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.

Unraveling the enigma of NPP variation in Chinese vegetation ecosystems: The interplay of climate change and land use change.

Global carbon emissions have exacerbated the greenhouse effect, exerting a profound impact on ecosystems worldwide. Gaining an understanding of the fluctuations in vegetation net primary productivity (NPP) is pivotal in the assessment of environmental quality, estimation of carbon source/sink potential, and facilitation of ecological restoration. Employing MODIS and meteorological data, we conducted a comprehensive analysis of NPP evolution in Chinese vegetation ecosystems (VESs), employing Theil-Sen median trend analysis and the Mann-Kendall test. Furthermore, utilizing scenario-based analysis, we quantitatively determined the respective contributions of climate change and land use change to NPP variations across various scales. The overall NPP exhibited a discernible upward trend from 2000 to 2020, with a growth rate of 5.83 gC·m-2·year-1. Forestland ecosystem (FES) displayed the highest rate of increase (9.40 gC·m-2·year-1), followed by cropland ecosystem (CES) (4.00 gC·m-2·year-1) and grassland ecosystem (GES) (3.40 gC·m-2·year-1). Geographically, NPP exhibited a spatial pattern characterized by elevated values in the southeast and diminished values in the northwest. In addition, climate change had elevated 76.39 % of CES NPP, 90.62 % of FES NPP, and 71.78 % of GES NPP. At the national level, climate change accounted for 83.14 % of the NPP changes, while land use change contributed 14.14 %. Notably, climate change emerged as the primary driving force behind NPP variations across all VEGs, with land use change exerting the most pronounced influence on CES. At the grid scale (2 km × 2 km), land use change played a substantial role in all VEGs, contributing 60.01 % in CES, 54.20 % in FES, and 55.61 % in GES of the NPP variations.

Proline interacts with Ca2+-dependent signaling to enhance chromium tolerance in rice by manipulating nitrate reductase and sucrose phosphate synthase.

The entrance of chromium (Cr) into the agricultural system would exert a negative influence on the carbon/nitrogen metabolism (CNM) of plants. In this study, we investigated the role of exogenous proline-mediated Ca2+-dependent signaling in the regulation of CNM in rice subjected to Cr(VI) stress, with emphasis on the involvement of nitrate reductase (NR) and sucrose phosphate synthase (SPS). Results demonstrated that proline effectively mitigated the growth inhibition of rice imposed by Cr(VI) stress, which is achieved by a reduction in cytoplasmic Ca and Cr content and the activation of the downstream Ca2+-dependent signaling pathway. Additionally, proline displayed a positive effect in modulating the expression and activities of NR and SPS under Cr(VI) stress, which are attributed to the cross-regulation between calcium-dependent protein kinases (CDPKs) and 14-3-3 proteins (14-3-3s). Consequently, nitrogen use efficiency and sucrose content in rice under Cr(VI) + proline treatments were higher than Cr(VI) treatments. Gene expression variation factors underscored that the regulation of proline on NR is crucial to the Ca2+-dependent signaling pathway, initiated by the interaction between CDPKs and 14-3-3s in rice plants during Cr(VI) stress. These results reveal that proline interacts with Ca2+-dependent signaling pathways to enhance Cr tolerance in rice by regulating NR and SPS.

Proline-mediated activation of glyoxalase II improve methylglyoxal detoxification in Oryza sativa L. under chromium injury: Clarification via vector analysis of enzymatic activities and gene expression.

Environmental factors affect plants in several ways including the excessive accumulation of methylglyoxal (MG), resulting in dysfunctions of many biological processes. Exogenous proline (Pro) application is one of the successful strategies to increase plant tolerance against various environmental stresses, including chromium (Cr). This study highlights the alleviation role of exogenous Pro on MG detoxification in rice plants induced by Cr(Vl) through modifying the expression of glyoxalase I (Gly I)- and glyoxalase II (Gly II)-related genes. The MG content in rice roots was significantly reduced by Pro application under Cr(VI) stress, however, there was little effect on the MG content in shoots. In this connection, the vector analysis was used to compare the involvement of Gly l and Gly II on MG detoxification in 'Cr(VI)' and 'Pro+Cr(VI)' treatments. Results exhibited that vector strength in rice roots increased with an increase in Cr concentrations, while there was a negligible difference in the shoots. The comparative analysis demonstrated that the vector strengths in roots under 'Pro+Cr(VI)' treatments were higher than 'Cr(VI)' treatments, suggesting that Pro improved Gly II activity more efficiently to reduce MG content in roots. Calculation of the gene expression variation factors (GEFs) indicated a positive effect of Pro application on the expression of Gly I and Gly ll-related genes, wherein a stronger impact was in roots than the shoots. Together, the vector analysis and gene expression data reveal that exogenous Pro chiefly improved Gly ll activity in rice roots which subsequently enhanced MG detoxification under Cr(VI) stress.

