Selenium improved antioxidant response and photosynthesis in fragrant rice (Oryza sativa L.) seedlings during drought stress

Overexpression of FERONIA receptor kinase MdMRLK2 regulates lignin accumulation and enhances water use efficiency in apple under long-term water deficit condition

Water use efficiency (WUE) is crucial for apple tree fitness and survival, especially in response to climatic changes. The receptor-like kinase FERONIA is reportedly an essential regulator of plant stress responses, but its role in regulating WUE under water deficit conditions is unclear. Here, we found that overexpressing the apple FERONIA receptor kinase gene, MdMRLK2, enhanced apple WUE under long-term water deficit conditions. Under drought treatment, 35S::MdMRLK2 apple plants exhibited higher photosynthetic capacity and antioxidant enzyme activities than wild-type (WT) plants. 35S::MdMRLK2 apple plants also showed increased biomass accumulation, root activity, and water potential compared to WT plants. Moreover, MdMRLK2 physically interacts with and phosphorylates cinnamoyl-CoA reductase 1, MdCCR1, an enzyme essential for lignin synthesis, at position Ser260. This interaction likely contributed to increased vessel density, vascular cylinder area, and lignin content in 35S::MdMRLK2 apple plants under drought conditions. Therefore, our findings reveal a novel function of MdMRLK2 in regulating apple WUE under water deficit conditions.

Exogenous application of selenium on sunflower (Helianthus annuus L.) to enhance drought stress tolerance by morpho-physiological and biochemical adaptations

Drought stress poses a significant obstacle to agricultural productivity, particularly in the case of oilseed crops such as sunflower (Helianthus annuus L.). Selenium (Se) is a fundamental micronutrient that has been recognized for its ability to enhance plant resilience in the face of various environmental stresses. The FH-770 sunflower variety was cultivated in pots subjected to three stress levels (100% FC, 75% FC, and 50% FC) and four Se application rates (0 ppm, 30 ppm, 60 ppm, and 90 ppm). This research aimed to investigate the effect of exogenously applied Se on morpho-physiological and biochemical attributes of sunflower to improve the drought tolerance. Foliar Se application significantly lowered H2O2 (hydrogen peroxide; ROS) (20.89%) accumulation that markedly improved glycine betaine (GB) (74.46%) and total soluble protein (Pro) (68.63%), improved the accumulation of ascorbic acid (AA) (25.51%), total phenolics (TP) (39.34%), flavonoids (Flv) (73.16%), and anthocyanin (Ant) (83.73%), and improved the activity of antioxidant system superoxide dismutase (SOD) (157.63%), peroxidase (POD) (100.20%), and catalase (CAT) (49.87%), which ultimately improved sunflower growth by 36.65% during drought stress. Supplemental Se significantly increased shoot Se content (93.86%) and improved calcium (Ca2+), potassium (K+), and sodium (Na+) ions in roots by 36.16%, 42.68%, and 63.40%, respectively. Selenium supplements at lower concentrations (60 and 90 ppm) promoted the growth, development, and biochemical attributes of sunflowers in controlled and water-deficient circumstances. However, selenium treatment improved photosynthetic efficiency, plant growth, enzymatic activities, osmoregulation, biochemical characteristics, and nutrient balance. The mechanisms and molecular processes through which Se induces these modifications need further investigation to be properly identified.

De novo assembly and characterization of the transcriptome of Morchella esculenta growth with selenium supplementation

Although Morchella esculenta (L.) Pers. is an edible and nutritious mushroom with significant selenium (Se)-enriched potential, its biological response to selenium stimuli remains unclear. This study explored the effect of selenium on mushroom growth and the global gene expression profiles of M. esculenta. While 5 µg mL-1selenite treatment slightly promoted mycelia growth and mushroom yield, 10 µg mL-1significantly inhibited growth. Based on comparative transcriptome analysis, samples treated with 5 µg mL-1 and 10 µg mL-1 of Se contained 16,061 (452 upregulated and 15,609 downregulated) and 14,155 differentially expressed genes (DEGs; 800 upregulated and 13,355 downregulated), respectively. Moreover, DEGs were mainly enriched in the cell cycle, meiosis, aminoacyl-tRNA biosynthesis, spliceosome, protein processing in endoplasmic reticulum pathway, and mRNA surveillance pathway in both selenium-treated groups. Among these, MFS substrate transporter and aspartate aminotransferase genes potentially involved in Se metabolism and those linked to redox homeostasis were significantly upregulated, while genes involved in isoflavone biosynthesis and flavonoid metabolism were significantly downregulated. Gene expression levels increased alongside selenite treatment concentration, suggesting that high Se concentrations promoted M. esculenta detoxification. These results can be used to thoroughly explain the potential detoxification and Se enrichment processes in M. esculenta and edible fungi.

