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D Bartels

Publications and source records attributed to D Bartels.

At least 19 recordsLinked to original sources
PubMed2005

Identification of further Craterostigma plantagineum cdt mutants affected in abscisic acid mediated desiccation tolerance.

The resurrection plant (Craterostigma plantagineum) is desiccation tolerant. However, callus derived from this plant, when propagated in vitro, requires exogenously applied abscisic acid (ABA) in order to survive desiccation. Treatment of callus tissue with ABA induces most of the genes that are induced by dehydration in the whole plant. This property has been exploited for the isolation of mutants that show dominant phenotypes resulting from the ectopic expression of endogenous genes induced by the insertion of a foreign promoter. Here we describe new T-DNA tagged Craterostigma desiccation-tolerant (cdt) mutants with different molecular and physiological characteristics, suggesting that different pathways of desiccation tolerance are affected. One of the mutants, cdt-2, constitutively expresses known osmoprotective Lea genes in callus and leaf tissue. Further analysis of this mutant revealed that the tagged locus is similar to a previously characterised gene, CDT-1, which codes for a signalling molecule that confers desiccation tolerance. The nature of the T-DNA insertion provides insight into the mechanism by which the CDT-1/2 gene family functions in ABA signal transduction.

Abscisic Acid↗
PubMed2005

BRIGEP--the BRIDGE-based genome-transcriptome-proteome browser.

The growing amount of information resulting from the increasing number of publicly available genomes and experimental results thereof necessitates the development of comprehensive systems for data processing and analysis. In this paper, we describe the current state and latest developments of our BRIGEP bioinformatics software system consisting of three web-based applications: GenDB, EMMA and ProDB. These applications facilitate the processing and analysis of bacterial genome, transcriptome and proteome data and are actively used by numerous international groups. We are currently in the process of extensively interconnecting these applications. BRIGEP was developed in the Bioinformatics Resource Facility of the Center for Biotechnology at Bielefeld University and is freely available. A demo project with sample data and access to all three tools is available at https://www.cebitec.uni-bielefeld.de/groups/brf/software/brigep/. Code bundles for these and other tools developed in our group are accessible on our FTP server at ftp.cebitec.uni-bielefeld.de/pub/software/.

Bacterial Proteins↗
PubMed2005

The Linderniaceae and Gratiolaceae are further lineages distinct from the Scrophulariaceae (Lamiales).

The Lamiales are one of the largest orders of angiosperms, with about 22,000 species. The Scrophulariaceae, as one of their most important families, has recently been shown to be polyphyletic. As a consequence, this family was re-classified and several groups of former scrophulariaceous genera now belong to different families, such as the Calceolariaceae, Plantaginaceae, or Phrymaceae. In the present study, relationships of the genera Craterostigma, Lindernia and its allies, hitherto classified within the Scrophulariaceae, were analyzed. Sequences of the chloroplast trnK intron and the matK gene (approximately 2.5 kb) were generated for representatives of all major lineages of the Lamiales and the former Scrophulariaceae. Bayesian and parsimony analyses revealed two isolated lineages, one of which consists of Lindernia and its allies, the other of Gratiola and allies. Gratiola was previously assumed to be related to Lindernia and was therefore included here. It is proposed to treat the two clades as separate families, Linderniaceae and Gratiolaceae. For the Linderniaceae, several morphological synapomorphies exist in addition to molecular data, such as conspicuous club-shaped stamen appendages.

Bayes Theorem↗
PubMed2002

Reverse genetic approaches in plants and yeast suggest a role for novel, evolutionarily conserved, selenoprotein-related genes in oxidative stress defense.

