Spermidine Synthase Research Articles

Melatonin confers enhanced polyamine metabolism and cell tolerance in Vitis vinifera against oxidative damage: Quantitative proteomic evidence

Melatonin (MLT) exhibited pleiotropic effects in multiple plant physiological processes; however, its role in the polyamine metabolism and quality performance of postharvest Vitis vinifera berry remain unknown. In the present study, MLT was applied to postharvest Vitis vinifera cv. Kyoho berry, which delayed berry abscission, berry rotten, and promoted cell tolerance to oxidative stress. Notably, the malondialdehyde content of berries was reduced to 40.8 % on the application of 200 μmol L−1 MLT. Furthermore, tandem mass tags (TMT)-based quantitative proteomic analysis identified 5,156 proteins from berry skin, among which 158 proteins showed quantitatively differences in response to MLT application. These differentially expressed proteins were mainly upregulated in the arginine and proline metabolism pathways, lysine degradation, and ascorbate and aldarate metabolism pathways. The abundance of proteins involved in polyamine metabolisms, including N-carbamoylputrescine amidase, spermidine synthase, and aldehyde dehydrogenases were also upregulated. Moreover, MLT application enhanced contents of arginine, proline, 4-aminobutanoic acid, and polyamines, which played an essential role in oxidative stress response. Further, the transcript level of key enzymes involved in polyamine metabolism, including VvADC, VvODC, VvNAC, VvSPDS and VvCuAO were up-regulated on MLT application. Overall, the role of MLT in regulating the polyamine metabolism and subsequently in cell tolerance against oxidative damage was scientifically established for the first time for Vitis vinifera. The empirical findings of this study may propose new insights on MLT application in postharvest berry physiology and provide theoretical regulation for the preservation of berries, perhaps other fruits.

Overexpression of EiKCS confers paraquat‐resistance in rice (Oryza sativaL.) by promoting the polyamine pathway

BACKGROUNDParaquat is used widely as one of the bipyridine herbicides, which generates reactive oxygen species to cause cell death. With a growing number of paraquat‐resistant weeds, the mechanism of paraquat‐resistance in plants remains unclear. This research verified the functions of a previously confirmed putative paraquat‐resistant gene, EiKCS, from paraquat‐resistant goosegrass by genetic engineering in a single overexpressing line in rice.RESULTSOverexpression of EiKCS improved paraquat resistance in transgenic rice (KCSox). Pre‐applied (12 h) exogenous spermidine (1.5 mmol L−1), alleviated the injury of paraquat in rice. Paraquat induced injury in KCSox was 19.57%, which was lower than 32.22% injury it induced in wild‐type (WT) rice. The paraquat‐resistant mechanism was through the increased activity of antioxidant enzymes and the overproduction of endogenous polyamines. The spermine content in KCSox was more than 30 μg mL−1, while that in WT rice was less than 5 μg mL−1. Quantitative proteomics showed that β‐ketoacyl‐coenzyme A (CoA) synthase (51.81 folds) encoded by the transgenic EiKCS gene promoted the synthesis of the proteins involved with the polyamine pathway. The synthesized putrescine was promoted by the arginine decarboxylase (ADC) pathway. The spermidine synthase I (1.10‐fold) and three eceriferum cofactors (CERs) were responsive to the paraquat stress. We validated putrescine (C18H20N2O2) spermidine (C28H31N3O3), and spermine (C38H42N4O4) in this study.CONCLUSION EiKCS encoding β‐ketoacyl‐CoA synthase from goosegrass has been shown as an ideal candidate gene for engineering genetically modified organism (GMO) crops, as its overexpression does not only bring paraquat‐resistance, but also have potential benefits without decreasing yield and rice grain quality. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterizing the homeostatic regulation of the polyamine pathway using the Drosophila melanogaster model system

Polyamines are small, naturally occurring polycations that are essential for normal cell growth and development. Maintaining a homeostatic level of both the polyamine pathway enzymes and the levels of the polyamines putrescine, spermidine and spermine is important because the dysregulation of the polyamine pathway has been associated with physical anomalies including cancer, Parkinson's disease, Snyder-Robinson syndrome and aging in mammals. To date, little is understood regarding how the polyamine pathway maintains polyamine homeostasis in the fly, an emerging model for polyamine studies. The aim of these studies was to better characterize how the downregulation or ablation of the polyamine biosynthetic enzymes ornithine decarboxylase, spermidine synthase and spermine synthase influence the expression of the genes coding for other polyamine pathway enzymes and the levels of the polyamines themselves utilizing the model organism, Drosophila melanogaster. We demonstrate the complexities of the polyamine metabolic pathway and show that downregulation of any of these polyamine pathway enzymes can lead to an array of changes in other parts of the pathway as well as alter the cellular levels of polyamines themselves. These data highlight the complex nature of regulation of this pathway and underscore the need to better understand its self-regulation in this and other model systems.

