Polyamine Metabolism In Plants Research Articles

Unraveling the genetics of polyamine metabolism in barley for senescence-related crop improvement

We explored the polyamine (PA) metabolic pathway genes in barley (Hv) to understand plant development and stress adaptation in Gramineae crops with emphasis on leaf senescence. Bioinformatics and functional genomics tools were utilized for genome-wide identification, comprehensive gene features, evolution, development and stress effects on the expression of the polyamine metabolic pathway gene families (PMGs). Three S-adenosylmethionine decarboxylases (HvSAMDCs), two ornithine decarboxylases (HvODCs), one arginine decarboxylase (HvADC), one spermidine synthase (HvSPDS), two spermine synthases (HvSPMSs), five copper amine oxidases (HvCuAOs) and seven polyamine oxidases (HvPAOs) members of PMGs were identified and characterized in barley. All the HvPMG genes were found to be distributed on all chromosomes of barley. The phylogenetic and comparative assessment revealed that PA metabolic pathway is highly conserved in plants and the prediction of nine H. vulgare miRNAs (hvu-miR) target sites, 18 protein-protein interactions and 961 putative CREs in the promoter region were discerned. Gene expression of HvSAMDC3, HvCuAO7, HvPAO4 and HvSPMS1 was apparent at every developmental stage. SPDS/SPMS gene family was found to be the most responsive to induced leaf senescence. This study provides a reference for the functional investigation of the molecular mechanism(s) that regulate polyamine metabolism in plants as a tool for future breeding decision management systems.

Short-Term Salicylic Acid Treatment Affects Polyamine Metabolism Causing ROS-NO Imbalance in Tomato Roots.

The phytohormone salicylic acid (SA) can influence the polyamine metabolism in plants. Additionally, polyamines (PAs) can regulate the synthesis of SA, providing an exciting interplay between them not only in plant growth and development but also in biotic or abiotic stress conditions. The effect of SA on polyamine metabolism of leaves is well-studied but the root responses are rarely investigated. In this study, tomato roots were used to investigate the effect of short-term exposition of SA in two different concentrations, a sublethal 0.1 mM and a lethal 1 mM. To explore the involvement of SA in regulating PAs in roots, the degradation of PAs was also determined. As both SA and PAs can induce reactive oxygen species (ROS) and nitric oxide (NO) production, the balance of ROS and NO was analyzed in root tips. The results showed that 0.1 mM SA induced the production of higher PAs, spermidine (Spd), and spermine (Spm), while 1 mM SA decreased the PA contents by activating degrading enzymes. Studying the ROS and NO levels in root tips, the ROS production was induced earlier than NO, consistent with all the investigated zones of roots. This study provides evidence for concentration-dependent rapid effects of SA treatments on polyamine metabolism causing an imbalance of ROS–NO in root tips.

Effect of the fungal endophyte Epichloë bromicola on polyamines in wild barley (Hordeum brevisubulatum) under salt stress

The endophytic fungus Epichloe bromicola forms mutualistic symbiotic associations with wild barley (Hordeum brevisubulatum) in the saline-alkali areas of northwestern China. E. bromicola enhances the tolerance of H. brevisubulatum to salt stress. Because plant polyamine metabolism is closely related to microbial infection and tolerance to diverse abiotic stresses, we hypothesized that in symbiotic plants polyamine modification may result from E. bromicola infection, and that improved tolerance to abiotic stress by the presence of this endophyte might be related to polyamine modification. Our focus in this study was to investigate whether E. bromicola affects polyamine metabolism in host plants under salt stress. E. bromicola infected (E+) and endophyte free (E-) wild barley plants were subjected to NaCl treatments (0, 100, 200 and 300 mM). Dry weight, diamine putrescine (Put), triamine spermidine (Spd) and tetramine spermine (Spm) content and the content of their free, soluble conjugated and insoluble bound forms were measured after 21 d exposure to stress. E. bromicola infection led to significant amelioration of salt stress in H. brevisubulatum. The presence of the endophyte significantly increased dry weight, spermidine and spermine content, but decreased putrescine content and the putrescine: (spermidine + spermine) ratio. E. bromicola infection also lowered the proportion of putrescine in total polyamines, but increased the proportion of spermidine and spermine in total polyamines. Furthermore, E. bromicola infection significantly increased the proportion of insoluble bound forms of polyamines, and decreased the proportion of free forms of polyamines and soluble conjugated forms of polyamines. H. brevisubulatum salinity stress tolerance induced by E. bromicola infection correlated with enhanced conversion of putrescine to spermidine and spermine, as well as improved shift ability from free forms and soluble conjugated forms of polyamines to insoluble bound forms of polyamines.

Transcriptional regulation of the rice arginine decarboxylase (Adc1) and S-adenosylmethionine decarboxylase (Samdc) genes by methyl jasmonate

We investigated the effect of methyl jasmonate (MeJa) treatment on the expression of two genes in the rice polyamine biosynthesis pathway and on the polyamine content in wild type plants and transgenic rice plants expressing a Datura stramonium (Ds) Adc cDNA, the latter accumulating up to three-fold the normal level of putrescine. Exogenous MeJa transiently inhibited the expression of OsAdc1, OsSamdc and Spermidine synthase (OsSpds) genes in the polyamine biosynthesis pathway, probably through transcriptional repression. There was also a similar negative impact on the DsAdc transgene in transgenic plants, even though a constitutive promoter was used to drive transgene expression. The free putrescine content was reduced significantly in the leaves of both wild type and transgenic plants in response to MeJa, although the magnitude of the effect was greater in wild type plants. We discuss our findings with respect to the previously proposed threshold model of polyamine metabolism in plants subjected to abiotic stress.