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.

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.

Spatial-temporal variations of proline and related amino acids reveal distinct nitrogenous utilization strategies in rice during detoxification of exogenous cyanide.

Cyanide (CN-) pollution in agricultural systems impairs amino acid metabolism in rice plants, hence decreasing their quality and yield. Meanwhile, little is known about the effects of CN- assimilation on the innate pool of proline (Pro) and its synthesis-related amino acids (Pro-AAs) in rice plants. In this study, a hydroponic experiment was carried out to investigate the effect of exogenous KCN on indigenous levels of Pro-AAs, i.e., Pro, glutamate (Glu), arginine (Arg), and ornithine (Orn) in rice seedlings fertilized with either nitrate (NO3-) or ammonium (NH4+) through the biochemical and RT-qPCR analysis. At the same KCN treatment concentration, the relative growth rate of NH4+-fed rice seedlings was considerably higher than that of NO3--fed rice seedlings, but the residual concentration of CN- in NH4+-fed rice tissues was lower than that of NO3--fed rice tissues. Based on the UPLC and stoichiometry molar ratio calculations, it is evident that the Glu pathway contributed significantly to Pro synthesis in rice under KCN + NO3- treatments; whereas the Orn pathway governed the synthesis of Pro in rice under KCN + NH4+ treatments. Moreover, transcriptional and bioinformatics analysis revealed that NH4+ fertilization resulted in spatial-temporal differences in the genetic response in rice tissue during detoxification of CN- compared with KCN + NO3- treatments. These findings suggested that the innate level of Pro serves as "a fishing float" to balance the flux between Pro and Pro-AAs in exogenous KCN-treated rice plants under different nitrogenous nutritional conditions.

Evaluating the significance of amino acids (AAs) in cyanide-treated rice plants under different nitrogen fertilization using the relative importance index of AA.

The biosynthesis of amino acids (AAs) in plants is affected by different nitrogen (N) sources. The effects of exogenous cyanide (KCN) on the concentrations and profiles of AAs in rice seedlings were carried out in the presence of nitrate (+NO3-)/ammonium (+NH4+) or N deficiency (-N). Targeted metabolomics analysis indicated that the highest accumulation of AAs in CN--treated rice seedlings was detected in the "CN-+NH4+" treatments than in other treatments, wherein the doses of exogenous KCN did not significantly affect the total amount of AAs in rice seedlings at the same N fertilized condition. The total content of AAs in rice shoots under "CN-+NH4+" treatments was higher than other treatments, while the total content of AAs in rice roots under "CN-+NO3-" treatments was higher than other treatments. Also, the profiles of 21 AAs in CN--treated rice seedlings showed tissue-specific under different N fertilization. The relative importance index (RII) of AA was used to evaluate the importance of AAs in CN--treated rice seedlings under different N fertilization. The common AAs with higher RII values were compared between three different treatments of KCN (e.g., 0, 1, and 2 mg CN/L). Under "CN-+(-N)" treatments, Ala, Asp, Glu, Val, and Gly (Ala, Gly, Val, and Lys) were the common AAs in rice roots (shoots). Under "CN-+NO3-" treatments, Ala, Glu, Asp, Ser, and Thr (Asp, Ala, Thr, Ser, and Asn) were the common AAs with higher RII values in rice roots (shoots) between all CN- treatments. Under "CN-+NH4+" treatments, Asp, Gln, Asn, and Ala (Asp, Glu, and Thr) were the common AAs with higher RII values in rice roots (shoots) between all CN- treatments. These results suggested that using the RII to describe the change and fluctuation of AAs in rice plants may reflect the different N utilization strategies in response to exogenous CN- exposure.

