Response of Roses (Rosa hybrida L. 'Herbert Stevens') to Foliar Application of Polyamines on Root Development, Flowering, Photosynthetic Pigments, Antioxidant Enzymes Activity and NPK

Exogenous protectants alleviate ozone stress in Trifolium repens: Impacts on plant growth and endophytic fungi

Industrialization-driven surface ozone (O3) pollution significantly impairs plant growth. This study evaluates the effectiveness of exogenous protectants [3 mg L⁻1 abscisic acid (ABA), 400 mg L⁻1 ethylenediurea (EDU), and 80 mg L⁻1 spermidine (Spd)] on Trifolium repens subjected to O3 stress in open-top chambers, focusing on plant growth and dynamics of culturable endophytic fungal communities. Results indicate that O3 exposure adversely affects photosynthesis, reducing root biomass and altering root structure, which further impacts the ability of plant to absorb essential nutrients such as potassium (K), magnesium (Mg), and zinc (Zn). Conversely, the application of ABA, EDU, and Spd significantly enhanced total biomass and chlorophyll content in T. repens. Specifically, ABA and Spd significantly improved root length, root surface area, and root volume, while EDU effectively reduced leaves' malondialdehyde levels, indicating decreased oxidative stress. Moreover, ABA and Spd treatments significantly increased leaf endophytic fungal diversity, while root fungal abundance declined. The relative abundance of Alternaria in leaves was substantially reduced by these treatments, which correlated with enhanced chlorophyll content and photosynthesis. Concurrently, EDU and Spd treatments increased the abundance of Plectosphaerella, enhance the absorption of K, Ca, and Mg. In roots, ABA treatment increased the abundance of Paecilomyces, while Spd treatment enhanced the presence of Stemphylium, linked to improved nitrogen (N), phosphorus (P), and K uptake. These findings suggest that specific symbiotic fungi mitigate O3-induced stress by enhancing nutrient absorption, promoting growth. This study highlights the potential of exogenous protectants to enhance plant resilience against O3 pollution through modulating interactions with endophytic fungal communities.

The influence of spermidine on the build-up of fucoxanthin in Isochrysis sp. Acclimated to varying light intensities

Spermidine is a type of important growth regulator, which involved in the biosynthesis of photosynthetic pigments, and has the function of promoting cell proliferation. In this study, Isochrysis sp. was selected as the research object to explore the effects of spermidine supplementation on the growth of algal cells and fucoxanthin synthesis under different light intensities. The results showed that the cell density (5.40 × 106 cells/mL) of algae were the highest at 11 days under the light intensity of 200 μmol·m-2·s-1 and spermidine content of 150 μM. The contents of diadinoxanthin (1.09 mg/g) and fucoxanthin (6.11 mg/g) were the highest when spermidine was added under low light intensity, and the growth of algal cells and fucoxanthin metabolism were the most significant. In the carotenoid synthesis pathway, PDS (phytoene desaturase) was up-regulated by 1.96 times and VDE (violaxanthin de-epoxidase) was down-regulated by 0.95 times, which may promote fucoxanthin accumulation.

Two polyamines -responsive WRKY transcription factors from Anoectochilus roxburghii play opposite functions on flower development

Anoectochilus roxburghii is a rare and precious plant with medicinal and healthcare functions. Embryo abortion caused the lack of resources. Polyamine promoted its flowering and stress resistance in our previous study. But the mechanism remains unclear. The WRKY transcription factor family has been linked to a variety of biological processes in plants. In this study, two WRKY TFs (ArWRKY5 and ArWRKY20) of A. roxburghii, which showed significant response to Spd treatment, were identified and functionally analyzed. Tissue specific expression analyzation showed both of them mostly present in the flower. And ArWRKY5 expressed highest in the flower bud stage (-1 Flowering), while ArWRKY20 showed the highest expression in earlier flower bud stage (-2 Flowering) and the expression gradually decreased with flowering. The transcriptional activation activity assay and subcellular localization revealed that ArWRKY5 and ArWRKY20 were located in the nucleus and ArWRKY20 showed transcriptional activity. The heterologous expression of ArWRKY5 in Arabidopsis thaliana showed earlier flowering, while overexpression of ArWRKY20 delayed flowering. But the OE-ArWRKY20 lines had a robust body shape and a very significant increase in the number of rosette leaves. Furthermore, stamens and seed development were positively regulated by these two ArWRKYs. These results indicated that ArWRKY5 and ArWRKY20 not only play opposite roles in the floral development, but also regulate the plant growth and seed development in A. thaliana. But their specific biological functions and mechanism in A. roxburghii need to be investigated further.

