Ascorbate peroxidase (APX), as a participant in the ascorbate—glutathione cycle, has been suggest... more Ascorbate peroxidase (APX), as a participant in the ascorbate—glutathione cycle, has been suggested to be a particularly important antioxidant enzyme in helping plants survive oxidative stress, but direct evidence for this has not been reported. We demonstrate that expressing antisense RNA comprising 45% of the 3′‐coding region of the tobacco cytosolic APX, can reduce significantly both the endogenous APX mRNA levels and the APX catalytic activity in transgenic tobacco plants. Those transgenic plants showing a reduction in both endogenous APX mRNA levels and extractable APX activity display a significant increase in ozone injury following high‐level ozone exposure. Lower‐level ozone exposure reveals even more drastic differences between the antisense and control plants, suggesting that even a partial loss of APX function in oxidative defence cannot be fully compensated for by other antioxidant measures.
Proceedings of the National Academy of Sciences, 1999
Reactive oxygen intermediates (ROI) play a critical role in the defense of plants against invadin... more Reactive oxygen intermediates (ROI) play a critical role in the defense of plants against invading pathogens. Produced during the “oxidative burst,” they are thought to activate programmed cell death (PCD) and induce antimicrobial defenses such as pathogenesis-related proteins. It was shown recently that during the interaction of plants with pathogens, the expression of ROI-detoxifying enzymes such as ascorbate peroxidase (APX) and catalase (CAT) is suppressed. It was suggested that this suppression, occurring upon pathogen recognition and coinciding with an enhanced rate of ROI production, plays a key role in elevating cellular ROI levels, thereby potentiating the induction of PCD and other defenses. To examine the relationship between the suppression of antioxidative mechanisms and the induction of PCD and other defenses during pathogen attack, we studied the interaction between transgenic antisense tobacco plants with reduced APX or CAT and a bacterial pathogen that triggers the ...
A mixture of growth factors derived from the growth factor, or weight barter or a transgenic plan... more A mixture of growth factors derived from the growth factor, or weight barter or a transgenic plant the purified form purified from the transformed plant extract, or a transformed plant containing a growth factor for use in the topical therapy, dermatological and cosmetic fields relates to a cosmetic and dermatological composition for (cosmetic and dermatologic composition) comprising a. Importantly, the present invention is stabilized, which can be used for cosmetic and topical treatment, and provides a safer growth factors. Preferred compositions plants - including manufacturing (plant-produced) growth factors and hyaluronic acid. Containing the stabilized growth factors, skin-care / dermatological composition is an unwanted degradation product and the resulting composition does not have a risk of loss of activity. In addition, the compositions of the invention do not contain contaminants and infectious agents (transmissible agent), which may be originating from animal or bacterial cell-based expression system.
Environmental factors, such as temperature and water availability, are important determinants of ... more Environmental factors, such as temperature and water availability, are important determinants of plant growth, development and geographical distribution. Thus crop production is severely limited by stresses due to freezing temperatures and drought. The vulnerability of plants to environmental stresses is primarily due to their sessile growth habit. However, the same growth habit, by enforcing a selection pressure, has also led to the development of sophisticated mechanisms by which plants constantly monitor their environment and activate mechanisms to tolerate these stresses. Plants incapable of mounting such responses succumb to the stressful environment. Thus, freezing tolerant plants can survive sub-zero temperatures for months. They do so by sensing the non-lethal initial decline in temperature as seen in nature at the onset of winter and launching the processes involved in cold acclimation. Cold acclimation is a complex process comprising perception of non-freezing low temperature, transmission of this perception to the nucleus through a cascade of transduction events, and activation of gene transcription; products resulting from this step then confer freezing tolerance on the plant. Cold acclimation is a time-dependent process, the completion of which may take days or weeks. The state of acclimation temporally coincides with the stress and as the latter is relieved, de-acclimation occurs rapidly. Therefore, in order to improve crop production, and to extend geographical range of crop growth, a clear understanding of the processes involved in cold acclimation is essential.
