Molybdenum inhibited the growth of Phytophthora nicotiana and improved the resistance of Nicotiana tabacum L. against tobacco black shank.

Tobacco black shank (TBS) is a soil-borne fungal disease caused by Phytophthora nicotiana (P. nicotianae), significantly impeding the production of high-quality tobacco. Molybdenum (Mo), a crucial trace element for both plants and animals, plays a vital role in promoting plant growth, enhancing photosynthesis, bolstering antioxidant capacity, and maintaining ultrastructural integrity. However, the positive effect of Mo on plant biotic stress is little understood. This study delves into the inhibitory effects of Mo on P. nicotianae and seeks to unravel the underlying mechanisms. The results showed that 16.32 mg/L of Mo significantly inhibited mycelial growth, altered mycelial morphological structure, damaged mycelial cell membrane, and ultimately led to the leakage of cell inclusions. In addition, 0.6 mg/kg Mo applied in soil significantly reduced the severity of TBS. Mo increased photosynthetic parameters and photosynthetic pigment contents of tobacco leaves, upregulated expression of NtPAL and NtPPO resistance genes, as well as improved activities of SOD, POD, CAT, PPO, and PAL in tobacco plants. Furthermore, Mo could regulate nitrogen metabolism and amino acids metabolism to protect tobacco plants against P. nicotianae infection. These findings not only present an ecologically sound approach to control TBS but also contribute valuable insights to the broader exploration of the role of microelements in plant disease management.

Selenium Modulates the Level of Auxin to Alleviate the Toxicity of Cadmium in Tobacco.

Cadmium (Cd) is an environmental pollutant that potentially threatens human health worldwide. Developing approaches for efficiently treating environmental Cd is a priority. Selenium (Se) plays important role in the protection of plants against various abiotic stresses, including heavy metals. Previous research has shown that Se can alleviate Cd toxicity, but the molecular mechanism is still not clear. In this study, we explore the function of auxin and phosphate (P) in tobacco (Nicotiana tabacum), with particular focus on their interaction with Se and Cd. Under Cd stress conditions, low Se (10 µM) significantly increased the biomass and antioxidant capacity of tobacco plants and reduced uptake of Cd. We also measured the auxin concentration and expression of auxin-relative genes in tobacco and found that plants treated with low Se (10 µM) had higher auxin concentrations at different Cd supply levels (0 µM, 20 µM, 50 µM) compared with no Se treatment, probably due to increased expression of auxin synthesis genes and auxin efflux carriers. Overexpression of a high affinity phosphate transporter NtPT2 enhanced the tolerance of tobacco to Cd stress, possibly by increasing the total P and Se content and decreasing Cd accumulation compared to that in the wild type (WT). Our results show that there is an interactive mechanism among P, Se, Cd, and auxin that affects plant growth and may provide a new approach for relieving Cd toxicity in plants.

OsPht1;8, a phosphate transporter, is involved in auxin and phosphate starvation response in rice.

The responses of plants to auxin and phosphate (Pi) starvation are closely linked. However, the underlying mechanisms connecting the Pi starvation (-Pi) responses to auxin are largely unclear. Here, we show that OsPht1;8 (OsPT8), a phosphate transporter, functions in both the auxin and -Pi responses in rice (Oryza sativa L.) and tobacco (Nicotiana tabacum). The overexpression of OsPT8 (OsPT8-Oe) led to the loss of sensitivity to auxin and -Pi in adventitious roots, lateral roots, and root hairs in rice. The expression levels of OsPT8 and pOsPT8::GUS staining in roots, root-shoot junctions and leaves of rice were induced by IAA treatments. The number of young lateral roots in the OsPT8-Oe transgenic rice, which had higher auxin concentrations, was distinctly more than that in the wild-type, possibly as a result of increased expression of auxin-related genes under normal Pi condition. Moreover, tobacco overexpressing OsPT8 had a similar root phenotype to OsPT8-Oe rice. These data reveal a novel biological function of OsPT8 in the cross-talk between Pi and auxin signaling, and provide new evidence for the linkage between auxin and -Pi responses.

NtARF11 positively regulates cadmium tolerance in tobacco by inhibiting expression of the nitrate transporter NtNRT1.1.

Heavy metal cadmium (Cd) is widespread in contaminated soil and an important factor limiting plant growth. NO3- (nitrate) affects Cd uptake and thus changes Cd tolerance in plants; however, the underlying molecular regulatory mechanisms have not yet been elucidated. Here, we analyzed a novel gene, NtARF11 (auxin response factor), which regulates Cd tolerance in tobacco via the NO3- uptake pathway, through experiments with NtARF11-knockout and NtARF11-overexpression transgenic tobacco lines. NtARF11 was highly expressed under Cd stress in tobacco plants. Under Cd stress, overexpression of NtARF11 enhanced Cd tolerance in tobacco compared to that in wild-type tobacco, as shown by the low Cd concentration, high chlorophyll concentration, and low accumulation of reactive oxygen species in NtARF11-overexpressing tobacco. Moreover, low NO3- concentrations were observed in NtARF11-overexpressing tobacco plants. Further analyses revealed direct binding of NtARF11 to the promoter of the nitrate transporter NtNRT1.1, thereby negatively regulating its expression in tobacco. Notably, NtNRT1.1 knockout reduced NO3- uptake, which resulted in low Cd concentrations in tobacco. Altogether, these results demonstrate that the NtARF11-NtNRT1.1 module functions as a positive regulator of Cd tolerance by reducing the Cd uptake in tobacco, providing new insights for improving Cd tolerance of plants through genetic engineering.

