a nitrogen source in plant cells has been the subject of thorough investigation, the fate of sulfur resulting from the assimilation of exogenous SCN- has not been fully explored. There is burgeoning curiosity in probing the fate of SCN- within plant systems, especially considering the possible generation of the gaseous signaling molecule, hydrogen sulfide (H2S) during the metabolism of SCN-. Notably, the endogenous synthesis of H2S occurs predominantly within chloroplasts, the cytosol, and mitochondria. In contrast, the production of H2S following the assimilation of exogenous SCN- is explicitly confined to chloroplasts and mitochondria. This phenomenon indicates complex interplay and communication among various subcellular organelles, influencing signal transduction and other vital physiological processes. This review, augmented by a small-scale experimental study, endeavors to provide insights into the functional characteristics of H2S signaling in plants subjected to SCN--stress. Furthermore, a comparative analysis of the occurrence and trajectory of endogenous H2S and H2S derived from SCN--assimilation within plant organisms was performed, providing a focused lens for a comprehensive examination of the multifaceted roles of H2S in rice plants. By delving into these dimensions, our objective is to enhance the understanding of the regulatory mechanisms employed by the gasotransmitter H2S in plant adaptations and responses to SCN--stress, yielding invaluable insights into strategies for plant resilience and adaptive capabilities.

Exogenous Hemin enhances the antioxidant defense system of rice by regulating the AsA-GSH cycle under NaCl stress

Abiotic stress caused by soil salinization remains a major global challenge that threatens and severely impacts crop growth, causing yield reduction worldwide. In this study, we aim to investigate the damage of salt stress on the leaf physiology of two varieties of rice (Huanghuazhan, HHZ, and Xiangliangyou900, XLY900) and the regulatory mechanism of Hemin to maintain seedling growth under the imposed stress. Rice leaves were sprayed with 5.0 μmol·L-1 Hemin or 25.0 μmol·L-1 ZnPP (Zinc protoporphyrin IX) at the three leaf and one heart stage, followed by an imposed salt stress treatment regime (50.0 mmol·L-1 sodium chloride (NaCl)). The findings revealed that NaCl stress increased antioxidant enzymes activities and decreased the content of nonenzymatic antioxidants such as ascorbate (AsA) and glutathione (GSH). Furthermore, the content of osmoregulatory substances like soluble proteins and proline was raised. Moreover, salt stress increased reactive oxygen species (ROS) content in the leaves of the two varieties. However, spraying with Hemin increased the activities of antioxidants such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) and accelerated AsA-GSH cycling to remove excess ROS. In summary, Hemin reduced the effect of salt stress on the physiological characteristics of rice leaves due to improved antioxidant defense mechanisms that impeded lipid peroxidation. Thus, Hemin was demonstrated to lessen the damage caused by salt stress.

Plant growth regulators mitigate oxidative damage to rice seedling roots by NaCl stress

The aim of this experiment was to investigate the effects of exogenous sprays of 5-aminolevulinic acid (5-ALA) and 2-Diethylaminoethyl hexanoate (DTA-6) on the growth and salt tolerance of rice (Oryza sativa L.) seedlings. This study was conducted in a solar greenhouse at Guangdong Ocean University, where 'Huanghuazhan' was selected as the test material, and 40 mg/L 5-ALA and 30 mg/L DTA-6 were applied as foliar sprays at the three-leaf-one-heart stage of rice, followed by treatment with 0.3% NaCl (W/W) 24 h later. A total of six treatments were set up as follows: (1) CK: control, (2) A: 40 mg⋅ L-1 5-ALA, (3) D: 30 mg⋅ L-1 DTA-6, (4) S: 0.3% NaCl, (5) AS: 40 mg⋅ L-1 5-ALA + 0.3% NaCl, and (6) DS: 30 mg⋅ L-1 DTA-6+0.3% NaCl. Samples were taken at 1, 4, 7, 10, and 13 d after NaCl treatment to determine the morphology and physiological and biochemical indices of rice roots. The results showed that NaCl stress significantly inhibited rice growth; disrupted the antioxidant system; increased the rates of malondialdehyde, hydrogen peroxide, and superoxide anion production; and affected the content of related hormones. Malondialdehyde content, hydrogen peroxide content, and superoxide anion production rate significantly increased from 12.57% to 21.82%, 18.12% to 63.10%, and 7.17% to 56.20%, respectively, in the S treatment group compared to the CK group. Under salt stress, foliar sprays of both 5-ALA and DTA-6 increased antioxidant enzyme activities and osmoregulatory substance content; expanded non-enzymatic antioxidant AsA and GSH content; reduced reactive oxygen species (ROS) accumulation; lowered malondialdehyde content; increased endogenous hormones GA3, JA, IAA, SA, and ZR content; and lowered ABA content in the rice root system. The MDA, H2O2, and O2- contents were reduced from 35.64% to 56.92%, 22.30% to 53.47%, and 7.06% to 20.01%, respectively, in the AS treatment group compared with the S treatment group. In the DS treatment group, the MDA, H2O2, and O2- contents were reduced from 24.60% to 51.09%, 12.14% to 59.05%, and 12.70% to 45.20%. In summary, NaCl stress exerted an inhibitory effect on the rice root system, both foliar sprays of 5-ALA and DTA-6 alleviated damage from NaCl stress on the rice root system, and the effect of 5-ALA was better than that of DTA-6.