Developmental and phytochemical changes in pot marigold (Calendula officinalis L.) using exogenous application of polyamines

Polyamines (PAs) are natural active compounds having more than two amino groups that play important roles in many physiological and developmental processes in plants. The purpose of this research was to see how foliar polyamine spray affected growth and photosynthetic indices, as well as secondary metabolites and antioxidant activity of the aqueous and methanolic extracts of pot marigold (Calendula officinalis L.). The experiment lasted for three months and was arranged in a randomized complete design with four replications. Three separate concentrations (0.5, 1 and 2.5 mM) of spermine (SPM), spermidine (SPD), and putrescine (PUT) were sprayed at four/five fully expanded leaf stage and some physiochemical attributes were evaluated. The treatments caused a significant increase in morphological and photosynthetic parameters and total oil. There were also significant variations in total phenolic and flavonoid content. Compared to other polyamines, 1 mM SPD foliar spraying showed the greatest effect. Furthermore, the highest antioxidant capacity (DPPH* scavenging assay, ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC) and β-carotene bleaching activity) was observed in the 1 mM SPD treatment. The results showed that the calendula essential oils (EOs) were rich in sesquiterpenes hydrocarbons (55.92-95.94%), with c-Cadinene and d-Cadinene as the major sesquiterpenes in the EOs. Also, the flowers were rich sources of carotenoids (lutein, flavoxanthin and luteoxanthin) following polyamines application. Hence, it can be inferred that polyamines specially spermidine would find a wide range of application in pharmaceutical industries due to its impact on antioxidant properties of phenolic and flavonoid compounds.

Tilapia Skin Peptides Ameliorate Cyclophosphamide-Induced Anxiety- and Depression-Like Behavior via Improving Oxidative Stress, Neuroinflammation, Neuron Apoptosis, and Neurogenesis in Mice

Anxiety- and depression-like behavior following chemotherapy treatment occurs in cancer patients with high probability and no specific therapeutics are available for treatment and prevention of this complication. Here, tilapia skin peptides (TSP), a novel enzymatically hydrolyzed bioactive peptide mixture, obtained from tilapia (Oreochromis mossambicus) scraps, were studied on cyclophosphamide (CP)-induced anxiety- and depression-like behavior in mice. Mice were received intraperitoneal injection of CP for 2 weeks, while TSP was administered for 4 weeks. After the end of the animal experiment, behavioral, biochemical, and molecular tests were carried out. The mice decreased preference for sugar water, increased immobility time in the forced swimming and tail suspension test, and decreased travel distance in the open field test in the Model group, compared with the Control group. Abnormal changes in behavioral tests were significantly improved after the TSP treatment. Additionally, abnormalities on superoxide dismutase, malondialdehyde, glutathione peroxidase were rescued by administration of 1000 mg/kg/d TSP in mice than that of the Model group. TSP has normalized the expression of Iba-1 and the levels of TNF-α and IL-1β in the hippocampus of mice, which indicated that TSP could observably ameliorate neuroinflammatory response in the hippocampus of mice. TSP ameliorated the apoptosis of hippocampal neurons of CA1 and CA3 regions in the TSP group vs. the Model group. The number of doublecortin positive cells was drastically increased by administering 1000 mg/kg/d TSP in mice vs. the Model group. Furthermore, TSP reversed the Nrf2/HO-1 signaling pathway, BDNF/TrkB/CREB signaling pathway, and reduced the Bcl-2/Bax/caspase-3 apoptosis pathway. In conclusion, TSP could restore CP-induced anxiety- and depression-like behavior via improving oxidative stress, neuroinflammation, neuron apoptosis, and neurogenesis in mice hippocampus.

Putrescine: A Key Metabolite Involved in Plant Development, Tolerance and Resistance Responses to Stress

Putrescine (Put) is the starting point of the polyamines (PAs) pathway and the most common PA in higher plants. It is synthesized by two main pathways (from ornithine and arginine), but recently a third pathway from citrulline was reported in sesame plants. There is strong evidence that Put may play a crucial role not only in plant growth and development but also in the tolerance responses to the major stresses affecting crop production. The main strategies to investigate the involvement of PA in plant systems are based on the application of competitive inhibitors, exogenous PAs treatments, and the most efficient approaches based on mutant and transgenic plants. Thus, in this article, the recent advances in understanding the role of this metabolite in plant growth promotion and protection against abiotic and biotic stresses will be discussed to provide an overview for future research.