Purification, crystallization, and X-ray crystallographic analysis of spermidine synthase from Kluyveromyces lactis

Purification, crystallization, and X-ray crystallographic analysis of spermidine synthase from <i>Kluyveromyces lactis</i>

Transcriptomic Analysis of Resistant and Susceptible Responses in a New Model Root-Knot Nematode Infection System Using Solanum torvum and Meloidogyne arenaria.

Root-knot nematodes (RKNs) are among the most devastating pests in agriculture. Solanum torvum Sw. (Turkey berry) has been used as a rootstock for eggplant (aubergine) cultivation because of its resistance to RKNs, including Meloidogyne incognita and M. arenaria. We previously found that a pathotype of M. arenaria, A2-J, is able to infect and propagate in S. torvum. In vitro infection assays showed that S. torvum induced the accumulation of brown pigments during avirulent pathotype A2-O infection, but not during virulent A2-J infection. This experimental system is advantageous because resistant and susceptible responses can be distinguished within a few days, and because a single plant genome can yield information about both resistant and susceptible responses. Comparative RNA-sequencing analysis of S. torvum inoculated with A2-J and A2-O at early stages of infection was used to parse the specific resistance and susceptible responses. Infection with A2-J did not induce statistically significant changes in gene expression within one day post-inoculation (DPI), but afterward, A2-J specifically induced the expression of chalcone synthase, spermidine synthase, and genes related to cell wall modification and transmembrane transport. Infection with A2-O rapidly induced the expression of genes encoding class III peroxidases, sesquiterpene synthases, and fatty acid desaturases at 1 DPI, followed by genes involved in defense, hormone signaling, and the biosynthesis of lignin at 3 DPI. Both isolates induced the expression of suberin biosynthetic genes, which may be triggered by wounding during nematode infection. Histochemical analysis revealed that A2-O, but not A2-J, induced lignin accumulation at the root tip, suggesting that physical reinforcement of cell walls with lignin is an important defense response against nematodes. The S. torvum-RKN system can provide a molecular basis for understanding plant-nematode interactions.

Polyamine Metabolism in Scots Pine Embryogenic Cells under Potassium Deficiency.

Polyamines (PA) have a protective role in maintaining growth and development in Scots pine during abiotic stresses. In the present study, a controlled liquid Scots pine embryogenic cell culture was used for studying the responses of PA metabolism related to potassium deficiency. The transcription level regulation of PA metabolism led to the accumulation of putrescine (Put). Arginine decarboxylase (ADC) had an increased expression trend under potassium deficiency, whereas spermidine synthase (SPDS) expression decreased. Generally, free spermidine (Spd) and spermine (Spm)/ thermospermine (t-Spm) contents were kept relatively stable, mostly by the downregulation of polyamine oxidase (PAO) expression. The low potassium contents in the culture medium decreased the potassium content of the cells, which inhibited cell mass growth, but did not affect cell viability. The reduced growth was probably caused by repressed metabolic activity and cell division, whereas there were no signs of H2O2-induced oxidative stress or increased cell death. The low intracellular content of K+ decreased the content of Na+. The decrease in the pH of the culture medium indicated that H+ ions were pumped out of the cells. Altogether, our findings emphasize the specific role(s) of Put under potassium deficiency and strict developmental regulation of PA metabolism in Scots pine.

The Role of Spermidine Synthase (SpdS) and Spermine Synthase (Sms) in Regulating Triglyceride Storage in Drosophila.

