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Showing papers on "Arabidopsis published in 1995"


Journal ArticleDOI
30 Jun 1995-Science
TL;DR: A Pseudomonas aeruginosa strain (UCBPP-PA14) is infectious both in an Arabidopsis thaliana leaf infiltration model and in a mouse full-thickness skin burn model, indicating that these genes encode virulence factors required for the full expression of pathogenicity in both plants and animals.
Abstract: A Pseudomonas aeruginosa strain (UCBPP-PA14) is infectious both in an Arabidopsis thaliana leaf infiltration model and in a mouse full-thickness skin burn model. UCBPP-PA14 exhibits ecotype specificity for Arabidopsis, causing a range of symptoms from none to severe in four different ecotypes. In the mouse model, UCBPP-PA14 is as lethal as other well-studied P. aeruginosa strains. Mutations in the UCBPP-PA14 toxA, plcS, and gacA genes resulted in a significant reduction in pathogenicity in both hosts, indicating that these genes encode virulence factors required for the full expression of pathogenicity in both plants and animals.

1,297 citations


Journal ArticleDOI
24 Mar 1995-Cell
TL;DR: Double mutants were constructed containing co and mutations affecting gibberellic acid responses, meristem identity, or phytochrome function, and their phenotypes suggested a model for the role of CO in promoting flowering.

1,284 citations


Journal ArticleDOI
11 Aug 1995-Science
TL;DR: The Arabidopsis thaliana RPM1 gene enables dual specificity to pathogens expressing either of two unrelated Pseudomonas syringae avr genes, and encodes a protein sharing molecular features with recently described single-specificity R genes.
Abstract: Plants can recognize pathogens through the action of disease resistance (R) genes, which confer resistance to pathogens expressing unique corresponding avirulence (avr) genes. The molecular basis of this gene-for-gene specificity is unknown. The Arabidopsis thaliana RPM1 gene enables dual specificity to pathogens expressing either of two unrelated Pseudomonas syringae avr genes. Despite this function, RPM1 encodes a protein sharing molecular features with recently described single-specificity R genes. Surprisingly, RPM1 is lacking from naturally occurring, disease-susceptible Arabidopsis accessions.

934 citations


Journal ArticleDOI
12 Oct 1995-Nature
TL;DR: Transgenic plants in which the flower-meristem-identity gene LEAFY of Arabidopsis is constitutively expressed are generated, suggesting a new level of regulation during flower development, as indicated by the competence of the main shoot to respond to LEAFy activity.
Abstract: We have generated transgenic plants in which the flower-meristem-identity gene LEAFY of Arabidopsis is constitutively expressed. LEAFY is sufficient to determine floral fate in lateral shoot meristems of both Arabidopsis and the heterologous species aspen, with the consequence that flower development is induced precociously. Our results also suggest a new level of regulation during flower development, as indicated by the competence of the main shoot to respond to LEAFY activity.

791 citations


Journal ArticleDOI
TL;DR: The development of an efficient insertional mutagenesis system in Arabidopsis that permits identification of genes by their patterns of expression during development and suggests that the identification and cloning ofArabidopsis genes expressed in any developmental process is feasible using this system.
Abstract: The crucifer Arabidopsis thaliana has been used widely as a model organism for the study of plant development. We describe here the development of an efficient insertional mutagenesis system in Arabidopsis that permits identification of genes by their patterns of expression during development. Transposable elements of the Ac/Ds system carrying the GUS reporter gene have been designed to act as enhancer traps or gene traps. A novel selection scheme maximizes recovery of unlinked transposition events. In this study 491 plants carrying independent transposon insertions were generated and screened for expression patterns. One-half of the enhancer trap insertions and one-quarter of the gene trap insertions displayed GUS expression in seedlings or flowers, including expression patterns specific to organs, tissues, cell types, or developmental stages. The patterns identify genes that act during organogenesis, pattern formation, or cell differentiation. Transposon insertion lines with specific GUS expression patterns provide valuable markers for studies of Arabidopsis development and identify new cell types or subtypes in plants. The diversity of gene expression patterns generated suggests that the identification and cloning of Arabidopsis genes expressed in any developmental process is feasible using this system.

