erwin witters - Academia.edu (original) (raw)
Papers by erwin witters
The Plant Cell, Feb 1, 2011
Jasmonates (JAs) trigger an important transcriptional reprogramming of plant cells to modulate bo... more Jasmonates (JAs) trigger an important transcriptional reprogramming of plant cells to modulate both basal development and stress responses. In spite of the importance of transcriptional regulation, only one transcription factor (TF), the Arabidopsis thaliana basic helix-loop-helix MYC2, has been described so far as a direct target of JAZ repressors. By means of yeast two-hybrid screening and tandem affinity purification strategies, we identified two previously unknown targets of JAZ repressors, the TFs MYC3 and MYC4, phylogenetically closely related to MYC2. We show that MYC3 and MYC4 interact in vitro and in vivo with JAZ repressors and also form homo-and heterodimers with MYC2 and among themselves. They both are nuclear proteins that bind DNA with sequence specificity similar to that of MYC2. Loss-of-function mutations in any of these two TFs impair full responsiveness to JA and enhance the JA insensitivity of myc2 mutants. Moreover, the triple mutant myc2 myc3 myc4 is as impaired as coi1-1 in the activation of several, but not all, JA-mediated responses such as the defense against bacterial pathogens and insect herbivory. Our results show that MYC3 and MYC4 are activators of JAregulated programs that act additively with MYC2 to regulate specifically different subsets of the JA-dependent transcriptional response.
The adjective natural is morphologically and semantically derived from the noun nature. In the te... more The adjective natural is morphologically and semantically derived from the noun nature. In the terminology of Magnusson and Persson 1986, it is a morphologically marked transcategorial hyponym of nature. Nature as a preexisting world is Man's environment, and any attempts he makes at modifying it to suit his needs rather than passively adjusting to it lead to its contrasting phenomena 'culture 1 and 'civilisation'. Nature is that which is expected in the world around us, and thus in no need of explanation, while culture represents the unexpected results of activities outside the domain of natural laws, that is, human creativity. In other words culture, or civilisation, is Man's systematic endeavour to escape the principle of natural selection. 2. The semantic dimensions of the lexeme nature The semantic dimensions along which nature is specified may be said to consist of: Categorial meaning: Nouniness, which interprets the concept NATURE as an entity. Mass, which indicates an unindividuated essence. Lexical meaning: (a) 'The totality of observable mineral formations and plant and animal life' Ex: Nothing in visible nature, except the crystal, is perfectly symmetric. (COUBILD) (b) 'The inherent charac ter of this totality, that is, its governing principle' Ex: This is one of the many examples of how smoothly Nature works things out.
Biotechnology in Agriculture and Forestry
Biotechnology in Agriculture and Forestry
Rapid Communications in Mass Spectrometry, 1996
ABSTRACT
New Phytologist, 1999
ABSTRACT
Journal of Plant Physiology, 2001
Melatonin is an animal hormone that regulates photoperiodic reactions in many vertebrates. Its le... more Melatonin is an animal hormone that regulates photoperiodic reactions in many vertebrates. Its level is usually higher at night, and the duration of elevated melatonin levels is proportional to the length of the night, thus giving information about day length. We have previously identified melatonin in the dicotyledonous plant Chenopodium rubrum. We compared melatonin daily profiles in C. rubrum shoots when given three different photoperiodic regimes with 8 h, 12 h, and 16 h of darkness. As in vertebrates, melatonin levels reached its maximum at night, but the duration of elevated melatonin content did not change with the photoperiod. The maximum melatonin content occurred at later times after lights off as night length increased, but always 6 h before lights on in all light/dark cycles. These results indicate differences in the regulation of melatonin levels between vertebrates and higher plants. We suggest that the timing of melatonin maximum relative to lights off may provide photoperiodic information for C. rubrum.
