Showing papers on "Arabidopsis published in 1992"
TL;DR: Arabidopsis, a tractable genetic system, is shown to develop resistance to a bacterial and a fungal pathogen following 2,6-dichloroisonicotinic acid (INA) treatment and three proteins that accumulated to high levels in the apoplast in response to INA treatment were purified and characterized.
Abstract: Acquired resistance is an important component of the complex disease resistance mechanism in plants, which can result from either pathogen infection or treatment with synthetic, resistance-inducing compounds In this study, Arabidopsis, a tractable genetic system, is shown to develop resistance to a bacterial and a fungal pathogen following 2,6-dichloroisonicotinic acid (INA) treatment Three proteins that accumulated to high levels in the apoplast in response to INA treatment were purified and characterized Expression of the genes corresponding to these proteins was induced by INA, pathogen infection, and salicylic acid, the latter being a putative endogenous signal for acquired resistance Arabidopsis should serve as a genetic model for studies of this type of immune response in plants
1,052 citations
TL;DR: Results suggest that the defect in jar1 affects a general jasmonate response pathway, which may regulate multiple genes in different plant organs, and seeds of jar1 plants were more sensitive than wild type to inhibition of germination by abscisic acid.
Abstract: Jasmonic acid and its methyl ester, methyl jasmonate (MeJA), are plant signaling molecules that affect plant growth and gene expression. Primary root growth of wild-type Arabidopsis thaliana seedlings was inhibited 50% when seedlings were grown on agar medium containing 0.1 M MeJA. An ethyl methanesulfonate mutant (jar1) with decreased sensitivity to MeJA inhibition of root elongation was isolated and characterized. Genetic data indicated the trait was recessive and controlled by a single Mendelian factor. MeJA-induced polypeptides were detected in Arabidopsis leaves by antiserum to a MeJA-inducible vegetative storage protein from soybean. The induction of these proteins by MeJA in the mutant was at least 4-fold less in jar1 compared to wild type. In contrast, seeds of jar1 plants were more sensitive than wild type to inhibition of germination by abscisic acid. These results suggest that the defect in jar1 affects a general jasmonate response pathway, which may regulate multiple genes in different plant organs.
837 citations
TL;DR: A gene from the flowering plant Arabidopsis thaliana that encodes an omega-3 desaturase was cloned on the basis of the genetic map position of a mutation affecting membrane and storage lipid fatty acid composition.
Abstract: A gene from the flowering plant Arabidopsis thaliana that encodes an omega-3 desaturase was cloned on the basis of the genetic map position of a mutation affecting membrane and storage lipid fatty acid composition. Yeast artificial chromosomes covering the genetic locus were identified and used to probe a seed complementary DNA library. A complementary DNA clone for the desaturase was identified and introduced into roots of both wild-type and mutant plants by Ti plasmid-mediated transformation. Transgenic tissues of both mutant and wild-type plants had significantly increased amounts of the fatty acid produced by this desaturase.
547 citations
TL;DR: Dark-grown Arabidopsis seedlings with recessive mutations at the constitutively photomorphogenic (COP1) locus indicate that the wild-type COP1 protein represses photomorphogenesis in darkness and that light reverses this repressive activity.
544 citations
TL;DR: In this article, the authors showed that expression of R caused augmented anthocyanin pigmentation in both plant species and augmented trichome (hair) production in Arabidopsis.
Abstract: Anthocyanin pathway-specific transcriptional activators R and C1 from the monocot maize were expressed in two dicots, Arabidopsis thaliana and Nicotiana tabacum. Expression of R caused augmented anthocyanin pigmentation in both plant species and augmented trichome (hair) production in Arabidopsis. Alone, C1 had no effect. Hybrid transgenic Arabidopsis expressing both C1 and R produced anthocyanins in root, petal, and stamen tissues that normally never express anthrocyanins. When R was expressed in the transparent testa glabrous (without anthocyanins and trichomes) mutant of Arabidopsis, the deficiency was complemented and both anthocyanins and trichomes were restored.
507 citations
TL;DR: The defect in the sin1 mutants appears to block the conversion of ferulate to 5-hydroxyferulate in the general phenylpropanoid pathway, and the lignin of the mutant lacks the sinapic acid-derived components typical of wild-type lign in Arabidopsis.
