Polyamine Accumulation Research Articles

Physiological and biomolecular interventions in the bio-decolorization of Methylene blue dye by Salvinia molesta D. Mitch

Methylene blue, a cationic dye as a pollutant is discharged from industrial effluent into aquatic bodies. The dye is biomagnified through the food chain and is detrimental to the sustainability of aquatic flora. Despite of number of physico-chemical techniques of dye removal, the use of aquatic flora for bio-adsorption is encouraged. Thus, we used Salvinia molesta D. Mitch in bio-reduction of methylene blue on concentrations of 0, 10, 20, and 30 mg L−1 through 5 days with biosorption kinetics. The dye removal was concentration-dependent, maximized at 2 days with 30 mg L−1 which altered the relative growth rate (44%) of plants. Biosorption recorded 71% capacity at optimum pH (8.0), 24 h reducing major bond energies of amide, hydroxyl groups, etc. Bioaccumulation of dye changed potassium content (446%) under maximum dye concentration modifying tissues for dye sequestration. Reactive oxygen species were altered on dye reduction by oxidase (33%) with redox homeostasis by enzymes. Plants altered the metabolism with over accumulation of polyamines (51%), abscisic acids (448%), and phosphoenolpyruvate carboxylase (83%) on dye reduction. Thus, this study is rationalized with a sustainable approach where aquatic ecosystems can be decontaminated from dye toxicity with the exercise of bioresources like Salvinia molesta D. Mitch as herein.

Cysteamine dioxygenase (ADO) governs cancer cell mitochondrial redox homeostasis through proline metabolism.

2-Aminoethanethiol dioxygenase (ADO) is a thiol dioxygenase that sulfinylates cysteamine and amino-terminal cysteines in polypeptides. The pathophysiological roles of ADO remain largely unknown. Here, we demonstrate that ADO expression represents a vulnerability in cancer cells, as ADO depletion led to loss of proliferative capacity and survival in cancer cells and reduced xenograft growth. In contrast, generation of the ADO knockout mouse revealed high tolerance for ADO depletion in adult tissues. To understand the mechanism underlying ADO's essentiality in cancer cells, we characterized the cell proteome and metabolome following depletion of ADO. This revealed that ADO depletion leads to toxic levels of polyamines which can be driven by ADO's substrate cysteamine. Polyamine accumulation in turn stimulated expression of proline dehydrogenase (PRODH) which resulted in mitochondrial hyperactivity and ROS production, culminating in cell toxicity. This work identifies ADO as a unique vulnerability in cancer cells, due to its essential role in maintenance of redox homeostasis through restraining polyamine levels and proline catabolism.

Nutraceutical Properties of the Hydroalcoholic Extract and Phenolic Compounds from Yucca aloifolia Edible Flowers.

The flowers of Yucca aloifolia ("flor de izote") are considered a millenary food in the Northeastern Highlands of Puebla, Mexico. The present investigation reports on the chemical and biological activities of the hydroalcoholic extract (YAHF) obtained from this edible source. HPLC-MS profiling revealed twenty bioactive phenolic compounds with chlorogenic acid (16.5 mg g-1 DW), quercetin (9.5 mg g-1 FW), and their glycosides (rutin and quercitrin), as well as caffeic acid (8.4 mg g-1 DW) and ferulic acid (7.9 mg g-1 DW) as major compounds dissolved in YAHF. Six metabolites had potent anti-lipase (IC50<100 μg mL-1) and anti-ornithine decarboxylase activity (IC50<100 μg mL-1), whereas thirteen exerted strong anti-alpha-glucosidase properties (IC50<100 μg mL-1). The evaluation of YAHF in mice subjected to standard oral glucose tolerance tests and prolonged administration of hypercaloric/atherogenic diet (30 days), unraveled their ability to improve glucose and lipid profiles. YAHF and six phenolic compounds significantly reduced DLD-1 cell viability (IC50, 117.9 μg mL-1) and avoided polyamine accumulation linked to anti-ornithine decarboxylase activity. YAHF and its twenty constituents exerted low toxicity in probiotics (>1000 μg mL-1) and 3T3 fibroblasts (>2.5 mg-mL-1), sustaining their safeness for human consumption.