Many plants acquire freezing tolerance through cold acclimatization (CA), a prolonged exposure to... more Many plants acquire freezing tolerance through cold acclimatization (CA), a prolonged exposure to low but non-freezing temperatures at the onset of winter. CA is associated with gene expression that requires transient calcium in¯ux into the cytosol. Alfalfa (Medicago sativa) cells treated with agents blocking this in¯ux are unable to cold-acclimatize. Conversely, chemical agents causing increased calcium in¯ux induce cold acclimatization-speci®c (cas) gene expression in alfalfa at 25LC. How low temperature triggers calcium in¯ux is, however, unknown. We report here that induction of a CA-speci®c gene (cas30), calcium in¯ux and freezing tolerance at 4LC are all prevented by cell membrane¯uidization, but, conversely, are induced at 25LC by membrane rigidi®cation. cas30 expression and calcium in¯ux at 4LC are also prevented by jasplakinolide (JK), an actin micro®lament stabilizer, but induced at 25LC by the actin micro®lament destabilizer cytochalasin D (CD). JK blocked the membrane rigidi®er-induced, but not the calcium channel agonist-induced cas30 expression at 25LC. These ®ndings indicate that cytoskeleton reorganization is an integral component in low-temperature signal transduction in alfalfa cell suspension cultures, serving as a link between membrane rigidi®cation and calcium in¯ux in CA.
In tobacco, both wounding and treatment with jasmonates prior to exposure of the tissue to high c... more In tobacco, both wounding and treatment with jasmonates prior to exposure of the tissue to high concentrations of ozone (250 to 500 p.p.b.) produce a dramatic decrease in ozone injury. A systemic pattern of increased ozone tolerance developed within 3–6 h after wounding and also after local application of jasmonates. Ozone treatment of transgenie (NahG) tobacco plants showed that the inability of these plants to accumulate salicylic acid is also accompanied by increased ozone tolerance. Expression of mRNA encoding the anti‐oxidant enzyme ascorbate peroxidase is upregulated by ozone challenge, wounding and by methyl jasmonate exposure within 3–4 h, while levels of carbonic anhydrase mRNA are simultaneously depressed following ozone exposure and methyl jasmonate treatment. The pattern of these results shows that the response to ozone challenge in tobacco involves signalling mechanisms similar to those induced in plants by other environmental stresses that generate reactive oxygen spec...
SummaryMitogen‐activated protein kinases (MAPKs) appear to be ubiquitously involved in signal tra... more SummaryMitogen‐activated protein kinases (MAPKs) appear to be ubiquitously involved in signal transduction during eukaryotic responses to extracellular stimuli. In plants, no heat shock‐activated MAPK has so far been reported. Also, whereas cold activates specific plant MAPKs such as alfalfa SAMK, mechanisms of such activation are unknown. Here, we report a heat shock‐activated MAPK (HAMK) immunologically related to ERK (Extracellular signal‐Regulated Kinase) superfamily of protein kinases. Molecular mechanisms of heat‐activation of HAMK and cold‐activation of SAMK were investigated. We show that cold‐activation of SAMK requires membrane rigidification, whereas heat‐activation of HAMK occurs through membrane fluidization. The temperature stress‐ and membrane structure‐dependent activation of both SAMK and HAMK is mimicked at 25°C by destabilizers of microfilaments and microtubules, latrunculin B and oryzalin, respectively; but is blocked by jasplakinolide, a stabilizer of actin micr...
APX is a hydrogen peroxide-scavenging enzyme whose presumed function is to protect the cell from ... more APX is a hydrogen peroxide-scavenging enzyme whose presumed function is to protect the cell from hydrogen peroxide accumulation, particularly under stress conditions. APX catalyzes the reduction of hydrogen peroxide using ascorbate as an electron donor, to yield water and oxidized ascorbate. In plants, three different isoforms of APX are known: a cytosolic form and two chloroplastic forms. The cytosolic form is quite distinct from the other two (Miyake et al., 1993). The cytosolic APX cDNA nucleotide sequences from six different species are known (Pisum sativum L.