Transgenic cell lines as a useful tool to study the biochemistry of down-regulation of an endogenous rice gene using a heterologous diamine-oxidase cDNA

Transgenic rice ( Oryza sativa L.) cell lines engineered with the pea diamine oxidase cDNA in antisense orientation under the control of two different promoters were recovered using particle bombardment. Plasmids p35S daoa and pE daoa contained the pea diamine oxidase cDNA driven by the CaMV35S and the pea ENOD12 nodulin promoter, respectively. Molecular analyses confirmed the stable integration of the transgene and active transcription (mRNA) with both promoters driving the gene of interest. We observed a 2-fold decrease in diamine oxidase activity ( P < 0.01) in transformed callus lines expressing p35S daoa compared to wild-type or lines expressing the selectable marker gene alone ( hpt). In cell lines transformed with pE daoa, a 2.5-fold reduction in enzyme activity was measured ( P < 0.01). Biochemical analysis of cellular polyamines from p35S daoa transformants indicated up to a 6-fold increase in putrescine levels ( P < 0.001). Concentrations of higher polyamines also increased, with spermidine and spermine levels increasing 8- ( P < 0.05) and 3.5-fold ( P < 0.01) respectively. A maximum of 2.5-fold increase in putrescine ( P < 0.001) and spermidine ( P < 0.001) was measured in lines transformed with pE daoa. No significant variation ( P > 0.05) was observed in spermine levels in pE daoa transformants. We demonstrate for the first time the down-regulation of an endogenous enzyme involved in polyamine metabolism in plants accompanied by a concomitant increase in the concentration of putrescine and spermidine.

Improved method for HPLC analysis of polyamines, agmatine and aromatic monoamines in plant tissue.

The high performance liquid chromatographic (HPLC) method of Flores and Galston (1982 Plant Physiol 69: 701) for the separation and quantitation of benzoylated polyamines in plant tissues has been widely adopted by other workers. However, due to previously unrecognized problems associated with the derivatization of agmatine, this important intermediate in plant polyamine metabolism cannot be quantitated using this method. Also, two polyamines, putrescine and diaminopropane, also are not well resolved using this method. A simple modification of the original HPLC procedure greatly improves the separation and quantitation of these amines, and further allows the simulation analysis of phenethylamine and tyramine, which are major monoamine constituents of tobacco and other plant tissues. We have used this modified HPLC method to characterize amine titers in suspension cultured carrot (Daucas carota L.) cells and tobacco (Nicotiana tabacum L.) leaf tissues.

Partial Purification and Characterization of Arginine Decarboxylase from Avocado Fruit, A Thermostable Enzyme

A partially purified preparation of arginine decarboxylase (EC 4.1.1.19), a key enzyme in polyamine metabolism in plants, was isolated from avocado (Persea americana Mill. cv Fuerte) fruit. The preparation obtained from the crude extract after ammonium sulfate precipitation, dialysis, and heat treatment, had maximal activity between pH 8.0 and 9.0 at 60 degrees C, in the presence of 1.2 millimolar MnCl(2), 2 millimolar dithiothreitol, and 0.06 millimolar pyridoxal phosphate. The K(m), of arginine for the decarboxylation reaction was determined for enzymes prepared from the seed coat of both 4-week-old avocado fruitlet and fully developed fruit, and was found to have a value of 1.85 and 2.84 millimolar, respectively. The value of V(app) (max) of these enzymes was 1613 and 68 nanomoles of CO(2) produced per milligram of protein per hour for the fruitlet and the fully developed fruit, respectively. Spermine, an end product of polyamine metabolism, caused less than 5% inhibition of the enzyme from fully developed fruit and 65% inhibition of the enzyme from the seed coat of 4-week-old fruitlets at 1 millimolar under similar conditions. The effect of different inhibitors on the enzyme and the change in the nature of the enzyme during fruit development are discussed.

Interaction of polyamines and light on biochemical processes involved in leaf senescence

Abstract The rapid senescence of detached oat leaves in darkness is first manifested by a sharp rise in RNase activity (about 50% within 1 h), then by a rise in protease activity (indicated by an increase in non‐protein α‐amino nitrogen within 6 h) and ultimately by chlorophyll degradation (beginning after 18 h). These degradative changes are delayed or prevented by low concentrations (1–10 mM) of the naturally‐occurring polyamines cadaverine, putrescine, spermidine and spermine. The tetraamine spermine is generally more active than the triamine spermidine, which is in turn more active than the diamines putrescine and cadaverine. All the polyamines are more active than kinetin or cycloheximide. As little as 10 min of exposure to 1 mM spermine, especially at the beginning of the dark period, produces a marked retardation of chlorophyll degradation over a 48 h period, and 60 min of exposure saturates the effect.In the light, all polyamines promote, rather than retard, the disappearance of chlorophyll but, as in the dark, they inhibit the rise in RNase and non‐protein α‐amino nitrogen. The photobleaching of chlorophyll in the presence of polyamines is proportional to the duration of exposure to high irradiance (16.5 Wm−2) fluorescent light. Such light is more effective toward the end of the 48 h post‐excision test period than at the beginning.Calcium ion (1–10 mM) supplied together with the polyamines diminishes their action in dark and light, indicating probable involvement of an initial ionic attachment mechanism.The loss of chlorophyll from the leaves of four species of dicotyledonous plants (pea, bean, rape, tobacco) in the darkness is similarly retarded by 1–10 mM polyamines. In rape, the most rapidly senescing species, 1 mM spermine almost completely arrests chlorophyll degradation over a 96 h period. It is suggested that polyamine metabolism in plants may be related to normal physiological control mechanisms as in microorganisms and animals, and that polyamines could find use as anti‐senescence agents for plants.