Polyamines are small organic cations that are important for several biological processes such as cell proliferation, cell cycle progression, and apoptosis. The dysregulation of intracellular polyamines is often associated with diseases such as cancer, diabetes, and developmental disorders. Although polyamine metabolism has been well studied, the effects of key enzymes in the polyamine pathway on lipid metabolism are not well understood. Here, we determined metabolic effects resulting from the absence of spermidine synthase (SpdS) and spermine synthase (Sms) in Drosophila. While SpdS mutants developed normally and accumulated triglycerides, Sms mutants had reduced viability and stored less triglyceride than the controls. Interestingly, when decreasing SpdS and Sms, specifically in the fat body, triglyceride storage increased. While there was no difference in triglycerides stored in heads, thoraxes and abdomen fat bodies, abdomen fat body DNA content increased, and protein/DNA decreased in both SpdS- and Sms-RNAi flies, suggesting that fat body-specific knockdown of SpdS and Sms causes the production of smaller fat body cells and triglycerides to accumulate in non-fat body tissues of the abdomen. Together, these data provide support for the role that polyamines play in the regulation of metabolism and can help enhance our understanding of polyamine function in metabolic diseases.

Effects of ODC on polyamine metabolism, hormone levels, cell proliferation and apoptosis in goose ovarian granulosa cells

Ornithine decarboxylase (ODC) plays an indispensable role in the process of polyamine biosynthesis. Polyamines are a pivotal part of living cells and have diverse roles in the regulation of cell proliferation and apoptosis, aging and reproduction. However, to date, there have been no reports about ODC regulating follicular development in goose ovaries. Here, we constructed ODC siRNA and overexpression plasmids and transfected them into goose primary granulosa cells (GCs) to elucidate the effects of ODC interference and overexpression on the polyamine metabolism, hormone levels, cell apoptosis and proliferation of granulosa cells. After interfering with ODC in GCs, the mRNA and protein levels of ODC and the content of putrescine were greatly decreased (P < 0.05). When ODC was overexpressed, ODC mRNA and protein levels and putrescine content were greatly increased (P < 0.05). The polyamine-metabolizing enzyme genes ornithine decarboxylase antizyme 1 (OAZ1) and spermidine / spermine-N1-acetyltransferase (SSAT) were significantly increased, and spermidine synthase (SPDS) was significantly decreased when ODC was downregulated (P < 0.05). OAZ1, SPDS and SSAT were significantly increased when ODC was upregulated (P < 0.05). In addition, after interference with ODC, progesterone (P4) levels in the culture medium of GCs increased greatly (P < 0.05), while the overexpression of ODC caused the P4 level to decrease significantly (P < 0.05). After ODC downregulation, granulosa cell activity was significantly reduced, the apoptosis rate was significantly increased, and the BCL-2 / BAX ratio was downregulated (P < 0.05). Under ODC overexpression, the activity of GCs was notably increased, the apoptosis rate was significantly reduced, and the BCL-2 / BAX protein ratio was upregulated (P < 0.05). Our study successfully induced ODC interference and overexpression in goose ovarian GCs, and ODC regulated mainly putrescine content in GCs with a slight influence on spermidine and spermine. Moreover, ODC participated in the adjustment of P4 levels in the culture medium of GCs, promoted granulosa cell proliferation and inhibited granulosa cell apoptosis.

The regulation of polyamine pathway proteins in models of skeletal muscle hypertrophy and atrophy: a potential role for mTORC1.

Polyamines have been shown to be absolutely required for protein synthesis and cell growth. The serine/threonine kinase, the mechanistic target of rapamycin complex 1 (mTORC1), also plays a fundamental role in the regulation of protein turnover and cell size, including in skeletal muscle, where mTORC1 is sufficient to increase protein synthesis and muscle fiber size, and is necessary for mechanical overload-induced muscle hypertrophy. Recent evidence suggests that mTORC1 may regulate the polyamine metabolic pathway, however, there is currently no evidence in skeletal muscle. This study examined changes in polyamine pathway proteins during muscle hypertrophy induced by mechanical overload (7 days), with and without the mTORC1 inhibitor, rapamycin, and during muscle atrophy induced by food deprivation (48 h) and denervation (7 days) in mice. Mechanical overload induced an increase in mTORC1 signaling, protein synthesis and muscle mass, and these were associated with rapamycin-sensitive increases in adenosylmethione decarboxylase 1 (Amd1), spermidine synthase (SpdSyn), and c-Myc. Food deprivation decreased mTORC1 signaling, protein synthesis, and muscle mass, accompanied by a decrease in spermidine/spermine acetyltransferase 1 (Sat1). Denervation, resulted increased mTORC1 signaling and protein synthesis, and decreased muscle mass, which was associated with an increase in SpdSyn, spermine synthase (SpmSyn), and c-Myc. Combined, these data show that polyamine pathway enzymes are differentially regulated in models of altered mechanical and metabolic stress, and that Amd1 and SpdSyn are, in part, regulated in a mTORC1-dependent manner. Furthermore, these data suggest that polyamines may play a role in the adaptive response to stressors in skeletal muscle.

