Spermidine Synthase Research Articles

Physiological, transcriptomic, and metabolomic analyses of the chilling stress response in two melon (Cucumis melo L.) genotypes

BackgroundChilling stress is a key abiotic stress that severely restricts the growth and quality of melon (Cucumis melo L.). Few studies have investigated the mechanism of response to chilling stress in melon.ResultsWe characterized the physiological, transcriptomic, and metabolomic response of melon to chilling stress using two genotypes with different chilling sensitivity (“162” and “13-5A”). “162” showed higher osmotic regulation ability and antioxidant capacity to withstand chilling stress. Transcriptome analysis identified 4395 and 4957 differentially expressed genes (DEGs) in “162” and “13-5A” under chilling stress, respectively. Metabolome analysis identified 615 and 489 differential enriched metabolites (DEMs) were identified in “162” and “13-5A” under chilling stress condition, respectively. Integrated transcriptomic and metabolomic analysis showed enrichment of glutathione metabolism, and arginine (Arg) and proline (Pro) metabolism, with differential expression patterns in the two genotypes. Under chilling stress, glutathione metabolism-related DEGs, 6-phosphogluconate dehydrogenase (G6PDH), glutathione peroxidase (GPX), and glutathione s-transferase (GST) were upregulated in “162,” and GSH conjugates (L-gamma-glutamyl-L-amino acid and L-glutamate) were accumulated. Additionally, “162” showed upregulation of DEGs encoding ornithine decarboxylase, Pro dehydrogenase, aspartate aminotransferase, pyrroline-5-carboxylate reductase, and spermidine synthase and increased Arg, ornithine, and Pro. Furthermore, the transcription factors (TFs), MYB, ERF, MADS-box, and bZIP were significantly upregulated, suggesting their crucial role in chilling tolerance of melon.ConclusionsThese findings elucidate the molecular response mechanism to chilling stress in melon and provide insights for breeding chilling-tolerant melon.

Impact of polyamine supplementation on GnRH expression, folliculogenesis, and puberty onset in young mice

BackgroundThe hypothalamic-pituitary-gonadal (HPG) axis is pivotal in regulating reproductive functions, with gonadotropin-releasing hormone (GnRH) acting as a central regulator. Recently, polyamines have been shown to regulate the HPG axis, including GnRH expression and ovarian biology in old and adult rodents. The present study firstly highlights the age-specific variation in the polyamine and their corresponding biosynthetic enzymes in the ovary during aging, and further, the study focuses on the effect of polyamines, putrescine, and agmatine, in young female mice. Method and resultImmunofluorescence analysis revealed age-related differences in the expression of ornithine decarboxylase 1 (ODC1), spermine (SPM), and spermidine (SPD) in the ovaries, with adult mice exhibiting significantly higher expression levels compared to young and old mice. Likewise, qPCR analysis showed the mRNA levels of Odc1, Spermidine synthase (Srm), and Spermine synthase (Sms) show a significant increase in adult ovaries, which is then followed by a significant decline in old age. Histological examination demonstrated morphological alterations in the ovaries with age, including decreased follicle numbers and increased stromal cells in old mice. Furthermore, treatment with putrescine, a polyamine, in young mice resulted in larger ovaries and increased follicle numbers compared to controls. Additionally, serum levels of gonadotropin-releasing hormone (GnRH) and progesterone (P4) were measured, showing elevated levels in polyamine-treated mice. GnRH mRNA expression also increased significantly. Gene expression analysis revealed upregulation of genes associated with folliculogenesis such as Fshr, Bmp15, Gdf9, Amh, Star, Hsdb3, and Plaur in the ovaries and onset of puberty such as Tac2, and Kiss1, and a decrease in Mkrn3 in the hypothalamus of polyamine-treated mice. ConclusionThis study investigates the effect of polyamines in young immature female mice, shedding light on their role in upregulating GnRH, and enhancing folliculogenesis. Overall, these findings suggest that polyamines play a crucial role in ovarian aging and HPG axis regulation, offering potential therapeutics to reinstate fertility in reproductively challenged individuals.