Cadmium stress responses under white or blue light are influenced by putrescine pre-treatment in wheat

Blue light plays an important role in most plant functions: it influences plant morphology, photosynthesis, primary and secondary metabolism. Although certain studies have already revealed that blue light may have positive effects under certain stress conditions, its exact mechanism is largely unknown. The importance of polyamines in stress tolerance has been widely investigated; however, their interaction with the dependent processes is still poorly understood. In addition, the quality of light can also affect the polyamine metabolism, thus it can influence their roles and relationships with other protective compounds. According to these, the main question of the present work was that whether blue light induces different responses during Cd stress, especially which are related to polyamine metabolism, and whether it may be able to modify the protective effect of exogenous putrescine compared to white light conditions in wheat. It has been demonstrated that less pronounced Cd stress was detected under blue light than at white light conditions. Blue light had its own effect at metabolite and gene expression levels and the lower Cd uptake was accompanied by lower phytochelatin but higher conjugated polyamine accumulation at the same time. Putrescine pre-treatment had protective effect especially under white light conditions, and it highlighted certain differences observed under Cd stress between blue light and white light conditions, especially in phytochelatin synthesis, polyamine metabolism, and accumulation of phenolic compounds and plant hormones. Our data demonstrated that blue light regulated Cd tolerance in wheat and modified defence strategy when excess putrescine was present.

Pre and postharvest spraying of arginine enhanced the stress resistance and promoted wound healing in broccoli during storage

Broccoli rapidly yellows and dehydrates post-harvest, causing a short storage life. Although arginine post-harvest has been shown to enhance broccoli’s storage quality and shelf life, it remains unclear whether pre-harvest treatment yields similar benefits. The results showed that pre-harvest spraying of 5 mM arginine reduces the respiration rate and delays electrolyte leakage during broccoli’s storage period, minimizing weight loss and yellowing and chlorophyll degradation. It also inhibits the degradation of ascorbic acid (ASA) and promotes the synthesis of total phenols, thereby increasing the total antioxidant capacity. Further studies showed that pre-harvest arginine spraying enhanced the activity of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and nitric oxide synthase (NOS). This accelerated the nitric oxide (NO) and the polyamine (PA) accumulation. Additionally, arginine aids in reactive oxygen species (ROS) balance and wound healing. Notably, pre-harvest arginine spraying was found to inhibit the hydrogen peroxide (H2O2) accumulation and enhance the activities of superoxide dismutase (SOD) and catalase (CAT), while also activating the phenylalanine ammonia lyase (PAL) and cinnamic acid 4-hydroxylase (C4H) activities. In conclusion, pre-harvest arginine spraying extends the broccoli’s storage life and improves its storage quality by promoting endogenous arginine catabolism, ROS metabolism, and the wounds healing. Therefore, this study establishes a theoretical foundation for pre-harvest handling in post-harvest broccoli storage.

Osa-miR11117 Targets OsPAO4 to Regulate Rice Immunity against the Blast Fungus Magnaporthe oryzae.

The intricate regulatory process governing rice immunity against the blast fungus Magnaporthe oryzae remains a central focus in plant-pathogen interactions. In this study, we investigated the important role of Osa-miR11117, an intergenic microRNA, in regulating rice defense mechanisms. Stem-loop qRT-PCR analysis showed that Osa-miR11117 is responsive to M. oryzae infection, and overexpression of Osa-miR11117 compromises blast resistance. Green fluorescent protein (GFP)-based reporter assay indicated OsPAO4 is one direct target of Osa-miR11117. Furthermore, qRT-PCR analysis showed that OsPAO4 reacts to M. oryzae infection and polyamine (PA) treatment. In addition, OsPAO4 regulates rice resistance to M. oryzae through the regulation of PA accumulation and the expression of the ethylene (ETH) signaling genes. Taken together, these results suggest that Osa-miR11117 is targeting OsPAO4 to regulate blast resistance by adjusting PA metabolism and ETH signaling pathways.