Gaseous signaling molecule H2S as a multitasking signal molecule in ROS metabolism of Oryza sativa under thiocyanate (SCN-) pollution

The induction of disruption in the electronic transport chain by thiocyanate (SCN-) leads to an excessive generation of reactive oxygen species (ROS) within rice (Oryza sativa). Hydrogen sulfide (H2S) assumes a crucial role as a gaseous signaling molecule, holding significant potential in alleviating SCN--related stress. Nevertheless, there remains a dearth of understanding regarding the intricate interplay between H2S and ROS in Oryza sativa amidst SCN- pollution. In this investigation, a hydroponics-based experiment was meticulously devised to explore how H2S-mediated modifications influence the genetic feedback network governing ROS metabolism within the subcellular organelles of Oryza sativa when exposed to varying effective concentrations (EC20: 24 mg SCN/L; EC50: 96 mg SCN/L; EC75: 300 mg SCN/L) of SCN-. The findings unveiled the enhanced capacity of Oryza sativa to uptake SCN- under H2S + SCN- treatments in comparison to SCN- treatments alone. Notably, the relative growth rate (RGR) of seedlings subjected to H2S + SCN- exhibited a superior performance when contrasted with seedlings exposed solely to SCN-. Furthermore, the application of exogenous H2S yielded a significant reduction in ROS levels within Oryza sativa tissues during SCN- exposure. To elucidate the intricacies of gene regulation governing ROS metabolism at the mRNA level, the 52 targeted genes were categorized into four distinct types, namely: initial regulatory ROS generation genes (ROS-I), direct ROS scavenging genes (ROS-II), indirect ROS scavenging genes (ROS-III), and lipid oxidation genes (ROS-IV). On the whole, exogenous H2S exhibited the capacity to activate the majority of ROS-I ∼ ROS-IV genes within both Oryza sativa tissues at the EC20 concentration of SCN-. However, genetic positive/negative feedback networks emphasized the pivotal role of ROS-II genes in governing ROS metabolism within Oryza sativa. Notably, these genes were predominantly activated within the cytoplasm, chloroplasts, mitochondria, peroxisomes, and the cell wall.

Preparation of Salicylic Acid-Functionalized Nanopesticides and Their Applications in Enhancing Salt Stress Resistance

Soil salinization is one of the global ecological and environmental problems that are tremendously threatening to the sustainable development of agriculture and food supply. In this work, a facile strategy was proposed to enhance the salt stress resistance of plants by preparing salicylic acid (SA)-functionalized mesoporous silica nanocarriers loaded with emamectin benzoate (EB). The obtained nanopesticides demonstrated a particle size of less than 300 nm. As an endogenous plant hormone, the grafting of SA in this nanopesticide system improved the uptake and translocation of pesticides in cucumber plants by 145.06%, and the applications of such nanopesticides enhanced the salt stress resistance of plants. This phenomenon was accounted for by the SA-functionalized nanopesticides increasing the superoxide dismutase and peroxidase activities (640 and 175%, respectively) and reducing the malondialdehyde content (54.10%), correspondingly alleviating the accumulation of reactive oxygen species and cell damage in plants. The above results were also confirmed by Evans blue staining and NBT staining experiments on cucumber leaves. In addition, these nanopesticides exhibited high insecticidal toxicity, and they also demonstrated biosafety toward nontarget organisms due to their sustained release property. Therefore, this work developed a biosafe SA-functionalized nanopesticide system, and these newly developed nanopesticides have potential in the agricultural field for enhancing salt stress resistance of plants.