Current Opinion in Plant Biology, 1998
The evolution of adenosine 3P,5P-cyclic monophosphate (cAMP) levels was investigated in synchroni... more The evolution of adenosine 3P,5P-cyclic monophosphate (cAMP) levels was investigated in synchronised tobacco BY-2 cells by virtue of a method based on immunoaffinity purification and analysis on electrospray tandem mass spectrometry. A transient peak in cAMP content was observed during the S and G I phases of the cell cycle. Application of the prostaglandin inhibiting drug indomethacin at early S phase resulted in the loss of the cAMP peak in S phase and inhibited mitotic division. This inhibition of cAMP accumulation suggests the presence of a prostaglandin-dependent adenylyl cyclase activity, analogous to animal cyclases. A potential role for cAMP during the plant cell cycle is postulated.
Biologia plantarum, 2006
Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant o... more Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant ontogeny with the aim to elucidate their role in delayed senescence of transgenic Pssu-ipt tobacco. Control Nicotiana tabacum L. (cv. Petit Havana SR1) and transgenic tobacco with the ipt gene under the control of the promoter of small subunit of Rubisco (Pssu-ipt) were both grown either as grafts on control rootstocks or as rooted plants. Both control plant types showed a decline in total content of CKs with proceeding plant senescence. Contrary to this both transgenic plant types exhibited at least ten times higher content of CKs than controls and a significant increase of CK contents throughout the ontogeny with maximal values in the later stages of plant development. Significantly higher portion of O-glucosides was found in both transgenic plant types compared to control ones. In transgenic plants, zeatin and zeatin riboside were predominant type of CKs. Generally, Pssu-ipt tobacco exhibited elevated activities of antioxidant enzymes compared to control tobacco particularly in the later stages of plant development. While in control tobacco activity of glutathione reductase (GR) and superoxide dismutase (SOD) showed increasing activity up to the onset of flowering and then gradually decreased, in both transgenic types GR increased and SOD activity showed only small change throughout the plant ontogeny. Ascorbate peroxidase (APOD) was stimulated in both transgenic types. The manifold enhancement of syringaldazine and guaiacol peroxidase activities was observed in transgenic grafts throughout plant ontogeny in contrast to control and transgenic rooted plants, where the increase was found only in the late stages. Electron microscopic examination showed higher number of crystallic cores in peroxisomes and abnormal interactions among organelles in transgenic tobacco in comparison with control plant. The overproduction of cytokinins resulted in the stimulation of activities of AOE throughout the plant ontogeny of transgenic Pssu-ipt tobacco.
Journal of Chromatography B: Biomedical Sciences and Applications, 1997
An LC-MS method has been developed combining ion-pair chromatography with an electrospray interfa... more An LC-MS method has been developed combining ion-pair chromatography with an electrospray interface linking microbore and capillary HPLC to mass spectrometry. Separation of cyclic nucleotides on C18 reversed-phase columns, using tetrabutylammonium bromide as an ion pairing agent was evaluated with different mobile phase compositions. It was found that low ion-pairing agent concentration (50-500 microM) used in combination with low flow-rates (5-10 microl min(-1)) allowed the system to operate for up to several days without observing a reduced signal caused by source pollution. The loss of sensitivity expected in ion-pair chromatography could be remedied by using a 2-propanol coaxial sheath flow. Optimal conditions for negative ion electrospray resulted in a linear detection response in the femtomole to picomole range. Using biological samples this method was evaluated and compared with a classical ion-suppression RP-HPLC method using UV detection.
Plant Physiology, 1999
This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in di... more This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in distinct phases of development using immunocytochemistry and quantitative tandem mass spectrometry. In contrast to vegetative apices and flower buds, we detected no free cytokinin bases (zeatin, dihydrozeatin, or isopentenyladenine) in prefloral transition apices. We also observed a 3-fold decrease in the content of cytokinin ribosides (zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) during this transition phase. The group concluded that organ formation (e.g. leaves and flowers) is characterized by enhanced cytokinin content, in contrast to the very low endogenous cytokinin levels found in prefloral transition apices, which showed no organogenesis. The immunocytochemical analyses revealed a differing intracellular localization of the cytokinin bases. Dihydrozeatin and isopentenyladenine were mainly cytoplasmic and perinuclear, whereas zeatin showed a clear-cut nuclear la...