Hydrogen sulfide alleviates chilling injury of zucchini fruit by regulating antioxidant capacity, endogenous hydrogen sulfide, proline, and polyamine metabolism

Zucchini fruit was dipped in hydrogen sulfide (H2S) donor (1.0 mM NaHS) for 10 min and stored at 4 ± 1 °C to investigate the mechanism by which H2S treatment delays chilling injury (CI). The result showed that NaHS treatment inhibited the CI, and accumulations of malondialdehyde (MDA) and electrolyte leakage (EL), sustained hydrogen peroxide (H2O2) and superoxide anion (O2.−) production rate at a lower level, together with higher antioxidant enzyme activities of zucchini fruit. Furthermore, the research indicates that NaHS treatment can activate L-cysteine desulfhydrase (LCD) and D-cysteine desulfhydrase (DCD) to promote endogenous H2S accumulation which has a closely connection with alleviating chilling injury in zucchini. Meanwhile, the proline related synthetases enzyme was enhanced by NaHS treatment, which promoted proline accumulation. Likewise, higher polyamines (PAs) levels have been associated with inducing higher PAs related synthetases activities and lower PAs related degradation enzyme activities. Thus, NaHS treatment induced the antioxidant ability and improved cold stressed tolerance of zucchini by inducing endogenous H2S, proline, and PAs accumulation, maintaining membrane integrity and inhibiting oxidative stress to delay the CI of zucchini fruit.

Eggs of the mosquito Aedes aegypti survive desiccation by rewiring their polyamine and lipid metabolism.

Upon water loss, some organisms pause their life cycles and escape death. While widespread in microbes, this is less common in animals. Aedes mosquitoes are vectors for viral diseases. Aedes eggs can survive dry environments, but molecular and cellular principles enabling egg survival through desiccation remain unknown. In this report, we find that Aedes aegypti eggs, in contrast to Anopheles stephensi, survive desiccation by acquiring desiccation tolerance at a late developmental stage. We uncover unique proteome and metabolic state changes in Aedes embryos during desiccation that reflect reduced central carbon metabolism, rewiring towards polyamine production, and enhanced lipid utilisation for energy and polyamine synthesis. Using inhibitors targeting these processes in blood-fed mosquitoes that lay eggs, we infer a two-step process of desiccation tolerance in Aedes eggs. The metabolic rewiring towards lipid breakdown and dependent polyamine accumulation confers resistance to desiccation. Furthermore, rapid lipid breakdown is required to fuel energetic requirements upon water reentry to enable larval hatching and survival upon rehydration. This study is fundamental to understanding Aedes embryo survival and in controlling the spread of these mosquitoes.

Regulation of cold resistance by the polyamine biosynthetic gene SlSPDS2 via modulating the antioxidant enzyme system and osmotic regulatory substances in Solanum lycopersicum

The essential role of polyamine in cold stress resistance in tomato has been widely studied. However, the involvement of Spermidine synthase (SPDS) in the regulation of cold stress and their relationship with the antioxidant enzyme system and osmotic regulatory substances in tomato are not well characterized. In the current study, we found that cold stress induced the expression of polyamine biosynthetic genes and the accumulation of polyamine. The overexpression of SlSPDS2 (SlSPDS2-OE), a key Spermidine biosynthetic gene, significantly improved seedlings growth and increased seedlings index as well as alleviated the cold stress injury with decreased O2∙−, H2O2 and malondialdehyde contents. In SlSPDS2 overexpression lines, the contents of free polyamine, free salicylic acid, chlorophyll, proline and soluble sugar were increased compared with wild type (WT) under cold stress. The antioxidant enzyme activities and their coding genes expression were increased compared with WT under cold stress. SlSPDS2 silencing seedlings with weakened cold resistance showed oxidative damage and inhibition of growth. These results indicated that SlSPDS2 plays a positive role in tomato cold tolerance by regulating polyamine metabolism, antioxidants, and osmolytes.