Ascorbate peroxidase (APX), as a participant in the ascorbate—glutathione cycle, has been suggest... more Ascorbate peroxidase (APX), as a participant in the ascorbate—glutathione cycle, has been suggested to be a particularly important antioxidant enzyme in helping plants survive oxidative stress, but direct evidence for this has not been reported. We demonstrate that expressing antisense RNA comprising 45% of the 3′‐coding region of the tobacco cytosolic APX, can reduce significantly both the endogenous APX mRNA levels and the APX catalytic activity in transgenic tobacco plants. Those transgenic plants showing a reduction in both endogenous APX mRNA levels and extractable APX activity display a significant increase in ozone injury following high‐level ozone exposure. Lower‐level ozone exposure reveals even more drastic differences between the antisense and control plants, suggesting that even a partial loss of APX function in oxidative defence cannot be fully compensated for by other antioxidant measures.
Proceedings of the National Academy of Sciences, 1999
Reactive oxygen intermediates (ROI) play a critical role in the defense of plants against invadin... more Reactive oxygen intermediates (ROI) play a critical role in the defense of plants against invading pathogens. Produced during the “oxidative burst,” they are thought to activate programmed cell death (PCD) and induce antimicrobial defenses such as pathogenesis-related proteins. It was shown recently that during the interaction of plants with pathogens, the expression of ROI-detoxifying enzymes such as ascorbate peroxidase (APX) and catalase (CAT) is suppressed. It was suggested that this suppression, occurring upon pathogen recognition and coinciding with an enhanced rate of ROI production, plays a key role in elevating cellular ROI levels, thereby potentiating the induction of PCD and other defenses. To examine the relationship between the suppression of antioxidative mechanisms and the induction of PCD and other defenses during pathogen attack, we studied the interaction between transgenic antisense tobacco plants with reduced APX or CAT and a bacterial pathogen that triggers the ...
A mixture of growth factors derived from the growth factor, or weight barter or a transgenic plan... more A mixture of growth factors derived from the growth factor, or weight barter or a transgenic plant the purified form purified from the transformed plant extract, or a transformed plant containing a growth factor for use in the topical therapy, dermatological and cosmetic fields relates to a cosmetic and dermatological composition for (cosmetic and dermatologic composition) comprising a. Importantly, the present invention is stabilized, which can be used for cosmetic and topical treatment, and provides a safer growth factors. Preferred compositions plants - including manufacturing (plant-produced) growth factors and hyaluronic acid. Containing the stabilized growth factors, skin-care / dermatological composition is an unwanted degradation product and the resulting composition does not have a risk of loss of activity. In addition, the compositions of the invention do not contain contaminants and infectious agents (transmissible agent), which may be originating from animal or bacterial cell-based expression system.
Environmental factors, such as temperature and water availability, are important determinants of ... more Environmental factors, such as temperature and water availability, are important determinants of plant growth, development and geographical distribution. Thus crop production is severely limited by stresses due to freezing temperatures and drought. The vulnerability of plants to environmental stresses is primarily due to their sessile growth habit. However, the same growth habit, by enforcing a selection pressure, has also led to the development of sophisticated mechanisms by which plants constantly monitor their environment and activate mechanisms to tolerate these stresses. Plants incapable of mounting such responses succumb to the stressful environment. Thus, freezing tolerant plants can survive sub-zero temperatures for months. They do so by sensing the non-lethal initial decline in temperature as seen in nature at the onset of winter and launching the processes involved in cold acclimation. Cold acclimation is a complex process comprising perception of non-freezing low temperature, transmission of this perception to the nucleus through a cascade of transduction events, and activation of gene transcription; products resulting from this step then confer freezing tolerance on the plant. Cold acclimation is a time-dependent process, the completion of which may take days or weeks. The state of acclimation temporally coincides with the stress and as the latter is relieved, de-acclimation occurs rapidly. Therefore, in order to improve crop production, and to extend geographical range of crop growth, a clear understanding of the processes involved in cold acclimation is essential.