780 citations


Journal ArticleDOI
05 May 1995-Science
TL;DR: Genetic manipulation of genes in the ethylene signal transduction pathway will provide agriculture with new tools to prevent or modify ethylene responses in a variety of plants.
Abstract: Ethylene (C2H4), the chemically simplest plant hormone, is among the best-characterized plant growth regulators. It participates in a variety of stress responses and developmental processes. Genetic studies in Arabidopsis have defined a number of genes in the ethylene signal transduction pathway. Isolation of two of these genes has revealed that plants sense this gas through a combination of proteins that resemble both prokaryotic and eukaryotic signaling proteins. Ethylene signaling components are likely conserved for responses as diverse as cell elongation, cell fate patterning in the root epidermis, and fruit ripening. Genetic manipulation of these genes will provide agriculture with new tools to prevent or modify ethylene responses in a variety of plants.

718 citations


Journal ArticleDOI
TL;DR: Results demonstrate that, in A. thaliana, hydroxycinnamates are more effective UV-B protectants than flavonoids, and indicate that A.Thaliana responds toUV-B as an oxidative stress, and sunscreen compounds reduce the oxidative damage caused by UV- B.
Abstract: We have assessed ultraviolet-B (UV-B)-induced injury in wild-type Arabidopsis thaliana and two mutants with altered aromatic secondary product biosynthesis. Arabidopsis mutants defective in the ability to synthesize UV-B-absorbing compounds (flavonoids in transparent testa 5 [tt5] and sinapate esters in ferulic acid hydroxylase 1 [fah1]) are more sensitive to UV-B than is the wild-type Landsberg erecta. Despite its ability to accumulate UV-absorptive flavonoid compounds, the ferulic acid hydroxylase mutant fah1 exhibits more physiological injury (growth inhibition and foliar lesions) than either wild type or tt5. The extreme UV-B sensitivity of fah1 demonstrates the importance of hydroxycinnamate esters as UV-B protectants. Consistent with the whole-plant response, the highest levels of lipid and protein oxidation products were seen in fah1. Ascorbate peroxidase enzyme activity was also increased in the leaves of UV-B-treated plants in a dose- and genotype-dependent manner. These results demonstrate that, in A. thaliana, hydroxycinnamates are more effective UV-B protectants than flavonoids. The data also indicate that A. thaliana responds to UV-B as an oxidative stress, and sunscreen compounds reduce the oxidative damage caused by UV-B.

617 citations


Journal ArticleDOI
22 Sep 1995-Science
TL;DR: Double-mutant analysis indicates that ERS acts upstream of the CTR1 protein kinase gene in the ethylene-response pathway.
Abstract: ERS (ethylene response sensor), a gene in the Arabidopsis thaliana ethylene hormone-response pathway, was uncovered by cross-hybridization with the Arabidopsis ETR1 gene. The deduced ERS protein has sequence similarity with the amino-terminal domain and putative histidine protein kinase domain of ETR1, but it does not have a receiver domain as found in ETR1. A missense mutation identical to the dominant etr1-4 mutation was introduced into the ERS gene. The altered ERS gene conferred dominant ethylene insensitivity to wild-type Arabidopsis. Double-mutant analysis indicates that ERS acts upstream of the CTR1 protein kinase gene in the ethylene-response pathway.

