Effects of metalaxyl enantiomers stress on root activity and leaf antioxidant enzyme activities in tobacco seedlings

Metabolic and Antioxidant Responses of Different Control Methods to the Interaction of Sorghum sudangrass hybrids-Colletotrichum boninense

Colletotrichum boninense is the main pathogenic fungus causing leaf spot disease in Sorghum sudangrass hybrids, which seriously impairs its quality and yield. In order to find an efficient and green means of control, this study used the agar disk diffusion method to screen for a fungicide with the strongest inhibitory effect on C. boninense from among several bacteria, fungi, and chemicals. Then, the changes in the plant's antioxidant system and metabolic levels after treatment were used to compare the three means of control. The lowest inhibitory concentration of Zalfexam was 10 mg/mL, at which point C. boninense did not grow, and the inhibition rates of Bacillus velezensis (X7) and Trichoderma harzianum were 33.87-51.85% and 77.86-80.56%, respectively. Superoxide dismutase (SOD) and chitinase were up-regulated 2.43 and 1.24 folds in the Trichoderma harzianum group (M group) and SOD activity was up-regulated 2.2 folds in the Bacillus velezensis group (X7 group) compared to the control group (CK group). SOD, peroxidase (POD), and chitinase activities were elevated in the Zalfexam group (HX group). The differential metabolites in different treatment groups were mainly enriched in amino acid metabolism and production, flavonoid production, and lipid metabolism pathways. Compared with the diseased plants (ZB group), the M, X7, HX, and CK groups were co-enriched in the tryptophan metabolic pathway and glutamate-arginine metabolic pathway, and only the CK group showed a down-regulation of the metabolites in the two common pathways, while the metabolites of the common pathways were up-regulated in the M, X7, and HX groups. In addition, the salicylic acid-jasmonic acid pathway and ascorbic acid-glutathione, which were unique to the M group, played an important role in helping Sorghum sudangrass hybrids to acquire systemic resistance against stress. This study fills the gap in the control of Colletotrichum boninene, which causes leaf spot disease in Sorghum sudangrass hybrids. This paper represents the first reported case of biological control for leaf spot disease in Sorghum sudangrass hybrids and provides a reference for the control of leaf spot disease in Sorghum sudangrass hybrids as well as other crops infected with Colletotrichum boninense.

Alleviation of metal stress in rape seedlings (Brassica napus L.) using the antimony-resistant plant growth-promoting rhizobacteria Cupriavidus sp. S-8-2

This study investigated an effective strategy for remediating antimony (Sb)-contaminated soil using the bacterial strain screened from Sb-contaminated fern rhizospheres due to its superior growth-promoting, heavy-metal(loid) resistant, and antibiotic-tolerant characteristics. The strain that belongs to Cupriavidus sp. was determined by 16S rRNA sequencing and showed no morphological changes when grown with high concentrations of Sb (608.8 mg/L). The strain showed prominent indole acetic acid (IAA), phosphate-solubilizing abilities, and ACC deaminase activity under Sb stress. Moreover, IAA and soluble phosphate levels increased in the presence of 608.8 mg/L Sb. Inoculation of rape seedlings with Cupriavidus sp. S-8-2 enhanced several morphological and biochemical growth features compared to untreated seedlings grown under Sb stress. Inoculation of Cupriavidus sp. S-8-2 increased root weight by more than four-fold for fresh weight and over two-fold for dry weight, despite high environmental Sb. The strain also reduced Sb-mediated oxidative stress and malondialdehyde contents by reducing Sb absorption, thus alleviating Sb-induced toxicity. Environmental Scanning Electron Microscope (ESEM) imaging and dilution plating technique revealed Cupriavidus sp. S-8-2 is localized on the surface of roots. Identifying the Sb-resistant plant growth-promoting bacterium suggested its usefulness in the remediation of contaminated agricultural soil and for the promotion of crop growth. We highly recommend the strain for further implementation in field experiments.