The Effects of Quercetin on the Gene Expression of Arginine Metabolism Key Enzymes in Human Embryonic Kidney 293 Cells

Background: Arginine metabolism is an important factor involved in tumorigenesis, progression, and survival of tumor cells. Besides, other metabolites produced in the arginine metabolism process, such as polyamines, nitric oxide, argininosuccinate, and agmatine, play key roles in different stages of tumor development. On the other hand, herbal metabolites are widely used to treat cancer. One of these herbal flavonoids is quercetin. Methods: In this study, according to MTT assay data, two concentrations of quercetin flavonoid were selected (57.5 and 115 µM) to treat human embryonic kidney 293 (HEK293) cells. Then RNA was extracted from the cells and used as a template for cDNA synthesis. Using real-time PCR, the expression of key enzymes involved in arginine metabolism was evaluated, including arginase 2 (Arg2), ornithine carbamoyl transferase (OTC), agmatinase (AGMAT), arginase 1 (Arg1), nitric oxide synthase 1 (nNOS), arginine decarboxylase (ADC), ornithine decarboxylase 1 (ODC), ornithine carbamoyl transferase (OCT), spermidine synthase (SRM), spermine synthase (SMS), argininosuccinate synthase 1 (ASS1), and argininosuccinate lyase (ASL). The Student t-test was used to analyze the data considering a P value of &lt; 0.05 as the significance level. Results: Our results indicated significant changes in the expression of arginine metabolism enzymes after quercetin exposure, confirming a role for quercetin plant flavonoid in regulating arginine metabolism in HEK293 cells. Conclusions: Quercetin could alter the gene expression of the key enzymes involved in arginine metabolism. This was the first study investigating the effects of quercetin on arginine metabolism in HEK293 cells.

Proteomic Insight into the Symbiotic Relationship of Pinus massoniana Lamb and Suillus luteus towards Developing Al-Stress Resistance.

Global warming significantly impacts forest range areas by increasing soil acidification or aluminum toxicity. Aluminum (Al) toxicity retards plant growth by inhibiting the root development process, hindering water uptake, and limiting the bioavailability of other essential micronutrients. Pinus massoniana (masson pine), globally recognized as a reforestation plant, is resistant to stress conditions including biotic and abiotic stresses. This resistance is linked to the symbiotic relationship with diverse ectomycorrhizal fungal species. In the present study, we investigated the genetic regulators as expressed proteins, conferring a symbiotic relationship between Al-stress resistance and Suillus luteus in masson pine. Multi-treatment trials resulted in the identification of 12 core Al-stress responsive proteins conserved between Al stress conditions with or without S. luteus inoculation. These proteins are involved in chaperonin CPN60-2, protein refolding and ATP-binding, Cu-Zn-superoxide dismutase precursor, oxidation-reduction process, and metal ion binding, phosphoglycerate kinase 1, glycolytic process, and metabolic process. Furthermore, 198 Al responsive proteins were identified specifically under S. luteus-inoculation and are involved in gene regulation, metabolic process, oxidation-reduction process, hydrolase activity, and peptide activity. Chlorophyll a-b binding protein, endoglucanase, putative spermidine synthase, NADH dehydrogenase, and glutathione-S-transferase were found with a significant positive expression under a combined Al and S. luteus treatment, further supported by the up-regulation of their corresponding genes. This study provides a theoretical foundation for exploiting the regulatory role of ectomycorrhizal inoculation and associated genetic changes in resistance against Al stress in masson pine.

Effect of cold stress on polyamine metabolism and antioxidant responses in chickpea