Abstract: Mutants of Arabidopsis deficient in a major leaf phenylpropanoid ester, 2-O-sinapoyl-L-malate, were identified by thin-layer chromatographic screening of methanolic leaf extracts from several thousand mutagenized plants. Mutations at a locus designated SIN1 also eliminate accumulation of the sinapic acid esters characteristic of seed tissues. Because of increased transparency to UV light, the sin1 mutants exhibit a characteristic red fluorescence under UV light, whereas wild-type plants have a blue-green appearance due to the fluorescence of sinapoyl malate in the upper epidermis. As determined by in vivo radiotracer feeding experiments, precursor supplementation studies, and enzymatic assays, the defect in the sin1 mutants appears to block the conversion of ferulate to 5-hydroxyferulate in the general phenylpropanoid pathway. As a result, the lignin of the mutant lacks the sinapic acid-derived components typical of wild-type lignin.
460 citations
TL;DR: These experiments provide direct evidence of the proposed antagonism between AG and AP2 functions, and the results strongly suggest that AG does indeed inhibit AP2 function.
423 citations
TL;DR: Sequence analysis of the break points in both mutants indicate that repair of radiation-induced damage involves mechanisms similar or identical to those that mediate the integration of foreign sequences into the genome.
Abstract: Ionizing radiation is known to cause chromosomal alterations such as inversions and deletions and has been used extensively for inducing mutations. In Arabidopsis, two methods for the isolation of genes identified on the basis of mutant phenotypes--genomic subtraction and chromosome walking--either rely on or are greatly facilitated by the availability of these types of mutations. This article gives a detailed characterization of ionizing radiation-induced mutations in plants. The Arabidopsis genes encoding chalcone flavanone isomerase (CHI) and dihydroflavonol 4-reductase (DFR) were cloned and found to correspond to two transparent testa loci. A CHI allele, generated by fast-neutron irradiation, consisted of an inversion within the gene. A 272-bp fragment from 38 centimorgans away on the same chromosome was transferred to one end of this inversion. A DFR allele, induced by x-irradiation, contained two deletions and an inversion of the 2.8-centimorgan intervening region. Sequence analysis of the break points in both mutants indicate that repair of radiation-induced damage involves mechanisms similar or identical to those that mediate the integration of foreign sequences into the genome. The chromosome rearrangements found in these mutants have important implications for the use of ionizing radiation-induced alleles in classical and molecular genetic experiments in plants.
383 citations
TL;DR: The phenotypes of the ovule mutants described in Arabidopsis represent novel genetic tools for the study of this stage of reproductive development and indicate that normal morphological development of the integuments and proper embryo sac formation are interdependent or are governed in part by common pathways.
Abstract: Ovules are complex structures that are present in all seed bearing plants and are contained within the carpels in flowering plants. Ovules are the site of megasporogenesis and megagametogenesis and, following fertilization, develop into seeds. We combined genetic methods with anatomical and morphological analyses to dissect ovule development. Here, we present a detailed description of the morphological development of Arabidopsis ovules and report on the isolation of two chemically induced mutants, bell (bel1) and short integuments (sin1), with altered ovule development. Phenotypic analyses indicated that bel1 mutants initiate a single integument-like structure that develops aberrantly, sin1 mutants initiate two integuments, but growth of the integuments is disrupted such that cell division continues without normal cell elongation. Both mutants can differentiate archesporial cells, but neither forms a normal embryo sac. Genetic analyses indicated that bel1 segregates as a single recessive mutation, and complementation tests showed that the two mutants are not allelic. The phenotypes of the mutants indicate that normal morphological development of the integuments and proper embryo sac formation are interdependent or are governed in part by common pathways. The ovule mutants that we describe in Arabidopsis represent novel genetic tools for the study of this stage of reproductive development.
359 citations
Journal Article•
TL;DR: Isolation and maintenance of an Arabidopsis thaliana cell suspension culture, protoplast preparation from these cells and plasmid DNA transfection into the protoplasts by the polyethyleneglycol procedure are described.
340 citations
TL;DR: The enhanced disease tolerance of ein2 plants suggests that ethylene may mediate pathogen-induced damage, but the absence of tolerance in ein1 mutants has yet to be explained.