Comparison of selenite and selenate in alleviation of drought stress in Nicotiana tabacum L.

Exogenous selenium (Se) improves the tolerance of plants to abiotic stress. However, the effects and mechanisms of different Se species on drought stress alleviation are poorly understood. This study aims to evaluate and compare the different effects and mechanisms of sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) on the growth, photosynthesis, antioxidant system, osmotic substances and stress-responsive gene expression of Nicotiana tabacum L. under drought stress. The results revealed that drought stress could significantly inhibit growth, whereas both Na2SeO4 and Na2SeO3 could significantly facilitate the growth of N. tabacum under drought stress. However, compared to Na2SeO3, Se application as Na2SeO4 induced a significant increase in the root tip number and number of bifurcations under drought stress. Furthermore, both Na2SeO4 and Na2SeO3 displayed higher levels of photosynthetic pigments, better photosynthesis, and higher concentrations of osmotic substances, antioxidant enzymes, and stress-responsive gene (NtCDPK2, NtP5CS, NtAREB and NtLEA5) expression than drought stress alone. However, the application of Na2SeO4 showed higher expression levels of the NtP5CS and NtAREB genes than Na2SeO3. Both Na2SeO4 and Na2SeO3 alleviated many of the deleterious effects of drought in leaves, which was achieved by reducing stress-induced lipid peroxidation (MDA) and H2O2 content by enhancing the activity of antioxidant enzymes, while Na2SeO4 application showed lower H2O2 and MDA content than Na2SeO3 application. Overall, the results confirm the positive effects of Se application, especially Na2SeO4 application, which is markedly superior to Na2SeO3 in the role of resistance towards abiotic stress in N. tabacum.

Identification of engine oil-derived ash nanoparticles and ash formation process for a gasoline direct-injection engine.

Engine oil-derived ash particles emitted from internal combustion (IC) engines are unwanted by-products, after oil is involved in in-cylinder combustion process. Since they typically come out together with particulate emissions, no detail has been reported about their early-stage particles other than agglomerated particles loaded on aftertreatment catalysts and filters. To better understand ash formation process during the combustion process, differently formulated engine oils were dosed into a fuel system of a gasoline direct injection (GDI) engine that produces low soot mass emissions at normal operating conditions to increase the chances to find stand-alone ash particles separated from soot aggregates in the sub-20-nm size range. In addition to them, ash/soot aggregates in the larger size range were examined using scanning transmission electron microscopy (STEM)-X-ray electron dispersive spectroscopy (XEDS) to present elemental information at different sizes of particles from various oil formulations. The STEM-XEDS results showed that regardless of formulated oil type and particle size, Ca, P and C were always contained, while Zn was occasionally found on relatively large particles, suggesting that these elements get together from an early stage of particle formation. The S, Ca and P K-edge X-ray absorption near edge structure (XANES) analyses were performed for bulk soot containing raw ash. The linear combination approach & cross-checking among XANES results proposed that Ca5(OH)(PO4)2, Ca3(PO4)2 and Zn3(PO4)2 are potentially major chemical compounds in raw ash particles, when combined with the STEM-XEDS results. Despite many reports that CaSO4 is a major ash chemical when ash found in DPF/GFP systems was examined, it was observed to be rarely present in raw ashes using the S K-edge XANES analysis, suggesting ash transformation.

Metagenomic insights into effects of wheat straw compost fertiliser application on microbial community composition and function in tobacco rhizosphere soil.

The application of fertilisers incorporated with plant residues improves nutrient availability in soils, which shifts the microbial community structure and favours plant growth. To understand the impact of wheat straw compost fertiliser on soil properties and microbial community structure, tobacco planting soils were treated with four different fertilisers using varied amounts of straw compost fertiliser and a no fertiliser control (CK). Results showed that different fertilisers affected available soil nutrient contents differently. Treatment of tobacco soil with application of combined chemical fertiliser/wheat straw compost led to improved soil chemical properties, and increased soil organic matter and available phosphorus and potassium content. Treatment with FT1 200 kg/mu straw was found to be superior in improving soil fertility. Metagenomic DNA sequencing revealed that different fertiliser treatments resulted in changes in the microbial community composition. In soil treated with FT2 300 kg/mu straw for 60 days, the predominant bacterial phyla were Proteobacteria, Actinobacteria, and Verrucomicrobia, whereas Cyanobacteria, Basidiomycota, and Chlorophyta were found in high abundance in soil samples treated with FT1 200 kg/mu straw for 30 days. Functional annotation of metagenomic sequences revealed that genes involved in metabolic pathways were among the most abundant type. PCoA analysis clearly separated the samples containing straw compost fertiliser and chemical fertiliser. A significant correlation between soil properties and the dominant phyla was identified.