Molecular Plant-Microbe Interactions®, 2006
We report on the early response of Arabidopsis thaliana to the obligate biotrophic pathogen Plasm... more We report on the early response of Arabidopsis thaliana to the obligate biotrophic pathogen Plasmodiophora brassicae at the hormone and proteome level. Using a CYCB1;1::GUS construct, the re-initiation of infection-related cell division is shown from 4 days after inoculation on. Sensitivity to cytokinins and auxins as well as the endogenous hormone levels are evaluated. Both an enhanced cytokinin gene response and an accumulation of isopentenyl adenine and adenosine precede this re-initiation of cell division, whereas an enhanced auxin gene response is observed from 6 days after inoculation on. The alh1 mutant, impaired in the cross talk between ethylene and auxins, is resistant to P. brassicae. A differential protein analysis of infected versus noninfected roots and hypocotyls was performed using two-dimensional gel electrophoresis and quantitative image analysis, coupled to matrix-assisted laser desorption ionization time of flight-time of flight mass spectrometry-based protein id...
Tree Genetics & Genomes, 2008
In the temperate climate of the northern hemisphere, winter survival of woody plants is determine... more In the temperate climate of the northern hemisphere, winter survival of woody plants is determined by the ability to acclimate to freezing temperatures and to undergo a period of dormancy. Cold acclimation in many woody plants is initially induced by short photoperiod and low, non-freezing temperatures. These two factors (5°C and short photoperiod) were used to study changes in the proteome of bark tissues of 1-year-old peach trees. Difference in-gel electrophoresis technology, a gel-based approach involving the labeling of proteins with different fluorescent dyes, was used to conduct a quantitative
The Plant Cell, Feb 1, 2011
Jasmonates (JAs) trigger an important transcriptional reprogramming of plant cells to modulate bo... more Jasmonates (JAs) trigger an important transcriptional reprogramming of plant cells to modulate both basal development and stress responses. In spite of the importance of transcriptional regulation, only one transcription factor (TF), the Arabidopsis thaliana basic helix-loop-helix MYC2, has been described so far as a direct target of JAZ repressors. By means of yeast two-hybrid screening and tandem affinity purification strategies, we identified two previously unknown targets of JAZ repressors, the TFs MYC3 and MYC4, phylogenetically closely related to MYC2. We show that MYC3 and MYC4 interact in vitro and in vivo with JAZ repressors and also form homo-and heterodimers with MYC2 and among themselves. They both are nuclear proteins that bind DNA with sequence specificity similar to that of MYC2. Loss-of-function mutations in any of these two TFs impair full responsiveness to JA and enhance the JA insensitivity of myc2 mutants. Moreover, the triple mutant myc2 myc3 myc4 is as impaired as coi1-1 in the activation of several, but not all, JA-mediated responses such as the defense against bacterial pathogens and insect herbivory. Our results show that MYC3 and MYC4 are activators of JAregulated programs that act additively with MYC2 to regulate specifically different subsets of the JA-dependent transcriptional response.