Abstract: The plant hormone ethylene has been hypothesized to play roles both in disease resistance and in disease susceptibility. These processes were examined by using isogenic virulent and avirulent bacterial pathogens and mutants of Arabidopsis thaliana that were altered in ethylene physiology. Ethylene-insensitive ein1 and ein2 mutants of Arabidopsis were resistant to Pseudomonas syringae pv. tomato made avirulent by the addition of the cloned avirulence genes avrRpt2, avrRpm1, or avrB; this suggests that ethylene is not required for active resistance against avirulent bacteria. In a second set of experiments, susceptibility was monitored with virulent P. s. pv. tomato, P. s. pv. maculicola, or Xanthomonas campestris pv. campestris strains. Wild-type Arabidopsis and ein1 mutants were susceptible to these strains, but ein2 mutants developed only minimal disease symptoms. Despite these reduced symptoms, virulent P. s. pv. tomato grew extensively within ein2 leaves. The Pseudomonas phytotoxin coronatine induces ethylene biosynthesis and diseaselike symptoms on many plant species, but the reduced symptomology of ein2 mutants could not be attributed to insensitivity to coronatine. The enhanced disease tolerance of ein2 plants suggests that ethylene may mediate pathogen-induced damage, but the absence of tolerance in ein1 mutants has yet to be explained.
TL;DR: It is shown that sucrose can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants and further that Sucrose alone is sufficient for the full expression of nitrates reduct enzyme genes in etiolated Arabidoptera plants.
Abstract: Nitrate reductase, the first enzyme in nitrate assimilation, is located at the crossroad of two energy-consuming pathways: nitrate assimilation and carbon fixation. Light, which regulates the expression of many higher-plant carbon fixation genes, also regulates nitrate reductase gene expression. Located in the cytosol, nitrate reductase obtains its reductant not from photosynthesis but from carbohydrate catabolism. This relationship prompted us to investigate the indirect role that light might play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants. We show further that sucrose alone is sufficient for the full expression of nitrate reductase genes in etiolated Arabidopsis plants. Finally, using a reporter gene, we show that a 2.7-kilobase region of 5' flanking sequence of the nitrate reductase gene is sufficient to confer the light or the sucrose response.
TL;DR: Two-dimensional protein immunoblot analyses have resolved at least seven different beta-tubulin isoforms in Arabidopsis, indicating that most, if not all, of the TUB transcripts are translated.
Abstract: The goal of our investigations is to define the genetic control of microtubule-based processes in a higher plant. The available evidence suggests that we have achieved our first objective: the characterization of the complete alpha-tubulin and beta-tubulin gene families of Arabidopsis. Four additional alpha-tubulin genes (TUA2, TUA4, TUA5, and TUA6) of Arabidopsis have been cloned and sequenced to complete the analysis of the gene structure for all six alpha-tubulin genes detectable on DNA gel blots of Arabidopsis genomic DNA hybridized with alpha-tubulin coding sequences. TUA1 and TUA3 were characterized earlier in our laboratory. Noncoding gene-specific hybridization probes have been constructed for all six alpha-tubulin genes and used in RNA gel blot analyses to demonstrate that all six genes are transcribed. The six genes encode four different alpha-tubulin isoforms; TUA2 and TUA4 encode a single isoform, as do TUA3 and TUA5. Two-dimensional protein gel immunoblot analyses have resolved at least four alpha-tubulin isoforms from plant tissues, suggesting that all of the predicted TUA gene products are synthesized in vivo.
TL;DR: It is concluded that Arabidopsis encodes a large family of homeodomain proteins, including members that contain a homeodOMain/leucine-zipper (HD-Zip) motif.
Abstract: Homeobox genes encode a large family of homeodomain proteins in animal systems. To test whether such genes are also abundant in higher plants, degenerate oligonucleotides complementary to sequences encoding the recognition helix (helix three) of the homeodomain were used to screen genomic and cDNA libraries from the plant Arabidopsis thaliana. Analysis of 8 of the 41 cDNAs isolated revealed that each encodes a presumptive homeodomain; interestingly, most of these clones also contain a leucine zipper motif tightly linked to the homeodomain. It is concluded that Arabidopsis encodes a large family of homeodomain proteins, including members that contain a homeodomain/leucine-zipper (HD-Zip) motif.