Rational Combination of Selenium Application Rate and Planting Density to Improve Selenium Uptake, Agronomic Traits, and Yield of Dryland Maize

Exogenous selenium application could effectively improve the selenium absorption of crops affected by different climatic conditions due to changes in the planting environment and planting conditions. We planted maize at planting densities of 67,500 plants ha-1 (D1) and 75,000 plants ha-1 (D2). Five selenium fertilizer gradients of 0 mg m-2 (Se0), 7.5 mg m-2 (Se1), 15.0 mg m-2 (Se2), 22.5 mg m-2 (Se3), and 30.0 mg m-2 (Se4) were applied to investigate the response of the plants to selenium fertilizer application in terms of the gradient selenium absorption and substance accumulation. With the increase in the amount of selenium fertilizer applied, more of the selenium fertilizer will be absorbed and transported from the leaves to the grains, and the selenium content of the grains will gradually increase and exceed the selenium content of leaves. Under the D2 density in 2022, the selenium content of the grains under Se1, Se2, Se3, and Se4 treatments increased by 65.67%, 72.71%, and 250.53%, respectively, compared with that of Se0. A total of 260.55% of the plants showed a gradient of grain > leaf > cob > stalk from the Se2 treatment, and the overall selenium content of the plants increased first and then decreased. Under the D1 density, compared with the Se0, the dry matter mass of the Se1, Se2, Se3, and Se4 treatments significantly improved by 5.84%, 1.49%, and 14.26% in 2021, and significantly improved by 4.84%, 3.50%, and 2.85% in 2022. The 1000-grain weight under Se2, Se3, and Se4 treatments improved by 8.57%, 9.06%, and 15.56% compared to that under the Se0 treatment, and the yield per ha under the Se2, Se3, and Se4 treatments was 18.58%, 9.09%, and 21.42% higher than that under Se0 treatment, respectively. In addition, a reasonable combination of selenium application rate and density could improve the chlorophyll content and stem growth of dryland maize. This lays a foundation for the efficient application of selenium fertilizer and provides an important reference.

Harnessing microbial interactions with rice: Strategies for abiotic stress alleviation in the face of environmental challenges and climate change

Rice, which feeds more than half of the world's population, confronts significant challenges due to environmental and climatic changes. Abiotic stressors such as extreme temperatures, drought, heavy metals, organic pollutants, and salinity disrupt its cellular balance, impair photosynthetic efficiency, and degrade grain quality. Beneficial microorganisms from rice and soil microbiomes have emerged as crucial in enhancing rice's tolerance to these stresses. This review delves into the multifaceted impacts of these abiotic stressors on rice growth, exploring the origins of the interacting microorganisms and the intricate dynamics between rice-associated and soil microbiomes. We highlight their synergistic roles in mitigating rice's abiotic stresses and outline rice's strategies for recruiting these microorganisms under various environmental conditions, including the development of techniques to maximize their benefits. Through an in-depth analysis, we shed light on the multifarious mechanisms through which microorganisms fortify rice resilience, such as modulation of antioxidant enzymes, enhanced nutrient uptake, plant hormone adjustments, exopolysaccharide secretion, and strategic gene expression regulation, emphasizing the objective of leveraging microorganisms to boost rice's stress tolerance. The review also recognizes the growing prominence of microbial inoculants in modern rice cultivation for their eco-friendliness and sustainability. We discuss ongoing efforts to optimize these inoculants, providing insights into the rigorous processes involved in their formulation and strategic deployment. In conclusion, this review emphasizes the importance of microbial interventions in bolstering rice agriculture and ensuring its resilience in the face of rising environmental challenges.

Selenium nanoparticles improved biochemical and physiological properties and antioxidant systems of savoury under drought stress

To investigate the effectiveness of selenium (Se) and Se nanoparticles (Se-NPs) in improving biochemical and physiological characteristics of savoury in drought stress conditions, a factorial experiment based on the completely randomised design with three replications was used. Results demonstrate that Se-NPs considerably enhanced several biochemical parameters, such as relative water content (RWC), antioxidant enzymes activity, and total soluble protein in drought and normal conditions. At the stress level from 100 to 40% of field capacity, a gradual decrease in chlorophyll and CARs contents was observed and under stress and normal conditions, the application of Se-NPs (10 mg L-1) led to an increase in the content of pigments. Total soluble protein, total phenolic and flavonoid contents showed significant increases in plants treated with Se-NPs under drought stress. Generally, the use of Se-NPs in drought stress conditions can be effective in improving the growth, biochemical, and physiological characteristics of savoury.