HSF1 is a novel prognostic biomarker in high-risk prostate cancer that correlates with ferroptosis

BACKGROUND

Prostate cancer (PC) is the most common cancer in older men in Europe and the United States and has the second highest death rate among male cancers. The transcription of heat shock proteins by Heat shock factor 1 (HSF1) is known to regulate cell growth and stress. Nevertheless, the impact of HSF1 on ferroptosis in PC through heat shock protein 10 (HSPE1) remains unexplored.

METHODS

This study employed a range of analytical techniques, including proteomics sequencing, LC-MS/MS, CHIP-qPCR, Western blotting, immunohisto -chemistry, JC-1, CKK-8, MDA, and ROS assays. Bioinformatics analysis was performed using the UALCAN,GEPIA, PCaDB and Metascape platforms.

RESULTS

Compared with levels observed in tumor-adjacent tissue, the levels of proteins associated with fatty acids, amino acids and the oxidative phosphorylation metabolic pathway were significantly upregulated in high-risk PC tissue (Gleason score ≥ 8). HSF1 mRNA and protein levels in high-risk PC tissues were significantly higher than those observed in medium-risk PC (Gleason score = 7) and low-risk PC (Gleason score ≤ 6) tissues. ssGSEA showed that HSF1 was involved in the proliferation and anti-apoptotic processes of PC. Further bioinformatics analysis showed that HSF1 potentially affects the mitochondrial oxidative phosphorylation (OXPHOS) system by targeting HSPE1. In addition, HSF1 alleviates ROS and MDA levels to enhance the resistance of prostate cancer cells to ferroptosis by regulating HSPE1 in vitro, and HSF1 knockout promotes the susceptibility of PC to RSL3 treatment by increasing ferroptosis in vivo.

CONCLUSION

Collectively, our findings suggest that HSF1 exerts a significant influence on PC. HSF1 may represent a promising biomarker for identifying high-risk PC, and the elimination of HSF1 could potentially enhance the therapeutic effectiveness of RSL3.

Exogenous proline activated an integrated response of NER and HR pathways to reduce DNA damage in rice seedlings under chromium stress

The DNA damage induced by hexavalent chromium [Cr(VI)] pollutant causes a genotoxic effect on rice seedlings. Hereby, we examined the effects of exogenous proline (Pro) on the alleviation of DNA damage in rice seedlings under different effective concentrations of Cr(VI). Our results revealed that Cr(VI) stress induced reactive oxygen species (ROS), i.e., H₂O₂ and O₂^·- accumulation in rice seedlings, repressed genes expression activated in the homologous recombination (HR) and nucleotide excision repair (NER) pathways, and caused DNA damage. Exogenous application of Pro increased Cr accumulation in rice roots, but decreased Cr accumulation in rice shoots, wherein Pro application decreased ROS accumulation in both tissues of rice seedlings. The comet assays suggested that exogenous application of Pro significantly alleviated the DNA damage in rice seedlings during Cr(VI) treatments, judged by the Olive tail moment and tail DNA. Transcriptional assays revealed that exogenous Pro upregulated the expression level of genes associated with the HR and NER pathways and triggered coordinated actions of both repairing pathways to modulate DNA lesion in rice plants during exposure to Cr(VI). Calculations from gene expression variation factors showed that regulative effect of exogenous application of Pro on DNA repair pathways was highly activated at 2.0 mg Cr/L. The current study revealed that Cr(VI) affect rice plants and exogenous Pro rescue these effects by the activation of HR and NER pathways.