Circulating Metabolic Markers Identify Patients at Risk for Tumor Recurrence: A Prospective Cohort Study in Colorectal Cancer Surgery.

To investigate the spermidine pathway capability to predict patients at risk for tumor recurrence following colorectal cancer (CRC) surgery. Recurrence rates after CRC surgery remain at about 20% despite an optimal technique and adjuvant therapy when necessary. Identification of risk biomarkers of recurrence is an unmet need. The spermidine pathway is indispensable for cell proliferation and differentiation, and is suggested to accelerate tumor spread. This was a prospective cohort study of patients undergoing CRC surgery from 2015 to 2018. Plasma samples were collected before surgery and on postoperative day 4, and the spermidine pathway was assessed through mass spectrometry. Oncological outcomes were registered. A total of 146 patients were included and 24 (16.4%) developed tumor recurrence. Higher levels of preoperative spermidine pathway components (spermidine, spermine, spermidine synthase enzyme, and spermine/arginine balance) were positively associated with recurrence. Surgery promoted a decrease in these pathway elements. The greater the decline was, the lower the risk of recurrence. Preoperative spermidine over the cut-off of 0.198µM displayed a 4.69-fold higher risk of recurrence. The spermine synthase enzyme behaved in the opposite direction. The spermidine pathway is associated with tumor recurrence following CRC surgery and, after confirmation in larger cohorts, could be translated as a risk biomarker of recurrence into clinical practice.

Safety assessment of a novel marine multi-stress-tolerant yeast Meyerozyma guilliermondii GXDK6 according to phenotype and whole genome-sequencing analysis

The application of microorganisms as probiotics is limited due to lack of safety evaluation. Here, a novel multi-stress-tolerant yeast Meyerozyma guilliermondii GXDK6 with aroma-producing properties was identified from marine mangrove microorganisms. Its safety and probiotic properties were assessed in accordance with phenotype and whole-genome sequencing analysis. Results showed that the genes and phenotypic expression of related virulence, antibiotic resistance and retroelement were rarely found. Hyphal morphogenesis genes (SIT4, HOG1, SPA2, ERK1, ICL1, CST20, HSP104, TPS1, and RHO1) and phospholipase secretion gene (VPS4) were annotated. True hyphae and phospholipase were absent. Only one retroelement (Tad1-65_BG) was found. Major biogenic amines (BAs) encoding genes were absent, except for spermidine synthase (JA9_002594), spermine synthase (JA9_004690), and tyrosine decarboxylase (inx). The production of single BAs and total BAs was far below the food-defined thresholds. GXDK6 had no resistance to common antifungal drugs. Virulence enzymes, such as gelatinase, DNase, hemolytic, lecithinase, and thrombin were absent. Acute toxicity test with mice demonstrated that GXDK6 is safe. GXDK6 has a good reproduction ability in the simulation gastrointestinal tract. GXDK6 also has a strong antioxidant ability, β-glucosidase, and inulinase activity. To sum up, GXDK6 is considered as a safe probiotic for human consumption and food fermentation.

Spermidine Synthase Localization in Retinal Layers: Early Age Changes.

Polyamine (PA) spermidine (SPD) plays a crucial role in aging. Since SPD accumulates in glial cells, particularly in Müller retinal cells (MCs), the expression of the SPD-synthesizing enzyme spermidine synthase (SpdS) in Müller glia and age-dependent SpdS activity are not known. We used immunocytochemistry, Western blot (WB), and image analysis on rat retinae at postnatal days 3, 21, and 120. The anti-glutamine synthetase (GS) antibody was used to identify glial cells. In the neonatal retina (postnatal day 3 (P3)), SpdS was expressed in almost all progenitor cells in the neuroblast. However, by day 21 (P21), the SpdS label was pronouncedly expressed in multiple neurons, while GS labels were observed only in radial Müller glial cells. During early cell adulthood, at postnatal day 120 (P120), SpdS was observed solely in ganglion cells and a few other neurons. Western blot and semi-quantitative analyses of SpdS labeling showed a dramatic decrease in SpdS at P21 and P120 compared to P3. In conclusion, the redistribution of SpdS with aging indicates that SPD is first synthesized in all progenitor cells and then later in neurons, but not in glia. However, MCs take up and accumulate SPD, regardless of the age-associated decrease in SPD synthesis in neurons.