Regulation of enzymatic and non-enzymatic antioxidants in rice seedlings against chromium stress through sodium hydrosulfide and sodium nitroprusside.

Hydrogen sulfide (H2S) and nitric oxide (NO) play a well-organized protective mechanism in coping with oxidative stress induced by toxic metals. However, the comparative effects of H2S and NO on enzymatic and non-enzymatic antioxidants in plants under Cr(III) stress have not been defined. In this study, we mathematically evaluate the importance of sodium hydrosulfide (NaHS) and sodium nitroprusside (SNP) on these two antioxidant systems in rice seedlings under Cr(III) stress. The results displayed that the optimal dose of NaHS and SNP was 100 µM and 75 µM, respectively, in rice tissues under Cr(III) stress, judging by the reactive oxygen species (ROS) levels in rice tissues. When rice seedlings were exposed to Cr(III) at concentrations of 3.57, 7.24, 26.52 mg Cr/l, Cr-induced ROS accumulation had a significant (p < 0.05) effect on the lipid peroxidation of cell membrane in rice tissues, and decreased the response of SOD, CAT, Pro, GSH, and AsA in rice tissues. Application of exogenous NaHS and SNP effectively (p < 0.05) alleviated the toxic effects of Cr(III) in rice seedlings by activating different antioxidants. A novel physiological response model suggested that the regulatory effect of NaHS and SNP on non-enzymatic antioxidants was stronger than that of enzymatic antioxidants. Moreover, NaHS-mediated response intensity of both enzymatic and non-enzymatic antioxidants was greater than that of SNP, suggesting the importance of utilizing NaHS over SNP as antioxidant regulators during detoxification of Cr(III) in rice seedlings.

Transcriptome reveals the crucial role of exogenous hydrogen sulfide in alleviation of thiocyanate (SCN-) toxicity in rice seedlings.

Application of exogenous hydrogen sulfide (H2S) is a novel strategy for alleviation of the adverse effects caused by abiotic stresses. However, little is known about H2S-mediated global molecular response of rice seedlings to thiocyanate (SCN-) exposure. Herein, a hydroponic experiment was carried out to investigate the crucial role of exogenous H2S in alleviation of SCN- toxicity generated at different effective concentrations (EC20: 24.0 mg SCN/L, EC50: 96.0 mg SCN/L, and EC75: 300.0 mg SCN/L) in rice seedlings through transcriptome analysis. The results showed that the total numbers of differentially expressed genes (DEGs, upregulated genes/downregulated genes) in rice roots were 755/313, 1114/3303, and 2184/7427, while they were 427/292, 2134/526, and 2378/890 in rice shoots at EC20, EC50, and EC75 of SCN-, respectively. When exogenous H2S was supplied to rice seedlings exposed to SCN-, the total number of DEGs (upregulated genes/downregulated genes) in rice roots was 1158/316, 1943/2959, and 1737/5392, while it was 2067/937, 2689/683, and 3492/1062 in rice shoots at EC20, EC50, and EC75 of SCN-, respectively. Upregulated DEGs in shoots were positively correlated with SCN- concentration in the presence of exogenous H2S, suggesting its crucial role in regulating the phytotoxicity of SCN-. Gene function and pathway enrichment analyses showed that exogenous H2S triggered "secondary metabolite synthesis," "metabolic pathways," and "signal transduction mechanisms" in rice seedlings corresponding to different effective concentrations of SCN- exposure.

Transcriptional analysis of heavy metal P1B-ATPases (HMAs) elucidates competitive interaction in metal transport between cadmium and mineral elements in rice plants.