01 Jan 1992
TL;DR: The authors used the genomic subtraction technique to clone DNA sequences that are present in wild-type Arabidopsis (ecotype Landsberg erecta, Ler) but are missing in a presumptive g a l deletion mutant, gal-3.
Abstract: Arabidopsis thaliana ga l mutants are gibberellin-responsive dwarfs. We used the genomic subtraction technique to clone DNA sequences that are present in wild-type Arabidopsis (ecotype Landsberg erecta, Ler) but are missing in a presumptive g a l deletion mutant, gal-3. The cloned sequences correspond to a 5.0-kb deletion in the gal-3 genome. Three lines of evidence indicated that the 5.0-kb deletion in the gal-3 mutant is located at the GAl locus. First, restriction fragment length polymorphism mapping showed that DNA sequences within the 5.0-kb deletion map to the GAl locus. Second, cosmid clones that contain wild-type DNA inserts spanning the deletion in gal-3 complemented the dwarf phenotype when integrated into the gal-3 genome by Agrobacterium tumefaciens-mediated transformation. Third, we identified molecular lesions in four additional ga l alleles within the 5.0-kb region deleted in mutant gal-3. One of these lesions is a large insertion or inversion located within the most distal intron encoded by the GAl locus. The three other lesions are all single base changes located within the two most distal exons. RNA gel blot analysis indicated that the GAl locus encodes a 2.8-kb mRNA. We calculated a recombination rate of 10-5 cM per nucleotide for the GAl region of the Arabidopsis genome.
TL;DR: The genomic subtraction technique was used to clone DNA sequences that are present in wild-type Arabidopsis but are missing in a presumptive ga1 deletion mutant, ga1-3, and showed that DNA sequences within the 5.0-kb deletion map to the GA1 locus.
Abstract: Arabidopsis thaliana ga1 mutants are gibberellin-responsive dwarfs. We used the genomic subtraction technique to clone DNA sequences that are present in wild-type Arabidopsis (ecotype Landsberg erecta, Ler) but are missing in a presumptive ga1 deletion mutant, ga1-3. The cloned sequences correspond to a 5.0-kb deletion in the ga1-3 genome. Three lines of evidence indicated that the 5.0-kb deletion in the ga1-3 mutant is located at the GA1 locus. First, restriction fragment length polymorphism mapping showed that DNA sequences within the 5.0-kb deletion map to the GA1 locus. Second, cosmid clones that contain wild-type DNA inserts spanning the deletion in ga1-3 complemented the dwarf phenotype when integrated into the ga1-3 genome by Agrobacterium tumefaciens-mediated transformation. Third, we identified molecular lesions in four additional ga1 alleles within the 5.0-kb region deleted in mutant ga1-3. One of these lesions is a large insertion or inversion located within the most distal intron encoded by the GA1 locus. The three other lesions are all single base changes located within the two most distal exons. RNA gel blot analysis indicated that the GA1 locus encodes a 2.8-kb mRNA. We calculated a recombination rate of 10-5 cM per nucleotide for the GA1 region of the Arabidopsis genome.
TL;DR: It is demonstrated that GBF1, GBF2 and GBF3 heterodimerize and these heterodimers also interact with the G‐box, suggesting a potential mechanism for generating additional diversity from these GBF proteins.
Abstract: The promoters of a variety of plant genes are characterized by the presence of a G-box (CCACGTGG) or closely related DNA motifs. These genes often exhibit quite diverse expression characteristics and in many cases the G-box sequence has been demonstrated to be essential for expression. The G-box of the Arabidopsis rbcS-1A gene is bound by a protein, GBF, identified in plant nuclear extracts. Here we report the isolation of three Arabidopsis thaliana cDNA clones encoding GBF proteins referred to as GBF1, GBF2 and GBF3. GBF1 and GBF2 mRNA is present in light and dark grown leaves as well as in roots. In contrast, GBF3 mRNA is found mainly in dark grown leaves and in roots. The deduced amino acid sequences of the three cDNAs indicate that each encodes a basic/leucine zipper protein. In addition, all three proteins are characterized by an N-terminal proline-rich domain. Homodimers of the three proteins specifically recognize the G-box motif, with GBF1 and GBF3 binding symmetrically to this palindromic sequence. In contrast, GBF2 binds to the symmetrical G-box sequence in such a way that the juxtaposition of the protein and the DNA element is clearly asymmetric and hence distinct from that observed for the other two proteins. The fact that GBF1, GBF2 and GBF3 possess both distinct DNA binding properties and expression characteristics prompt us to entertain the notion that these proteins may individually mediate distinct subclasses of expression properties assigned to the G-box. Furthermore, we demonstrate that GBF1, GBF2 and GBF3 heterodimerize and these heterodimers also interact with the G-box, suggesting a potential mechanism for generating additional diversity from these GBF proteins.