TMT-based proteomic and transcriptomic analysis reveal new insights into heat stress responsive mechanism in edible mushroom Grifola frondosa

High temperature can lead to severe retardation in the growth and development of mushrooms, which influence the quality of fruiting bodies. Grifola frondosa is a popular and wide-cultivated mushroom in Asia; however, little information about the heat response mechanism in this commercially cultivated mushroom has been reported. The growth test was performed to determine the heat tolerance of different strains. Then, the TMT-based proteome and transcriptome analysis of major G. frondosa cultivar Qinghui-151 under different temperatures were performed. High temperature seriously affected the growth and recovery growth of mycelia. Thirty-four heat shock proteins (HSPs) were identified in the multiomics data and the expressions of most HSPs were induced by high temperature. The accumulation of HSPs under the control of HSFs is assumed to play a central role in the heat stress response (HSR) in G. frondosa. mTOR and Ca2+ signaling pathways were found to be activated under high temperature and might involved in heat stress signaling transduction. Polyamines synthesis enzymes were also up-regulated, suggesting the accumulation of stress protector polyamines under heat stress. In addition, expression of an L-phenylalanine ammonia-lyase (GfPAL) gene was significantly up-regulated under high temperature, which might be related to secondary metabolites synthesis. Taken together, these findings improve our understanding of the molecular mechanisms underlying the response to heat stress in G. frondosa, which could promote the breeding of new heat-tolerant G. frondosa cultivars.

Integrated Transcriptome and Metabolome Analysis of Salinity Tolerance in Response to Foliar Application of β-Alanine in Cotton Seedlings.

Salinity is amongst the serious abiotic stresses cotton plants face, impairing crop productivity. Foliar application of β-alanine is employed to improve salt tolerance in various crops, but the exact mechanism behind it is not yet completely understood. An advanced line SDS-01 of upland cotton Gossypium hirsutum L. was utilized to determine its salt tolerance. Foliar treatment with the β-alanine solution at different concentrations was applied to the seedlings stressed with 0.8% NaCl solution. On the 10th day of treatment, samples were collected for transcriptome and metabolome analyses. β-alanine solution at a concentration of 25 mM was found to be the best treatment with the lowest mortality rate and highest plant height and above-ground biomass under salt stress. Both differentially expressed genes and accumulated metabolites analyses showed improved tolerance of treated seedlings. The photosynthetic efficiency improved in seedlings due to higher expression of photosynthesis-antenna proteins and activation of hormones signal transduction after treatment with β-alanine. Highly expressed transcription factors observed were MYB, HD-ZIP, ARF, MYC, EREB, DELLA, ABF, H2A, H4, WRKY, and HK involved in the positive regulation of salinity tolerance in β-alanine-treated seedlings. Furthermore, compared to the control, the high accumulation of polyamines, coumarins, organic acids, and phenolic compounds in the β-alanine-treated seedlings helped regulate cellular antioxidant (glutathione and L-Cysteine) production. Hence, to improve salt tolerance and productivity in cotton, foliar application of β-alanine at the seedling stage can be a valuable management practice.

Herbivory by Striped Stem Borer Triggers Polyamine Accumulation in Host Rice Plants to Promote Its Larval Growth.

Polyamines (PAs) are ubiquitous low-molecular-weight aliphatic polycations in all living organisms, which are crucial for plant response to abiotic and biotic stresses. The role of PAs in plant disease resistance has been well documented. However, their involvement in plant-pest interactions remains unclear. Here, the role of PAs in rice against striped stem borer (SSB, Chilo suppressalis Walker), a destructive pest in rice production worldwide, was investigated. SSB larval infestation led to a substantial accumulation of free putrescine (Put) in rice seedlings, which was in parallel with an elevated expression of host PA biosynthesis genes Arginine Decarboxylase1 (ADC1) and ADC2. Moreover, SSB larval oral secretion application with wounding further raised the transcripts of ADC1 and ADC2 in rice compared with wounding treatment alone. The larval growth on both rice plants and artificial diet was promoted by the exogenous application of PA and inhibited by a PA biosynthesis inhibitor. On the other hand, the rice defense responses, including polyphenol oxidase (PPO) and peroxidase (POD) activities, as well as protease inhibitor level, were enhanced by a Put supplement and reduced by an ADC inhibitor. Our results indicate that SSB herbivory triggers polyamine accumulation in host rice plants, which is beneficial to SSB in rice-SSB interaction.