Soft material with intense photoluminescence obtained by dissolving Eu2O3 and organic ligand into a task-specific ionic liquid.

A task-specific ionic liquid containing a carboxylate group with the ability to dissolve metal oxide and organic ligands has been used as the solvent to prepare lanthanide complexes without the addition of extra solvent; thus a soft material with intense photoluminescence has been obtained by directly dissolving Eu(2)O(3), 2-thenoyltrifluoroacetone (TTA) and 1,10-phenanthroline (Phen) into the task-specific ionic liquid.

Influence of high-carbon basal fertiliser on the structure and composition of a soil microbial community under tobacco cultivation.

Soil microorganisms play a crucial role in cycling soil nutrients and providing organic nutrients for plant growth and development. Fertilisation balances soil fertility and quality, and affects soil microbial communities. Fertilisation is a frontier subject in agricultural and environmental sciences. Here we showed that the application of high-carbon basal fertiliser treatment could improve the tobacco yield and quality when compared to chemical fertiliser, high-carbon basal fertiliser and mixed high-carbon chemical fertiliser. The potential reason is that different fertiliser treatments influence soil fertility, such as nitrogen, phosphorus, and other contents, besides soil organic matter. Further experiments revealed that populations of bacteria, fungi and actinomycetes fluctuated during tobacco development under different fertilisation treatments. Then we performed high-throughput sequencing of the 16S rRNA gene, and the results showed that the fertilisation treatments had significant effects on the microbial community, particularly within the finer taxonomic divisions or non-dominant taxa. Moreover, proteobacteria and fungal genera had significantly different relative abundances during tobacco growth under various tobacco developmental stages and fertilisation treatments. These results indicated that mixed high-carbon chemical fertiliser could improve soil fertility by influencing the soil microorganism, and that the fertilisation treatments impacted on the structure and composition of the microbial community, and especially the diversity of non-dominant taxa. However, more studies are needed to confirm their reliability.

Rheological properties of concentrated aqueous injectable calcium phosphate cement slurry.

In this paper, the steady and dynamic rheological properties of concentrated aqueous injectable calcium phosphate cement (CPC) slurry were investigated. The results indicate that the concentrated aqueous injectable CPC showed both plastic and thixotropic behavior. As the setting process progressed, the yield stress of CPC slurry was raised, the area of the thixotropic hysteresis loop was enlarged, indicating that the strength of the net structure of the slurry had increased. The results of dynamic rheological behavior indicate that the slurry presented the structure similar to viscoelastic body and the property of shear thinning at the beginning. During the setting process, the slurry was transformed from a flocculent structure to a net structure, and the strength increased. Different factors had diverse effects on the rheological properties of the CPC slurry in the setting process, a reflection of the flowing properties (or injection), and the microstructure development of this concentrated suspension. Raising the powder-to-liquid ratio decreased the distance among the particles, increased the initial strength, and shortened the setting time. In addition, raising the temperature improved the initial strength, increased the order of reaction, and shortened the setting time, which was favorable to the setting process. The particle size of the raw material had much to do with the strength of original structure and setting time. The storage module G' of CPC slurry during the setting process followed the rule of power law function G'=A exp(Bt), which could be applied to forecast the setting time, and the calculated results thereafter are in agreement with the experimental data.

Effects of the granularity of raw materials on the hydration and hardening process of calcium phosphate cement.

Effects of the granularity of the raw materials on the hydration and hardening process of calcium phosphate cement (CPC) composed of equimolar tetracalcium phosphate (TECP) and dicalcium phosphate anhydrous (DCPA) were investigated systematically. The variation of pH value in CPC slurry indicated that the control step of CPC hydration was the dissolution of DCPA under these experimental conditions. Reducing the particle size of DCPA could accelerate the hydration rate, and decreasing the particle size of TECP would expedite the dissolution of DCPA, which would obviously result in a faster hydration rate. The results of isothermal conduction calorimetry showed that reducing the particle size of TECP could increase the conversion ratio of starting materials to hydration products, which would lead to an increase in the compressive strength of the hardened body of CPC. The sample composed of the smallest particle size of DCPA and TECP obtained the compressive strength of 41 MPa, which would not attain the highest compressive strength, 49 MPa. The smaller the particle size of either DCPA or TECP, the shorter the setting time was. During the setting process of CPC, the microstructure progresses from a gel structure to an agglomeration-crystallization structure. The calculated values of setting time from the rheological model coincided with the experimental data very well. The parameters of AC impedance spectroscopy were closely correlated with the mean pore diameter and porosity of the CPC hardened body. The results of AC impedance spectroscopy further verified that a small particle size of raw materials could result in high hydration rate and the compressive strength of 49.1 MPa.