Transcriptome analysis of Oryza sativa in responses to different concentrations of thiocyanate

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.

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.

Estimating the synergistic and antagonistic effects of dual antibiotics on plants through root elongation test

Antibiotics are recently recognized as a group of emerging environmental contaminants that are frequently detected in various environmental matrixes. Relative root elongation (RRE) test is a rapid and effective strategy to evaluate the water/soil quality and the toxic effects of environmental contaminants on plants. In the present study, we examine the toxicity effect of ciprofloxacin (CIP), norfloxacin (NOR), and tetracycline (TET) to pakchoi individually and in combinations. Both independent action (IA) and concentration addition (CA) models are used for toxicity assessment. Results showed that the EC₅₀ values of CIP, NOR, and TET are 193.59, 60.81, and 40.37 μM, respectively. Combinations of TET + CIP and TET + NOR caused more inhibitory effects on root elongation than those of CIP + NOR. Toxic Unit (TU) and Synergistic Ratio (SR) analysis showed that the relatively lower (higher) EC values are observed in the combinations with lower (higher) antibiotic concentrations, suggesting an effect of low-dose synergism and high-dose antagonism. The reliability of the simulation results from IA and CA models to predict that combined toxicity is highly dependent upon the results from the analysis of TU or SR.

Integration of RT-qPCR analysis and grey situation decision-making model for evaluating the effects of plant growth regulators on the gene expression in rice seedlings under thiocyanate exposure

Thiocyanate (SCN^-) present in irrigation water can have negative effects on plant growth and crop yields. Addition of plant growth regulators (PGRs) can alleviate toxic stress to plants. In the current study, we established a grey situation decision-making model (GSDM) to integrate the data of RT-qPCR analysis for screening the optimal addition of PGRs to minimise pollution stress. The effects of PGRs (i.e., jasmonic acid [JA], indole-3-acetic acid [IAA] and sodium hydrosulfide [NaHS]) on the abundance of IAA oxidation and conjugation-related genes in rice seedlings under potassium thiocyanate (KSCN) exposure was examined. The results obtained from RT-qPCR analysis can roughly present the mitigating effects of IAA, JA, and NaHS on rice seedlings under KSCN stress. Integration of RT-qPCR analysis and GSDM further quantified the regulatory effects of PGRs. Simulation results showed that the effect of NaHS on the gene expression at KSCN exposure is apparently better than that of JA and IAA. Our study provides a new simple, efficient, and cheap approach to identify the optimal plant growth regulators under the stress of environmental pollution.

Fuzzy synthetic evaluation of the impact of plant growth regulators on the root phenotype traits of rice seedlings under thiocyanate stress

Application of plant growth regulators (PGRs) is a novel strategy for allay of the adverse effects caused by biotic/abiotic stresses. However, no studies have vividly executed mathematic evaluation for the assessment of various PGRs on root phenotype traits (RPTs) against pollutants. In the present study, a microcosm hydroponic experiment was conducted to examine responses of RPTs under SCN^- (0, 24, 96, and 300 mg SCN/L) stress in the presence of PGRs such as jasmonic acid (JA), indole-3-acetic acid (IAA), and sodium hydrosulfide (NaHS) in rice plants. Fuzzy synthetic evaluation was applied to determine the outcome of the effects of various PGRs on the RPTs under SCN^- exposure. Root scanning results indicated that exogenous IAA and NaHS has the greater potential for improving the RPTs of rice seedlings under SCN^- stress, while JA failed to uplift the RPTs in response to SCN^- stress. Fuzzy synthetic evaluation indicated that in control plants (without SCN^-), the effect of three PGRs applied on the RPTs is as follows: NaHS > IAA > JA. At 24 mg SCN/L, NaHS and IAA had consistent actuate in regulating RPTs of rice seedlings, while all PGRs amended have an affirmative impact on RPTs at 96 and 300 mg SCN/L. The present research highlights the utilization of contemporary mathematic method to screen the superior species of PGRs through the RPTs test of plants under pollutant belt.

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

Repression of the electron transport in mitochondria can result in an increase of reactive oxygen species (ROS) in plant cells. This study was to clarify inhibition of the mitochondrial respiratory components (Complex I and Complex III) as stimuli to induce oxidative damage in Oryza sativa L. under exogenous SCN^- exposure with special emphasis on lipid peroxidation, protein modification, and DNA damage at the biochemical and molecular levels. Our results showed that enzymatic activity and gene expression of cytochrome c reductase (Complex III) in roots and shoots of rice seedlings were significantly repressed by SCN^- exposure, where significant inhibition of NADH dehydrogenase (Complex I) was only detected in shoots, suggesting that Complex III was the main target attacked by SCN^- ligand in rice roots, and both components were arrested in shoots. ROS analysis in tissues indicated that SCN^- exposure caused significant accumulation of H₂O₂ and O₂^-•, increased malondialdehyde (MDA) and carbonyl content in rice materials in a dose-dependent manner. Similarly, a remarkable elevation of electrolyte leakage was observed in rice tissue samples. The comet assay indicated a positive correlation between DNA damage and external SCN^- exposure. In conclusion, oxidative burst generated from the inhibitions of the electron transport in mitochondria in rice seedlings under SCN^- exposure can cause lipid peroxidation, protein modification and DNA damage, eventually decreasing fresh weight of rice seedlings.

Interaction of cyanate uptake by rice seedlings with nitrate assimilation: gene expression analysis

Cyanate (CNO^-) has been produced in the environment through either natural or anthropogenic sources. However, due to industrialization, it has been led more over-loads. In this study, interaction of CNO^- uptake by rice seedlings with nitrate assimilation was investigated using gene expression analysis after an acute phytotoxicity assay. Our results showed that CNO^- exposure caused inhibition on relative growth rates of plants. CNO^- analysis demonstrated that rice seedlings had higher potential for CNO^- uptake and the removal rates showed a zero-order kinetic. PCR analysis exposed that OsCYN transcript was not significantly induced by CNO^- treatments in rice tissues and CNO^- exposure also repressed gene expression of the collaborative enzyme carbonic anhydrase (CA), suggesting that assimilation of CNO^- initiated by the enzyme cyanase (CYN) in rice seedlings was an enzyme-limitation reaction. Gene expression of other enzymes involved in nitrate metabolism was tissue-specific under CNO^- exposure, suggesting that rice seedlings were able to trigger its intrinsic regulative and responsive mechanisms to cope up with uneven N conditions. Significant upregulation of three OsGDH isogenes, except for OsGDH1 in roots, was detected in both rice materials with enhancing CNO^- concentrations, suggesting that GDH may play a primary role to maintain the balance of C and N in plants under CNO^- exposure. In conclusion, because the innate pool of CYN activity was non-sufficient to degrade exogenous CNO^- by rice seedlings, CNO-derived ammonium only can serve as a supporting N source to support growth of rice seedling under non-effective doses of CNO^- exposure.