Nutraceutical Activity of Anthocyanins from the Edible Berries of Rhamnus pompana.

We present the inhibitory properties of the R. pompana anthocyanin fraction (RPAF) and its major constituents on alpha-glucosidase (AG), pancreatic lipase (PL), HMG-CoA reductase, and ornithine decarboxylase (ODC). The effect of RPAF was also evaluated in ICR male mice subjected to oral glucose tolerance test (OGTT) and hypercaloric/atherogenic diet for 30 days. RP-HPLC/MS profiling revealed that RPAF contained five major anthocyanins and induced slight inhibition on PL and HMG-CoA reductase (IC50 , 245-338 μg mL-1 ) whereas strong activity on AG and ODC (IC50 , 130-133 μg mL-1 ) was observed. Kinetic studies and molecular docking with pelargonidin-3-O-rutinoside (P3R) on ODC, revealed changes in Km (0.9514-0.9746 mM) and Vmax (1.96-2.32 μmol mg-1 min-1 ) suggesting mixed inhibition and molecular interaction with two active sites of ODC. P3R showed antiproliferative activity (IC50, 46.5 μM) and decreased polyamine accumulation in DLD-1 cells. The results of OGTT confirmed that RPAF regulates postprandial glucose levels in diabetic animals which experienced a significant glucose depletion (30 %; p<0.001) from 30 to 120 min post-treatment. Prolonged supplementation of RPAF caused significant decrease (p<0.001) in plasma glucose, total cholesterol, LDL-c and triglycerides as well as significant increase (p<0.001) of HDL-c compared with normoglycemic untreated animals.

Illustrate the distribution and metabolic regulatory effects of pterostilbene in cerebral ischemia-reperfusion rat brain by mass spectrometry imaging and spatial metabolomics

Pterostilbene is a promising molecule with superior pharmacological activities and pharmacokinetic characteristics compared to its structural analogue resveratrol, which could be used to treat ischemic stroke. However, its mechanism is still unclear. The cutting-edge air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) and spatial metabolomics analysis were applied to investigate the distribution of pterostilbene in ischemic rat brain and the changes of related small molecule metabolic pathways to further explore the potential mechanisms of pterostilbene against cerebral ischemia-reperfusion injury. This research found that pterostilbene could significantly restore cerebral microcirculation blood flow, reduce infarct volume, improve neurological function and ameliorate neuronal damage in ischemic rats. Moreover, pterostilbene was widely and abundantly distributed in ischemic brain tissue, laying a solid foundation for the rescue of ischemic penumbra. Further study revealed that pterostilbene played a therapeutic role in restoring energy supply, rebalancing neurotransmitters, reducing abnormal polyamine accumulation and phospholipid metabolism. These findings offer an opportunity to illustrate novel mechanisms of pterostilbene in the treatment of cerebral ischemia/reperfusion injury resulting from ischemic stroke.

Experimental study of processing sweet cherries with ultraviolet radiation

The paper considers an experimental study of processing sweet cherries with ultraviolet radiation. Ultraviolet irradiation is an alternative to chemical sterilization used to reduce the growth of microorganisms in foods. Ultraviolet radiation further induces defense mechanisms in metabolically active plant tissues, in the same way that ultraviolet treatment has been observed to cause accumulation of polyamines, which can act as antioxidants in fruit, causing a reduction in microorganism spoilage symptoms.

