Biochemical and pharmaceutical traits of Marrubium vulgare L. plants treated with plant growth-promoting bacteria and elevated CO2.

The present research aimed to understand the influence of plant growth-promoting bacteria (PGPB) on various biochemical, nutritional, and pharmaceutical characteristics of Marrubium vulgare plants grown under elevated carbon dioxide (eCO2). To achieve this objective, a pot experiment was carried out, consisting of two treatments, namely: (i) biofertilization (Bf) by a PGPB strain (Micromonospora sp.) and (ii) two different air CO2 levels, including ambient CO2 (aCO2) and eCO2 concentrations (410 and 710 µmol CO2 mol-1, respectively). The improvement in the photosynthesis rate of eCO2 and Bf-treated plants can explain the increase in the production of carbohydrate. This is evidenced by a substantial rise, reaching up to + 75% and 25% in the total sugar and starch content in plants subjected to eCO2 treatment, respectively. Additionally, eCO2-treated plants exhibited a remarkable 102% increase in soluble sugar synthesis, while plants subjected to Bf treatment showed a notable increase of 66%. Such modifications could be the main factor affecting plants carbon and nitrogen metabolism. Although the level of certain amino acids (such as glycine, tyrosine, and phenylalanine) in plants exhibited significant increases in response to eCO2 and Bf, the levels of other amino acids demonstrated enhancements in plants grown under eCO2 (e.g., histidine) or under treatments containing Bf (e.g., alanine and ornithine). Improvements in primary metabolites led to more benefits in plants treated with Bf and CO2 by boosting secondary metabolites accumulation, including phenolics (+ 27-100%), flavonoids (+ 30-92%), and essential oils (up to + 296%), as well as improved antioxidant capacity (FRAP). This remarkable effectiveness was evident in the significant increase in the biomass production, highlighting the synergistic impact of the treatments. Therefore, the interaction of Bf and eCO2 not only induced plant biomass accumulation but also improved the nutritional and pharmaceutical value of M. vulgare plants.

Elevated CO2 reduced antimony toxicity in wheat plants by improving photosynthesis, soil microbial content, minerals, and redox status.

Introduction: Antimony (Sb), a common rare heavy metal, is naturally present in soils at low concentrations. However, it is increasingly used in industrial applications, which in turn, leads to an increased release into the environment, exerting a detrimental impact on plant growth. Thus, it is important to study Sb effects on plants under the current and future CO2 (eCO2). Methods: To this end, high Sb concentrations (1500 mg/kg soil) effects under ambient (420 ppm) and eCO2 (710 ppm) on wheat growth, physiology (photosynthesis reactions) and biochemistry (minerals contents, redox state), were studied and soil microbial were evaluated. Results and discussion: Our results showed that Sb uptake significantly decreased wheat growth by 42%. This reduction could be explained by the inhibition in photosynthesis rate, Rubisco activity, and photosynthetic pigments (Cha and Chb), by 35%, 44%, and 51%, respectively. Sb significantly reduced total bacterial and fungal count and increased phenolic and organic acids levels in the soil to decrease Sb uptake. Moreover, it induced oxidative markers, as indicated by the increased levels of H2O2 and MDA (1.96 and 2.8-fold compared to the control condition, respectively). To reduce this damage, antioxidant capacity (TAC), CAT, POX, and SOD enzymes activity were increased by 1.61, 2.2, 2.87, and 1.86-fold, respectively. In contrast, eCO2 mitigated growth inhibition in Sb-treated wheat. eCO2 and Sb coapplication mitigated the Sb harmful effect on growth by reducing Sb uptake and improving photosynthesis and Rubisco enzyme activity by 0.58, 1.57, and 1.4-fold compared to the corresponding Sb treatments, respectively. To reduce Sb uptake and improve mineral availability for plants, a high accumulation of phenolics level and organic acids in the soil was observed. eCO2 reduces Sb-induced oxidative damage by improving redox status. In conclusion, our study has provided valuable insights into the physiological and biochemical bases underlie the Sb-stress mitigating of eCO2 conditions. Furthermore, this is important step to define strategies to prevent its adverse effects of Sb on plants in the future.

Arbuscular mycorrhizal fungi as an effective approach to enhance the growth and metabolism of soybean plants under thallium (TI) toxicity.

Thallium (TI) is a toxic metal that can trigger harmful impacts on growth and metabolism of plants. Utilizing arbuscular mycorrhizal fungi (AMF) proves to be an effective strategy for alleviating heavy metal toxicity in plants. To this end, AMF were applied to mitigate TI toxic effects on the growth, primary and secondary metabolism of soybean plants. Here, TI stress inhibited the growth and photosynthetic parameters of soybean plants. It also increased the oxidative damage as demonstrated by increased levels of oxidative markers, (MDA and lipoxygenase (LOX) activity). However, AMF could mitigate the reduction in growth and photosynthesis induced by TI, as well as the induction of oxidative damage. To overcome TI toxicity, AMF increased the levels and metabolism of osmolytes such as proline in soybean plants. This was in line with the increased activities of key enzymes that involved in proline biosynthesis (e.g., P5CS (pyrroline-5-carboxylate synthetase), P5CR (pyrroline-5-carboxylate reductase) and OAT (ornithine aminotransferase) under the AMF and/or TI treatments. Furthermore, soybean plants could benefit from the synergism between AMF and TI to enhance the contents of individual (e.g., spermine and spermidine) and total polyamines as well as their metabolic enzymes (e.g., arginine decarboxylase and ornithine decarboxylase). Overall, the combined application of AMF emerges as a viable approach for alleviating TI toxicity in soybean plants.