TL;DR: Comparative analysis of structural and expression characteristics of ACC synthase genes from Arabidopsis and other plant species suggests that the sequence divergence of the ACC synthasing genes arose early in plant evolution and before the divergence of monocots and dicots.
Abstract: Genomic sequences encoding five divergent 1-aminocyclopropane-1-carboxylic acid (ACC) synthase polypeptides (ACC1, ACC2, ACC3, ACC4, and ACC5) have been isolated from Arabidopsis thaliana by using heterologous cDNAs and PCR fragments amplified from genomic DNA with degenerate oligonucleotide primers. Each gene is located on a different chromosome in the Arabidopsis genome. The genes are differentially expressed during development and in response to environmental stimuli. Protein-synthesis inhibition derepresses the expression of all genes but most dramatically derepresses that of ACC2, suggesting that their expression may be under negative control. The sequence of ACC2 was determined, and its transcription initiation site was defined. Authenticity of the polypeptide encoded by the gene was confirmed by expression experiments in Escherichia coli. The predicted size of the protein is 55,623 Da, and it contains the 11 invariant amino acid residues conserved between aminotransferases and ACC synthases from various plant species. Comparative analysis of structural and expression characteristics of ACC synthase genes from Arabidopsis and other plant species suggests that the sequence divergence of the ACC synthase genes and possibly the distinct regulatory networks governing the expression of ACC synthase subfamilies arose early in plant evolution and before the divergence of monocots and dicots.
TL;DR: regulation of key steps in aromatic amino acid biosynthesis in Arabidopsis appears to involve differential expression of duplicated genes, suggesting a novel role for ASA1 in the production of tryptophan pathway metabolites as part of anArabidopsis defense response.
Abstract: Arabidopsis thaliana has two genes, ASA1 and ASA2, encoding the alpha subunit of anthranilate synthase, the enzyme catalyzing the first reaction in the tryptophan biosynthetic pathway. As a branchpoint enzyme in aromatic amino acid biosynthesis, anthranilate synthase has an important regulatory role. The sequences of the plant genes are homologous to their microbial counterparts. Both predicted proteins have putative chloroplast transit peptides at their amino termini and conserved amino acids involved in feedback inhibition by tryptophan. ASA1 and ASA2 cDNAs complement anthranilate synthase alpha subunit mutations in the yeast Saccharomyces cerevisiae and in Escherichia coli, confirming that both genes encode functional anthranilate synthase proteins. The distributions of ASA1 and ASA2 mRNAs in various parts of Arabidopsis plants are overlapping but nonidentical, and ASA1 mRNA is approximately 10 times more abundant in whole plants. Whereas ASA2 is expressed at a constitutive basal level, ASA1 is induced by wounding and bacterial pathogen infiltration, suggesting a novel role for ASA1 in the production of tryptophan pathway metabolites as part of an Arabidopsis defense response. Regulation of key steps in aromatic amino acid biosynthesis in Arabidopsis appears to involve differential expression of duplicated genes.
TL;DR: Data suggest that PsMTA protein binds Cu in planta and that uncoupled (constitutive) expression of thePsMTA gene causes enhanced Cu accumulation, which is consistent with a role in Cu homoeostasis.
Abstract: The PsMTA gene from pea (Pisum sativum) shares similarity with metallothionein (MT) genes and related sequences have also been isolated from a number of other higher-plant species. The proteins encoded by these genes have not yet been purified from plants and their functions remain unclear although, by analogy to MT, roles in the metabolism and detoxification of metal ions have been proposed. By contrast, correlation between transcript abundance and Fe availability has led to an alternative proposal that these genes are involved in mechanisms of Fe efficiency.
