Overexpression of OsLCT2, a Low-Affinity Cation Transporter Gene, Reduces Cadmium Accumulation in Shoots and Grains of Rice

Cadmium (Cd)-contaminated rice is a serious issue affecting food safety. Understanding the molecular regulatory mechanisms of Cd accumulation in rice grains is crucial to minimizing Cd concentrations in grains. We identified a member of the low-affinity cation transporter family, OsLCT2 in rice. It was a membrane protein. OsLCT2 was expressed in all tissues of the elongation and maturation zones in roots, with the strongest expression in pericycle and stele cells adjacent to the xylem. When grown in Cd-contaminated paddy soils, rice plants overexpressing OsLCT2 significantly reduced Cd concentrations in the straw and grains. Hydroponic experiment demonstrated its overexpression decreased the rate of Cd translocation from roots to shoots, and reduced Cd concentrations in xylem sap and in shoots of rice. Moreover, its overexpression increased Zn concentrations in roots by up-regulating the expression of OsZIP9, a gene responsible for Zn uptake. Overexpression of OsLCT2 reduces Cd accumulation in rice shoots and grains by limiting the amounts of Cd loaded into the xylem and restricting Cd translocation from roots to shoots of rice. Thus, OsLCT2 is a promising genetic resource to be engineered to reduce Cd accumulation in rice grains.

Silver Nanoparticles Increase Nitrogen, Phosphorus, and Potassium Concentrations in Leaves and Stimulate Root Length and Number of Roots in Tomato Seedlings in a Hormetic Manner

Background Silver nanoparticles (AgNPs) display unique biological activities and may serve as novel biostimulators. Nonetheless, their biostimulant effects on germination, early growth, and major nutrient concentrations (N, P, and K) in tomato ( Solanum lycopersicum) have been little explored. Methods Tomato seeds of the Vengador and Rio Grande cultivars were germinated on filter paper inside plastic containers in the presence of 0, 5, 10, and 20 mg/L AgNPs. Germination parameters were recorded daily, while early growth traits of seedlings were determined 20 days after applying the treatments (dat). To determine nutrient concentrations in leaves, a hydroponic experiment was established, adding AgNPs to the nutrient solution. Thirty-day-old plants were established in the hydroponic system and kept there for 7 days, and subsequently, leaves were harvested and nutrient concentrations were determined. Results The AgNPs applied did not affect germination parameters, whereas their application stimulated length and number of roots in a hormetic manner. In 37-day-old plants, low AgNP applications increased the concentrations of N, P, and K in leaves. Conclusion As novel biostimulants, AgNPs promoted root development, especially when applied at 5 mg/L. Furthermore, they increased N, P, and K concentration in leaves, which is advantageous for seedling performance during the early developmental stages.

Boron Efficient Sugar Beet (Beta Vulgaris L.) Variety Relieve The Symptoms of Boron Deficiency By Enhancing The Antioxidation And Boron Utilization Capacity of The Root System

(Aims) Sugar beet is one of the most sensitive crops to boron and boron deficiency inhibits the root growth and causes hollow symptoms in beets. However, how the roots of boron efficient sugar beet variety adapt to the morphology, physiological, and transcriptome mechanisms of boron deficiency are rarely reported. (Method) Thus, the present study was carried out with B efficient sugar beet variety (H, KWS1197) and B inefficient variety (L, KWS0143), and two B levels i.e., B0.1 (0.1 μM H3BO3, deficiency) and B50 (50 μM H3BO3, control) were designed for hydroponic experiment. (Result) Boron deficiency reduced the total root length, root forks, and root biomass of sugar beet. Compared with L variety, H variety have higher boron transport coefficient, boron distribution ratio above ground, peroxidase and catalase activities, lower malondialdehyde content and reactive oxygen species accumulation. Transcriptome data showed that the two comparison groups, HB0.1 vs HB50 and LB0.1 vs LB50, were enriched for 537 and 257 differentially expressed genes, respectively. The H variety mainly induced and regulated the GO term enrichment associated with antioxidant and stress resistance. On the contrary, the L variety induced cell death and negative regulation of biological and metabolic processes. (Conclusion) B efficient variety specifically up-regulated boron deficiency response genes to activate the antioxidant enzyme system, promoted rational root configuration, and enhance plant growth anti-oxidation and resistance to boron deficiency. The results of this study serve as a theoretical basis of screening candidate genes that respond to boron deficiency and adaptation mechanism of boron deficiency.