Metabolic and genomic characteristics of polyamines (PAs) may be associated with the induction of cold tolerance (CT) responses in plants. Characteristics of PAs encoding genes in chickpea (Cicer arietinum L.) and their function under cold stress (CS) are currently unknown. In this study, the potential role of PAs along with the antioxidative defense systems were assessed in two chickpea genotypes (Sel96th11439, cold-tolerant and ILC533, cold-sensitive) under CS conditions. Six days after exposure to CS, the leaf H2O2 content and electrolyte leakage index increased in the sensitive genotype by 47.7 and 59 %, respectively, while these values decreased or remained unchanged, respectively, in the tolerant genotype. In tolerant genotype, the enhanced activity of superoxide dismutase (SOD) (by 50 %) was accompanied by unchanged activities of ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT) as well as the accumulation of glutathione (GSH) (by 43 %) on the sixth day of CS. Higher levels of putrescine (Put) (322 %), spermidine (Spd) (45 %), spermine (Spm) (69 %) and the highest ratio of Put/(Spd + Spm) were observed in tolerant genotype compared to the sensitive one on the sixth day of CS. Gamma-aminobutyric acid (GABA) accumulation was 74 % higher in tolerant genotype compared to the sensitive one on the sixth day of CS. During CS, the activity of diamine oxidase (DAO) and polyamine oxidase (PAO) increased in tolerant (by 3.02- and 2.46-fold) and sensitive (by 2.51- and 2.8-fold) genotypes, respectively, in comparison with the respective non-stressed plants (normal conditions). The highest activity of DAO and PAO in the tolerant genotype was accompanied by PAs decomposition and a peak in GABA content on the sixth day of CS. The analysis of chickpea genome revealed the presence of five PAs biosynthetic genes, their chromosomal locations, and cis-regulatory elements. A significant increase in transcript levels of arginine decarboxylase (ADC) (24.26- and 7.96-fold), spermidine synthase 1 (SPDS1) (3.03- and 1.53-fold), SPDS2 (5.5- and 1.62-fold) and spermine synthase (SPMS) (3.92- and 1.65-fold) genes was detected in tolerant and sensitive genotypes, respectively, whereas the expression of ornithine decarboxylase (ODC) genes decreased significantly under CS conditions in both genotypes. Leaf chlorophyll and carotenoid contents exhibited declining trends in the sensitive genotype, while these photosynthetic pigments were stable in the tolerant genotype due to the superior performance of defensive processes under CS conditions. Overall, these results suggested the specific roles of putative PAs genes and PAs metabolism in development of effective CT responses in chickpea.

A two-enzyme cascade system for the bio-production of spermidine from putrescine

Abstract In vitro multiple-enzyme cascade system is becoming a promising biomanufacturing platform for producing biochemicals. Spermidine is a natural polyamine substance that is widely used in health care products and medicine. In this study, spermidine was synthesized by S-adenosylmethionine(SAM) decarboxylase and spermidine synthase through a two-enzyme cascade system in vitro. The factors influencing the efficiency of this cascade system, including the source of SAM decarboxylase, the expression conditions, the ratio of enzyme addition, reaction temperature, reaction pH, and metal ion additives were identified to determine the optimal conditions for spermidine production. With the optimized system, 3.7 g/L spermidine was finally produced from 2.5 g/L putrescine and 15 g/L SAM with the yield of 91.1 %.

Arbuscular Mycorrhizal Fungi Regulate Polyamine Homeostasis in Roots of Trifoliate Orange for Improved Adaptation to Soil Moisture Deficit Stress.

Soil arbuscular mycorrhizal fungi (AMF) enhance the tolerance of plants against soil moisture deficit stress (SMDS), but the underlying mechanisms are still not fully understood. Polyamines (PAs) as low-molecular-weight, aliphatic polycations have strong roles in abiotic stress tolerance of plants. We aimed to investigate the effect of AMF (Funneliformis mosseae) inoculation on PAs, PA precursors, activities of PA synthases and degrading enzymes, and concentration of reactive oxygen species in the roots of trifoliate orange (Poncirus trifoliata) subjected to 15 days of SMDS. Leaf water potential and total chlorophyll levels were comparatively higher in AMF-inoculated than in non-AMF-treated plants exposed to SMDS. Mycorrhizal plants recorded a significantly higher concentration of precursors of PA synthesis such as L-ornithine, agmatine, and S-adenosyl methionine, besides higher putrescine and cadaverine and lower spermidine during the 15 days of SMDS. AMF colonization raised the PA synthase (arginine decarboxylase, ornithine decarboxylase, spermidine synthase, and spermine synthase) activities and PA-degrading enzymes (copper-containing diamine oxidase and FAD-containing polyamine oxidase) in response to SMDS. However, mycorrhizal plants showed a relatively lower degree of membrane lipid peroxidation, superoxide anion free radical, and hydrogen peroxide than non-mycorrhizal plants, whereas the difference between them increased linearly up to 15 days of SMDS. Our study concluded that AMF regulated PA homeostasis in roots of trifoliate orange to tolerate SMDS.