TL;DR: The isolation of the second member, kin2, of a family of two cold-inducible genes of Arabidopsis thaliana, where both mRNAs are induced by 10 μM ABA but only kin2 responds strongly to drought and salinity stresses.
Abstract: We report the isolation of the second member, kin2, of a family of two cold-inducible genes of Arabidopsis thaliana. The proteins corresponding to the two genes have similarities to the small antifreeze proteins from Winter flounder. Kin1 and kin2 are organized in a close tandem array in the genome of a. thaliana. Both have three exons separated by introns with approximately the same length and location. The coding regions are highly conserved while the introns and especially the 3′ flanking sequences of the mRNAs have diverged. The kin1 and kin2 genes are coordinately regulated in the cold. Unlike kin1, the kin2 mRNA has a detectable basal level, and accumulates to a higher level during acclimation. Both mRNAs are induced by 10 μM ABA but only kin2 responds strongly to drought and salinity stresses.
TL;DR: The results suggest that the cop9 and cop1 mutations result in the the same range of phenotypes and therefore COP9 and COP1 loci may encode closely related components in the same regulatory pathway.
Abstract: We report here the identification and characterization of a new Arabidopsis light-regulatory locus, COP9, mutation that leads to a constitutive photomorphogenic phenotype. Dark-grown cop9 seedlings exhibit many morphological characteristics of light-grown seedlings, including short hypocotyls and open and enlarged cotyledons with cell-type and chloroplast differentiation. Furthermore, the cop9 mutation leads to high-level expression of light-inducible genes in the absence of light, probably by altering the promoter activities of these genes. These properties imply that the mutation in the COP9 locus uncouples the light/dark signals from morphogenesis and light-regulated gene expression. In addition, light-grown cop9 mutants are severely dwarfed and are unable to reach maturation and flowering. This adult-lethal phenotype indicates that the COP9 locus also plays a critical role for normal development of the light-grown plant. Similar to cop1 mutants, but not det1, the cop9 mutants show (1) no effect on the phytochrome control of seed germination and (2) deficiency in the dark-adaptive change of expression of light-regulated genes. Our results suggest that the cop9 and cop1 mutations result in the same range of phenotypes and therefore COP9 and COP1 loci may encode closely related components in the same regulatory pathway.
TL;DR: Histochemical analysis showed that the gusA gene expression increased as the period of preincubation on CIM was extended, suggesting that dividing cells are susceptible to Agrobacterium infection.
Abstract: The efficiency of Agrobacterium-mediated transformation of Arabidopsis thaliana was compared with different organs, Arabidopsis ecotypes, and Agrobacterium strains. Efficiency of shoot regeneration was examined using hypocotyl, cotyledon and root explants prepared from young seedlings. Hypocotyl expiants had the highest regeneration efficiency in all of the four Arabidopsis ecotypes tested, when based on a tissue culture system of callus-inducing medium (CIM: Valvekens et al. 1988) and shoot-inducing medium (SIM: Feldmann and Marks 1986). Histochemical analysis using the s-glucuronidase (GUS) reporter gene showed that the gusA gene expression increased as the period of preincubation on CIM was extended, suggesting that dividing cells are susceptible to Agrobacterium infection. In order to obtain transgenic shoots, hypocotyl explants preincubated for 7 or 8 days on CIM were infected with Agrobacterium containing a binary vector which carries two drug-resistant genes as selection markers, and transferred to SIM for selection of transformed shoots. Of four Arabidopsis ecotypes and of three Agrobacterium strains examined, Wassilewskija ecotype and EHA101 strain showed the highest efficiency of regeneration of transformed shoots. By combining the most efficient factors of preincubation period, Arabidopsis ecotype, tissue, and bacterial strain, we obtained a transformation efficiency of about 80-90%. Southern analysis of 124 transgenic plants showed that 44% had one copy of inserted T-DNA while the others had more than one copy.
TL;DR: A manipulable cell culture system in which TCH gene expression is regulated has been developed, and in response to increased external calcium or heat shock, TCH2, -3, and -4 mRNA levels significantly increased.