Cadmium (Cd) pollution has become a major threat to crop production and quality globally. The heavy metal P1B-ATPases (HMAs) play a crucial role in metal transport in plants. In the present study, we investigated the interaction in metal transport by HMAs between Cd and mineral elements in rice plants. Rice seedlings were treated with cadmium nitrate either in the nutrient solution ("Cd+M") or in the ultrapure water ("Cd-M"). Result showed that phytotoxicity of Cd to rice seedlings was evident from both Cd treatments, judged by relative growth rate (RGR), where more severe repression (p < 0.05) of RGR was observed in the "Cd-M" treatments than the "Cd+M" treatments. More Cd (p < 0.05) was accumulated in rice tissues from the "Cd-M" treatments than the "Cd+M" treatments, while there is a significant difference (p < 0.05) in distribution and translocation of mineral elements in rice tissues between the "Cd+M" and the "Cd-M" treatments. RT-qPCR analysis displayed that the expression patterns of HMAs related genes were quite different between "Cd+M" and "Cd-M" treatments, suggesting their different regulatory effects during the transport of Cd and mineral elements within rice plants. The competition in metal transport by HMAs mainly occurs between Cd and micro-elements of Zn and Cu in rice tissues during Cd exposure. Overall, this study provides new evidence to clarify the different translocation mechanisms of HMAs in metal transport between Cd and mineral elements in rice seedlings during Cd exposure.

Chemical Modification, Characterization, and Activity Changes of Land Plant Polysaccharides: A Review.

Plant polysaccharides are widely found in nature and have a variety of biological activities, including immunomodulatory, antioxidative, and antitumoral. Due to their low toxicity and easy absorption, they are widely used in the health food and pharmaceutical industries. However, low activity hinders the wide application. Chemical modification is an important method to improve plant polysaccharides' physical and chemical properties. Through chemical modification, the antioxidant and immunomodulatory abilities of polysaccharides were significantly improved. Some polysaccharides with poor water solubility also significantly improved their water solubility after modification. Chemical modification of plant polysaccharides has become an important research direction. Research on the modification of plant polysaccharides is currently increasing, but a review of the various modification studies is absent. This paper reviews the research progress of chemical modification (sulfation, phosphorylation, acetylation, selenization, and carboxymethylation modification) of land plant polysaccharides (excluding marine plant polysaccharides and fungi plant polysaccharides) during the period of January 2012-June 2022, including the preparation, characterization, and biological activity of modified polysaccharides. This study will provide a basis for the deep application of land plant polysaccharides in food, nutraceuticals, and pharmaceuticals.

Proline-mediated modulation on DNA repair pathway in rice seedlings under chromium stress by integrating gene chip and co-expression network analysis.

Chromium (Cr) stress can cause oxidative burst to plants. Application of exogenous proline (Pro) is one of the most effective approaches to improve the tolerance of plants to Cr stress. In this study, we integrated the data of gene chip with co-expression network analysis to identify the key pathways involved in the DNA repair processes in rice seedlings under Cr(VI) stress. Based on KEGG pathway analysis, 158 genes identified are activated in five different types of DNA repair pathways, namely base excision repair (BER, 20 genes), mismatch repair (MMR, 30 genes), nonhomologous end joining (NHEJ, 8 genes), nucleotide excision repair (NER, 56 genes) and homologous recombination (HR, 44 genes). Co-expression network analysis showed that genes activated in DNA repair pathways were categorized into six different modules, wherein Module 1 (45.36%), Module 2 (27.84%) and Module 3 (19.59%) carried more weight than others. Integrating the data of gene chip and co-expression network analysis indicated that coordinated actions of HR and NER pathways are mainly associated with DNA repair processes in Cr(VI)-treated rice seedlings supplied with exogenous Pro. OsCSB, OsXPG, OsBRIP1, OsRAD51C, OsRAD51A2, OsRPA, OsTOPBP1C, OsTOP3, and OsXRCC3 activated in the HR pathway had a stronger impact on repairing DNA damage induced by Cr(VI) stress in rice seedlings supplied with exogenous Pro, while OsXPB1, OsTTDA2, OsTFIIH1, OsXPC, OsRAD23, OsDSS1, and OsRPA located at the NER pathway showed more contribution to repairing DNA damage than others.

Proline-mediated regulation on jasmonate signals repressed anthocyanin accumulation through the MYB-bHLH-WDR complex in rice under chromium exposure.

