Exogenous cadaverine induces oxidative burst and reduces cadaverine conjugate content in the common ice plant

The effect of free cadaverine (Cad) on its conjugates formation was analyzed in roots of the common ice plants (Mesembryanthemum crystallinum L.). It was found for the first time that Cad could induce oxidative burst in the roots of adult plants, as was evident from the sharp decrease in the content of Cad soluble or insoluble conjugates. This unusual effect was associated with the increased oxidative degradation of exogenous Cad (1 mM, 1.5 h) and intense H2O2 production in the root cells of adult plants. Root treatment of both juvenile and adult plants with H2O2 (1 mM, 1.5 h) reduced the content of soluble Cad conjugates and increased the content of their components, free Cad and phenols. We also found that one of the possible reasons of the negative effect of exogenous diamine on the formation of conjugated forms in adult roots was alkalization of the root apoplast at Cad addition to nutrient medium and the unusual O2 {radical dot}- synthase function as a pH-dependent guaiacol peroxidase in the presence of a high content of H2O2. This was confirmed by the data on the accumulation of O2 {radical dot}- and enhanced superoxide dismutase activity in adult roots under treatment with Cad. It is possible that the accumulation of O2 {radical dot}- together with H2O2 was also responsible for oxidative burst, which induced a decrease in the content of Cad conjugates in adult roots of the common ice plants. © 2008

Exogenous cadaverine induces oxidative burst and reduces cadaverine conjugate content in the common ice plant

The effect of free cadaverine (Cad) on its conjugates formation was analyzed in roots of the common ice plants (Mesembryanthemum crystallinum L.). It was found for the first time that Cad could induce oxidative burst in the roots of adult plants, as was evident from the sharp decrease in the content of Cad soluble or insoluble conjugates. This unusual effect was associated with the increased oxidative degradation of exogenous Cad (1 mM, 1.5 h) and intense H2O2 production in the root cells of adult plants. Root treatment of both juvenile and adult plants with H2O2 (1 mM, 1.5 h) reduced the content of soluble Cad conjugates and increased the content of their components, free Cad and phenols. We also found that one of the possible reasons of the negative effect of exogenous diamine on the formation of conjugated forms in adult roots was alkalization of the root apoplast at Cad addition to nutrient medium and the unusual O2 {radical dot}- synthase function as a pH-dependent guaiacol peroxidase in the presence of a high content of H2O2. This was confirmed by the data on the accumulation of O2 {radical dot}- and enhanced superoxide dismutase activity in adult roots under treatment with Cad. It is possible that the accumulation of O2 {radical dot}- together with H2O2 was also responsible for oxidative burst, which induced a decrease in the content of Cad conjugates in adult roots of the common ice plants. © 2008

Heat shock-induced cadaverine accumulation and translocation throughout the plant

To test the possibility of heat shock (HS)-induced cadaverine accumulation and translocation throughout the plant, the titres of free polyamines in different plant organs, xylem and phloem exudates of the common ice plant (Mesembryanthemum crystallinum L.) were studied. Cadaverine level was relatively low in young leaves and apexes, while this diamine occurred in roots and stems at higher concentrations (20-29 nmol g-1 FW). The level of spermidine (60-300 nmol g-1 FW) in plants grown under normal conditions (23-25 °C, 55% RH, 14 h photoperiod) was 10-fold higher than the levels of all other polyamines (6-25 nmol g-1 FW). The plants responded to HS with a change in polyamine balance, as well as with a fast and transient increase in ethylene evolution. Local heating of plant aerial parts (47 °C, 2 h, 100% RH) primarily induced the accumulation of cadaverine and, to a lesser extent, putrescine and spermidine in roots and an increase in cadaverine concentration in the phloem exudate. The HS treatment of the root system resulted in accumulation of cadaverine in plant stems and in the xylem exudate. In contrast, spermine was not able for the long distance transport and stress induced accumulation. Exposure of detached leaves to exogenous ethylene (1-10 μ1 1-1, 4 h) was accompanied by accumulation of cadaverine. Arabidopsis wild type (Col-0) plants contained cadaverine in leaves and roots. In contrast, this diamine was not found in roots of ethylene- insensitive mutant strain (ein4) and accumulated only under HS treatment (45 °C, 1 h). These findings demonstrate ethylene dependent inter-organ translocation of cadaverine, as well as the possible involvement of ethylene in regulation of cadaverine level in plants under stress. © 2001 Elsevier Science Ireland Ltd. All rights reserved

Functioning of defense systems in halophytes and glycophytes under progressing salinity