Sophora tonkinensis: response and adaptation of physiological characteristics, functional traits, and secondary metabolites to drought stress

The medicinal plant Sophora tonkinensis is a characteristic Chinese shrub of karst areas. The arid climate in karst areas produces high-quality S. tonkinensis; however, the mechanisms of drought tolerance are not clear, which restricts sustainable plantings of S. tonkinensis. This study involved a 20-day drought stress experiment with potted S. tonkinensis and threee soil water regimes: control (CK), mild drought (MDT), and severe drought (SDT). Plant morphology, biomass, physiological indicators, alkaloid content, and other changes under drought stress were monitored. The content of soluble sugars and proteins, and activity of antioxidant enzymes in leaves and roots were higher under drought than CK, indicating that S. tonkinensis is tolerant to osmotic stress in early drought stages. Content of matrine and oxymatrine increased gradually with increasing drought duration in the short term. The epidermis of S. tonkinensis leaves have characteristics of desert plants, including upper epidermal waxy layer, lower epidermal villi, and relatively sunken stomata, suggesting that S. tonkinensis has strong drought tolerance. In conclusion, drought stress changed the cell structure of S. tonkinensis, induced antioxidant enzyme activity and increased its resistance to drought.

Foliar Selenium Application to Reduce the Induced-Drought Stress Effects in Coffee Seedlings: Induced Priming or Alleviation Effect?

This study aimed to investigate the role of Se supply in improving osmotic stress tolerance in coffee seedlings while also evaluating the best timing for Se application. Five times of Se foliar application were assessed during induced osmotic stress with PEG-6000 using the day of imposing stress as a default, plus two control treatments: with osmotic stress and without Se, and without osmotic stress and Se. Results demonstrated that osmotic stress (OS) promoted mild stress in the coffee plants (ψw from -1.5MPa to -2.5 MPa). Control plants under stress showed seven and five times lower activity of the enzymes GR and SOD compared with the non-stressed ones, and OS was found to further induce starch degradation, which was potentialized by the Se foliar supply. The seedlings that received foliar Se application 8 days before the stress exhibited higher CAT, APX, and SOD than the absolute control (-OS-Se)-771.1%, 356.3%, and 266.5% higher, respectively. In conclusion, previous Se foliar spray is more effective than the Se supply after OS to overcome the adverse condition. On the other hand, the post-stress application seems to impose extra stress on the plants, leading them to reduce their water potential.

Application of glutamic acid improved As tolerance in aromatic rice at early growth stage

To alleviate the arsenic (As) toxicity in aromatic rice, a hydroponic experiment of two As concentrations (0 and 100 μM sodium arsenite: A0, A1), three glutamic acid (Glu) concentrations (0, 100, and 500 μM l-glutamic acid: G0, G1, and G2) with Xiangyaxiangzhan and Meixiangzhan 2 was conducted. Results showed that the root As content were increased under A1G2 but reduced under A1G1 for Xiangyaxiangzhan as compared with A1G0. A decrement of As was transported from root to shoot caused by up-regulated OsABCC1 relative expression in Meixiangzhan 2. Likewise, As stress enhanced the H₂O₂ and malondialdehyde content, resulting in the impaired cell wall observed by transmission electron microscopy. However, compared with A1G0, the superoxide dismutase activity, ascorbic acid, glutathione, proline, and soluble sugar content were increased under A1G1. Additionally, arsenate reductase, monodehydroascorbate reductase activity, Glu, proline, and soluble sugar content were found positively associated with the As accumulation. Further, the metabolome analysis indicated that the pathway of amino acid and arginine biosynthesis were notably enriched after Glu application. Generally, 100 μM Glu application was the better treatment to enhance As tolerance in aromatic rice through up-regulating amino acid biosynthesis with increasing antioxidants and osmolytes to scavenge excessive reactive oxygen species.

The role of selenium and nano selenium on physiological responses in plant: a review

Selenium (Se), being an essential micronutrient, enhances plant growth and development in trace amounts. It also protects plants against different abiotic stresses by acting as an antioxidant or stimulator in a dose-dependent manner. Knowledge of Se uptake, translocation, and accumulation is crucial to achieving the inclusive benefits of Se in plants. Therefore, this review discusses the absorption, translocation, and signaling of Se in plants as well as proteomic and genomic investigations of Se shortage and toxicity. Furthermore, the physiological responses to Se in plants and its ability to mitigate abiotic stress have been included. In this golden age of nanotechnology, scientists are interested in nanostructured materials due to their advantages over bulk ones. Thus, the synthesis of nano-Se or Se nanoparticles (SeNP) and its impact on plants have been studied, highlighting the essential functions of Se NP in plant physiology. In this review, we survey the research literature from the perspective of the role of Se in plant metabolism. We also highlight the outstanding aspects of Se NP that enlighten the knowledge and importance of Se in the plant system.