The adjective natural is morphologically and semantically derived from the noun nature. In the te... more The adjective natural is morphologically and semantically derived from the noun nature. In the terminology of Magnusson and Persson 1986, it is a morphologically marked transcategorial hyponym of nature. Nature as a preexisting world is Man's environment, and any attempts he makes at modifying it to suit his needs rather than passively adjusting to it lead to its contrasting phenomena 'culture 1 and 'civilisation'. Nature is that which is expected in the world around us, and thus in no need of explanation, while culture represents the unexpected results of activities outside the domain of natural laws, that is, human creativity. In other words culture, or civilisation, is Man's systematic endeavour to escape the principle of natural selection. 2. The semantic dimensions of the lexeme nature The semantic dimensions along which nature is specified may be said to consist of: Categorial meaning: Nouniness, which interprets the concept NATURE as an entity. Mass, which indicates an unindividuated essence. Lexical meaning: (a) 'The totality of observable mineral formations and plant and animal life' Ex: Nothing in visible nature, except the crystal, is perfectly symmetric. (COUBILD) (b) 'The inherent charac ter of this totality, that is, its governing principle' Ex: This is one of the many examples of how smoothly Nature works things out.
Biotechnology in Agriculture and Forestry
Biotechnology in Agriculture and Forestry
Rapid Communications in Mass Spectrometry, 1996
ABSTRACT
New Phytologist, 1999
ABSTRACT
Journal of Plant Physiology, 2001
Melatonin is an animal hormone that regulates photoperiodic reactions in many vertebrates. Its le... more Melatonin is an animal hormone that regulates photoperiodic reactions in many vertebrates. Its level is usually higher at night, and the duration of elevated melatonin levels is proportional to the length of the night, thus giving information about day length. We have previously identified melatonin in the dicotyledonous plant Chenopodium rubrum. We compared melatonin daily profiles in C. rubrum shoots when given three different photoperiodic regimes with 8 h, 12 h, and 16 h of darkness. As in vertebrates, melatonin levels reached its maximum at night, but the duration of elevated melatonin content did not change with the photoperiod. The maximum melatonin content occurred at later times after lights off as night length increased, but always 6 h before lights on in all light/dark cycles. These results indicate differences in the regulation of melatonin levels between vertebrates and higher plants. We suggest that the timing of melatonin maximum relative to lights off may provide photoperiodic information for C. rubrum.
Current Opinion in Plant Biology, 1998
The evolution of adenosine 3P,5P-cyclic monophosphate (cAMP) levels was investigated in synchroni... more The evolution of adenosine 3P,5P-cyclic monophosphate (cAMP) levels was investigated in synchronised tobacco BY-2 cells by virtue of a method based on immunoaffinity purification and analysis on electrospray tandem mass spectrometry. A transient peak in cAMP content was observed during the S and G I phases of the cell cycle. Application of the prostaglandin inhibiting drug indomethacin at early S phase resulted in the loss of the cAMP peak in S phase and inhibited mitotic division. This inhibition of cAMP accumulation suggests the presence of a prostaglandin-dependent adenylyl cyclase activity, analogous to animal cyclases. A potential role for cAMP during the plant cell cycle is postulated.
Biologia plantarum, 2006
Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant o... more Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant ontogeny with the aim to elucidate their role in delayed senescence of transgenic Pssu-ipt tobacco. Control Nicotiana tabacum L. (cv. Petit Havana SR1) and transgenic tobacco with the ipt gene under the control of the promoter of small subunit of Rubisco (Pssu-ipt) were both grown either as grafts on control rootstocks or as rooted plants. Both control plant types showed a decline in total content of CKs with proceeding plant senescence. Contrary to this both transgenic plant types exhibited at least ten times higher content of CKs than controls and a significant increase of CK contents throughout the ontogeny with maximal values in the later stages of plant development. Significantly higher portion of O-glucosides was found in both transgenic plant types compared to control ones. In transgenic plants, zeatin and zeatin riboside were predominant type of CKs. Generally, Pssu-ipt tobacco exhibited elevated activities of antioxidant enzymes compared to control tobacco particularly in the later stages of plant development. While in control tobacco activity of glutathione reductase (GR) and superoxide dismutase (SOD) showed increasing activity up to the onset of flowering and then gradually decreased, in both transgenic types GR increased and SOD activity showed only small change throughout the plant ontogeny. Ascorbate peroxidase (APOD) was stimulated in both transgenic types. The manifold enhancement of syringaldazine and guaiacol peroxidase activities was observed in transgenic grafts throughout plant ontogeny in contrast to control and transgenic rooted plants, where the increase was found only in the late stages. Electron microscopic examination showed higher number of crystallic cores in peroxisomes and abnormal interactions among organelles in transgenic tobacco in comparison with control plant. The overproduction of cytokinins resulted in the stimulation of activities of AOE throughout the plant ontogeny of transgenic Pssu-ipt tobacco.