609 citations


Journal ArticleDOI
TL;DR: Seven allelic recessive Arabidopsis mutants, designated superroot, are isolated, displaying several abnormalities reminiscent of auxin effects, including small and epinastic cotyledons, an elongated hypocotyl, the development of excess adventitious and lateral roots, a reduced number of leaves, and the absence of an inflorescence.
Abstract: We have isolated seven allelic recessive Arabidopsis mutants, designated superroot (sur1-1 to sur1-7), displaying several abnormalities reminiscent of auxin effects. These characteristics include small and epinastic cotyledons, an elongated hypocotyl in which the connection between the stele and cortical and epidermal cells disintegrates, the development of excess adventitious and lateral roots, a reduced number of leaves, and the absence of an inflorescence. When germinated in the dark, sur1 mutants did not develop the apical hook characteristic of etiolated seedlings. We were able to phenocopy the Sur1- phenotype by supplying auxin to wild-type seedlings, to propagate sur1 explants on phytohormone-deficient medium, and to regenerate shoots from these explants by the addition of cytokinins alone to the culture medium. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of both free and conjugated indole-3-acetic acid. sur1 was crossed to the mutant axr2 and the altered-auxin response mutant ctr1. The phenotype of both double mutants was additive. The sur1 gene was mapped on chromosome 2 at 0.5 centimorgans from the gene encoding phytochrome B.

604 citations


Journal ArticleDOI
15 Dec 1995-Science
TL;DR: It was concluded that ETR1 acts as an ethylene receptor in Arabidopsis and that the amino-terminal hydrophobic domain of the protein is the site of ethylene binding.
Abstract: Mutations in the ETR1 gene of Arabidopsis thaliana confer insensitivity to ethylene, which indicates a role for the gene product in ethylene signal transduction. Saturable binding sites for [14C]ethylene were detected in transgenic yeast expressing the ETR1 protein, whereas control yeast lacking ETR1 showed no detectable ethylene binding. Yeast expressing a mutant form of ETR1 (etr1-1) also showed no detectable ethylene binding, which provides an explanation for the ethylene-insensitive phenotype observed in plants carrying this mutation. Expression of truncated forms of ETR1 in yeast provided evidence that the amino-terminal hydrophobic domain of the protein is the site of ethylene binding. It was concluded from these results that ETR1 acts as an ethylene receptor in Arabidopsis.

593 citations


Journal ArticleDOI
24 Feb 1995-Science
TL;DR: The cycling bioluminescence of Arabidopsis plants carrying a firefly luciferase fusion construct was used to identify mutant individuals with aberrant cycling patterns, and a semidominant short-period mutation, toc1, was mapped to chromosome 5.
Abstract: The cycling bioluminescence of Arabidopsis plants carrying a firefly luciferase fusion construct was used to identify mutant individuals with aberrant cycling patterns. Both long- and short-period mutants were recovered. A semidominant short-period mutation, timing of CAB expression (toc1), was mapped to chromosome 5. The toc1 mutation shortens the period of two distinct circadian rhythms, the expression of chlorophyll a/b-binding protein (CAB) genes and the movements of primary leaves, although toc1 mutants do not show extensive pleiotropy for other phenotypes.

Journal ArticleDOI
TL;DR: Tissue- and locus-specific differences in the flavonols and anthocyanidins synthesized by mutant and wild-type plants are identified and evidence was uncovered that tt8 and ttg specifically affect dihydroflavonol reductase gene expression.
Abstract: Eleven loci that play a role in the synthesis of flavonoids in Arabidopsis are described. Mutations at these loci, collectively named transparent testa (tt), disrupt the synthesis of brown pigments in the seed coat (testa). Several of these loci (tt3, tt4, tt5 and ttg) are also required for the accumulation of purple anthocyanins in leaves and stems and one locus (ttg) plays additional roles in trichome and root hair development. Specific functions were previously assigned to tt1-7 and ttg. Here, the results of additional genetic, biochemical and molecular analyses of these mutants are described. Genetic map positions were determined for tt8, tt9 and tt10. Thin-layer chromatography identified tissue- and locus-specific differences in the flavonols and anthocyanidins synthesized by mutant and wild-type plants. It was found that UV light reveals distinct differences in the floral tissues of tt3, tt4, tt5, tt6 and ttg, even though these tissues are indistinguishable under visible light. Evidence was also uncovered that tt8 and ttg specifically affect dihydroflavonol reductase gene expression. A summary of these and previously published results are incorporated into an overview of the genetics of flavonoid biosynthesis in Arabidopsis.