Comparing the Effects of Calcium and Magnesium Ions on Accumulation and Translocation of Cadmium in Rice

Rice is one of China's most important food crops, and it is considered the primary source of human exposure to cadmium (Cd) pollution. A hydroponic experiment was performed to investigate the effect of calcium (Ca) and magnesium (Mg) on the absorption, distribution, and translocation of Cd in rice. Under the concentration gradient of Ca, Mg, and Cd, the concentrations of Cd in rice tissues were determined. The results revealed that the existence of Ca and Mg in the environment could benefit rice growth and limit the accumulation and translocation of Cd in plants. Cd concentrations in rice plants were as orders: roots > stems > leaves ≈ panicles ≈ husks > grains. While Cd content in rice grains decreased significantly under high Ca and Mg concentrations, this pattern was not observed under low and medium concentrations. Ca2+ and Mg2+ ions significantly influenced the translocation of Cd in the environment-rice system. Under the Ca (Mg)-deficient and Ca (Mg)-rich conditions, the husk and panicle played an essential role in hindering Cd transport to the rice grain, respectively. At the same concentration, the effect of Ca on the decrease of Cd bioconcentration was greater than that of Mg. An apparent antagonism was observed between Cd and Ca (Mg) in different parts of the rice plant. Altogether, the results of this study indicate that it was possible to plant and grow rice in Cd-polluted soil and that the accumulation and translocation of Cd in rice plants could be reduced by optimizing soil nutrient elements.

Acetaminophen Induces an Antioxidative Response in Lettuce Plants

Contaminants of environmental concern, like pharmaceuticals, are being detected in increasing amounts in soils and irrigation waters and can thus be taken up by plants. In this work, the uptake of acetaminophen (ACT) by lettuce plants was evaluated through a hydroponic experiment at different concentrations (0, 0.1, 1 and 5 mg L−1 ACT). The pathways related to oxidative stress induced by ACT were studied in lettuce leaves and roots at 1, 8 and 15 days after exposure. Stress indicators such as hydrogen peroxide and malondialdehyde (MDA) contents were analyzed, revealing increases in plants contaminated with ACT in comparison to control, confirming the occurrence of oxidative stress, with the exception of MDA in leaves. The enzymatic activities of catalase, superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and glutathione peroxidase, directly involved in the antioxidative system, showed significant differences when compared to control plants, and, depending on the enzyme and the tissue, different trends were observed. Glutathione reductase revealed a decrease in contaminated leaves, which may imply a specific impact of ACT in the glutathione cycle. Significant increases were found in the anthocyanin content of leaves, both with exposure time and ACT concentration, indicating an antioxidative response induced by ACT contamination.

Antimony induced structural and ultrastructural changes in Trapa natans

Antimony (Sb) is considered as a priority toxic metalloid in the earth crust having no known biological function. The current study was carried out in a hydroponic experiment to study the accumulation of ecotoxic Sb in subcellular level, and to find out the ultrastructural damage caused by Sb in different vegetative parts of Trapa natans. Sb-induced structural and ultrastructural changes of T. natans were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). Experimental plants were exposed to different Sb(III) treatments: SbT1 (1.5 μmol/L), SbT2 (40 μmol/L) and SbT3 (60 μmol/L). Calculated bioconcentration factor (BCF) and translocation factor (TF) showed that at higher concentration (SbT2, SbT3), T. natans is a potent phytoexcluder whereas it can translocate a substantial amount of Sb to the aerial parts at lower concentration (SbT1). SEM analysis revealed Sb-mediated structural changes in the size of stomatal aperture, intercellular spaces and vascular bundles of different vegetative tissues of T. natans. TEM results showed subcellular compartmentalization of Sb in vacuole and cell wall as electron dense deposition. This is considered as a part of strategy of T. natans to detoxify the deleterious effects under Sb stress conditions. Fourier transform infrared spectroscopy (FTIR) study of plant biomass revealed possible metabolites of T. natans which can bind Sb.

Moderate Boron Concentration Beneficial for Flue-cured Tobacco Seedlings Growth and Development