Nitrate-responsive OsMADS27 promotes salt tolerance in rice

Salt stress is a major constraint on plant growth and yield. Nitrogen (N) fertilizers are known to alleviate salt stress. However, the underlying molecular mechanisms remain unclear. Here, we show that nitrate-dependent salt tolerance is mediated by OsMADS27 in rice. The expression of OsMADS27 is specifically induced by nitrate. The salt-inducible expression of OsMADS27 is also nitrate dependent. OsMADS27 knockout mutants are more sensitive to salt stress than the wild type, whereas OsMADS27 overexpression lines are more tolerant. Transcriptomic analyses revealed that OsMADS27 upregulates the expression of a number of known stress-responsive genes as well as those involved in ion homeostasis and antioxidation. We demonstrate that OsMADS27 directly binds to the promoters of OsHKT1.1 and OsSPL7 to regulate their expression. Notably, OsMADS27-mediated salt tolerance is nitrate dependent and positively correlated with nitrate concentration. Our results reveal the role of nitrate-responsive OsMADS27 and its downstream target genes in salt tolerance, providing a molecular mechanism for the enhancement of salt tolerance by nitrogen fertilizers in rice. OsMADS27 overexpression increased grain yield under salt stress in the presence of sufficient nitrate, suggesting that OsMADS27 is a promising candidate for the improvement of salt tolerance in rice.

GmMPK6 Positively Regulates Salt Tolerance through Induction of GmRbohI1 in Soybean

Salt stress is a critical environmental stress that impairs plant growth and development, especially in crop productivity; therefore, understanding the salt response in plants is the basis for their development of salt tolerance. Under salinity, soybean mitogen-activated protein kinase 6 (GmMPK6) is activated and positively regulates reactive oxygen species (ROS) generation. However, it is not yet elucidated how GmMPK6 regulates ROS generation and its role in salt tolerance. Here, we show that GmMPK6, solely activated in NaCl treatment, and gene expression of GmRbohI1 was not only reduced by MPK inhibitor SB202190 in NaCl treatment, but also increased in a GMKK1-expressing protoplast. Furthermore, SB202190 and the NADPH-oxidase inhibitor, diphenyleneiodonium chloride, increased susceptibility to salt stress. The expression of GmRD19A was induced by NaCl treatment, but this expression was compromised by SB202190. Consequently, we revealed that GmMPK6 induces ROS generation through the transcriptional regulation of GmRbohI1 and increases salt tolerance in soybean.

A newly developed consortium with a highly efficient thiocyanate degradation capacity: A comprehensive investigation of the degradation and detoxification potential

Thiocyanate-containing wastewater harms ecosystems and can cause serious damage to animals and plants, so it is urgent to treat it effectively. In this study, a new efficient thiocyanate-degrading consortium was developed and its degradation characteristics were studied. It was found that up to 154.64 mM thiocyanate could be completely degraded by this consortium over 6 days of incubation, with a maximum degradation rate of 1.53 mM h^-1. High-throughput sequencing analysis showed that Thiobacillus (77.78%) was the predominant thiocyanate-degrading bacterial genus. Plant toxicology tests showed that the germination index of mung bean and rice seeds cultured with media obtained after thiocyanate degradation by the consortium increased by 94% and 84.83%, respectively, compared with the control group without thiocyanate degradation. Cytotoxicity tests showed that thiocyanate without degradation significantly decreased the Neuro-2a cell activity and mitochondrial membrane potential; induced reactive oxygen species generation and apoptosis; increased the cellular Ca²⁺ concentration; and damaged the cell nucleus and DNA. Furthermore, the thiocyanate degradation products produced the consortium were almost totally non-toxic, revealing the same characteristics as those of the control using distilled water. This study shows that the consortium has a high degradation efficiency and detoxification characteristics, as well as great application potential in bioremediation of industrial thiocyanate-containing wastewater.

Individual and mutual effects of elevated carbon dioxide and temperature on salt and cadmium uptake and translocation by rice seedlings

Plant kingdoms are facing increasingly harsh environmental challenges marked by the coexposure of salinity and pollution in the pedosphere and elevated CO₂ and temperature in the atmosphere due to the rapid acceleration of industrialization and global climate change. In this study, we deployed a hydroponics-based experiment to explore the individual and mutual effects of different temperatures (low temperature, T1: 23°C; high temperature, T2: 27°C) and CO₂ concentrations (ambient CO₂: 360 ppm; medium CO₂: 450 ppm; high CO₂: 700 ppm) on the uptake and translocation of sodium chloride (NaCl, 0.0, 0.2, 0.6, and 1.1 g Na/L) and cadmium nitrate (Cd(NO₃)₂·4H₂O, 0.0, 0.2, 1.8, and 5.4 mg Cd/L) by rice seedlings. The results indicated that Cd and Na exposure significantly (P< 0.05) inhibited plant growth, but T2 and medium/high CO₂ alleviated the effects of Cd and Na on plant growth. Neither significant synergistic nor antagonistic effects of Cd and Na were observed, particularly not at T1 or high CO₂. At increasing temperatures, relative growth rates increased despite higher concentrations of Cd and Na in both rice roots and shoots. Similarly, higher CO₂ stimulated the growth rate but resulted in significantly lower concentrations of Na, while the Cd concentration was highest at medium CO₂. Coexposure experiments suggested that the concentration of Cd in roots slightly declined with additional Na and more at T2. Overall, our preliminary study suggested that global climate change may alter the distribution of mineral and toxic elements in rice plants as well as the tolerance of the plants.