Journal ArticleDOI
02 Nov 1995-Nature
TL;DR: It is demonstrated that positional signals can be perpetuated from more mature to initial cells to guide the pattern of meristem cell differentiation, offering an alternative to the general opinion that meristems are the source of patterning information.
Abstract: Postembryonic development in plants is achieved by apical meristems. Surgical studies and clonal analysis have revealed indirectly that cells in shoot meristems have no predictable destiny and that position is likely to play a role in the acquisition of cell identity. In contrast to animal systems, there has been no direct evidence for inductive signalling in plants until now. Here we present evidence for such signalling using laser ablation of cells in the root meristem of Arabidopsis thaliana. Although these cells show rigid clonal relationships, we now demonstrate that it is positional control that is most important in the determination of cell fate. Positional signals can be perpetuated from more mature to initial cells to guide the pattern of meristem cell differentiation. This offers an alternative to the general opinion that meristems are the source of patterning information.

Journal ArticleDOI
TL;DR: The characterization of LOX2 indicates that the protein is targeted to chloroplasts, and suggests that wound-induced JA (or some other LOx2-requiring component of the wound response pathway) is involved in the wound- induced regulation of this gene.
Abstract: Plant lipoxygenases are thought to be involved in the biosynthesis of lipid-derived signaling molecules. The potential involvement of a specific Arabidopsis thaliana lipoxygenase isozyme, LOX2, in the biosynthesis of the plant growth regulators jasmonic acid (JA) and abscisic acid was investigated. Our characterization of LOX2 indicates that the protein is targeted to chloroplasts. The physiological role of this chloroplast lipoxygenase was analyzed in transgenic plants where cosuppression reduced LOX2 accumulation. The reduction in LOX2 levels caused no obvious changes in plant growth or in the accumulation of abscisic acid. However, the wound-induced accumulation of JA observed in control plants was absent in leaves of transgenic plants that lacked LOX2. Thus, LOX2 is required for the wound-induced synthesis of the plant growth regulator JA in leaves. We also examined the expression of a wound- and JA-inducible Arabidopsis gene, vsp, in transgenic and control plants. Leaves of transgenic plants lacking LOX2 accumulated less vsp mRNA than did control leaves in response to wounding. This result suggests that wound-induced JA (or some other LOX2-requiring component of the wound response pathway) is involved in the wound-induced regulation of this gene.

Journal ArticleDOI
12 Oct 1995-Nature
TL;DR: It is shown that trans-genic plants which constitutively express the AP1 gene show transformations of apical and lateral shoots into flowers, and that these plants flower much earlier than wild-type plants.
Abstract: In Arabidopsis, the apical shoot meristem produces lateral meristems that develop into either shoots or flowers. The decision to form flowers instead of shoots is mediated by the action of floral-meristem-identity genes, such as APETALA1 (AP1) and LEAFY (LFY), which specify meristem fate. Here we show that transgenic plants which constitutively express the AP1 gene show transformations of apical and lateral shoots into flowers, and that these plants flower much earlier than wild-type plants. These results indicate that AP1 alone can convert infloresence shoot meristems into floral meristems, and that ectopic AP1 expression can dramatically reduce the time to flowering.

Journal ArticleDOI
TL;DR: The L6 rust resistance gene from flax was cloned after tagging with the maize transposable element Activator and the truncated product of L6, which lacks most of the leucine-rich C-terminal region, is similar to the truncation product that is predicted from an alternative transcript of the N gene.
Abstract: The L6 rust resistance gene from flax was cloned after tagging with the maize transposable element Activator. The gene is predicted to encode two products of 1294 and 705 amino acids that result from alternatively spliced transcripts. The longer product is similar to the products of two other plant disease resistance genes, the tobacco mosaic virus resistance gene N of tobacco and the bacterial resistance gene RPS2 of Arabidopsis. The similarity involves the presence of a nucleotide (ATP/GTP) binding site and several other amino acid motifs of unknown function in the N-terminal half of the polypeptides and a leucine-rich region in the C-terminal half. The truncated product of L6, which lacks most of the leucine-rich C-terminal region, is similar to the truncated product that is predicted from an alternative transcript of the N gene. The L6, N, and RPS2 genes, which control resistance to three widely different pathogen types, are the foundation of a class of plant disease resistance genes that can be referred to as nucleotide binding site/leucine-rich repeat resistance genes.