A Bacillus velezensis strain isolated from oats with disease-preventing and growth-promoting properties

Endophytes have been shown to promote plant growth and health. In the present study, a Bacillus velezensis CH1 (CH1) strain was isolated and identified from high-quality oats, which was capable of producing indole-3-acetic acid (IAA) and strong biofilms, and capabilities in the nitrogen-fixing and iron carriers. CH1 has a 3920 kb chromosome with 47.3% GC content and 3776 code genes. Compared genome analysis showed that the largest proportion of the COG database was metabolism-related (44.79%), and 1135 out of 1508 genes were associated with the function “biosynthesis, transport, and catabolism of secondary metabolites.” Furthermore, thirteen gene clusters had been identified in CH1, which were responsible for the synthesis of fifteen secondary metabolites that exhibit antifungal and antibacterial properties. Additionally, the strain harbors genes involved in plant growth promotion, such as seven putative genes for IAA production, spermidine and polyamine synthase genes, along with multiple membrane-associated genes. The enrichment of these functions was strong evidence of the antimicrobial properties of strain CH1, which has the potential to be a biofertilizer for promoting oat growth and disease resistance.

Overexpression of wheat spermidine synthase gene enhances wheat resistance to Fusarium head blight

Polyamines, such as putrescine, spermidine, and spermine, are crucial for plant defense against both abiotic and biotic stresses. Putrescine is also known as a significant inducer of deoxynivalenol (DON) production in Fusarium graminearum, the primary causal agent of Fusarium head blight (FHB). However, the impact of other polyamines on DON production and whether modifying polyamine biosynthesis could improve wheat resistance to FHB are currently unknown. In this study, we demonstrate that key precursor components of putrescine synthesis, including arginine, ornithine, and agmatine, can induce DON production, albeit to a lesser extent than putrescine in trichothecene biosynthesis-inducing (TBI) culture under the same total nitrogen conditions. Intriguingly, spermidine and spermine, downstream products of putrescine in the polyamine biosynthesis pathway, do not induce DON production under the same conditions. Additionally, externally applying either spermidine or spermine to wheat heads significantly reduces the diseased spikelet number caused by F. graminearum. Furthermore, our results show that overexpression of the wheat spermidine synthase (SPDS) gene TaSPDS-7D1 significantly enhances the spermidine content and wheat resistance to FHB. In addition, the TaSPDS-7D1-overexpressing line OE3 exhibited a 1000-grain weight and plant height increase compared to the wild type. Our findings reveal that overexpression of the spermidine synthase gene can enhance wheat resistance to FHB without compromising wheat yield.

Exogenous Spermidine Alleviated Low-Temperature Damage by Affecting Polyamine Metabolism and Antioxidant Levels in Apples.