Red yeast rice dietary intervention reduces oxidative stress-related inflammation and improves intestinal microbiota

Inflammation and oxidative stress play key roles in the aging process, while red yeast rice (RYR), a traditional Chinese fermented food, has anti-oxidant and anti-inflammatory effects. To understand the anti-aging function of RYR in vivo, this study established a D-galactose-induced aging mouse model to verify the positive effects of RYR dietary intervention on aging and explore the related underlying mechanism. Eight weeks of RYR dietary intervention was shown to have a significant inhibitory effect on cognitive decline and hippocampal damage. The molecular mechanistic studies showed that the anti-aging effects of RYR were achieved by (i) improving the oxidative stress-related damage (increasing SOD, CAT, and GSH, and reducing MDA), (ii) regulating the NF-κB inflammation pathway induced by oxidative stress (decreasing the pro-inflammatory cytokines IL-6, TNF-α, IFN-γ, iNOs, and IL-1β, increasing the anti-inflammatory cytokine IL-10, and decreasing the expression of the NF-κB protein), (iii) slowing down apoptosis caused by oxidative stress (reducing the expression of P21 and P53), (iv) restoring the abundance of Lactobacillus, Lachnospiraceae and Rikenellaceae downregulated by D-galactose, and (v) reducing the abundance of Akkermansia and Helicobacter enriched by D-galactose. Mass spectrometry revealed orange pigments (rubropunctatin and monascorubrin) as the main antioxidant components in RYR, which might play key roles in aging inhibition. This study provides theoretical support for the wide application of orange pigments as an antioxidant dietary supplement.

Co-inoculation of Arbuscular Mycorrhizal Fungi and the Plant Growth-Promoting Rhizobacteria Improve Growth and Photosynthesis in Tobacco Under Drought Stress by Up-Regulating Antioxidant and Mineral Nutrition Metabolism

Drought stress is a major environmental concern that limits crop growth on a large scale around the world. Significant efforts are required to overcome this issue in order to improve crop production. Therefore, the exciting role of beneficial microorganisms under stress conditions needs to be deeply explored. In this study, the role of two biotic entities, i.e., Arbuscular mycorrhizal fungi (AMF, Glomus versiforme) and plant growth-promoting rhizobacteria (PGPR, Bacillus methylotrophicus) inoculation in drought tolerance of tobacco (Nicotiana tabacum L.), was investigated. The present results showed that drought stress considerably reduced tobacco plant's growth and their physiological attributes. However, the plants co-inoculated with AMF and PGPR showed higher drought tolerance by bringing up significant improvement in the growth and biomass of tobacco plants. Moreover, the co-inoculation of AMF and PGPR considerably increased chlorophyll a, b, total chlorophylls, carotenoids, photosynthesis, and PSII efficiency by 96.99%, 76.90%, and 67.96% and 56.88%, 53.22%, and 33.43% under drought stress conditions, respectively. Furthermore, it was observed that drought stress enhanced lipid peroxidation and electrolyte leakage. However, the co-inoculation of AMF and PGPR reduced the electrolyte leakage and lipid peroxidation and significantly enhanced the accumulation of phenols and flavonoids by 57.85% and 71.74%. Similarly, the antioxidant enzymatic activity and the plant nutrition status were also considerably improved in co-inoculated plants under drought stress. Additionally, the AMF and PGPR inoculation also enhanced abscisic acid (ABA) and indole-3-acetic acid (IAA) concentrations by 67.71% and 54.41% in the shoots of tobacco plants. The current findings depicted that inoculation of AMF and PGPR (alone or in combination) enhanced the growth and mitigated the photosynthetic alteration with the consequent up-regulation of secondary metabolism, osmolyte accumulation, and antioxidant system.