Merging the occurrence possibility into gene co-expression network deciphers the importance of exogenous 2-oxoglutarate in improving the growth of rice seedlings under thiocyanate stress

Thiocyanate (SCN^-) can find its way into cultivated fields, which might hamper the harmony in carbon and nitrogen metabolism (CNM) of plants, ebbing their quality and productivity. In the current study, we investigated the role of the exogenous application of 2-oxoglutarate (2-OG) in maintaining homeostasis of CNM in rice seedlings under SCN^- stress. Results showed that SCN^- exposure significantly repressed the gene expression and activities of CNM-related enzymes (e.g., phosphoenolpyruvate carboxylase, NADP-dependent isocitrate dehydrogenases, and isocitrate dehydrogenases) in rice seedlings, thereby reducing their relative growth rate (RGR). Exogenous application of 2-OG effectively mitigated the toxic effects of SCN^- on rice seedlings, judged by the aforementioned parameters. The co-expression network analysis showed that genes activated in CNM pathways were categorized into four modules (Modules 1-4). In order to identify the key module activated in CNM in rice seedlings exposed to SCN^-, the results from real-time quantitative PCR (RT-qPCR) tests were used to calculate the possibility of the occurrence of genes grouped in four different modules. Notably, Module 3 showed the highest occurrence probability, which is mainly related to N metabolism and 2-OG synthesis. We can conclude that exogenous application of 2-OG can modify the imbalance of CNM caused by SCN^- exposure through regulating N metabolism and 2-OG synthesis in rice seedlings.

Implications of the fate of hydrogen sulfide derived from assimilation of thiocyanate in rice plants

Thiocyanate (SCN^-) is a sulfur-containing pollutant, which is frequently detected in irrigation water and has negative effects on plant growth and crop yields. Uptake and assimilation of exogenous SCN^- in rice plants was evident, in which two metabolic pathways, carbonyl sulfide (COS) and cyanate (CNO), are activated. Hydrogen sulfide (H₂S) is an important concomitant derived from detoxification of exogenous SCN^- in rice plants, which may cause coupling action on the endogenous source of H₂S from sulfur metabolism. Since H₂S has dual regulatory effects, the fate of H₂S derived from assimilation of SCN^- in plants is critical for clarifying the inclusiveness of H₂S in various physiological activities. In fact, application of exogenous H₂S not only positively changed the root phenotype traits of SCN^--treated seedlings, but also effectively mitigated the toxic effects of SCN^- in rice seedlings by stimulating the process of the PSII repair cycle. In this study, it is tempting to analyze and clarify the flux of the concomitant production of H₂S from assimilation of exogenous SCN^- into the innate pool, which may function in signaling regulation and other physiological processes in rice plants. This study would update our understanding of the fate of H₂S derived from assimilation of SCN^- in plants and provide new insights into the affirmative actions of H₂S in direct proximity to SCN^- exposure.

Impairment of Respiratory Chain Function and Involvement of Alternative Respiratory Pathway in Mitochondria of Potato Tubers Infected by Pectobacteriumcarotovorum subsp. carotovorum

The significance of alternative respiratory pathway (AOXs) during the interaction between soft rot bacteria (Pectobacterium carotovorum subsp. carotovorum, (Pcc.)) and potato tubers is well-defined. However, the role of the AOXs in impaired mitochondrial respiratory chain function during the Pcc. infection is yet to be studied. In this study, the results show that with the aggravation of infection of Pcc., the capacity for alternative respiration in mitochondria of potato tubers increased gradually. The mitochondrial membrane potential increased more significantly after infection with Pcc. when the AOXs in potato tubers was partially blocked using salicylhydroxamic acid (SHAM) beforehand. In addition, the activity of complex III decreased more drastically while the activity of complex IV increased more significantly in the partial absence of the AOXs in the mitochondria. Furthermore, the mitochondrial endogenous respiration, mitochondrial respiratory state 3 and respiratory control rate (RCR) decreased more significantly and the value of RCR reached around 1.0 with the aggravation of infection of Pcc. in the partially absence of AOXs in the mitochondria.