Six-week-old Plantago major L. and Thellungiella halophila Mey. plants were subjected to progressing salinity by a daily increase in the NaCl concentration by 100 mM until the final concentration of 400 mM. A dynamics of stress-dependent accumulation of Na+ and Cl- ions, proline, and free polyamines and also activities of antioxidant enzymes, superoxide oxidase (SOD) and free, ion-bound, and covalently bound guaiacol-dependent peroxidases was studied. We also examined the intensity of gene expression encoding enzymes of proline metabolism and polyamine biosynthesis. It was shown that the high salt-resistance of the halophyte T. halophila was determined by plant capability of ion accumulation and stress-dependent proline accumulation. An important role in the maintenance of this plant homeostasis under salinity plays a high constitutive levels of activities of three types of peroxidases tested and also of proline manifesting a polyfunctional protective action. In contrast, P. major plants characterized by a lower tolerance to salt excess did not display a high constitutive level of proline or the activity of guaiacol-dependent peroxidases; they also were not capable of stress-induced accumulation of compatible osmolytes and did not accumulate the salt. However, this glycophyte contained relatively much spermidine and active SOD, which provided for a decrease in the damaging effects of reactive oxygen species under salt shock. In both plant species, it was established that salinity changed the intracellular content of polyamines, which was not dependent on the activity of gene transcription encoding the enzymes of their biosynthesis. The results obtained support a hypothesis that halophytes and glycophytes have some common mechanisms of tolerance to salinity, but the control of these mechanisms differs substantially. © 2007 Pleiades Publishing, Ltd

Proline controls the level of polyamines in common sage plants under normal conditions and at UV-B irradiation

Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4-5 true leaves were treated for 12, 24, 36, or 48 h with proline added to nutrient medium to a final concentration of 5 mM, or irradiated with UV-B light (12.3 kJ/m2 for 10 min), or subjected to combined action of these factors. In these plants, activity of proline dehydrogenase (PDH), the content of proline, and the contents of free and conjugated polyamines were determined in the leaves and roots. It was shown that, in control plants, the content of endogenous proline was close to zero. In the presence of proline in medium, its total content in the roots was 9 μmol/g fr wt in 12 h of exposure, whereas in the leaves the content of proline increased only in 24 h and achieved only 1 μmol/g fr wt. The content of free putrescine increased in the leaves and especially in the roots after 10-min irradiation with UV-B light. The biosynthesis of putrescine was induced in the presence of proline in medium and was observed earlier than after UV-B irradiation. UV-B irradiation affected not only the synthesis of putrescine but also that of spermidine and spermine; it also induced accumulation of their soluble conjugates. Exogenous proline enhanced putrescine synthesis but inhibited the formation of polyamine soluble conjugates. At combined treatment of the two factors, the content of free putrescine in the leaves displayed a tendency to the rise and in the roots, to the decrease. At the same time, the content of polyamine free conjugates increased in both leaves and roots. All these facts could be considered as an indirect indication of relationship between proline and polyamine biosyntheses. We can also state that an artificially created high proline concentration in common sage tissues characterized of its low constitutive level resulted in disturbances in the homeostasis of low-molecular cell metabolites and induced a requirement in its restoration by diverse ways. This agrees with activation of PDH, a key enzyme of proline degradation. Induction of polyamine biosynthesis and changes in the content of their soluble conjugates might be one of the ways for such restoration. Under stress conditions, the high proline concentration is not toxic for plants because polyamines and proline are the components of the plant defense system, thus weakening damaging effects of abiotic stressors. © Pleiades Publishing, Ltd., 2010

Functioning of defense systems in halophytes and glycophytes under progressing salinity

Six-week-old Plantago major L. and Thellungiella halophila Mey. plants were subjected to progressing salinity by a daily increase in the NaCl concentration by 100 mM until the final concentration of 400 mM. A dynamics of stress-dependent accumulation of Na+ and Cl- ions, proline, and free polyamines and also activities of antioxidant enzymes, superoxide oxidase (SOD) and free, ion-bound, and covalently bound guaiacol-dependent peroxidases was studied. We also examined the intensity of gene expression encoding enzymes of proline metabolism and polyamine biosynthesis. It was shown that the high salt-resistance of the halophyte T. halophila was determined by plant capability of ion accumulation and stress-dependent proline accumulation. An important role in the maintenance of this plant homeostasis under salinity plays a high constitutive levels of activities of three types of peroxidases tested and also of proline manifesting a polyfunctional protective action. In contrast, P. major plants characterized by a lower tolerance to salt excess did not display a high constitutive level of proline or the activity of guaiacol-dependent peroxidases; they also were not capable of stress-induced accumulation of compatible osmolytes and did not accumulate the salt. However, this glycophyte contained relatively much spermidine and active SOD, which provided for a decrease in the damaging effects of reactive oxygen species under salt shock. In both plant species, it was established that salinity changed the intracellular content of polyamines, which was not dependent on the activity of gene transcription encoding the enzymes of their biosynthesis. The results obtained support a hypothesis that halophytes and glycophytes have some common mechanisms of tolerance to salinity, but the control of these mechanisms differs substantially. © 2007 Pleiades Publishing, Ltd

Contribution of the ornithine pathway to proline accumulation in radish cotyledons exposed to salt stress

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Heat shock-induced cadaverine accumulation and translocation throughout the plant