Biosynthesis of a Novel Bioactive Metabolite of Spermidine from Bacillus amyloliquefaciens: Gene Mining, Sequence Analysis, and Combined Expression

Spermidine is a biologically active polyamine with extensive application potential in functional foods. However, previously reported spermidine titers by biosynthesis methods are relatively low, which hinders its industrial application. To improve the spermidine titer, key genes affecting the spermidine production were mined to modify Bacillus amyloliquefaciens. Genes of S-adenosylmethionine decarboxylase (speD) and spermidine synthase (speE) from different microorganisms were expressed and compared in B. amyloliquefaciens. Therein, the speD from Escherichia coli and speE from Saccharomyces cerevisiae were confirmed to be optimal for spermidine synthesis, respectively. Gene and amino acid sequence analysis further confirmed the function of speD and speE. Then, these two genes were co-expressed to generate a recombinant strain B. amyloliquefaciens HSAM2(PDspeD-SspeE) with a spermidine titer of 105.2 mg/L, improving by 11.0-fold compared with the control (HSAM2). Through optimization of the fermentation medium, the spermidine titer was increased to 227.4 mg/L, which was the highest titer among present reports. Moreover, the consumption of the substrate S-adenosylmethionine was consistent with the accumulation of spermidine, which contributed to understanding its synthesis pattern. In conclusion, two critical genes for spermidine synthesis were obtained, and an engineering B. amyloliquefaciens strain was constructed for enhanced spermidine production.

Podocyte healthy self-eating boosted by a spermidine meal?

The mechanisms sustaining a high level of autophagy in podocytes are not well delineated. Seminal studies had unraveled that the polyamine pathway is involved in the regulation of aging and autophagy. Polyamines (e.g., spermine, spermidine, and putrescine) are ubiquitous molecules essential for the physiological processes, including cell growth, development, and differentiation. Liang etal. examined the role of ornithine decarboxylase, and spermidine synthase, and demonstrated that endogenous spermidine is required to maintain intact podocyte autophagy.

Drought tolerant maize cultivar accumulates putrescine in roots

We compared putrescine metabolism in roots of tolerant maize cultivar (Karoon) to a susceptible cultivar (260) under drought stress. The experiment was conducted in growth chamber under controlled condition in 80 pots. Drought stress led to significant increase in root growth indices, H2O2 content and activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase). The qPCR analysis revealed that expression of maize polyamine oxidase (ZmPAO) genes including ZmPAO1, ZmPAO2, ZmPAO4 and ZmPAO6 as well as ornithine decarboxylase (ZmODC) significantly increased in root of both cultivars in response to drought. However, up-regulation of ZmPAO3 and ZmPAO5 was only observed in root of tolerant cultivar. Consistently, drought caused increased polyamine oxidase activity in the tolerant cultivar. Transcription of spermidine synthase (ZmSPDS) was down-regulated by drought stress. Transcript levels of ZmPOA, ZmODC and ZmSPDS were more affected by drought in tolerant cultivar compared to susceptible cultivar. Increase in putrescine content under drought stress was more prominent in roots of tolerant cultivar, compared to susceptible cultivar. We attribute the accumulation of putrescine to increased rate of putrescine synthesis, due to higher expression of ZmPAOs and ZmODC and decreased rate of its depletion for biosynthesis of higher polyamines due to down-regulation of ZmSPDS.

SP_0916 Is an Arginine Decarboxylase That Catalyzes the Synthesis of Agmatine, Which Is Critical for Capsule Biosynthesis in Streptococcus pneumoniae

The global burden of invasive pneumococcal diseases, including pneumonia and sepsis, caused by Streptococcus pneumoniae, a Gram-positive bacterial pathogen, remains a major global health risk. The success of pneumococcus as a pathogen can be attributed to its ability to regulate the synthesis of capsular polysaccharide (CPS) during invasive disease. We previously reported that deletion of a putative lysine decarboxylase (LDC; ΔSP_0916) in pneumococcal serotype 4 (TIGR4) results in reduced CPS. SP_0916 locus is annotated as either an arginine or a LDC in pneumococcal genomes. In this study, by biochemical characterization of the recombinant SP_0916, we determined the substrate specificity of SP_0916 and show that it is an arginine decarboxylase (speA/ADC). We also show that deletion of the polyamine transporter (potABCD) predicted to import putrescine and spermidine results in reduced CPS, while deletion of spermidine synthase (speE) for the conversion of putrescine to spermidine had no impact on the capsule. Targeted metabolomics identified a correlation between reduced levels of agmatine and loss of capsule in ΔspeA and ΔpotABCD, while agmatine levels were comparable between the encapsulated TIGR4 and ΔspeE. Exogenous supplementation of agmatine restored CPS in both ΔpotABCD and ΔspeA. These results demonstrate that agmatine is critical for regulating the CPS, a predominant virulence factor in pneumococci.