Osmotic Adjustment and Antioxidant System Regulated by Nitrogen Deposition Improve Photosynthetic and Growth Performance and Alleviate Oxidative Damage in Dwarf Bamboo Under Drought Stress

Dwarf bamboo (Fargesia denudata) is a staple food for the endangered giant pandas and plays a critical role in the sub-alpine ecosystem. Characterized by shallow roots and expeditious growth, it is exceedingly susceptible to drought stress and nitrogen (N) deposition in the context of a changing global environment. However, a comprehensive picture about the interactive response mechanism of dwarf bamboo to the two factors, water regime and N deposition, is far from being given. Therefore, a completely randomized design with two factors of water regimes (well-watered and water-stressed) and N deposition levels (with and without N addition) of F. denudata was conducted. In view of the obtained results, drought stress had an adverse impact on F. denudata, showing that it destroyed ultrastructure integrity and induced oxidative damage and restricted water status in leaves and roots, as well as declined photosynthetic efficiency in leaves, especially in N non-deposition plants. Nevertheless, F. denudata significantly increased heat dissipation in leaves, regulated antioxidant enzymes activities, antioxidants contents, and osmoregulation substances concentrations in leaves and roots, as well as shifted biomass partitioning in response to drought stress. However, regardless of water availability, N deposition maintained better ultrastructure in leaves and roots, resulting in superior photosynthesis and growth of F. denudata. Additionally, although N deposition did not cause oxidative damage in well-watered plants, ameliorated the effects of drought stress on F. denudata through co-deploying heat dissipation in leaves, the antioxidant system in roots as well as osmotic adjustment in leaves and roots. Noticeably, the leaves and roots of F. denudata expressed quite distinct acclimation responses to drought resistance under N deposition.

Transcriptome Profiles of Leaves and Roots of Goldenrain Tree (Koelreuteria paniculata Laxm.) in Response to Cadmium Stress

Cadmium (Cd) pollution is a widespread environmental problem. In this study, we explored the transcriptome and biochemical responses of goldenrain tree (Koelreuteria paniculata Laxm.) leaves and roots to Cd stress. Leaf and root growth decreased substantially under Cd stress (50 mg/L CdCl2), but leaf and root antioxidant mechanisms were significantly activated. In RNA-seq analysis, roots treated with 25 mg/L CdCl2 featured enriched GO terms in cellular components related to intracellular ribonucleoprotein complex, ribonucleoprotein complex, and macromolecular complex. In leaves under Cd stress, most differentially expressed genes were enriched in the cellular component terms intrinsic component of membrane and membrane part. Weighted gene co-expression network analysis and analysis of module-trait relations revealed candidate genes associated with superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and malondialdehyde (MDA). Ten transcription factors responded to Cd stress expression, including those in C2H2, MYB, WRKY, and bZIP families. Transcriptomic analysis of goldenrain tree revealed that Cd stress rapidly induced the intracellular ribonucleoprotein complex in the roots and the intrinsic component of membrane in the leaves. The results also indicate directions for further analyses of molecular mechanisms of Cd tolerance and accumulation in goldenrain tree.

Phytotoxic Activity of Alkaloids in the Desert Plant Sophora alopecuroides

Sophora alopecuroides is known to produce relatively large amounts of alkaloids; however, their ecological consequences remain unclear. In this study, we evaluated the allelopathic potential of the main alkaloids, including aloperine, matrine, oxymatrine, oxysophocarpine, sophocarpine, sophoridine, as well as their mixture both in distilled H₂O and in the soil matrix. Our results revealed that all the alkaloids possessed inhibitory activity on four receiver species, i.e., Amaranthus retroflexus, Medicago sativa, Lolium perenne and Setaria viridis. The strength of the phytotoxicity of the alkaloids was in the following order: sophocarpine > aloperine > mixture > sophoridine > matrine > oxysophocarpine > oxymatrine (in Petri dish assays), and matrine > mixture > sophocarpine > oxymatrine > oxysophocarpine > sophoridine > aloperine (in pot experiments). In addition, the mixture of the alkaloids was found to significantly increase the IAA content, MDA content and POD activity of M. sativa seedlings, whereas CTK content, ABA content, SOD activity and CAT activity of M. sativa seedlings decreased markedly. Our results suggest S. alopecuroides might produce allelopathic alkaloids to improve its competitiveness and thus facilitate the establishment of its dominance; the potential value of these alkaloids as environmentally friendly herbicides is also discussed.