Involvement of β-cyanoalanine synthase (β-CAS) and sulfurtransferase (ST) in cyanide (CN-) assimilation in rice seedlings

In spite of available information demonstrating the assimilation of cyanide (CN^-) by β-cyanoalanine synthase (β-CAS) in plants, involvement of sulfurtransferase (ST) in CN^- assimilation in rice plants is still undefined. In this study, a microcosmic hydroponic system was used to investigate the involvement of β-cyanoalanine synthase (β-CAS) and sulfurtransferase (ST) in the CN^- assimilation in rice seedlings under the exposure of potassium cyanide (KCN) in presence or absence of 1-amino-cyclopropane-1-carboxylic acid (ACC). Our results indicated that the measurable thiocyanate (SCN^-) was detected in both rice roots and shoots under KCN exposure, and the abundances of ST-related transcripts were up-regulated significantly (p < 0.05), suggesting that the ST pathway is involved in CN^- assimilation in the rice plants. The application of exogenous ACC significantly (p < 0.05) decreased the accumulation of CN^- and SCN^- in rice tissues after KCN exposures, and also up-regulated the expression of β-CAS and ST genes and their enzymatic activities, suggesting a positive interaction between aminocyclopropane-1-carboxylate oxidase (ACO), β-CAS and ST in rice plants during the CN^- assimilation. This is the first attempt to experimentally clarify the involvement of ST in CN^- assimilation in rice seedlings.

The importance of utilizing nitrate (NO3-) over ammonium (NH4+) as nitrogen source during detoxification of exogenous thiocyanate (SCN-) in Oryza sativa

Thiocyanate (SCN^-) is a nitrogen-containing pollutant, which can be involved in the nitrogen (N) cycle and interferes with plant growth. The current study highlights a new insight into the N (nitrate [NO₃^-] and ammonium [NH₄⁺]) utilization ways in rice seedlings under SCN^- exposure to clarify the interactive effect on uptake and assimilation between these N-containing chemicals. Phenotypically, relative growth rates (RGR) of NO₃^--fed seedlings were significantly higher than NH₄⁺-fed rice seedlings at the same SCN^- concentration. Both N fertilizations have no significant influence on SCN^- content and its assimilation in rice seedlings. However, significant accumulation of NO₃^- and NH₄⁺ were detected in shoots prior to roots under SCN^- stress. Enzymatic assay and mRNA analysis showed that the carbonyl sulfide (COS) pathway of SCN^- degradation occurred in both roots and shoots of NO₃^--fed seedlings but only evident in roots of NH₄⁺-fed seedlings. Moreover, the effect of SCN^- on the activity of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) was negligible in NO₃^--fed seedlings, while GOGAT activity was significantly inhibited in shoots of NH₄⁺-fed seedlings. Nitrogen use efficiency (NUE) estimation provided positive evidence in utilizing NO₃^- over NH₄⁺ as the main N source to support rice seedling growth during detoxification of exogenous SCN^-. Overall, SCN^- pollution has unexpectedly changed the rice preference for N source which shifted from NH₄⁺ to NO₃^-, suggesting that the interactions of SCN^- with different N sources in terms of uptake and assimilation in rice plants should not be overlooked, especially at the plant N nutritional level.

Plant salt response: Perception, signaling, and tolerance

Salt stress is one of the significant environmental stressors that severely affects plant growth and development. Plant responses to salt stress involve a series of biological mechanisms, including osmoregulation, redox and ionic homeostasis regulation, as well as hormone or light signaling-mediated growth adjustment, which are regulated by different functional components. Unraveling these adaptive mechanisms and identifying the critical genes involved in salt response and adaption are crucial for developing salt-tolerant cultivars. This review summarizes the current research progress in the regulatory networks for plant salt tolerance, highlighting the mechanisms of salt stress perception, signaling, and tolerance response. Finally, we also discuss the possible contribution of microbiota and nanobiotechnology to plant salt tolerance.