Synergistic Impacts of Plant-Growth-Promoting Bacteria and Selenium Nanoparticles on Improving the Nutritional Value and Biological Activities of Three Cultivars of Brassica Sprouts.

Due to the growing world population and increasing environmental stress, improving the production, nutritional quality, and pharmaceutical applications of plants have become an urgent need. Therefore, current research was designed to investigate the impact of seed priming using plant-growth-promoting bacteria (PGPB) along with selenium nanoparticles (SeNPs) treatment on chemical and biological properties of three Brassica oleracea cultivars [Southern star (VA1), Prominence (VA2), Monotop (VA3)]. With this aim, one out of five morphologically different strains of bacteria, namely, JM18, which was further identified via 16S rRNA gene sequencing as a Nocardiopsis species with strong plant-growth-promoting traits, isolated from soil, was used. To explore the growth-promoting potential of Nocardiopsis species, seeds of three varieties of B. oleracea were primed with JM18 individually or in combination with SeNP treatment. Seed treatments increased sprout growth (fresh and dry weights) and glucosinolate accumulation. The activity of myrosinase was significantly increased through brassica sprouts and consequently enhanced the amino-acid-derived glucosinolate induction. Notably, a reduction in effective sulforaphane nitrile was detected, being positively correlated with a decrease in epithiospecifier protein (EP). Consequently, the antioxidant activities of VA2 and VA3, determined by the ferric reducing antioxidant power (FRAP) assay, were increased by 74 and 79%, respectively. Additionally, the antibacterial activities of JM18-treated cultivars were improved. However, a decrease was observed in SeNP- and JM18 + SeNP-treated VA2 and VA3 against Serratia marcescens and Candida glabrata and VA1 against S. marcescens. In conclusion, seed priming with the JM18 extract is a promising method to enhance the health-promoting activities of B. oleracea sprouts.

Potential use of a novel actinobacterial species to ameliorate tungsten nanoparticles induced oxidative damage in cereal crops.

Tungsten nanoparticles (WNPs) could induce hazard impact on plant growth and development; however, no study investigated their phytotoxicity. On the other hand, plant growth-promoting bacteria (PGPB) can effectively reduce WNPs toxicity. To this end, Nocardiopsis sp. was isolated and employed to mitigate the phytotoxic effect of WNPs on three crops (wheat, barley, and oat). Soil contamination with WPNs induced the W accumulation in all tested crops, inhibited both growth and photosynthesis and induced oxidative damage. On the other hand, pre-inoculation with Nocardiopsis sp. significantly reduced W level in treated plants. Concomitantly, Nocardiopsis sp. strikingly mitigated the inhibitory effect of WNPs by augmenting both growth and reactive oxygen species (ROS) homeostasis. To cope with heavy metal stress, all the tested species orchestrated their antioxidant homeostasis through enhancing the production of antioxidant metabolites (e.g., phenolics, flavonoids and tocopherols) and elevated the activities of ROS-scavenging enzymes (e.g., APX, POX, CAT, as well as the enzymes involved in AsA/GSH cycle). Moreover, pre-inoculation with Nocardiopsis sp. improved the detoxification metabolism by enhancing the accumulation of phytochelatins (PCs), metallothionein (MTC) and glutathione-S-transferase (GST) in grasses grown in WNPs-contaminated soils. Overall, restrained ROS homeostasis and improved WNPs detoxification systems were the bases underlie the WNPs stress mitigating impact of Nocardiopsis sp treatment.

Protective Effect of Kaempferol on the Transgenic Drosophila Model of Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) is characterized by the accumulation and deposition of ß-amyloid peptides leading to a progressive neuronal damage and cell loss. Besides several hypotheses for explaining the neurodegenerative mechanisms, oxidative stress has been considered to be one of them. Till date, there is no cure for AD, but the pathogenesis of the disease could be delayed by the use of natural antioxidants. In this context, we decided to study the effect of kaempferol against the transgenic Drosophila expressing human amyloid beta-42. METHOD: The AD flies were allowed to feed on the diet having 10, 20, 30 and 40µM of kaempferol for 30 days. After 30 days of exposure, the amyloid beta flies were studied for their climbing ability and Aversive Phototaxis Suppression assay. Amyloid beta flies head homogenate was prepared for estimating the oxidative stress markers, Caspase and acetylcholinesterase activity. RESULTS: The results of the present study reveal that the exposure of AD flies to kaempferol delayed the loss of climbing ability, memory, reduced the oxidative stress and acetylcholinesterase activity. CONCLUSION: Kaempferol could be used as a possible therapeutic agent against the progression of the Alzheimer's disease.