Low-temperature stress significantly limits the growth, development, and geographical distribution of apple cultivation. Spermidine (Spd), a known plant growth regulator, plays a vital role in the plant's response to abiotic stress. Yet, the mechanisms by which exogenous Spd enhances cold resistance in apples remain poorly understood. Therefore, the present study analyzed the effects of exogenous Spd on antioxidant enzyme activity, polyamine metabolism, and related gene expression levels of 1-year-old apple branches under low-temperature stress. Treatment with exogenous Spd was found to stabilize branch tissue biofilms and significantly reduce the levels of reactive oxygen species by elevating proline content and boosting the activity of antioxidants such as superoxide dismutase. It also upregulated the activities of arginine decarboxylase, S-adenosylmethionine decarboxylase, and spermidine synthase and the expression levels of MdADC1, MdSAMDC1, and MdSPDS1 under low-temperature stress and led to the accumulation of large amounts of Spd and spermine. Moreover, compared with the 2 mmol·L-1 Spd treatment, the 1 mmol·L-1 Spd treatment increased the expression levels of cold-responsive genes MdCBF1/2/3, MdCOR47, and MdKIN1, significantly. The findings suggest that exogenous Spd can enhance cold resistance in apple branches significantly. This enhancement is achieved by modulating polyamine metabolism and improving antioxidant defense mechanisms, which could be exploited to improve apple cultivation under cold stress conditions.

Two novel PCR-based assays for sexing of Silene latifolia and Silene dioica plants

Silene latifolia and S. dioica are model systems in studies of plant reproduction, chromosome evolution and sexual dimorphism, but sexing of plants based on morphology is only possible from flowering stage onwards. Both species show homogametic females (XX) and heterogametic males (XY).•Here we developed two assays (primer pairs ss816 and ss441) for molecular sexing of S. latifolia and S. dioica, targeting length polymorphisms between the X and Y-linked copies of the spermidine synthase gene.The two assays were successful in identifying known (flowering-stage) males and females from UK and Spanish populations, with an error rate of 3.1% (ss816; successful for both species) and 0% (ss441, only successful for S. latifolia). Our assays therefore represent novel tools for rapid, robust and simple determination of the genotypic sex of S. latifolia and S. dioica.

Functional identification of bacterial spermine, thermospermine, norspermine, norspermidine, spermidine, and N1-aminopropylagmatine synthases

Spermine synthase is an aminopropyltransferase that adds an aminopropyl group to the essential polyamine spermidine to form tetraamine spermine, needed for normal human neural development, plant salt and drought resistance, and yeast CoA biosynthesis. We functionally identify for the first time bacterial spermine synthases, derived from phyla Bacillota, Rhodothermota, Thermodesulfobacteriota, Nitrospirota, Deinococcota and Pseudomonadota. We also identify bacterial aminopropyltransferases that synthesize the spermine same mass isomer thermospermine, from phyla Cyanobacteriota, Thermodesulfobacteriota, Nitrospirota, Dictyoglomota, Armatimonadota and Pseudomonadota, including the human opportunistic pathogen Pseudomonas aeruginosa. Most of these bacterial synthases were capable of synthesizing spermine or thermospermine from the diamine putrescine, and so possess also spermidine synthase activity. We found that most thermospermine synthases could synthesize tetraamine norspermine from triamine norspermidine, i.e., they are potential norspermine synthases. This finding could explain the enigmatic source of norspermine in bacteria. Some of the thermospermine synthases could synthesize norspermidine from diamine 1,3-diaminopropane, demonstrating that they are potential norspermidine synthases. Of 18 bacterial spermidine synthases identified, 17 were able to aminopropylate agmatine to form N1-aminopropylagmatine, including the spermidine synthase of Bacillus subtilis, a species known to be devoid of putrescine. This suggests that the N1-aminopropylagmatine pathway for spermidine biosynthesis, which bypasses putrescine, may be far more widespread than realized and may be the default pathway for spermidine biosynthesis in species encoding L-arginine decarboxylase for agmatine production. Some thermospermine synthases were able to aminopropylate N1-aminopropylagmatine to form N12-guanidinothermospermine. Our study reveals an unsuspected diversification of bacterial polyamine biosynthesis, and suggests a more prominent role for agmatine.