Journal ArticleDOI
27 Jan 1995-Science
TL;DR: It is demonstrated that two Arabidopsis genes, CAULIFLOWER and APETALA1, encode partially redundant activities involved in the formation of floral meristems, the first step in the development of flowers.
Abstract: Genetic studies demonstrate that two Arabidopsis genes, CAULIFLOWER and APETALA1, encode partially redundant activities involved in the formation of floral meristems, the first step in the development of flowers. Isolation of the CAULIFLOWER gene from Arabidopsis reveals that it is closely related in sequence to APETALA1. Like APETALA1, CAULIFLOWER is expressed in young flower primordia and encodes a MADS-domain, indicating that it may function as a transcription factor. Analysis of the cultivated garden variety of cauliflower (Brassica oleracea var. botrytis) reveals that its CAULIFLOWER gene homolog is not functional, suggesting a molecular basis for one of the oldest recognized flower abnormalities.

Journal ArticleDOI
TL;DR: It is shown that, in plants, the developmental controls defining shape can act independently from cell division rates, and Morphogenesis, histogenesis and developmental timing were unaffected.
Abstract: Because plant cells do not move and are surrounded by a rigid cell wall, cell division rates and patterns are believed to be directly responsible for generating new structures throughout development. To study the relationship between cell division and morphogenesis, transgenic tobacco and Arabidopsis plants were constructed expressing dominant mutations in a key regulator of the Arabidopsis cell cycle, the Cdc2a kinase. Plants constitutively overproducing the wild-type Cdc2a or the mutant form predicted to accelerate the cell cycle did not exhibit a significantly altered development. In contrast, a mutation expected to arrest the cell cycle abolished cell division when expressed in Arabidopsis, whereas some tobacco plants constitutively producing this mutant protein were recovered. These plants had a reduced histone H1 kinase activity and contained considerably fewer cells. These cells were, however, much larger and underwent normal differentiation. Morphogenesis, histogenesis and developmental timing were unaffected. The results indicate that, in plants, the developmental controls defining shape can act independently from cell division rates.

Journal ArticleDOI
TL;DR: In the floral shoots of the ga1–2 mutant, transcript levels corresponding to each cDNA decreased dramatically after GA3 application, suggesting that GA biosynthesis may be controlled, at least in part, through down-regulation of the expression of the 20-oxidase genes.
Abstract: Using degenerate oligonucleotide primers based on a pumpkin (Cucurbita maxima) gibberellin (GA) 20-oxidase sequence, six different fragments of dioxygenase genes were amplified by polymerase chain reaction from Arabidopsis thaliana genomic DNA. One of these was used to isolate two different full-length cDNA clones, At2301 and At2353, from shoots of the GA-deficient Arabidopsis mutant ga1–2. A third, related clone, YAP169, was identified in the Database of Expressed Sequence Tags. The cDNA clones were expressed in Escherichia coli as fusion proteins, each of which oxidized GA12 at C-20 to GA15, GA24, and the C19 compound GA9, a precursor of bioactive GAs; the C20 tricarboxylic acid compound GA25 was formed as a minor product. The expression products also oxidized the 13-hydroxylated substrate GA53, but less effectively than GA12. The three cDNAs hybridized to mRNA species with tissue-specific patterns of accumulation, with At2301 being expressed in stems and inflorescences, At2353 in inflorescences and developing siliques, and YAP169 in siliques only. In the floral shoots of the ga1–2 mutant, transcript levels corresponding to each cDNA decreased dramatically after GA3 application, suggesting that GA biosynthesis may be controlled, at least in part, through down-regulation of the expression of the 20-oxidase genes.