Oxidation of methionine residues during periods of oxidative stress can lead to loss of protein function. Organisms have developed defense strategies to minimize such damage. The PilB protein, which is involved in pilus formation in the pathogen Neisseria gonorrhoeae, is composed of three functional protein domains (I-III) with putative roles in oxidative stress defense. These domains are evolutionarily conserved and homologs have been discovered in diverse prokaryotes and eukaryotes. Domain III shows similarities to selenoproteins which contain selenium instead of sulfur in a conserved cysteine residue. The substitution of selenium for sulfur alters the redox properties of such proteins. Knock-out mutants were used to elucidate the function of these novel selenoprotein-like domains in yeast and in Arabidopsis thaliana. We show that organisms with non-functional genes for selenoprotein-like polypeptides accumulate higher levels of oxidized methionine residues on exposure to oxidative stress. The behavior of the mutants suggests that these novel selenoprotein-like gene products are part of a ubiquitous detoxification system that interacts with other redox-related proteins such as the thioredoxin-related protein and methionine sulfoxide reductase which are encoded by domains I and II of PilB. These proteins may be encoded by one gene as in the case of several prokaryotes, or by separate genes as in the eukaryotes examined here.

Amino Acid Sequence↗
PubMed2002

Quantification of thrombopoietic activity in bone marrow aspirates of dogs.

The aims of the study were to investigate possible influences of different numbers of counted fields on slides, and different slides on the counting of platelet precursors, and to establish guidelines for bone marrow examination in dogs. The study was based on bone marrow slides of 131 healthy dogs. The slides were prepared by a squash technique. On each slide the number of thrombopoietic cells at different levels of maturation were counted in all fragment-containing fields. The results of a variance component model revealed no influence of different slides, in contrast to a high variance related to different fields. Between 20 and 25 low power fields (100x magnification) had to be examined to achieve an imprecision of 20%. An imprecision of 10% required the counting of 100 fields. The lowest thrombopoietic activity was seen in the bone marrow of dogs aged one to six years. The total number of platelet percursors per field was significantly higher in adult female (10.4 +/- 2.67) than in male dogs (7.84 +/- 2.04, P = 0.0008) as was the number of megakaryocytes. We recommend assessment of thrombopoiesis on the basis of 20-25 fragment-containing low power fields and that age- and sex-related differences should be considered.

Aging↗
PubMed2001

Effects of desiccation on photosynthesis pigments and the ELIP-like dsp 22 protein complexes in the resurrection plant Craterostigma plantagineum.

Desiccation and abscisic acid treatment lead to major changes in thylakoid membranes of the desiccation-tolerant plant Craterostigma plantagineum. The chlorophyll contents and proteins of the light harvesting complexes decrease during desiccation, although some chlorophyll is retained in the dehydrated state. The xanthophyll cycle pigment zeaxanthin, however, increased. Under these conditions, a 22 kDa ELIP-like desiccation-induced protein (dsp 22) accumulated in the thylakoid membranes. Fractionation of pigment-protein complexes of stressed plants revealed that the dsp 22 protein co-localized with the carotenoid zeaxanthin. Inhibition of zeaxanthin production had a negative effect on the accumulation of the dsp 22 protein. It is suggested that dsp 22 contributes to the protection against photoinhibition caused by dehydration.

Journal Article↗
PubMed2001

Targeting detoxification pathways: an efficient approach to obtain plants with multiple stress tolerance?

A serious factor limiting the engineering of stress tolerance has been our ignorance about the function of stress-induced genes. A stress-activated novel aldose-aldehyde reductase was cloned from alfalfa. The ectopic expression of this gene in tobacco resulted in tolerance to oxidative stress and dehydration. Physiological analysis suggested that aldose reductase probably functions by reducing the level of reactive aldehydes. This provides a promising perspective for the development of crop plants with improved stress tolerance.

Adaptation, Physiological↗
PubMed2001

Novel ABA- and dehydration-inducible aldehyde dehydrogenase genes isolated from the resurrection plant Craterostigma plantagineum and Arabidopsis thaliana.