Enantioselective Fungicidal Activity and Toxicity to Early Wheat Growth of the Chiral Pesticide Triticonazole

In this study, the enantioselective activity of the chiral fungicide triticonazole (TRZ) against target pathogens of seed-borne diseases and the effect on the early phenotypic indexes and physiological and biochemical indexes of wheat following the soaking of seeds were studied. S-TRZ had low fungicidal activity and significantly inhibited the germination of wheat seeds. Seedlings in the S-TRZ treatment group suffered severe oxidative damage; the contents of glutathione (GSH) and malondialdehyde (MDA) were significantly increased. S-TRZ significantly inhibited the synthesis of gibberellin (GA) and ethylene (ETH), while it significantly increased that of jasmonic acid (JA). R-TRZ showed the highest activity against two smut fungi; the treatment of seeds with 5 g (ai)/100 kg R-TRZ had little influence on early wheat growth. The plant hormones were synthesized normally; seedlings grew well, and the fresh weight increased significantly following this treatment. Based on these data, we propose to develop and apply R-TRZ using the national recommended doses to control seed-borne diseases of wheat.

Arbuscular mycorrhizal fungi improve growth, essential oil, secondary metabolism, and yield of tobacco (Nicotiana tabacum L.) under drought stress conditions

Drought is a major environmental threat limiting worldwide crop production. Drought stress affects the tobacco quality and yield; therefore, the current research studies were undertaken to investigate the effectiveness of arbuscular mycorrhizal fungi (AMF) under drought stress on morphological and biochemical attributes of tobacco (Nicotiana tabacum L. variety Yunyan 87). AMF-inoculated and AMF-non-inoculated plants were maintained in a greenhouse and irrigated with a half-strength Hoagland solution (100 mL pot-1) once a week. At harvesting, the plant height, number of leaves, fresh and dry weights, mycorrhizal colonization, and concentration of leaf photosynthetic pigments and photosynthetic rate were measured. Data were statistically analyzed by ANOVA and the principal component (PCA) analyses. The effect of root colonization significantly increased biomass production and essential oil accumulation. Results showed that drought at mild and severe stressed levels significantly affected tobacco growth by decreasing plant height, biomass, and a number of leaves. However, inoculation of AMF considerably increased plant height, fresh and dry weights, chlorophyll (a, b), total chlorophyll, and carotenoid content by 43.84, 40.87 and 49.76, 185.29, 325.60, 173.12, and 211.49%, respectively. Compared with non-inoculated plants, AMF inoculation significantly enhanced the essential oil yield and the uptake of nitrogen, phosphorus, and potassium with the increase of 257.36, 102.71, and 90.76, 62.32, and 84.51%, respectively, in mild drought + AMF-treated plants. Similarly, the antioxidant enzymatic activity, glomalin-related soil protein (GRSP), and accumulation of phenols and flavonoids and osmolytes content were also significantly improved in inoculated plants under drought stress. Additionally, AMF inoculation significantly upregulated the lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) enzymes by 197 and 298.44% under drought conditions. These findings depicted that the symbiotic association of AMF improved the overall growth pattern and secondary metabolism in tobacco plants under severe drought stress conditions and may be used as an approaching source of important drugs in the field of pharmacology.

24-Epibrassinolide promotes NO3- and NH4+ ion flux rate and NRT1 gene expression in cucumber under suboptimal root zone temperature

BACKGROUND

Suboptimal root zone temperature (RZT) causes a remarkable reduction in growth of horticultural crops during winter cultivation under greenhouse production. However, limited information is available on the effects of suboptimal RZT on nitrogen (N) metabolism in cucumber seedlings. The aim of this study is to investigate the effects of 24-Epibrassinolide (EBR) on nitrate and ammonium flux rate, N metabolism, and transcript levels of NRT1 family genes under suboptimal RZT in cucumber seedlings.