Journal ArticleDOI
TL;DR: The isolation of the CER1 gene, which encodes a novel protein involved in the conversion of long chain aldehydes to alkanes, a key step in was biosynthesis, is described.
Abstract: The aerial parts of plants are coated with an epicuticular wax layer, which is important as a first line of defense against external influences. In Arabidopsis, the ECERIFERUM (CER) genes effect different steps of the wax biosynthesis pathway. In this article, we describe the isolation of the CER1 gene, which encodes a novel protein involved in the conversion of long chain aldehydes to alkanes, a key step in was biosynthesis. CER1 was cloned after gene tagging with the heterologous maize transposable element system Enhancer-Inhibitor, also known as Suppressor-mutator. cer1 mutants display glossy green stems and fruits and are conditionally male sterile. The similarity of the CER1 protein with a group of integral membrane enzymes, which process highly hydrophobic molecules, points to a function of the CER1 protein as a decarbonylase.

Journal ArticleDOI
TL;DR: It appears that the NPH1 protein is most likely a 120-kD plasma membrane-associated phosphoprotein because all of the nph1 mutations negatively affected the abundance of this protein, providing strong support for the hypothesis that more than one blue light photoreceptor is required for the normal growth and development of a seedling.
Abstract: The phototropic response is an important component of seedling establishment in higher plants because it orients the young seedlings for maximal photosynthetic light capture. Despite their obvious importance, little is known about the mechanisms underlying the perception and transduction of the light signals that induce phototropic curvatures. Here, we report the isolation of eight mutants of Arabidopsis that lack or have severely impaired phototropic responses. These nph (for nonphototropic hypocotyl) mutants comprise four genetic loci: nph1, nph2, nph3, and nph4. Physiological and biochemical characterization of the nph1 allele series indicated that the NPH1 locus may encode the apoprotein for a dual-chromophoric or multichromophoric holoprotein photoreceptor capable of absorbing UV-A, blue, and green light and that this photoreceptor regulates all the phototropic responses of Arabidopsis. It appears that the NPH1 protein is most likely a 120-kD plasma membrane-associated phosphoprotein because all of the nph1 mutations negatively affected the abundance of this protein. In addition, the putative NPH1 photoreceptor protein is genetically and biochemically distinct from the HY4 protein, which most likely acts as a photoreceptor for blue light-mediated hypocotyl growth inhibition. Furthermore, the NPH1 and HY4 proteins are not functionally redundant because mutations in either gene alone affect only one physiological response but not the other, thus providing strong support for the hypothesis that more than one blue light photoreceptor is required for the normal growth and development of a seedling.

Journal ArticleDOI
TL;DR: The characterization of transgenic Arabidopsis plants that express the bacterial nahG gene encoding salicylate hydroxylase, an enzyme that can metabolize SA, supports the critical role of SA in SAR and shows that ethylene sensitivity is not required for SAR induction.
Abstract: Systemic acquired resistance (SAR) is an inducible plant response to infection by a necrotizing pathogen. In the induced plant, SAR provides broad-spectrum protection against not only the inducing pathogen, but also against other, unrelated pathogens. Both salicylic acid (SA) and SAR-gene expression have been implicated as playing important roles in the initiation and maintenance of SAR. Here, we describe the characterization of transgenic Arabidopsis plants that express the bacterial nahG gene encoding salicylate hydroxylase, an enzyme that can metabolize SA. Strong, constitutive expression of this gene prevents pathogen-induced accumulation of SA and the activation of SAR by exogenous SA. We show that SAR in Arabidopsis can be induced by inoculation with Pseudomonas syringe pv. tomato against infection by a challenge inoculation with Peronospora parasitica. This response is abolished in transgenic, nahG-expressing Arabidopsis, but not in ethylene-insensitive mutants. These experiments support the critical role of SA in SAR and show that ethylene sensitivity is not required for SAR induction. The NahG Arabidopsis plants will be important for future studies aimed at understanding the role of SA in plant disease resistance mechanisms.