Journal of Chromatography B: Biomedical Sciences and Applications, 1997
An LC-MS method has been developed combining ion-pair chromatography with an electrospray interfa... more An LC-MS method has been developed combining ion-pair chromatography with an electrospray interface linking microbore and capillary HPLC to mass spectrometry. Separation of cyclic nucleotides on C18 reversed-phase columns, using tetrabutylammonium bromide as an ion pairing agent was evaluated with different mobile phase compositions. It was found that low ion-pairing agent concentration (50-500 microM) used in combination with low flow-rates (5-10 microl min(-1)) allowed the system to operate for up to several days without observing a reduced signal caused by source pollution. The loss of sensitivity expected in ion-pair chromatography could be remedied by using a 2-propanol coaxial sheath flow. Optimal conditions for negative ion electrospray resulted in a linear detection response in the femtomole to picomole range. Using biological samples this method was evaluated and compared with a classical ion-suppression RP-HPLC method using UV detection.
Plant Physiology, 1999
This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in di... more This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in distinct phases of development using immunocytochemistry and quantitative tandem mass spectrometry. In contrast to vegetative apices and flower buds, we detected no free cytokinin bases (zeatin, dihydrozeatin, or isopentenyladenine) in prefloral transition apices. We also observed a 3-fold decrease in the content of cytokinin ribosides (zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) during this transition phase. The group concluded that organ formation (e.g. leaves and flowers) is characterized by enhanced cytokinin content, in contrast to the very low endogenous cytokinin levels found in prefloral transition apices, which showed no organogenesis. The immunocytochemical analyses revealed a differing intracellular localization of the cytokinin bases. Dihydrozeatin and isopentenyladenine were mainly cytoplasmic and perinuclear, whereas zeatin showed a clear-cut nuclear la...
Molecular Plant-Microbe Interactions®, 2006
We report on the early response of Arabidopsis thaliana to the obligate biotrophic pathogen Plasm... more We report on the early response of Arabidopsis thaliana to the obligate biotrophic pathogen Plasmodiophora brassicae at the hormone and proteome level. Using a CYCB1;1::GUS construct, the re-initiation of infection-related cell division is shown from 4 days after inoculation on. Sensitivity to cytokinins and auxins as well as the endogenous hormone levels are evaluated. Both an enhanced cytokinin gene response and an accumulation of isopentenyl adenine and adenosine precede this re-initiation of cell division, whereas an enhanced auxin gene response is observed from 6 days after inoculation on. The alh1 mutant, impaired in the cross talk between ethylene and auxins, is resistant to P. brassicae. A differential protein analysis of infected versus noninfected roots and hypocotyls was performed using two-dimensional gel electrophoresis and quantitative image analysis, coupled to matrix-assisted laser desorption ionization time of flight-time of flight mass spectrometry-based protein id...
Tree Genetics & Genomes, 2008
In the temperate climate of the northern hemisphere, winter survival of woody plants is determine... more In the temperate climate of the northern hemisphere, winter survival of woody plants is determined by the ability to acclimate to freezing temperatures and to undergo a period of dormancy. Cold acclimation in many woody plants is initially induced by short photoperiod and low, non-freezing temperatures. These two factors (5°C and short photoperiod) were used to study changes in the proteome of bark tissues of 1-year-old peach trees. Difference in-gel electrophoresis technology, a gel-based approach involving the labeling of proteins with different fluorescent dyes, was used to conduct a quantitative