RESULTS

Suboptimal RZT (LT) negatively affected on cucumber growth and proportionately decreased EBR contents, bleeding rate, root activity, enzyme activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT), nitrate (NO₃^-) influx rate, ammonium (NH₄⁺) efflux rate, and transcript levels of nitrate transporter (NRT1) encoding genes. However, exogenous EBR reduced the harmful effects of suboptimal RZT and increased endogenous EBR contents, bleeding rate, root activity, enzyme activities of NR, NiR, GS, and GOGAT, NH₄⁺ and NO₃^- flux rates and contents, and N accumulation. EBR-treated seedlings also upregulated the transcript levels of nitrate transporters CsNRT1.1, CsNRT1.2A, CsNRT1.2B, CsNRT1.2C, CsNRT1.3, CsNRT1.4A, CsNRT1.5B, CsNRT1.5C, CsNRT1.9, and CsNRT1.10, and downregulated CsNRT1.5A and CsNRT1.8. LT treatment upregulated the expression level of CsNRT1.5A, while exogenous BZR application downregulated the expression level of NRT1 genes.

CONCLUSION

These results indicate that exogenous application of EBR alleviated the harmful effects of suboptimal RZT through changes in N metabolism, NH₄⁺ and NO₃^- flux rates, and NRT1 gene expression, leading to improved cucumber seedlings growth. Our study provides the first evidence of the role of EBR in the response to suboptimal RZT in cucumber, and can be used to improve vegetable production.

Enantioselective Oxidative Stress Induced by S- and Rac-metolachlor in Wheat (Triticum aestivum L.) Seedlings

The unfounded use of chiral pesticides has caused widespread concern. In this study, the enantioselective effects of S- and racemic (Rac)-metolachlor on the oxidative stress of wheat seedlings was determined based on physiological and gene transcription differences. Growth inhibition increased with increasing concentrations of tested metolachlor, and S-metolachlor had a stronger inhibitory effect than did Rac-metolachlor. Root growth was also significantly inhibited, but no enantioselective effects from the tested concentrations of the metolachlor enantiomers were observed. At a concentration of 5 mg L^-1, the maximal fresh weight inhibition reached 63.7% and 53.8% for S-metolachlor and Rac-metolachlor, respectively. In response to the S-metolachlor treatment, the maximum level of superoxide anions and malondialdehyde (MDA) increased to 1.73 and 2.55 times that in response to the control treatment, both of which were greater than those in response to the Rac-metolachlor treatment. The activity of superoxide dismutase (SOD) also increased in response to the S-metolachlor treatment, but the activity of peroxidase (POD) decreased. Real-time polymerase chain reaction (PCR) revealed that, compared with the Rac-metolachlor treatment, the S-metolachlor treatment attenuated the expression of several antioxidant genes. Together, these results demonstrate that S-metolachlor has a greater effect than does Rac-metolachlor on wheat seedlings.

Phytoremediation of Mn-contaminated paddy soil by two hyperaccumulators (Phytolacca americana and Polygonum hydropiper) aided with citric acid

The purpose of this study was to investigate the phytoremediation potential of two hyperaccumulator plants, Phytolacca americana L. and Polygonum hydropiper L., on manganese-contaminated paddy soils. The biomass growth, Mn concentrations in plant tissues, and potential Mn removal efficiency from soils of these two plants were studied with citric acid, and the mechanisms of citric acid on these two plants were analyzed by examining the root activity, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves, as well as the concentrations of O₂·^- and H₂O₂ in leaves. The results showed that the biomass of these two plants were both promoted under low level of citric acid (3 mmol kg^-1). The concentration of Mn in the plants and the amount of Mn removed from the soil by the plants through harvesting were enhanced at low and intermediate (10 mmol kg^-1) citric acid application levels. The results also showed that root activity was enhanced at the low citric acid level and significantly inhibited under the intermediate and high levels (15 mmol kg^-1), which indicates the facilitative function of the low level of citric acid and the inhibitive function of the high level of citric acid application on plant biomass growth. Under the low and intermediate levels of citric acid application, O₂·^- in the plant leaves increased sharply, and the SOD, POD, and CAT activities also increased sharply, which made the level of H₂O₂ very similar to that of the control, ensuring the health of the plants. At the high level of citric acid application, however, the O₂·^- continued to rise sharply, while the activity of the three antioxidant enzymes declined sharply, causing the concentration of hydrogen peroxide to be much higher than that in the control, thus endangering the plants. The present study shows the potential of P. hydropiper for use in the phytoremediation of soil contaminated with a relatively low level of manganese.