Evaluation of the effect of urea foliar application on polyamine content, grain protein content, and the agronomic traits of bread wheat cultivars under dryland and supplemental irrigation conditions

The purpose of the experiment was to investigate the relationship between the accumulation of polyamines during the filling period of wheat grain with yield and grain protein under dryland and supplemental irrigation (SI) conditions and also the effect of foliar spraying of urea on the amount of polyamines in grain a factorial experiment was conducted based on randomized complete block design with three replications during two cropping seasons. The examined treatments included water availability (dryland and SI), wheat cultivars (Homa, Sardari, Rijaw, Ouhadi, and Azar2), and foliar application of urea (control and 4% urea foliar application). The results demonstrated that SI (10%) reduced and urea foliar (12%) application increased the percent of grain protein. SI reduced the contents of three PAs by 24%: spermine, spermidine, and putrescine. But urea foliar application increased the three PAs in the first and second years by 31% and 27% in dryland conditions and 12% and 4% in SI conditions, respectively. These results indicated that there is less need for PAs in SI conditions, and they thus exhibit poorer accumulation in the grain; in dryland conditions, however, their content increases with greater access to foliar nitrogen. Older cultivars Sardari and Azar 2 had more polyamines. According to the observed positive correlation between 1000-grain weight and the three PAs under stress conditions, PAs are probably involved in the improvement of grain filling, and urea foliar application can affect drought tolerance by increasing PA accumulation. Moreover, cadaverine exhibited a different function from the other PAs.

Polyamines dynamics in buds and flowers in response to fall foliar fertilisation in ‘Hayward’ kiwifruit

ABSTRACT The present study aimed to optimise a fertiliser combination and find the effective timing for foliar fertilisation in the fall to determine whether the application of N, B and Zn fertilisers can improve fruit set and alter endogenous polyamines. ‘Hayward’ Kiwi vines were sprayed with CO(NH2)2 (urea), H3BO3 and ZnSO4 (alone and in combination) on different dates (September 17, October 7 and October 28). Buds were sampled at three stages (before dormancy, during dormancy and full bloom) to determine endogenous polyamines content. In the following growing season, bud break, percentage of flowering shoots and effective pollination period (EPP) were determined. Our results showed CO(NH2)2: H3BO3: ZnSO4 (10, 1.5 and 2 g l−1 respectively) on October 28 was the best fertiliser combination and application time. This treatment significantly increased putrescine, spermine and spermidine accumulation in bud and flower tissues, as well as bud break and flowering. In vines treated with this combination on October 28, EPP was at least 2 days longer than control. The foliar fertiliser treatment applied the previous fall increased fruit set to 83% (absolute). This improvement was associated with an increased accumulation of endogenous polyamines in bud and flower tissues.

The drought-tolerant rhizobacterium, Pseudomonas putida AKMP7, suppresses polyamine accumulation under well-watered conditions and diverts putrescine into GABA under water-stress, in Oryza sativa

Drought-tolerant plant growth promoting rhizobacteria (PGPR) have been reported to alleviate water-stress in plants that they associate with. Here, we report the impact of a free-living, drought-tolerant PGPR strain, Pseudomonas putida AKMP7 on (a) morpho-physiological responses and (b) metabolism of the three major polyamines-namely, putrescine (Put), spermidine (Spd) and spermine (Spm) in well-watered and water-stressed Oryza sativa (BPT5204). The bacterium significantly improved the plant growth and biomass, decreased membrane damage, electrolyte leakage and plant proline levels under water-stress, indicating drought alleviation. Dehydration did not affect the root colonization efficiency of the bacterium. We observed that the concentrations of all three polyamines were downregulated in rice leaves under well-watered conditions by AKMP7 inoculation. Under water-stress, however, AKMP7 caused a significant decrease only in the levels of foliar Spm, while Put and Spd levels did not majorly fluctuate. Transcript levels of most of the polyamine biosynthetic genes studied (AIH involved in Put biosynthesis; SPD/SPM2, SPD/SPM3 and SAMDC2, involved in Spd and Spm biosynthesis) positively correlated with the low polyamine levels in the inoculated plants, vs. the non-inoculated ones under well-watered conditions. While similar trends were observed in the water-stressed, inoculated plants vs. water-stressed, non-inoculated plants, the reduction in only Spm (and not Put and Spd) was a potential consequence of the interplay of both, its biosynthesis and back-conversion. In water-stressed plants, AKMP7 caused a small downregulation in AIH, while stronger downregulations in the expressions of SPD/SPM2 as well as SAMDC2 were seen. Furthermore, the Spd to Put back-conversion gene, PAO3 exhibited a downregulation on AKMP7 treatment under water-stressed conditions. There was also an increase in the expression of BADH2 gene, leading to a concomitant increase in foliar GABA levels in inoculated, water-stressed plants vs. their non-inoculated counterparts. The overall conclusion from this study is- P. putida AKMP7 tightly regulates polyamine homeostasis in rice plants, both under well-watered and water-stressed conditions by lowering polyamine levels, through (a) transcriptional control of polyamine biosynthetic genes under well-watered conditions and (b) a combination of biosynthesis, back-conversion and catabolism of polyamines under water-stress.