Abstract 18: The polyamine-hypusine axis is a promising avenue to improve T-cell metabolism and persistence for adoptive cell therapy

Abstract There are significant barriers to the application of Adoptive Cell Therapy (ACT) to many cancer types. One of these barriers is a result of poor metabolic fitness of T cells, leading to poor proliferation, persistence, and dampened anti-tumor function. Leveraging T-cell metabolism to improve their function is becoming increasingly important to make significant strides in immunotherapy. Stat5a has been shown to be a master regulator of energy and metabolism in T cells, highlighting it as a promising avenue to improve T-cell metabolism for ACT. We have established that the expression of Constitutively Active Signal Transducer and Activator of Transcription 5A (CASTAT5) on tumor-specific CD4+ T cells improves their persistence, polyfunctionality, and anti-tumor effects in a mouse model. This study further examines Stat5a and its downstream metabolic targets in the context of ACT. We carried out scRNAseq analysis and found that Stat5a directly interacts with genes involved in polyamine metabolism. More specifically, Stat5a activation increases the expression of ornithine decarboxylase (Odc1), spermidine synthase (Srm), deoxyhypusine synthase (Dhps), and deoxyhypusine hydroxylase (Dohh) in a subset of CD4+ T cells expressing CASTAT5. Cleavage Under Targets and Tagmentation (Cut&Tag) analysis of histone H3K27ac also demonstrated increased H3K27ac at promoter and enhancer regions of polyamine pathway genes in CASTAT5 compared to control CD4+ T cells. To further examine the function of Stat5a, the murine pro-B cell line, Ba/F3, is being used as a model to study Stat5a-mediated signaling. We have found that upon withdrawal of IL-3 from Ba/F3 cells, Stat5a activation is significantly downregulated. Our scRNA-seq-based metabolic flux estimation showed a significant reduction in metabolic fluxes and related genes, including polyamines, following IL-3 withdrawal. Correspondingly, Stat5a ChIP-Seq and Cut&Tag analyses of H3K27ac revealed Stat5a binding to active enhancer regions in the presence of IL-3 that are lost following its withdrawal. Untargeted metabolomics confirmed the marked Stat5a-mediated reduction in metabolite abundance after IL-3 deprivation, in a time-dependent manner. The polyamine-hypusine axis revealed in our studies is a promising avenue to improve T-cell function. This axis has been shown to regulate T-cell function, and potentially modulate mitochondrial respiration and T-cell activation. Hence, our studies have identified polyamine supplementation and gene modulation as promising strategies to improve the metabolism of Adoptive T cells in a Stat5a-mediated manner. Further studies will evaluate the effectiveness of this avenue in improving T-cell function, improving their efficacy for ACT, and improving patient outcomes. Citation Format: Mercy Kehinde-Ige, Ogacheko Okoko, Gang Zhou, Huidong Shi. The polyamine-hypusine axis is a promising avenue to improve T-cell metabolism and persistence for adoptive cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 18.

Enhancing the Spermidine Synthase-Based Polyamine Biosynthetic Pathway to Boost Rapid Growth in Marine Diatom Phaeodactylum tricornutum.

Diatoms, efficient carbon capture organisms, contribute to 20% of global carbon fixation and 40% of ocean primary productivity, garnering significant attention to their growth. Despite their significance, the synthesis mechanism of polyamines (PAs), especially spermidine (Spd), which are crucial for growth in various organisms, remains unexplored in diatoms. This study reveals the vital role of Spd, synthesized through the spermidine synthase (SDS)-based pathway, in the growth of the diatom Phaeodactylum tricornutum. PtSDS1 and PtSDS2 in the P. tricornutum genome were confirmed as SDS enzymes through enzyme-substrate selectivity assays. Their distinct activities are governed primarily by the Y79 active site. Overexpression of a singular gene revealed that PtSDS1, PtSDS2, and PtSAMDC from the SDS-based synthesis pathway are all situated in the cytoplasm, with no significant impact on PA content or diatom growth. Co-overexpression of PtSDS1 and PtSAMDC proved essential for elevating Spd levels, indicating multifactorial regulation. Elevated Spd content promotes diatom growth, providing a foundation for exploring PA functions and regulation in diatoms.