To test the possibility of heat shock (HS)-induced cadaverine accumulation and translocation throughout the plant, the titres of free polyamines in different plant organs, xylem and phloem exudates of the common ice plant (Mesembryanthemum crystallinum L.) were studied. Cadaverine level was relatively low in young leaves and apexes, while this diamine occurred in roots and stems at higher concentrations (20-29 nmol g-1 FW). The level of spermidine (60-300 nmol g-1 FW) in plants grown under normal conditions (23-25 °C, 55% RH, 14 h photoperiod) was 10-fold higher than the levels of all other polyamines (6-25 nmol g-1 FW). The plants responded to HS with a change in polyamine balance, as well as with a fast and transient increase in ethylene evolution. Local heating of plant aerial parts (47 °C, 2 h, 100% RH) primarily induced the accumulation of cadaverine and, to a lesser extent, putrescine and spermidine in roots and an increase in cadaverine concentration in the phloem exudate. The HS treatment of the root system resulted in accumulation of cadaverine in plant stems and in the xylem exudate. In contrast, spermine was not able for the long distance transport and stress induced accumulation. Exposure of detached leaves to exogenous ethylene (1-10 μ1 1-1, 4 h) was accompanied by accumulation of cadaverine. Arabidopsis wild type (Col-0) plants contained cadaverine in leaves and roots. In contrast, this diamine was not found in roots of ethylene- insensitive mutant strain (ein4) and accumulated only under HS treatment (45 °C, 1 h). These findings demonstrate ethylene dependent inter-organ translocation of cadaverine, as well as the possible involvement of ethylene in regulation of cadaverine level in plants under stress. © 2001 Elsevier Science Ireland Ltd. All rights reserved

Proline controls the level of polyamines in common sage plants under normal conditions and at UV-B irradiation

Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4-5 true leaves were treated for 12, 24, 36, or 48 h with proline added to nutrient medium to a final concentration of 5 mM, or irradiated with UV-B light (12.3 kJ/m2 for 10 min), or subjected to combined action of these factors. In these plants, activity of proline dehydrogenase (PDH), the content of proline, and the contents of free and conjugated polyamines were determined in the leaves and roots. It was shown that, in control plants, the content of endogenous proline was close to zero. In the presence of proline in medium, its total content in the roots was 9 μmol/g fr wt in 12 h of exposure, whereas in the leaves the content of proline increased only in 24 h and achieved only 1 μmol/g fr wt. The content of free putrescine increased in the leaves and especially in the roots after 10-min irradiation with UV-B light. The biosynthesis of putrescine was induced in the presence of proline in medium and was observed earlier than after UV-B irradiation. UV-B irradiation affected not only the synthesis of putrescine but also that of spermidine and spermine; it also induced accumulation of their soluble conjugates. Exogenous proline enhanced putrescine synthesis but inhibited the formation of polyamine soluble conjugates. At combined treatment of the two factors, the content of free putrescine in the leaves displayed a tendency to the rise and in the roots, to the decrease. At the same time, the content of polyamine free conjugates increased in both leaves and roots. All these facts could be considered as an indirect indication of relationship between proline and polyamine biosyntheses. We can also state that an artificially created high proline concentration in common sage tissues characterized of its low constitutive level resulted in disturbances in the homeostasis of low-molecular cell metabolites and induced a requirement in its restoration by diverse ways. This agrees with activation of PDH, a key enzyme of proline degradation. Induction of polyamine biosynthesis and changes in the content of their soluble conjugates might be one of the ways for such restoration. Under stress conditions, the high proline concentration is not toxic for plants because polyamines and proline are the components of the plant defense system, thus weakening damaging effects of abiotic stressors. © Pleiades Publishing, Ltd., 2010

Role of antioxidant systems in wild plant adaptation to salt stress

Wild plants differing in the strategies of adaptation to salinity were grown for six weeks in the phytotron and then subjected to salt stress (100 mM NaCl, 24 h). The activities of principal antioxidant enzymes and the accumulation of sodium ions and proline were studied. Independently of the level of constitutive salt tolerance, plants of all species tested accumulated sodium ions under salinity conditions but differed in their capability of stress-dependent proline accumulation and superoxide dismutase (SOD) and guaiacol-dependent peroxidase activities. Proline-accumulating species were found among both halophytes (Artemisia lerchiana and Thellungiella halophila) and glycophytes (Plantago major and Mycelis muralis). The high activities of ionically-bound and covalently bound peroxidases were characteristic of Th. halophila plants. High constitutive and stress-induced SOD activities were, as a rule, characteristic of glycophytes with the low constitutive proline level: Geum urbanum and Thalictrum aquilegifolium. Thus, a negative correlation was found between proline content and SOD activity in wild species tested; it was especially bright in the halophyte Th. halophila and glycophyte G. urbanum. An extremely high constitutive and stress-induced levels of proline and peroxidase activity in Th. halophila maybe compensate SOD low activity in this plant, and this contributed substantially into its salt resistance. Thus, monitoring of stress-dependent activities of some antioxidant enzymes and proline accumulation in wild plant species allowed a supposition of reciprocal interrelations between SOD activity and proline accumulation. It was also established that the high SOD activity is not obligatory trait of species salt tolerance. Moreover, plants with the high activity of peroxidase and active proline accumulation could acclimate to salts stress (100 mM NaCl, 24 h) independently of SOD activity. © 2008 MAIK Nauka