Abstract: Expression of the calmodulin-related TCH genes of Arabidopsis is strongly and rapidly up-regulated in plants after a variety of stimuli, including touch. As an approach to investigating the mechanism(s) of TCH gene regulation, a manipulable cell culture system in which TCH gene expression is regulated has been developed. In response to increased external calcium or heat shock, TCH2, -3, and -4 mRNA levels significantly increased. Significantly, these two stimuli are known to result in cytoplasmic calcium increases, therefore implicating a role for calcium itself in the regulation of calmodulin-related genes. Further, external calcium is required for maximal heat-shock induction of expression of the TCH genes but not of the 70-kDa heat shock protein; therefore, there may exist at least two distinct mechanisms of heat shock induction of gene expression. Calcium ion regulation of genes encoding calcium-binding proteins may ensure the efficacy of calcium ion as a transient second messenger and the maintenance of cellular homeostasis. This possible regulatory circuit would likely be relevant not only for plant cells but also for the great variety of animal cells that transduce extracellular stimuli, such as hormones and electrical impulses, into calcium signals.
TL;DR: A detailed analysis of TUA1 expression during Arabidopsis development revealed several motifs that are repeated within the T UA1 promoter and are similar to sequences in other pollen-specific promoters.
Abstract: The pool of tubulin protein in tissues of Arabidopsis is provided by the expression of multiple alpha-tubulin (TUA) and beta-tubulin genes. Whereas most tubulin genes are expressed in many tissues, previous evidence suggested that the TUA1 gene might be expressed primarily in pollen. We now report a detailed analysis of TUA1 expression during Arabidopsis development. In RNA from tissues of dissected flowers, TUA1 transcripts were detected only in stamens and mature pollen. Chimeric genes containing TUA1 5' flanking DNA fused to the beta-glucuronidase (GUS) coding region were used to create transgenic Arabidopsis plants. Plants containing a chimeric gene with 533 bp of 5' flanking sequence were analyzed by histochemical assay to localize GUS expression within the plant. The blue product of GUS enzyme activity accumulated very rapidly in postmitotic pollen grains. Much lower levels of GUS activity were detected in anthers with uninucleate pollen grains, in flower receptacles, and in a few vegetative tissues. Analysis of 5' deletions of the TUA1 promoter suggested that 97 bp of 5' flanking DNA is sufficient to drive GUS expression in pollen and young anthers, whereas at least 380 bp is required to detect GUS expression in the receptacle. Examination of the TUA1 promoter sequence revealed several motifs that are repeated within the TUA1 promoter and are similar to sequences in other pollen-specific promoters.
TL;DR: The G box is a well-characterized cis-acting DNA regulatory element found in the promoters of several seemingly unrelated plant genes, including the alcohol dehydrogenase (Adh) gene of Arabidopsis thaliana, and a cDNA clone encoding a protein that is part of the in vitro protein/G box complex is isolated.
Abstract: The G box is a well-characterized cis-acting DNA regulatory element found in the promoters of several seemingly unrelated plant genes, including the alcohol dehydrogenase (Adh) gene of Arabidopsis thaliana. Using a monoclonal antibody screening approach coupled with electrophoretic mobility shift assays, we have isolated a cDNA clone encoding a protein that is part of the in vitro protein/G box complex. The derived amino acid sequence is homologous to a class of proteins in mammalian brains described as protein kinase C inhibitors and as activators of tyrosine and tryptophan hydroxylases, the rate-limiting enzymes in the pathways leading to the catecholamines and serotonin. The fact that a homologous member of this regulatory protein family is found in plants and is associated with binding to transcriptional regulatory elements suggests a much wider role for these proteins.
TL;DR: Cyc1At is encoded by a single gene, but the amplification by the polymerase chain reaction of other fragments homologous to cyclins indicates the presence of a family of cyclins in Arabidopsis.