Depletion of SAM leading to loss of heterochromatin drives muscle stem cell ageing.

The global loss of heterochromatin during ageing has been observed in eukaryotes from yeast to humans, and this has been proposed as one of the causes of ageing. However, the cause of this age-associated loss of heterochromatin has remained enigmatic. Here we show that heterochromatin markers, including histone H3K9 di/tri-methylation and HP1, decrease with age in muscle stem cells (MuSCs) as a consequence of the depletion of the methyl donor S-adenosylmethionine (SAM). We find that restoration of intracellular SAM in aged MuSCs restores heterochromatin content to youthful levels and rejuvenates age-associated features, including DNA damage accumulation, increased cell death, and defective muscle regeneration. SAM is not only a methyl group donor for transmethylation, but it is also an aminopropyl donor for polyamine synthesis. Excessive consumption of SAM in polyamine synthesis may reduce its availability for transmethylation. Consistent with this premise, we observe that perturbation of increased polyamine synthesis by inhibiting spermidine synthase restores intracellular SAM content and heterochromatin formation, leading to improvements in aged MuSC function and regenerative capacity in male and female mice. Together, our studies demonstrate a direct causal link between polyamine metabolism and epigenetic dysregulation during murine MuSC ageing.

Polyamine Metabolism for Drug Intervention in Trypanosomatids.

Neglected tropical diseases transmitted by trypanosomatids include three major human scourges that globally affect the world's poorest people: African trypanosomiasis or sleeping sickness, American trypanosomiasis or Chagas disease and different types of leishmaniasis. Different metabolic pathways have been targeted to find antitrypanosomatid drugs, including polyamine metabolism. Since their discovery, the naturally occurring polyamines, putrescine, spermidine and spermine, have been considered important metabolites involved in cell growth. With a complex metabolism involving biosynthesis, catabolism and interconversion, the synthesis of putrescine and spermidine was targeted by thousands of compounds in an effort to produce cell growth blockade in tumor and infectious processes with limited success. However, the discovery of eflornithine (DFMO) as a curative drug against sleeping sickness encouraged researchers to develop new molecules against these diseases. Polyamine synthesis inhibitors have also provided insight into the peculiarities of this pathway between the host and the parasite, and also among different trypanosomatid species, thus allowing the search for new specific chemical entities aimed to treat these diseases and leading to the investigation of target-based scaffolds. The main molecular targets include the enzymes involved in polyamine biosynthesis (ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine synthase), enzymes participating in their uptake from the environment, and the enzymes involved in the redox balance of the parasite. In this review, we summarize the research behind polyamine-based treatments, the current trends, and the main challenges in this field.

Calcium combined with vacuum treatment improves postharvest storage quality of Agaricus bisporus by regulating polyamine metabolism

Calcium (Ca) immersion treatment has been used for the preservation of Agaricus bisporus (A. bisporus), but the effective dosage of Ca absorption has often been disregarded. In our study, vacuum pretreatment was performed to promote Ca infiltration in A. bisporus. Vacuum pretreatment (−0.1 MPa, 5 min, Vac + Ca group) exhibited a super effectiveness in promoting Ca absorption. The results of Ca diffusion simulation using COMSOL Multiphysics showed that Ca level in the center of the sample in the Vac + Ca group increased from 0.1020 to 0.2028 g kg−1 during a period of 0 to 60 min. Additionally, the effects of Vac + Ca treatment on the polyamine (PA) metabolism during a 3-day room temperature storage of A. bisporus were investigated. Vac + Ca treatment resulted in a reduction of putrescine (Put) level and an elevation in spermidine (Spd) level, suggesting that the treatment may facilitate the conversion of Put to Spd. Interestingly, a negative linear correlation between changes in Spd level and both the browning index and weight loss, while a positive correlation was found with alterations in hardness were observed. Moreover, several amino acids and enzymes involved in PA metabolism, including arginine, methionine, ornithine decarboxylase, arginase, S-adenosylmethionine decarboxylase, and spermidine synthase, were also affected by this treatment. Therefore, the increase in Spd induced by Vac + Ca treatment may be one of the underlying mechanisms responsible for extending the postharvest lifespan of A. bisporus.