Yield-related agronomic traits evaluation for hybrid wheat and relations of ethylene and polyamines biosynthesis to filling at the mid-grain filling stage

Because of the yield increase of 3.5–15% compared to conventional wheat, hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future. In this study, we performed a principal component analysis (PCA) on two-line hybrids wheat and their parents using the grain weight (GW), the length of spike (LS), the kernel number of spike (KSN), and spike number (SPN) as variables. The results showed that the variables could be classified into three main factors, the weight factor (factor 1), the quantity factor 1 (factor 2) and the quantity factor 2 (factor 3), which accounted for 37.1, 22.6 and 18.5%, respectively of the total variance in different agronomic variables, suggesting that the GW is an important indicator for evaluating hybrid combinations, and the grain weight of restorer line (RGW) could be used as a reference for parents selection. The hybrid combination with a higher score in factor 1 direction and larger mid-parent heterosis (MPH) of the GW and its parents were used to carry out the analysis of grain filling, 1-aminocylopropane-1-carboxylicacid (ACC) and polyamine synthesis related genes. The results suggested that the GW of superior grain was significantly higher than that of inferior grains in BS1453×JS1 (H) and its parents. Both grain types showed a weight of H between BS1453 (M) and JS1(R), and a larger MPH, which may be caused by their differences in the active filling stage and the grain filling rate. The ADP-glucose pyrophosphorylase (AGPase), granule bound starch synthase I (GBSSI), starch synthase III (SSS), and starch branching enzyme-I (SBE-I) expression levels of H were intermediated between M and R, which might be closely related to MPH formation of the GW. Compared with R and H, the GW of M at maturity was the lowest. The expression levels of spermidine synthase 2 (Spd2), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) had significantly positive correlations with the grain filling rate (r=0.77*, 0.51*, 0.59*), suggesting their major roles in the grain filling and heterosis formation. These provide a theoretical basis for improving the GW of photo-thermo-sensitive male sterile lines (PTSMSL) by changing the endogenous polyamine synthesis in commercial applications.

VIRTUAL SCREENING TO IDENTIFY POTENTIAL INHIBITOR OF ARGINASE OF LEISHMANIASIS

Leishmaniasis is caused by Leishmania protozoan parasites transmitted by the female phlebotomine sandfly. The current treatment regimen of leishmaniasis is not up to the mark and there is a huge scope of improvement. Hence, the need to approve new drugs, a complete understanding of the pathophysiology of the parasite is required. Since polyamines are required by the parasites for their infection cycle, inhibitors of polyamine pathway can be targeted by the new drugs for restricting the infection. In Leishmania, the polyamine biosynthetic pathway comprises of four compounds: arginase (ARG), ornithine decarboxylase (ODC), spermidine synthase (SPD), and S-adenosylmethionine decarboxylase (ADOMETDC). To identify these novel medicines like compounds, a structure-based screening system was utilized against downloaded drug-like compounds. In total, 1279 compounds were downloaded from the ZINC database dependent on the properties like the known inhibitor nor-NOHA [N(omega)- hydroxy-nor-L-arginase]. Virtual-ligand screening approaches were applied to identify drug-related like compounds utilizing sub-atomic docking program AutoDockVina in PyRx 0.8, and five best novel medication like compounds were chosen and their hydrogen ties with the receptor were decided.ZINC84057569, ZINC87440467, ZINC04617649, ZINC33978586, ZINC01677572 and ZINC35794928, ZINC33978586, ZINC84057569. ZINC53751324, ZINC00204059 were finalized as inhibitors against Human Arginase I and L. mexicana arginase individually contrasted with nor-NOHA, based on their binding efficiency. These inhibitors may become the base for formulating new drugs against Leishmania's, focusing on both the protein for example Human Arginase I and L. mexicana arginase.&#x0D; Keywords: Leishmaniasis, Human Arginase I, Leishmania mexicana arginase, nor-NOHA, Polyamine pathway, Molecular docking, Virtual screening.