Comparative effects of sodium hydrosulfide and proline on functional repair in rice chloroplast through the D1 protein and thioredoxin system under simulated thiocyanate pollution

Various environmental contaminants can find their way to enter plant cells and disturb and/or damage the essential components of PSII repair cycle in chloroplast, thereby resulting in dysfunction of chloroplast. In the current research, a microcosm hydroponic experiment was set up to evaluate the comparative effects of sodium hydrosulfide (NaHS)- and proline (Pro)-mediated functional repairing of chloroplast in rice plants under SCN^- stress. Our results displayed that when exposed to environmental realistic SCN^- concentrations (24-300 mg L^-1), foist significant (p < 0.05) gene-dose repercussion on the pathways of photosynthetic reactions and energy metabolism in rice shoots, and a downturn in the level of total soluble starch, sugar, and chlorophyll. Sodium hydrosulfide application effectively mitigated (p < 0.05) the toxic effects of SCN^- in rice seedlings by stimulating the processes of phosphorylation, dephosphorylation and new-synthesis of D1 protein in the PSII repair cycle, and increased the turnover of D1 protein to recover CO₂ assimilation. Evidently, Pro treatment mainly enhanced (p < 0.05) the expression of magnesium chelatase (MgCh) and ribulose-1,5-bisphosphate carboxylase (Rubisco) related genes under simulated SCN^- stress, suggesting that the targeted repairing site in chloroplast by Pro was different from NaHS. The outcome of the present research contributes to a better understanding at molecular level for repairing of chloroplast functional disorder by NaHS and Pro at different key nodes under SCN^- stress.

Bacillus sp. and arbuscular mycorrhizal fungi consortia enhance wheat nutrient and yield in the second-year field trial: Superior performance in comparison with chemical fertilizers

AIMS

The aim of the study is to analyse the effect of microbial consortia for wheat biofortification, growth, yield and soil fertility as part of a 2-year field study and compare it with the use of chemical fertilizers.

METHODS AND RESULTS

A field trial (second year) was conducted with various combinations of plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) treatments, ranging from a single inoculant to multiple combinations. The microbial consortia used were Bacillus sp. and AMF based on first-year field trial results. The consortia based on native (CP4) and non-native (AHP3) PGPB (Bacillus sp.) and AMF performed better in terms of nutrients content in wheat grain tissue and yield-related traits compared with chemical fertilizer treated and untreated control. Dual treatment of PGPB (CP4+AHP3) combined with AMF resulted in a significant increase in antioxidants. The spatial colonization of AMF in roots indicated that both the isolates CP4 and AHP3 were able to enhance the AMF colonization in root tissue. Furthermore, soil enzymes' activities were higher with the PGPB and AMF combination giving the best results. A positive correlation was recorded between plant growth, grain yield and soil physicochemical parameters.

CONCLUSIONS

Our findings confirm that the combined treatment of CP4 and AHP3 and AMF functions as an effective microbial consortium with excellent application prospects for wheat biofortification, grain yield and soil fertility compared with chemical fertilizers.

SIGNIFICANCE AND IMPACT OF STUDY

The extensive application of chemical fertilizers on low-yielding field sites is a severe concern for cereal crops, especially wheat in the Asian continent. This study serves as a primer for implementing site-specific sustainable agricultural-management practices using a green technology leading to significant gains in agriculture.

Jasmonic acid and hydrogen sulfide modulate transcriptional and enzymatic changes of plasma membrane NADPH oxidases (NOXs) and decrease oxidative damage in Oryza sativa L. during thiocyanate exposure