Metabolomics Unveiled the Potential Role of N1-Acetylspermidine As a Biomarker in T-Lymphoblastic Lymphoma/Leukemia Monitoring

Objective: For adult patients with T lymphoblastic leukemia/lymphoma (T-ALL/LBL), current methods for therapeutic response monitoring based on bone marrow examinations lack convenience. A biomarker in blood with high sensitivity can make daily monitoring easier. Our team attempted to identify easily obtained and highly sensitive T-ALL/LBL tumor biomarkers through metabolomics, and meanwhile explore potential metabolic therapeutic targets. Methods: We performed non-targeted metabolomic analysis on archived plasma samples from 30 newly diagnosed T-ALL/LBL patients and matched controls from 2015-2018. Based on these results, we expanded the sample size to 50 patient and matched control plasmas for targeted metabolomic validation, and explored potential mechanisms using public databases. Results: A total of 90 differential compounds were detected in non-targeted analysis. Orthogonal partial least squares discriminant analysis showed that the metabolic patterns of the patients and the controls were significantly different (R2=0.915, Q2=0.723, pR2=0.010, PQ2=0.010). KEGG pathway enrichment showed that the detected differential compounds were involved in 41 known metabolic pathways, and the methionine metabolism pathway was highly ranked. Random forest analysis verified significant differentiation between cases and controls based on metabolic differences (ROC curve AUC=0.928, p<0.001), with acetylspermidine contributing most significantly. Targeted validation in the expanded cohort showed decreased methionine, increased methylthioadenosine, and significantly increased N1-acetylspermidine in patient plasma. All these three metabolites could be localized in methionine and related polyamine metabolism pathways, with N1-acetylspermidine upregulation particularly pronounced (fold change=3.590, p<0.001). Plasma N1-acetylspermidine alone could effectively differentiate patients from controls (ROC curve AUC=0.888, p<0.001). Public database records (GSE109231) suggested that upregulated spermidine synthase may explain this alteration in N1-acetylspermidine. Conclusion: N1-Acetylspermidine showed promising potential as a tumor biomarker for T-ALL/LBL therapeutic monitoring, while methionine and polyamine metabolism abnormalities may constitute new T-ALL/LBL metabolic therapeutic targets.

Dynamic Interplay of Metabolic and Transcriptional Responses in Shrimp during Early and Late Infection Stages of Enterocytozoon hepatopenaei (EHP)

Enterocytozoon hepatopenaei (EHP) is a microsporidian parasite that infects Litopenaeus vannamei, causing severe hepatopancreatic microsporidiosis (HPM) and resulting in significant economic losses. This study utilizes a combined analysis of transcriptomics and metabolomics to unveil the dynamic molecular interactions between EHP and its host, the Pacific white shrimp, during the early and late stages of infection. The results indicate distinct immunological, detoxification, and antioxidant responses in the early and late infection phases. During early EHP infection in shrimp, immune activation coincides with suppression of genes like Ftz-F1 and SEPs, potentially aiding parasitic evasion. In contrast, late infection shows a refined immune response with phagocytosis-enhancing down-regulation of Ftz-F1 and a resurgence in SEP expression. This phase is characterized by an up-regulated detoxification and antioxidant response, likely a defense against the accumulated effects of EHP, facilitating a stable host–pathogen relationship. In the later stages of infection, most immune responses return to baseline levels, while some immune genes remain active. The glutathione antioxidant system is suppressed early on but becomes activated in the later stages. This phenomenon could facilitate the early invasion of EHP while assisting the host in mitigating oxidative damage caused by late-stage infection. Notably, there are distinctive events in polyamine metabolism. Sustained up-regulation of spermidine synthase and concurrent reduction in spermine levels suggest a potential role of polyamines in EHP development. Throughout the infection process, significant differences in genes such as ATP synthase and hexokinase highlight the continuous influence on energy metabolism pathways. Additionally, growth-related pathways involving amino acids such as tryptophan, histidine, and taurine are disrupted early on, potentially contributing to the growth inhibition observed during the initial stages of infection. In summary, these findings elucidate the dynamic interplay between the host, Litopenaeus vannamei, and the parasite, EHP, during infection. Specific phase differences in immune responses, energy metabolism, and antioxidant processes underscore the intricate relationship between the host and the parasite. The disruption of polyamine metabolism offers a novel perspective in understanding the proliferation mechanisms of EHP. These discoveries significantly advance our comprehension of the pathogenic mechanisms of EHP and its interactions with the host.