Journal ArticleDOI
01 Jan 1995-Planta
TL;DR: The overall pattern of SUC2-GUS expression correlated well with that of the Arabidopsis thaliana AHA3 plasma-membrane H+ -ATPase which is also expressed in the phloem and most likely represents the primary pump generating the energy for secondary active transporters such as S UC2.
Abstract: The Arabidopsis thaliana (L.) Heynh. SUC2 gene encodes a plasma-membrane sucrose-H+ symporter. The DNA sequence of the SUC2 promoter has been determined. Using a translational fusion of this promoter to the N-terminus of beta-glucuronidase (GUS) and the GUS histochemical assay, the tissue specificity of the SUC2 promoter was studied in Arabidopsis plants transformed with this fusion construct. The SUC2 promoter directed expression of GUS activity with high specificity to the phloem of all green tissues of Arabidopsis such as rosette leaves, stems, and sepals. During leaf development the expression of SUC2-GUS activity was first seen in the tips of young rosette leaves. In older leaves and during their concomitant sink/source transition, expression proceeded from the tips to the bases of the leaves, indicating that expression of the SUC2 sucrose-H+ symporter is tightly coupled to the source-strength of Arabidopsis leaves. Expression of SUC2-GUS activity was also seen, however, in sink tissues such as roots and developing Arabidopsis pods, suggesting that the product of the SUC2 gene might not only be important for phloem loading, but also for phloem unloading. A possible regulatory effect of carbohydrates (glucose and sucrose) on the activity of the SUC2 promoter was studied and excluded, both in excised leaves and young seedlings of transgenic Arabidopsis plants. The overall pattern of SUC2-GUS expression correlated well with that of the Arabidopsis thaliana AHA3 plasma-membrane H(+)-ATPase which is also expressed in the phloem and most likely represents the primary pump generating the energy for secondary active transporters such as SUC2.

Journal ArticleDOI
TL;DR: It is demonstrated that PAL and CHS mRNAs accumulate in leaves of Arabidopsis thaliana (L.) Heynh upon exposure to low temperature in a light-dependent manner and that light may also be implicated in the regulation of the CHS gene in response to bacterial infiltration.
Abstract: Anthocyanins, which accumulate in leaves and stems in response to low temperature and changes in light intensity, are synthesized through the phenylpropanoid pathway that is controlled by key enzymes that include phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) In this work we demonstrate that PAL and CHS mRNAs accumulate in leaves of Arabidopsis thaliana (L) Heynh upon exposure to low temperature in a light-dependent manner The regulation of the PAL1 gene expression by low temperature and light was examined by analyzing the expression of the [beta]-glucuronidase (uidA) reporter gene in transgenic Arabidopsis plants containing the uidA gene of Escherichia coli under the control of the PAL1 promoter The results indicate that the accumulation of PAL1 mRNA is transcriptionally regulated Histochemical staining for [beta]-glucuronidase activity showed that the PAL1 promoter is preferentially activated in photosynthetically active cells, paralleling anthocyanin accumulation Moreover, we show that light may also be implicated in the regulation of the CHS gene in response to bacterial infiltration Finally, using two transparent testa Arabidopsis mutants that are unable to accumulate anthocyanins, we demonstrate that these pigments are not required for successful development of freezing tolerance in this species

Journal ArticleDOI
TL;DR: It is determined that TCH4 expression is regulated by auxin and brassinosteroids, by environmental stimuli, and during development, by a 1-kb region, and Expression was restricted to expanding tissues and organs that undergo cell wall modification.
Abstract: Adaptation of plants to environmental conditions requires that sensing of external stimuli be linked to mechanisms of morphogenesis. The Arabidopsis TCH (for touch) genes are rapidly upregulated in expression in response to environmental stimuli, but a connection between this molecular response and developmental alterations has not been established. We identified TCH4 as a xyloglucan endotransglycosylase by sequence similarity and enzyme activity. Xyloglucan endotransglycosylases most likely modify cell walls, a fundamental determinant of plant form. We determined that TCH4 expression is regulated by auxin and brassinosteroids, by environmental stimuli, and during development, by a 1-kb region. Expression was restricted to expanding tissues and organs that undergo cell wall modification. Regulation of genes encoding cell wall-modifying enzymes, such as TCH4, may underlie plant morphogenetic responses to the environment.