It is evident that the plasma membrane NADPH oxidases (NOXs) play an important role in the generation of superoxide radicals (O₂^-•) in plants during defense responses. This study was to clarify activation of NOXs in oxidative damage in Oryza sativa during SCN^- exposure, particularly in the roles of jasmonic acid (JA) and hydrogen sulfide (H₂S) on transcriptional and enzymatic changes of NOXs. Results indicated that enzymatic activity of NOXs in both roots and shoots was significantly enhanced during SCN^- exposure, whereas the application of JA and H₂S donor (NaHS) significantly repressed NOXs activity in SCN-treated rice seedlings. Similarly, ROS analysis showed that SCN^- exposure elevated the content of O₂^-•, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) in rice tissues significantly, whereas decreases in O₂^-• and H₂O₂ were detected in roots and shoots of SCN-treated rice seedlings due to application of JA and NaHS. PCR analysis revealed different expression patterns of 7 plasma membrane-localized NOX genes in rice roots and shoots against SCN^- exposure, suggesting that various isogenes of NOXs might regulate and determine activity of NOXs in rice organs. In conclusion, SCN^- exposure was able to trigger activation of NOXs effectively, and led to oxidative damage and lipid peroxidation; the effects of JA and NaHS on inactivation of NOXs was evident and tissue specific, which in turn modulated ROS accumulation in rice plants.

ROS Homeostasis and Plant Salt Tolerance: Plant Nanobiotechnology Updates

Salinity is an issue impairing crop production across the globe. Under salinity stress, besides the osmotic stress and Na+ toxicity, ROS (reactive oxygen species) overaccumulation is a secondary stress which further impairs plant performance. Chloroplasts, mitochondria, the apoplast, and peroxisomes are the main ROS generation sites in salt-stressed plants. In this review, we summarize ROS generation, enzymatic and non-enzymatic antioxidant systems in salt-stressed plants, and the potential for plant biotechnology to maintain ROS homeostasis. Overall, this review summarizes the current understanding of ROS homeostasis of salt-stressed plants and highlights potential applications of plant nanobiotechnology to enhance plant tolerance to stresses.

SlWHY2 interacts with SlRECA2 to maintain mitochondrial function under drought stress in tomato

Drought stress in plants leads to inhibition of photosynthesis and respiration, accumulation of reactive oxygen species (ROS), and reprogramming of gene expression. Here, we established that the tomato (Solanum lycopersicum) WHIRLY2 (SlWHY2) gene, which encodes a mitochondrial single-stranded DNA-binding protein, was significantly induced by drought stress. Under drought conditions, SlWHY2 RNAi plants showed more wilting and lower fresh weight, chlorophyll content, quantum yield of photosystem I (PSI; YI), and maximal photochemical efficiency of PSII (Fv/Fm) than the wild type (WT). Drought treatment also caused the SlWHY2 RNAi lines to accumulate more ROS than the WT, and the silenced lines had lower AOX (alternative oxidase) activity. As expected, the mitochondrial membrane potential (MMP) was less stable in the SlWHY2 RNAi lines. The expression levels of seven genes in the mitochondrial genome (SYCF15, NAD7, NAD4, COS2, COX1, COX2, and COX3) were decreased even more in the SlWHY2 RNAi lines than they were in the WT under drought stress. SlWHY2 interacted directly in vivo and in vitro with SlRECA2, a mitochondrial recombinase A that is important for mitochondrial DNA recombination and repair. These results suggest that SlWHY2 plays an essential role in maintaining mitochondrial function and enhancing drought tolerance in tomato.

Assimilation of exogenous cyanide cross talk in Oryza sativa L. to the key nodes in nitrogen metabolism

Exogenous cyanide (CN^-) effects on nitrogen (N) uptake, transport, and assimilation in rice seedlings were investigated at the biochemical and molecular levels. Seedlings were treated with either a 2-d or 4-d supply of potassium cyanide (KCN) in the nutrient solution containing nitrate (NO₃^-) or ammonium (NH₄⁺). Although a KCN-induced increase was recorded in the activity of β-cyanoalanine synthase (β-CAS) in rice tissues of both NH₄⁺-fed and NO₃^--fed seedlings, the former showed a significantly greater assimilation rate for CN^- than the latter. The addition of KCN decreased NO₃^- uptake and assimilation, whereas a negligible impact was observed in NH₄⁺ treatments. Enzymatic assays showed a marked activities enhancement of glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) in NH₄⁺-fed seedlings after KCN exposure. Similarly, the rises occurring in nitrate reductase (NR) and GDH activity in NO₃^--fed seedlings were also detected after 2-d exposure to KCN, whereas a significant reduction of GS and GOGAT activities was determined. The results suggest that although exogenous KCN at moderate or high concentrations caused repressively effects on biomass growth of both NH₄⁺-fed and NO₃^--fed rice seedlings, the nontoxic concentration of KCN supplied can serve as a supplemental N source in plant nutrition and N metabolism.