Toxic metal-induced overaccumulation of anthocyanin (ATH) in plants can oxidize proteins and break DNA. Herein, the role of exogenous proline (Pro) on the repression of ATH accumulation in rice seedlings during hexavalent chromium [Cr(VI)] exposure was studied. Results indicated that exogenous Pro-mediated regulation of jasmonate signals activated the MYB-bHLH-WDR complex to repress ATH accumulation in rice tissues under Cr(VI) stress. Biochemical and transcript analysis indicated that exogenous Pro promoted the synthesis of jasmonic acid (JA) and its molecularly active metabolite jasmonic acid isoleucine (JA-Ile) in rice tissues under Cr(VI) stress. Increment in the endogenous level of jasmonates positively triggered the expression of genes responsible for the JA signaling pathway and activated the MYB-bHLH-WDR complex, eventually repressing the glycosylation of anthocyanidin to form ATH in rice tissues. In conclusion, exogenous proline-mediated regulation on jasmonate signals was tissue-specific under Cr(VI) stress and a more positive effect was detected in shoots rather than roots.

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.

Mathematical quantification of interactive complexity of transcription factors involved in proline-mediated regulative strategies in Oryza sativa under chromium stress.

Involvement of transcription factor (TFs) in governing genes at transcription or post transcription level is known to have affirmative impact on plant physiological and morphological development, especially during environmental abuse. Application of exogenous proline (Pro) is one among the effective approaches to strengthen plant resistance against stresses. However, Pro-mediated regulative strategies of TFs in responses to the chromium (Cr) in rice plants through the gene interaction network are still not clear. In the current study, Pro-mediated interactive complexity of various TFs (i.e., MYB, NAC, WRKY, bHLH, and bZIP) under hexavalent chromium [Cr(VI)] was investigated using Agilent 4 × 44 K rice gene chip and gene interactive probability model (GIPM). Results showed that exogenous Pro had a negligible effect on Cr uptake in rice plants, while a small positive response in biomass accretion of rice seedlings was observed under Cr(VI)+Pro treatments which was to certain extend greater than single Cr(VI) treatments. Rice microarray analysis showed that Cr(VI) significantly (p < 0.05) repressed the expression of TFs in the rice roots and shoots, while the application of exogenous Pro significantly (p < 0.05) up-regulated the expression levels of some TFs in rice tissues. Mathematical modularization indicated that Pro-mediated interaction between MYB and NAC carried more weightage than other TFs in rice roots and shoots under Cr(VI) stress. Overall, our study provides convincing evidence to confirm a positive role of exogenous Pro on reducing the negative impact exerted by Cr(VI) on rice plants through regulating expression and interaction of different TFs.

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

In spite of available information demonstrating the assimilation of cyanide (CN-) by ß-cyanoalanine synthase (ß-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 ß-cyanoalanine synthase (ß-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 ß-CAS and ST genes and their enzymatic activities, suggesting a positive interaction between aminocyclopropane-1-carboxylate oxidase (ACO), ß-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.

Tracing the pollution and human risks of potentially toxic elements in agricultural area nearby the cyanide baths from an active private gold mine in Hainan Province, China.

Mining activities are well-known sources of potentially toxic elements (PTEs) pollution, which often jeopardize the biosphere, pedosphere, and hydrosphere. However, the soil and groundwater pollution caused by active private mining activities has long been neglected. This study investigated the occurrence of PTEs and cyanide (CN) in agricultural soils, mine tailings, and groundwater nearby the cyanide baths from a private gold mine in Hainan Province, southern China. Results indicated that concentrations of Pb, As, Cd, Hg, and CN in different soil depths and mine tailings were up to ten thousand mg/kg, and relatively higher content of As and Pb was detected in groundwater. The chemical forms of Cd, Pb, As, and Hg varied greatly in different soil depths; over 80% of Cd distributed in the water-soluble fraction, suggesting its higher mobility in soils, while approximately 60-90% of Pb, As, and Hg distributed in other chemical fractions, indicating relatively lower mobility in soils. The pollution indices also revealed the serious pollution and deterioration of site quality in this area. Human risk assessments also reflected a high non-carcinogenic/carcinogenic health risk in this area. The framework of integrated management strategies for private metal mines was proposed to mitigate PTEs pollution and reduce health risks.

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.