Boron (B) is a micronutrient tobacco needs in minute amounts, and Boron insufficient supply can causes significant tobacco yield loss, however, the appropriate concentration for flue-cured tobacco seedlings to growth remains unknown. In this sense, a hydroponic experiment was conduct to measure the agronomic traits, dry matter mass, chlorophyll content, photosynthetic performance, antioxidant enzymes, boron ion and nicotine content of flue-cured tobacco seedlings K326 under different boron concentrations of 0.000mmol/L (B1, CK), 0.125mmol/L (B2), 0.250mmol/L (B3), 0.750mmol/L (B4), 5.000mmol/L (B5), 10.000mmol/L (B6), 20.000mmol/L (B7), 40.000mmol/L (B8) after 30 days. B significantly influenced flue-tobacco seedlings growth on agronomic traits, photosynthetic performance, the activities of antioxidant enzymes, boron ion and nicotine content aspects. B linearly enhanced the accumulation of boron ion by 24.00%~96.44%, and decreased nicotine content by 21.60%~82.03% in tobacco seedlings. Solution B concentration at 0.750 and 5.000mmol/L markedly improved tobacco seedlings maximum leaf length by 4.83%~82.03% and leaf width by 0.77%~24.36%, root weight by 13.64%~56.82%, stem weight by 12.26%~52.36%, leaf weight by 9.68%~36.56%, dry matter mass by 10.65%~38.92%, the Pn parameter by 1.22%~80.28%, the Cond paramete by 33.40%~75.86%, while decreased the activities of SOD by 10.44%~91.67%, POD by 21.32%~65.62% and CAT by 50.05%~96.44%, and MDA by 16.23%~75.16%. The B concentration concluded in this study enhanced the agronomy traits, photosynthetic and biochemical characteristics of flue-cured tobacco seedlings, which lays a scientific theoretical foundation for rational application of B in tobacco production and improve the internal quality of flue-cured tobacco.

Toxicity of chlortetracycline and oxytetracycline on Vallisneria natans (Lour.) Hare

Tetracyclines are frequently detected in water bodies due to their widespread use in aquaculture and animal husbandry. A hydroponic experiment was conducted to explore the phytotoxic effects of Vallisneria natans (Lour.) Hare exposed to various concentrations of chlortetracycline (CTC) and oxytetracycline (OTC) (0, 0.1, 1, 10, 30, 50 and 100 mg/L) for 7 days (7 D) and 14 days (14 D), respectively. The results showed that similar to OTC treatment for 7 D, the relative growth rates (RGR) and catalase (CAT) activity of V. natans , after 7 D of CTC exposure, decreased significantly at 10 mg/L and 30 mg/L, respectively. The content of soluble protein notably decreased when CTC ≥ 10mg/L and OTC ≥ 30mg/L. The hydrogen peroxide (H 2 O 2 ) content was significantly stimulated when OTC ≥ 10mg/L, while it hardly changed when exposed to CTC. After 14 D, the malondialdehyde (MDA) and H 2 O 2 contents of V. natans were significantly higher than those of the control group under high concentration of OTC (≥ 30mg/L), but they didn’t change significantly under high concentration of CTC. The activity of polyphenol oxidase (PPO), under CTC treatment after 14 D, showed first a significant increase then decrease, the maximum value (125% of the control) was notice at 10 mg/L CTC, while it remained unchanged when exposed to OTC. The soluble protein content significantly decreased at 10 mg/L CTC and 0.1 mg/L OTC, respectively. The RGR, CAT and peroxidase (POD) activities, similar to OTC treatment after 14 D, decreased evidently when CTC was 10 mg/L, 30 mg/L and 0.1 mg/L, respectively. CTC and OTC harm the chlorophyll content of V. natans after 14 D, and the reduction of chlorophyll a and carotenoid were more pronounced than chlorophyll b. The results suggest that CTC and OTC both have negative effect on the growth of V. natans , and OTC can cause oxidative damage in V. natans but CTC harm the metabolism process without inducing oxidative damage. Overall, the toxicity of OTC to V. natans is stronger than that of CTC.

Exposure to Dodecamethylcyclohexasiloxane (D6) Affects the Antioxidant Response and Gene Expression of Procambarus clarkii

Dodecamethylcyclohexasiloxane (D6) is widely used daily in the chemical industry and exists in the environment; however, its eco-toxicity is not well documented. A hydroponic experiment was performed to investigate the effects of D6 exposure (10–1000 mg L−1) on oxidative stress induction and gene expression changes in crayfish (Procambarus clarkii). The results showed that superoxide dismutase (SOD) activity was enhanced by 20–32% at low D6 exposure (10 mg L−1) in muscle but reduced in gill tissue at high D6 exposure (1000 mg L−1). High D6 (1000 mg L−1) also increased catalase (CAT) and peroxidase (POD) activities in muscle tissue by 14–37% and 14–45%, respectively, and the same trend was observed in the carapace and gill tissue of crayfish. The Malondialdehyde (MDA), ascorbate (AsA), and glutathione (GSH) contents were increased by 16–31%, 19–31%, and 21–28% in the muscle of crayfish under D6 exposure. Additionally, silicon (Si) content increased in three organs (gill, carapace, and muscle) of crayfish. Related genes involved in enzyme and nonenzyme activities were detected, and when crayfish was exposed to D6, genes such as Sod3, Cat3, Pod3, and Gsh3 were up-regulated, while Asa3 and Oxido3 were significantly down-regulated in the muscle. The research results help us to understand the toxicity of D6 in crayfish and provide a basis for further research on the mechanism of D6-induced stress in crayfish and other aquatic organisms.