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E Heberle-Bors

Publications and source records attributed to E Heberle-Bors.

At least 19 recordsLinked to original sources
PubMed1997

A developmentally regulated MAP kinase activated by hydration in tobacco pollen.

A novel mitogen-activated protein (MAP) kinase signaling pathway has been identified in tobacco. This pathway is developmentally regulated during pollen maturation and is activated by hydration during pollen germination. Analysis of different stages of pollen development showed that transcriptional and translational induction of MAP kinase synthesis occurs at the mid-bicellular stage of pollen maturation. However, the MAP kinase is stored in an inactive form in the mature, dry pollen grain. Kinase activation is very rapid after hydration of the dry pollen, peaking at approximately 5 min and decreasing thereafter. Immunoprecipitation of the kinase activity by an anti-phosphotyrosine antibody is consistent with the activation of a MAP kinase. The kinetics of activation suggest that the MAP kinase plays a role in the activation of the pollen grain after hydration rather than in pollen tube growth.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1996

Developmental and cell cycle regulation of alfalfa nucMs1, a plant homolog of the yeast Nsr1 and mammalian nucleolin.

We report here the isolation and characterization of the nucMs1 alfalfa cDNA, whose predicted amino acid sequence structurally resembles the yeast Nsr1 protein and animal nucleolins. These proteins consist of an N-terminal acidic domain, centrally located RNA recognition motifs (RRMs), and a C-terminal glycine- and arginine-rich domain. In comparison with animal nucleolins that contain four RRMs, NucMs1 more closely resembles the yeast Nsr1 protein, which contains only two RRMs. A NucMs1 C-terminal peptide antibody specifically recognized a 95-kD nucleolar protein in alfalfa cells that changed its localization in a cell cycle-dependent manner. The nucMs1 transcript and p95nucMs1 protein levels correlated with cell proliferation, and nucMs1 gene expression was found to be induced in the G1 phase upon mitogenic stimulation of G0-arrested leaf cells. In situ hybridization analysis of different alfalfa organs during various developmental stages showed that nucMs1 gene expression is highest in root meristematic cells, but it is also found in other meristematic cells of the plant body. nucMs1 expression is tightly linked to cell proliferation but does not depend on a particular cell cycle phase. No nucMs1 expression was observed in cells that had exited the cell cycle and were undergoing differentiation or polar growth, indicating that nucMs1 may not be necessary for processes other than cell proliferation.

Animals↗
PubMed1995

Evaluation of sensitivity of flow cytometry in detecting aneuploidy in wheat using disomic and ditelosomic wheat-rye addition lines.

Flow cytometric DNA analysis was used to study changes in nuclear DNA content induced by the addition of complete or telosomic rye chromosomes into the genome of common wheat (Triticum aestivum L.). The DNA content of each addition line was determined by comparison with an internal reference value and was expressed as a difference with respect to the original wheat parental line. A 1.84% difference in the DNA content could be detected. Nuclei were flow sorted and the presence of rye chromatin in the nuclei with the higher DNA content was demonstrated by Southern hybridization. Flow cytometry was proven to be sensitive enough to detect the small DNA content deviations that are expected to occur in aneuploid plants of wheat.

Aneuploidy↗
PubMed1995

Molecular cloning, functional expression in Escherichia coli, and characterization of multiple mitogen-activated-protein kinases from tobacco.

A screening of four tobacco cDNA libraries by PCR, using degenerate oligonucleotides corresponding to motifs conserved in mitogen-activated-protein kinases from animals and yeasts, resulted in the isolation of five different PCR fragments that showed high sequence similarity to mitogen-activated-protein kinases from other organisms. Full-length cDNAs were obtained for two of these, ntf4 and ntf6, and we have previously reported the isolation of one of the other cDNAs, ntf3 [Wilson, C., Eller, N., Gartner, A., Vicente, O. & Heberle-Bors, E. (1993) Plant Mol. Biol. 23, 543-551]. The three cDNAs, ntf3, ntf4 and ntf6, as well as a mutated form of ntf3, were fused to the glutathione-S-transferase gene and expressed as fusion proteins in Escherichia coli. All three wild-type recombinant proteins, with or without the glutathione-S-transferase fragment, are capable of autophosphorylation and phosphorylate myelin basic protein, in a reaction that is more strongly supported by Mn2+ than by Mg2+, while the kinase-negative Ntf3 mutant did not show any activity. Western-blot analysis showed that the recombinant proteins autophosphorylate on tyrosine residues and are recognized by antibodies prepared against mammalian mitogen-activated-protein kinases.