Many plants acquire freezing tolerance through cold acclimatization (CA), a prolonged exposure to... more Many plants acquire freezing tolerance through cold acclimatization (CA), a prolonged exposure to low but non-freezing temperatures at the onset of winter. CA is associated with gene expression that requires transient calcium in¯ux into the cytosol. Alfalfa (Medicago sativa) cells treated with agents blocking this in¯ux are unable to cold-acclimatize. Conversely, chemical agents causing increased calcium in¯ux induce cold acclimatization-speci®c (cas) gene expression in alfalfa at 25LC. How low temperature triggers calcium in¯ux is, however, unknown. We report here that induction of a CA-speci®c gene (cas30), calcium in¯ux and freezing tolerance at 4LC are all prevented by cell membrane¯uidization, but, conversely, are induced at 25LC by membrane rigidi®cation. cas30 expression and calcium in¯ux at 4LC are also prevented by jasplakinolide (JK), an actin micro®lament stabilizer, but induced at 25LC by the actin micro®lament destabilizer cytochalasin D (CD). JK blocked the membrane rigidi®er-induced, but not the calcium channel agonist-induced cas30 expression at 25LC. These ®ndings indicate that cytoskeleton reorganization is an integral component in low-temperature signal transduction in alfalfa cell suspension cultures, serving as a link between membrane rigidi®cation and calcium in¯ux in CA.
In tobacco, both wounding and treatment with jasmonates prior to exposure of the tissue to high c... more In tobacco, both wounding and treatment with jasmonates prior to exposure of the tissue to high concentrations of ozone (250 to 500 p.p.b.) produce a dramatic decrease in ozone injury. A systemic pattern of increased ozone tolerance developed within 3–6 h after wounding and also after local application of jasmonates. Ozone treatment of transgenie (NahG) tobacco plants showed that the inability of these plants to accumulate salicylic acid is also accompanied by increased ozone tolerance. Expression of mRNA encoding the anti‐oxidant enzyme ascorbate peroxidase is upregulated by ozone challenge, wounding and by methyl jasmonate exposure within 3–4 h, while levels of carbonic anhydrase mRNA are simultaneously depressed following ozone exposure and methyl jasmonate treatment. The pattern of these results shows that the response to ozone challenge in tobacco involves signalling mechanisms similar to those induced in plants by other environmental stresses that generate reactive oxygen spec...
SummaryMitogen‐activated protein kinases (MAPKs) appear to be ubiquitously involved in signal tra... more SummaryMitogen‐activated protein kinases (MAPKs) appear to be ubiquitously involved in signal transduction during eukaryotic responses to extracellular stimuli. In plants, no heat shock‐activated MAPK has so far been reported. Also, whereas cold activates specific plant MAPKs such as alfalfa SAMK, mechanisms of such activation are unknown. Here, we report a heat shock‐activated MAPK (HAMK) immunologically related to ERK (Extracellular signal‐Regulated Kinase) superfamily of protein kinases. Molecular mechanisms of heat‐activation of HAMK and cold‐activation of SAMK were investigated. We show that cold‐activation of SAMK requires membrane rigidification, whereas heat‐activation of HAMK occurs through membrane fluidization. The temperature stress‐ and membrane structure‐dependent activation of both SAMK and HAMK is mimicked at 25°C by destabilizers of microfilaments and microtubules, latrunculin B and oryzalin, respectively; but is blocked by jasplakinolide, a stabilizer of actin micr...
APX is a hydrogen peroxide-scavenging enzyme whose presumed function is to protect the cell from ... more APX is a hydrogen peroxide-scavenging enzyme whose presumed function is to protect the cell from hydrogen peroxide accumulation, particularly under stress conditions. APX catalyzes the reduction of hydrogen peroxide using ascorbate as an electron donor, to yield water and oxidized ascorbate. In plants, three different isoforms of APX are known: a cytosolic form and two chloroplastic forms. The cytosolic form is quite distinct from the other two (Miyake et al., 1993). The cytosolic APX cDNA nucleotide sequences from six different species are known (Pisum sativum L.
Uploads
Papers by Björn Orvar