Boosting Polyamines to Enhance Shoot Regeneration in Potato (Solanum tuberosum L.) Using AgNO3

Advancements in shoot regeneration systems support biotechnology-based tools used in the genetic improvement of plant crops. This study aims to enhance shoot regeneration in potatoes by boosting polyamine content by adding AgNO3 to the shoot regeneration medium (MS medium supplemented with 30 g L−1 sucrose, 100 mg L−1 myoinositol, and 2.25 BA mg L−1). Five concentrations of AgNO3 (2, 4, 6, 8, and 10 mg L−1) were used in addition to a control. The effect of AgNO3 on regeneration assumed a more or less concentration-dependent bell-shaped curve peaking at 4 mg L−1. Enhancements in shoot regeneration were attributed to the known role of AgNO3 as an ethylene action blocker in addition to improvements in polyamine accumulation without an increase in H2O2 content, lipid peroxidation, or DNA damage. The uncoupling of shoot regeneration and polyamine content recorded at high AgNO3 concentrations can be attributed to the consumption of polyamines to counteract the synchronized oxidative stress manifested by increases in H2O2 content, lipid peroxidation, and DNA damage.

Flavonoids Modulate the Accumulation of Toxins From Aspergillus flavus in Maize Kernels

Aspergillus flavus is an opportunistic fungal pathogen capable of producing aflatoxins, potent carcinogenic toxins that accumulate in maize kernels after infection. To better understand the molecular mechanisms of maize resistance to A. flavus growth and aflatoxin accumulation, we performed a high-throughput transcriptomic study in situ using maize kernels infected with A. flavus strain 3357. Three maize lines were evaluated: aflatoxin-contamination resistant line TZAR102, semi-resistant MI82, and susceptible line Va35. A modified genotype-environment association method (GEA) used to detect loci under selection via redundancy analysis (RDA) was used with the transcriptomic data to detect genes significantly influenced by maize line, fungal treatment, and duration of infection. Gene ontology enrichment analysis of genes highly expressed in infected kernels identified molecular pathways associated with defense responses to fungi and other microbes such as production of pathogenesis-related (PR) proteins and lipid bilayer formation. To further identify novel genes of interest, we incorporated genomic and phenotypic field data from a genome wide association analysis with gene expression data, allowing us to detect significantly expressed quantitative trait loci (eQTL). These results identified significant association between flavonoid biosynthetic pathway genes and infection by A. flavus. In planta fungal infections showed that the resistant line, TZAR102, has a higher fold increase of the metabolites naringenin and luteolin than the susceptible line, Va35, when comparing untreated and fungal infected plants. These results suggest flavonoids contribute to plant resistance mechanisms against aflatoxin contamination through modulation of toxin accumulation in maize kernels.

Foliar Application of Polyamines Modulates Winter Oilseed Rape Responses to Increasing Cold

Cold stress is one of the most common abiotic stresses experienced by plants and is caused by low temperature extremes and variations. Polyamines (PAs) have been reported to contribute in abiotic stress defense processes in plants. The present study investigates the survival and responses of PA-treated non-acclimated (N) and acclimated (A) winter oilseed rape to increasing cold conditions. The study was conducted under controlled conditions. Seedlings were foliarly sprayed with spermidine (Spd), spermine (Spm), and putrescine (Put) solutions (1 mM) and exposed to four days of cold acclimation (4 °C) and two days of increasing cold (from −1 to −3 °C). Two cultivars with different cold tolerance were used in this study. The recorded traits included the percentage of survival, H⁺-ATPase activity, proline accumulation, and ethylene emission. Exogenous PA application improved cold resistance, maintained the activity of plasma membrane H⁺-ATPase, increased content of free proline, and delayed stimulation of ethylene emission under increasing cold. The results of the current study on winter oilseed rape revealed that foliar application of PAs may activate a defensive response (act as elicitor to trigger physiological processes), which may compensate the negative impact of cold stress. Thus, cold tolerance of winter oilseed rape can be enhanced by PA treatment.