Amino Acid Sequence↗
PubMed1995

Isolation and expression during pollen development of a tobacco cDNA clone encoding a protein kinase homologous to shaggy/glycogen synthase kinase-3.

We have isolated a tobacco (Nicotiana tabacum L.) cDNA clone encoding a putative serine/threonine protein kinase, which shows highest homology to previously described families of alfalfa and Arabidopsis protein kinases and to their homologues rat glycogen synthase kinase-3 and Drosophila shaggy kinases. Northern experiments showed that NtK-4 is expressed in all sporophytic tobacco tissues tested, as well as in gametophytic and embryogenic pollen.

Amino Acid Sequence↗
PubMed1995

Molecular cloning and characterization of profilin from tobacco (Nicotiana tabacum): increased profilin expression during pollen maturation.

Profilin has recently been identified as an actin-binding protein in higher plants. A cDNA coding for tobacco profilin, which shared an average sequence identity of 75% with other plant profilins, was isolated from a tobacco pollen cDNA library by antibody screening. Tobacco profilin was expressed in Escherichia coli and purified by affinity to poly-(L-proline) Sepharose. A rabbit antiserum was raised against recombinant tobacco profilin and used to estimate the amount of profilin expressed in different tobacco tissues. Profilin can be detected in different somatic tissues, but the expression is 50-100 fold higher in mature pollen. Immunofluorescence and confocal laser scanning microscopy showed a homogeneous distribution of profilin in the cytoplasm of in vitro cultured pollen grains and pollen tubes of tobacco whereas some growing pollen tubes were stained more intensively a their tip. A possible role of pollen profilin as a developmentally upregulated microfilament precursor in mature pollen is discussed.

Actins↗
PubMed1995

Inflorescence-specific expression of AtK-1, a novel Arabidopsis thaliana homologue of shaggy/glycogen synthase kinase-3.

We report here the isolation of the Arabidopsis thaliana gene AtK-1. The predicted protein sequence of AtK-1 shows 70% identity to the Arabidopsis ASK and alfalfa MsK kinases that are homologs of the Drosophila shaggy and rat GSK-3 serine/threonine protein kinases playing an important role in signal transduction processes in animals. Northern analysis of different organs revealed exclusive expression in inflorescences suggesting an involvement of the AtK-1 kinase in reproduction-specific processes.

Amino Acid Sequence↗
PubMed1995

The D-type alfalfa cyclin gene cycMs4 complements G1 cyclin-deficient yeast and is induced in the G1 phase of the cell cycle.

Cyclins are key regulators of the cell cycle in all eukaryotes. In alfalfa, we have previously isolated three B-type cyclins. The closely related cycMs1 and cycMs2 genes are expressed primarily during the G2 and M phases and are most likely mitotic cyclins; expression of the cycMs3 gene is induced in the G0-to-G1 transition, when cells reenter the cell cycle. By complementation of G1 cyclin-deficient yeast cells, a novel alfalfa cyclin, designated cycMs4, was isolated. The predicted amino acid sequence of the cycMs4 gene is most similar to that of the Arabidopsis cyclin delta 3 gene. CycMs4 and cyclin delta 3 belong to the class of D-type cyclins and contain PEST-rich regions and a retinoblastoma binding motif. When comparing expression levels in different organs, cycMs4 transcripts were present predominantly in roots. Whereas expression of the cycMs4 gene was cell cycle-regulated in suspension-cultured cells, transcription in roots was observed to depend also on the positional context of the cell. When differentiated G0-arrested leaf cells were induced to resume cell division by treatment with plant hormones, cycMs4 transcription was induced before the onset of DNA synthesis. Whereas this induction was preceded by that of the cycMs3 gene, cycMs2 expression occurred later and at the same time as mitotic activity. These data suggest that cycMs4 plays a role in the G1-to-S transition and provide a model to investigate the plant cell cycle at the molecular level.

Amino Acid Sequence↗
PubMed1995

cycMs3, a novel B-type alfalfa cyclin gene, is induced in the G0-to-G1 transition of the cell cycle.