Abstract: A key element of cell cycle control in eukaryotes is the M-phase kinase, composed of p34cdc2 and cyclin. To dissect the plant cell cycle, we have previously isolated a cdc2 gene homolog from Arabidopsis thaliana. We have now cloned an Arabidopsis cDNA corresponding to cyclins. This gene (cyc1At) encodes a protein with a predicted molecular mass of 48.4 kDa and a domain homologous to the cyclin box of mitotic cyclins. However, by sequence comparison the cyc1At gene could not be assigned to the A- or B-type group. The mRNA accumulates preferentially in actively dividing cells and when these cells are blocked during the cell cycle, the amount of transcripts decreases dramatically. cyc1At mRNA is found mainly in G2-phase nuclei, suggesting that its expression is periodic in the cell cycle. Microinjection of synthetic cyc1At mRNA induced meiotic maturation in Xenopus oocytes. Cyc1At is encoded by a single gene, but the amplification by the polymerase chain reaction of other fragments homologous to cyclins indicates the presence of a family of cyclins in Arabidopsis.
TL;DR: It is demonstrated that a bacterial avirulence (avr) gene function, avrPpiA1, from the pea pathogen Pseudomonas syringae pv pisi, is recognized by some, but not all, genotypes of Arabidopsis, and therefore bean, pea, and conceivably other crop species contain functional and potentially molecular homologs of RPM1.
Abstract: We showed that a bacterial avirulence (avr) gene function, avrPpiA1, from the pea pathogen Pseudomonas syringae pv pisi, is recognized by some, but not all, genotypes of Arabidopsis. Thus, an avr gene functionally defined on a crop species is also an avr gene on Arabidopsis. The activity of avrPpiA1 on a series of Arabidopsis genotypes is identical to that of the avrRpm1 gene from P.s. pv maculicola previously defined using Arabidopsis. The two avr genes are homologous and encode nearly identical predicted products. Moreover, this conserved avr function is also recognized by some bean and pea cultivars in what has been shown to be a gene-for-gene manner. We further demonstrated that the Arabidopsis disease resistance locus, RPM1, conditioning resistance to avrRpm1, also conditions resistance to bacterial strains carrying avrPpiA1. Therefore, bean, pea, and conceivably other crop species contain functional and potentially molecular homologs of RPM1.
TL;DR: Upon transfer of a genetically engineered Escherichia coli gene for glycerol‐3‐phosphate acyltransferase to Arabidopsis thaliana, an alteration in fatty acid composition of membrane lipids is observed and it is evident that the enzyme is located mainly inside the plastids.
Abstract: Upon transfer of a genetically engineered Escherichia coli gene for glycerol-3-phosphate acyltransferase (plsB) to Arabidopsis thaliana (L.) Heynh., the gene is transcribed and translated into an enzymatically active polypeptide. This leads to an alteration in fatty acid composition of membrane lipids. From these alterations it is evident that the enzyme is located mainly inside the plastids. The amount of saturated fatty acids in plastidial membrane lipids increased. In particular, the fraction of high-temperature melting species of phosphatidylglycerol is elevated. These molecules are thought to play a crucial role in determining chilling sensitivity of plants. An increase in sensitivity could be observed in the transgenic plants during recultivation after chilling treatment. Implications for the hypothesis of phosphatidylglycerol-determined chilling sensitivity are discussed.
TL;DR: The data are compatible with the idea that there are few, if any, restrictions on cell fate within the cell layers of the dry seed meristem, and the axillary meristems of Arabidopsis were found to be clonally related to two or more cells near the centre of the subtending leaf.
Abstract: Seeds of Arabidopsis thaliana, heterozygous for the alb1 mutation were treated with X-rays to generate sectors of albino tissue in the mature plants. Sectors were observed in tissues derived from L2 and L3 layers of the shoot meristem. Altogether 324 sectors were obtained affecting 512 leaves or the inflorescence. The majority of sectors affected only one or other of the first leaf pair. In later leaves, sectors were less frequent, and often affected more than one leaf. Sectors seen in the flowers almost invariably included some of the cauline leaves. Sectors in any region of the plant were of variable length and width. The axillary meristems of Arabidopsis were found to be clonally related to two or more cells near the centre of the subtending leaf. Overall the data are compatible with the idea that there are few, if any, restrictions on cell fate within the cell layers of the dry seed meristem. As in other higher plants, developmental fate could only be predicted in a general and probabilistic way. Such a pattern might be generated if the acquisition of cell fate occurred continuously as the plant grows, in a position-dependent, lineage-independent fashion. A general model of the meristem has been produced to accommodate the observations concerning the great majority of the sectors.