Journal ArticleDOI
TL;DR: The data suggest that auxin induces in a differential and hierarchical fashion a large family of early genes that encode a structurally diverse class of nuclear proteins that are proposed to mediate tissue-specific and cell-type restricted responses to the hormone during plant growth and development.

Journal ArticleDOI
TL;DR: RNA analysis showed that the Athb-8 gene is expressed during the vegetative and the reproductive phases of plant growth, and auxin, indole-3-acetic acid, which is involved in vascular development and differentiation, modulates the expression of the gene.
Abstract: We have characterized an Arabidopsis homeobox gene coding for a putative DNA binding protein that represents an early marker for vascular development. The full-length cDNA encodes a protein of 833 amino acids that we have designated Athb-8; it contains the conserved DNA binding domain that characterizes the HD-Zip family of transcription factors. RNA analysis showed that the Athb-8 gene is expressed during the vegetative and the reproductive phases of plant growth. A higher steady-state level of the Athb-8 mRNA was found in flowering stem and root. In situ mRNA analysis of Arabidopsis plants demonstrated that Athb-8 expression is restricted to the procambial cells of embryo and developing organs. Moreover, Athb-8-GUS expression was found in single parenchyma cells which are differentiating into tracheary elements in wounded tobacco transgenic plants. Finally, we showed that the auxin, indole-3-acetic acid, which is involved in vascular development and differentiation, modulates the expression of the gene. Taken together, these results suggest that Athb-8 might be a regulator of vascular development in Arabidopsis thaliana.

Journal ArticleDOI
TL;DR: Northern blot analysis showed that the AtPLC1 gene is expressed at very low levels in the plant under normal conditions but is induced to a significant extent under various environmental stresses, such as dehydration, salinity, and low temperature, and that an increase in the level of AtP LC1 might amplify the signal, in a manner that contributes to the adaptation of the plant to these stresses.
Abstract: A cDNA corresponding to a putative phosphatidylinositol-specific phospholipase C (PI-PLC) in the higher plant Arabidopsis thaliana was cloned by use of the polymerase chain reaction. The cDNA, designated cAtPLC1, encodes a putative polypeptide of 561 aa with a calculated molecular mass of 64 kDa. The putative product includes so-called X and Y domains found in all PI-PLCs identified to date. In mammalian cells, there are three types of PI-PLC, PLC-beta, -gamma, and -delta. The overall structure of the putative AtPLC1 protein is most similar to that of PLC-delta, although the AtPLC1 protein is much smaller than PLCs from other organisms. The recombinant AtPLC1 protein synthesized in Escherichia coli was able to hydrolyze phosphatidylinositol 4,5-bisphosphate and this activity was completely dependent on Ca2+, as observed also for mammalian PI-PLCs. These results suggest that the AtPLC1 gene encodes a genuine PI-PLC of a higher plant. Northern blot analysis showed that the AtPLC1 gene is expressed at very low levels in the plant under normal conditions but is induced to a significant extent under various environmental stresses, such as dehydration, salinity, and low temperature. These observations suggest that AtPLC1 might be involved in the signal-transduction pathways of environmental stresses and that an increase in the level of AtPLC1 might amplify the signal, in a manner that contributes to the adaptation of the plant to these stresses.

Journal ArticleDOI
TL;DR: A yeast mutant deficient in oligopeptide transport was constructed allowing to show that NTR1 functions as a high affinity, low specificity peptide transporter.

Journal ArticleDOI
TL;DR: A model is proposed in which either ethylene or ACC is a signal involved in specifying the pattern of cell differentiation in the Arabidopsis root epidermis.
Abstract: Summary Evidence is provided that ethylene is a positive regulator of hair cell development in the root epidermis of Arabidopsis thaliana. Treatment of seedlings with increasing concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) results in progressively more root hair cells developing in positions normally occupied by non-hair cells. Consistent with these findings are observations that treatments that block either ethylene synthesis or its perception reduce the number of root hairs. A model is proposed in which either ethylene or ACC is a signal involved in specifying the pattern of cell differentiation in the Arabidopsis root epidermis.