In order to identify genes that are critical for the ABA-dependent stress response in the resurrection plant Craterostigma plantagineum, a gene was isolated with homology to class 3 variable substrate aldehyde dehydrogenases (ALDH). The C. plantagineum gene Cp-ALDH constitutes a novel class of plant ALDHs. In a search for corresponding genes from Arabidopsis thaliana, Ath-ALDH3 and Ath-ALDH4 were isolated, showing 70% and 80% similarity to Cp-ALDH. Phylogenetically, the Cp- and Ath-ALDH3 and -ALDH4 proteins are closely related to aldehyde dehydrogenases from bacteria and mammalian species and are separated from known plant ALDHs and betaine-aldehyde dehydrogenases (BADH). Cp-ALDH transcript and polypeptide are up-regulated in vegetative tissues and callus in response to dehydration or ABA-treatment. Ath-ALDH3 expression was induced in response to dehydration and ABA treatment, while Ath-ALDH4 is constitutively expressed at a low level. Recombinant Cp-ALDH protein oxidizes nonanal, propionaldehyde and acetaldehyde, with Km values of 2.2 microm, 0.27 mm and 3.23 mm, respectively, in an NAD-dependent manner. Immunogold electron microscopy shows that Cp-ALDH is localized in plastids.

Abscisic Acid↗
PubMed2000

Hyperosmotic stress stimulates phospholipase D activity and elevates the levels of phosphatidic acid and diacylglycerol pyrophosphate.

In mammalian cells, phospholipase D (PLD) and its product phosphatidic acid (PA) are involved in a number of signalling cascades, including cell proliferation, membrane trafficking and defence responses. In plant cells a signalling role for PLD and PA is also emerging. Plants have the extra ability to phosphorylate PA to produce diacylglycerol pyrophosphate (DGPP), a newly discovered phospholipid whose formation attenuates PA levels, but which could itself be a second messenger. Here we report that increases in PA and its conversion to DGPP are common stress responses to water deficit. Increases occur within minutes of treatment and are dependent on the level of stress. Part of the PA produced is due to PLD activity as measured by the in vivo transphosphatidylation of 1-butanol, and part is due to diacylglycerol kinase activity as monitored via 32P-PA formation in a differential labelling protocol. Increases in PA and DGPP are found not only in the green alga Chlamydomonas moewusii and cell-suspension cultures of tomato and alfalfa when subjected to hyperosmotic stress, but also in dehydrated leaves of the resurrection plant Craterostigma plantagineum. These results provide further evidence that PLD and PA play a role in plant signalling, and provide the first demonstration that DGPP is formed during physiological conditions that evoke PA synthesis.

Animals↗
PubMed2000

Water deficit triggers phospholipase D activity in the resurrection plant Craterostigma plantagineum.

Phospholipids play an important role in many signaling pathways in animal cells. Signaling cascades are triggered by the activation of phospholipid cleaving enzymes such as phospholipases C, D (PLD), and A(2). Their activities result in the formation of second messengers and amplification of the initial signal. In this study, we provide experimental evidence that PLD is involved in the early events of dehydration in the resurrection plant Craterostigma plantagineum. The enzymatic activity of the PLD protein was activated within minutes after the onset of dehydration, and although it was not inducible by abscisic acid, PLD activity did increase in response to mastoparan, which suggests a role for heterotrimeric G proteins in PLD regulation. Two cDNA clones encoding PLDs, CpPLD-1 and CpPLD-2, were isolated. The CpPLD-1 transcript was constitutively expressed, whereas CpPLD-2 was induced by dehydration and abscisic acid. Immunological studies revealed changes in the subcellular localization of the PLD protein in response to dehydration. Taken together, the data on enzymatic activity as well as transcript and protein distributions allowed us to propose a role for PLD in the events leading to desiccation tolerance in C. plantagineum.

Abscisic Acid↗
PubMed2000

Fluoride concentrations in bottled water.

Bottled water use and lack of adequate labeling have given rise to questions regarding fluoride intake. This study examined fluoride concentration of commercially available bottled water products, determined if significant differences existed among the products, and explored packaging date as a variable on the concentration of fluoride. The values were compared to the ADA guideline for optimally fluoridated water and the American Academy of Pediatric Dentistry recommended schedule for fluoride supplementation. Five commercial brands were chosen for the study. Three bottles of each brand, each with different batch dates, were purchased. Following calibration, six tests were conducted on each bottle using the Hach DR-100 Colorimeter System for fluoride analysis and the values were recorded. Data were analyzed using a two-tailed ANOVA and Tukey's HSD Test (p = 0.05). The results showed that significant differences in fluoride concentrations existed among the five brands. For three brands, significant differences existed between the batches. All products had fluoride concentrations that fell below the ADA accepted standards for optimally fluoridated water. Due to the significant variability in fluoride concentration between products and batches, dental providers should advise their patients that bottled water might not contain optimal levels of fluoride.