Spermidine synthase is essential for vegetative growth, stress response, secondary metabolism and pathogenicity in Alternaria alternata

Black spot, caused by the fungus Alternaria alternata, is one of the postharvest diseases that cause significant economic losses. Polyamine metabolism in fungi plays key roles in cellular processes and pathogen-host interactions. However, little is known about their detailed regulatory mechanisms on pathogenicity of plant fungi. In this study, we characterized the spermidine synthase AaSPDS in A. alternata. Knocking out AaSPDS caused a total loss of vegetative growth and sporulation which was partially restored by exogenous spermidine (Spd), so supplying 0.5 mM exogenous Spd to medium for evaluating the characteristics of WT and ΔAaSPDS. The deletion strain showed albino colonies, sparse mycelial tips and significant decreased biomass accumulation and melanin production. ΔAaSPDS strain was also more sensitive to osmotic stress, oxidative stress and cell wall-perturbing agents. Interestingly, the expression level of AaSPDS was greatly up-regulated during infection structure differentiation stage of A. alternata, and appressorium formation of the AaSPDS deletion strain was completely blocked. In addition, deletion of the AaSPDS gene led to a significant reduction in pathogenicity to pear fruit, altenuene (ALT) mycotoxin accumulation and the activities of cellulase (CL), β-glucosidase (β-GC) and polygalacturonase (PG). The results presented in this study suggested that AaSPDS influences the pathogenicity of A. alternata by regulating infection structure formation, cell wall degrading enzyme (CWDE) activity and mycotoxin production.

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.

Discovery of a Hidden Trypanosoma cruzi Spermidine Synthase Binding Site and Inhibitors through In Silico, In Vitro, and X-ray Crystallography.

In drug discovery research, the selection of promising binding sites and understanding the binding mode of compounds are crucial fundamental studies. The current understanding of the proteins-ligand binding model extends beyond the simple lock and key model to include the induced-fit model, which alters the conformation to match the shape of the ligand, and the pre-existing equilibrium model, selectively binding structures with high binding affinity from a diverse ensemble of proteins. Although methods for detecting target protein binding sites and virtual screening techniques using docking simulation are well-established, with numerous studies reported, they only consider a very limited number of structures in the diverse ensemble of proteins, as these methods are applied to a single structure. Molecular dynamics (MD) simulation is a method for predicting protein dynamics and can detect potential ensembles of protein binding sites and hidden sites unobservable in a single-point structure. In this study, to demonstrate the utility of virtual screening with protein dynamics, MD simulations were performed on Trypanosoma cruzi spermidine synthase to obtain an ensemble of dominant binding sites with a high probability of existence. The structure of the binding site obtained through MD simulation revealed pockets in addition to the active site that was present in the initial structure. Using the obtained binding site structures, virtual screening of 4.8 million compounds by docking simulation, in vitro assays, and X-ray analysis was conducted, successfully identifying two hit compounds.