Cyclins are key regulators of the cell cycle in all eukaryotes. We have previously isolated two B-type cyclin genes, cycMs1 and cycMs2, from alfalfa that are primarily expressed during the G2-to-M phase transition and are most likely mitotic cyclin genes. Here, we report the isolation of a novel alfalfa cyclin gene, termed cycMs3 (for cyclin Medicago sativa), by selecting for mating type alpha-pheromone-induced cell cycle arrest suppression in yeast. The central region of the predicted amino acid sequence of the cycMs3 gene is most similar to the cyclin box of yeast B-type and mammalian A- and B-type cyclins. In situ hybridization showed that cycMs3 mRNA can be detected only in proliferating cells and not in differentiated alfalfa cells. When differentiated G0-arrested cells were induced to reenter the cell cycle in the G1 phase and resume cell division by treatment with plant hormones, cycMs3 transcript levels increased long before the onset of DNA synthesis. In contrast, histone H3-1 mRNA and cycMs2 transcripts were not observed before DNA replication and mitosis, respectively. In addition, cycMs3 mRNA was found in all stages of the cell cycle in synchronously dividing cells, whereas the cycMs2 and histone H3-1 genes showed a G2-to-M phase- or S phase-specific transcription pattern, respectively. These data suggest that the role of cyclin CycMs3 differs from that of CycMs1 and CycMs2. We propose that CycMs3 helps control reentry of quiescent G0-arrested cells into the G1 phase of the cell cycle.

Amino Acid Sequence↗
PubMed1994

A birch gene family encoding pollen allergens and pathogenesis-related proteins.

Bet v I, the major pollen allergen of birch (Betula verrucosa), shows high sequence homology to a family of pathogenesis-related (PR) proteins that have recently been identified in several other plant species. We have used a pollen Bet v I cDNA clone and anti-Bet v I antibodies as probes to study the expression of Bet v I genes in birch cell suspension cultures under different experimental conditions. Induction of Bet v I-related proteins was detected in immunoblots of cell extracts upon co-cultivation with microbial pathogens. Northern analysis revealed the rapid induction of Bet v I transcripts in the presence of bacteria and fungi, but not by stress treatments (heat shock, metal ions) or by chemical elicitors. RNase protection experiments showed that the pathogen-inducible RNAs did not correspond to the pollen cDNA clone but most likely to the products of transcription of other members of the Bet v I gene family, sharing high sequence homology with the pollen-specific gene within the 5'-half of the coding region. We conclude that the Bet v I gene family of pollen allergens includes a subset of defense-related genes that are transcriptionally activated in the presence of microbial pathogens.

Allergens↗
PubMed1994

Isolation and characterization of phosphoprotein phosphatase 1 from alfalfa.

Protein phosphatases are central regulatory components of diverse processes in eukaryotes and are among the most highly conserved proteins known. In this paper, we report the cloning and sequencing of a type 1 protein phosphatase (pp1Ms) cDNA from alfalfa. Southern analysis indicates the presence of a gene family of PP1 proteins in alfalfa. The pp1Ms open reading frame is very similar to one of five predicted Arabidopsis type 1 protein phosphatases, indicating that different subtypes are individually conserved. Expression of the alfalfa pp1Ms in a temperature-sensitive Schizosaccharomyces pombe PP1 mutant, dis2-11, revealed no complementation, suggesting that PP1Ms is not involved in mitotic regulation. In different plant organs, different pp1Ms transcript levels were observed; in contrast, mRNA levels remained constant in all phases of the cell cycle and in logarithmically growing cells. However, when cells entered stationary phase pp1Ms transcript levels decreased considerably.

Amino Acid Sequence↗
PubMed1994

MAP kinases: universal multi-purpose signaling tools.

MAP (mitogen-activated protein) kinases are serine/threonine protein kinases and mediate intracellular phosphorylation events linking various extracellular signals to different cellular targets. MAP kinase, MAP kinase kinase and MAP kinase kinase kinase are functional protein kinase units that are conserved in several signal transduction pathways in animals and yeasts. Isolation of all three components was also shown in plants and suggests conservation of a protein kinase module in all eukaryotic cells. In plants, MAP kinase modules appear to be involved in ethylene signaling and auxin-induced cell proliferation. Therefore, coupling of different extracellular signals to different physiological responses is mediated by MAP kinase cascades and appears to have evolved from a single prototypical protein kinase module which has been adapted to the specific requirements of different organisms.

Animals↗
PubMed1993

Identification of profilin as an actin-binding protein in higher plants.

Profilin is a low molecular weight protein involved in the organization of the mammalian and protozoan cytoskeleton as well as in signal transduction. In this study, profilin is identified as an actin-binding protein in higher plants which is present in monocot and dicot angiosperms. Birch pollen profilin and actin can be copurified as a complex, and purified recombinant birch profilin can be used as an affinity matrix to obtain birch pollen actin. The binding of 125I-labeled recombinant birch pollen profilin to plant and animal actins can be blocked by profilin-specific antibodies that react with different epitopes of birch profilin. One of the blocking antibodies was raised against the 25 COOH-terminal amino acids indicating the importance of this region in the profilactin complex formation.

Actins↗