Analysis of Variance↗
PubMed1999

Isolation and expression analysis of two stress-responsive sucrose-synthase genes from the resurrection plant Craterostigma plantagineum (Hochst.).

The enzyme sucrose synthase (UDP-glucose: D-fructose 2alpha-glucosyltransferase, EC 2.4.1.13) is a key enzyme in carbohydrate metabolism, catalyzing the reversible conversion of sucrose uridine-diphosphate into fructose and UDP-glucose. We report the molecular characterization of two classes of cDNA and genomic clones encoding sucrose synthase from Craterostigma plantagineum Hochst., a resurrection plant in which the turnover of sucrose is considered to have an important role in the unique phenomenon of surviving desiccation. Sucrose-synthase transcript and protein levels are modulated by dehydration and rehydration. In-situ hybridization revealed that transcripts preferentially accumulate in phloem tissues. Promoter analysis underlined a role for class-I sucrose-synthase genes in dehydration stress and in response to cis-abscisic acid. A DNA sequence motif common to class-I sucrose-synthase and sucrose-phosphate-synthase genes was discovered.

Amino Acid Sequence↗
PubMed1998

Gene structure and expression analysis of the drought- and abscisic acid-responsive CDeT11-24 gene family from the resurrection plant Craterostigma plantagineum Hochst.

In order to understand the molecular mechanisms which are responsible for desiccation tolerance in the resurrection plant Craterostigma plantagineum Hochst. a thorough analysis of the CDeT11-24 gene family was performed. CDeT11-24 comprises a small gene family whose genes are expressed in response to dehydration, salt stress and abscisic acid (ABA) treatment in leaves. The gene products are constitutively expressed in roots and disappear only when the plants are transferred to water. It is therefore suggested that the proteins are involved in sensing water status. The predicted proteins are very hydrophilic; they share some features with late-embryogenesis-abundant proteins, and sequence similarities were found with two ABA- and drought-regulated Arabidopsis genes. The analysis of beta-glucuronidase reporter genes driven by the CDeT11-24 promoter showed high activity in mature seeds in both transgenic Arabidopsis and tobacco. In vegetative tissues the promoter activity in response to ABA was restricted to young Arabidosis seedlings. The responsiveness to ABA during later developmental stages was regained in the presence of the Arabidopsis gene product ABI3. Dehydration-induced promoter activity was only observed in Arabidopsis leaves at a particular developmental stage. This analysis indicates that some components in the signal transduction pathway of the resurrection plant are not active in tobacco or Arabidopsis.

Abscisic Acid↗
PubMed1998

Desiccation- and abscisic acid-responsive genes encoding major intrinsic proteins (MIPs) from the resurrection plant Craterostigma plantagineum.

Major intrinsic proteins (MIPs) are a family of channel proteins that are mainly represented by aquaporins in plants. These are divided into TIPs (tonoplast intrinsic proteins) and PIPs (plasma membrane intrinsic proteins) according to their subcellular localization. Homologues to PIPs and TIPs were isolated from the desiccation-tolerant resurrection plant Craterostigma plantagineum by two approaches: firstly, a cDNA library constructed from RNA of dehydrated C. plantagineum leaves was screened with an Arabidopsis thaliana Ath-PIP1b cDNA probe and, secondly, a cDNA library was screened differentially to isolate early drought-induced transcripts. According to sequence homologies the isolated cDNA clones were grouped as follows: Cp-PIPa, Cp-PIPb, Cp-PIPc and Cp-TIP. Cp-PIPa, Cp-PIPc and Cp-TIP transcript accumulation was regulated by dehydration and abscisic acid (ABA). Within the Cp-PIPa group transcripts were regulated either by drought only or by drought and ABA, indicating that ABA-dependent and -independent signal transduction pathways lead to Cp-PIPa expression. Comparison of Cp-PIPa expression in detached leaves and in whole plants suggested the involvement of a signal transmitted in the whole plant in response to drought. Cp-PIPb transcript levels were constitutive in all organs tested. Antibodies raised against a Cp-PIPA protein recognized a polypeptide with an apparent molecular mass of 28 kDa. Using these antibodies it was shown that both Cp-PIPA and Cp-PIPB proteins were localized to the plasma membrane. The role of different members of the MIP group in the dehydration response is discussed.