Transcriptomic analysis revealed the candidate metabolic pathways and genes associated with cold tolerance in a mutant without anthocyanin accumulation in common vetch (Vicia sativa L.)

Common vetch (Vicia sativa L.) is a leguminous crop used to feed livestock with vegetative organs or fertilize soils by returning to the field. Survival of fall-seeded plants is often affected by freezing damage during overwintering. This study aims to investigate the transcriptomic profiling in response to cold in a mutant with reduced accumulation of anthocyanins under normal growth and low-temperature conditions for understanding the underlying mechanisms. The mutant had increased cold a tolerance with higher survival rate and biomass during overwintering compared to the wild type, which led to increased forage production. Transcriptomic analysis in combination with qRT-PCR and physiological measurements revealed that reduced anthocyanins accumulation in the mutant resulted from reduced expression of serial genes involving in anthocyanin biosynthesis, which led to the altered metabolism, with an increased accumulation of free amino acids and polyamines. The higher levels of free amino acids and proline in the mutant under low temperature were associated with improved cold tolerance. The altered expression of some genes involved in ABA and GA signaling was also associated with increased cold tolerance in the mutant.

Silicon-induced hypoxia tolerance in citrus rootstocks associated with modulation in polyamine metabolism

Polyamines (PAs) have a variety of roles in plant environment interactions and stress responses, which control the tolerance induction of plants under hypoxic stress. Citrus plants are sensitive to waterlogging conditions because it frequently causes root zone hypoxia (RZH) and severe abiotic stress to their growth. Therefore, the present study investigated whether silicon (SiO2) could improve hypoxia tolerance by modulating the activity of PAs biosynthesizing enzymes and, in turn, variation in different PAs profiles involved in critical metabolic processes. Three commercially used citrus rootstocks (Carrizo citrange, Rubidoux, and Rich16-6) were subjected to flooding environments (with and without oxygen) with different treatments in both the presence and absence of SiNP (silicon nanoparticles) through roots and foliar application. Hypoxia stress increased PA-synthesizing enzymes' activity and PAs' formation in plant leaves and roots. Under hypoxia stress, exogenous SiNP raised the concentration of endogenous silicon (SiO2) and a large concentration of polyamines (PAs) by regulating PA biosynthesis. In the response to SiNP, it was also observed that an increase in plant biomass (leaf, stem, and root tissues) resulted in an overall improvement in plant growth. Rich-16-6 rootstock was found to be more receptive to root application of SiNP than foliar application in contrast to Rubidoux and Carrizo citrange plants, indicating genotype variability of citrus rootstocks in silicon uptake. Our findings demonstrate that the accumulation of silicon-induced polyamine enhanced growth and reduced reactive oxygen species (ROS) that might help to reduce oxidative damage in citrus rootstocks under hypoxic stress, providing an optimal strategy for stress tolerance. This study enhances the impact of nanoparticles on fruit crop production, significantly relieving pressure, and is a potential platform for future research.