Graphical abstract

Effects of Basal Selenium Fertilizer Application on Agronomic Traits, Yield, Quality, and Se Content of Dryland Maize

To explore the efficiency of selenium (Se) fertilizer application in dryland maize, we tested five Se fertilizer application treatments: 0 g ha^-1 (Se0), 75 g ha^-1 (Se1), 150 g ha^-1 (Se2), 225 g ha^-1 (Se3), and 300 g ha^-1 (Se4). Compared with Se0, Se2 increased the leaf area, chlorophyll content, internode length, plant height, and ear height by 7.95%, 3.20%, 13.19%, 1.89%, and 7.98%, respectively. Se2 and Se3 significantly affected the stem internode diameter, cortex thickness, and cellulose content, which were positively correlated with lodging resistance. Compared with Se0, Se3 promoted the contents of soluble sugar, crude protein, crude fat, and starch in grains, which increased by 9.48%, 6.59%, 1.56%, and 4.82%, respectively. It implies that maize grain application of Se significantly improves their Se content. Se1 did not observably influence the growth of maize, and the promoting effect of Se4 on maize decreased. The lodging resistance of maize as analyzed by Pearson correlation analysis correlated with the application of Se fertilizer. It proved that higher yield, grain quality, grain Se content, and lodging resistance of stems were concerned with Se fertilizer application in the range of 150-225 g ha^-1. The results provide useful information for Se fertilizer treatment in dryland maize.

Zeolitic Imidazole Framework-90-Based Pesticide Smart-Delivery System with Enhanced Antimicrobial Performance

Multimodal antimicrobial technology is regarded as a promising strategy for controlling plant diseases because it enhances antimicrobial efficacy by blocking multiple pesticide-resistance pathways. In this work, a pH-responsive multimodal antimicrobial system was constructed based on ZIF-90 for the controlled release of kasugamycin (KSM). A series of physicochemical characterizations confirmed the successful fabrication of ZIF-90-KSM. The results indicated that the loading capacity of ZIF-90-KSM for KSM was approximately 6.7% and that the ZIF-90 nanocarriers could protect KSM against photodegradation effectively. The acid pH at the site of disease not only decompose the Schiff base bonds between KSM and ZIF-90, but also completely dissolved the nanocarriers. The simultaneous release of KSM and Zn²⁺ ions was able to achieve multimodal antimicrobial functions during disease occurs. A bioactivity survey indicated that ZIF-90-KSM had superior fungicidal activity and longer duration against Magnaporthe oryzae than KSM aqueous solution. In addition, the phytotoxicity assessment of ZIF-90-KSM on rice plants did not reveal any adverse effects. Therefore, ZIF-90-KSM prepared by Schiff base reaction has great potential for achieving synergistic antifungal functions and provides an eco-friendly approach to manage rice diseases.

Nano-selenium enhances the antioxidant capacity, organic acids and cucurbitacin B in melon (Cucumis melo L.) plants

Pesticides are widely used in melon production causing safety issues around the consumption of melon and increasing pathogen and insect tolerance to pesticides. This study investigated whether a nano-selenium (Nano-Se) spray treatment can improve resistance to biological stress in melon plants, reducing the need for pesticides, and how this mechanism is activated. To achieve this, we examine the ultrastructure and physio-biochemical responses of two melon cultivars after foliar spraying with Nano-Se. Nano-Se treatment reduced plastoglobulins in leaf mesophyll cells, thylakoid films were left intact, and compound starch granules increased. Nano-Se treatment also increased root mitochondria and left nucleoli intact. Nano-Se treatment enhanced ascorbate peroxidase, peroxidase, phenylalanine ammonia lyase, β-1,3-glucanase, chitinase activities and their mRNA levels in treated melon plants compared to control plants (without Nano-Se treatments). Exogenous application of Nano-Se improved fructose, glucose, galactitol, stachyose, lactic acid, tartaric acid, fumaric acid, malic acid and succinic acid in treated plants compared to control plants. In addition, Nano-Se treatment enhanced cucurbitacin B and up-regulated eight cucurbitacin B synthesis-related genes. We conclude that Nano-Se treatment of melon plants triggered antioxidant capacity, photosynthesis, organic acids, and up-regulated cucurbitacin B synthesis-related genes, which plays a comprehensive role in stress resistance in melon plants.