Abscisic Acid↗
PubMed1998

Two dehydration-inducible transcripts from the resurrection plant Craterostigma plantagineum encode interacting homeodomain-leucine zipper proteins.

The molecular dissection of desiccation tolerance in the resurrection plant Craterostigma plantagineum led to the isolation of two dehydration-stress inducible homeo-domain-leucine zipper genes (CPHB-1 and -2). When the coding region of CPHB-1 was used as bait in the yeast two-hybrid system, the ability of CPHB-1 to form homodimers was demonstrated. The two-hybrid system was also used to isolate CPHB-2, which heterodimerises with CPHB-1. Both transcripts are inducible by dehydration in leaves and roots, but steady state levels vary in response to exogenously applied ABA. Although expression of CPHB-1 is not inducible by ABA, the transcript level of CPHB-2 increases during ABA-treatment. Both genes are expressed at very early stages of dehydration and thus may be involved in the regulation of gene expression during dehydration. CPHB-1 and -2 differential expression in response to ABA suggests that they act in different branches of the dehydration-induced signalling network. In vitro binding studies revealed that CPHB-1 specifically binds to the pseudopalindromic sequence CAAT(C/G)ATTG. Using this element for in vitro binding studies with nuclear proteins from dehydrated leaves, an inducible DNA-protein complex was identified.

Abscisic Acid↗
PubMed1997

High level transcription of a member of a repeated gene family confers dehydration tolerance to callus tissue of Craterostigma plantagineum.

An experimental system has been developed which allows the identification of intermediates in the abscisic acid (ABA) signal transduction pathway leading to desiccation tolerance in plants. Desiccation tolerance in callus of the resurrection plant Craterostigma plantagineum is mediated via the plant hormone ABA, which induces the expression of gene products related to desiccation tolerance. Based on T-DNA activation tagging, a gene (CDT-1) was isolated which encodes a signalling molecule in the ABA transduction pathway. Constitutive overexpression of CDT-1 leads to desiccation tolerance in the absence of ABA and to the constitutive expression of characteristic transcripts. CDT-1 represents a novel gene with unusual features in its primary sequence. The CDT-1 gene resembles in several features SINE retrotransposons. Mechanisms by which CDT-1 activates the pathway could be via a regulatory RNA or via a short polypeptide.

Abscisic Acid↗
PubMed1997

Structure and function of the vp1 gene homologue from the resurrection plant Craterostigma plantagineum Hochst.

A gene that is homologous to the vp1 genes from maize and rice, the Arabidopsis abi3 gene and PvAlf from Phaseolus vulgaris was isolated from the resurrection plant, Craterostigma plantagineum Hochst, The C. plantagineum gene (epvp1) encodes a protein of 688 amino acids and contains five introns at positions identical to those in the Arabidopsis, maize and rice homologues. The cpvp1 transcript is present in mature seeds and in young seedlings up to 8 days following germination. The ability of the cpvp1 gene product to activate target genes was demonstrated by transient expression experiments in tobacco protoplasts using reporter gene constructs containing the beta-glucuronidase (GUS) gene fused to the promoter of two late embryogenesis abundant (LEA)-like genes, CDeT27-45 and CDeT6-19 from C. plantagineum, or the promoter of a maize gene encoding a 22-kDa zein seed storage protein.

Abscisic Acid↗