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J Chory

Publications and source records attributed to J Chory.

At least 37 records · Page 2Linked to original sources
PubMed2000

Natural variation in phytochrome signaling.

The phytochromes, photoreceptors sensitive to red and far-red light, are critical for sensing foliage shade, canopy breaks, and neighbor proximity. A combination of molecular genetic, evolutionary, and ecological techniques are being used to understand how phytochromes function in the natural environment. We discuss studies on the adaptive value of phytochrome mediated plasticity, as well as the role that variation in phytochrome expression and function might play in allowing plants to adapt to unique light environments. Continued study of phytochrome signaling variation may reveal how natural selection acts at the molecular level.

Adaptation, Physiological↗
PubMed2000

Brassinosteroid signal transduction: still casting the actors.

Significant advances in the genetic dissection of brassinosteroid biosynthesis and signaling have been made during the past few years. Genetic and biochemical data have helped to elucidate the pathways of biosynthesis of brassinolide, the most active brassinosteroid. In addition, several models have been put forward for the perception of brassinolide by its putative receptor, BRI1, a ubiquitously expressed plasma membrane localized protein kinase. These studies provide the basic framework for future analysis of brassinosteroid signaling.

Brassinosteroids↗
PubMed2000

Phytobilin biosynthesis: the Synechocystis sp. PCC 6803 heme oxygenase-encoding ho1 gene complements a phytochrome-deficient Arabidopsis thalianna hy1 mutant.

The phytobilin chromophores of phycobiliproteins and phytochromes are biosynthesized from heme in a pathway that begins with the opening of the tetrapyrrole macrocycle of protoheme to form biliverdin IXalpha, in a reaction catalyzed by heme oxygenase. An Arabidopsis thaliana hy1 mutant was previously shown to be deficient in phytochrome responses, and these responses were regained when the plants were administered biliverdin IXalpha. A heme oxygenase-encoding gene, ho1, was recently cloned from the cyanobacterium Synechocystis sp. PCC 6803. When ho1 was expressed in Escherichia coli, the cells produced active ferredoxin-dependent soluble heme oxygenase. The open reading frame of ho1 was fused in frame with a chloroplast transit peptide-encoding sequence from the oli gene of Antirrhinum majus. This construct was placed in a binary plasmid vectorcontaining a kanamycin resistance marker and a cauliflower mosaic virus 35S promoter to control expression of the chimeric oli-ho1 gene and used to transform A. thaliana hy1 plants. Two independent transformed lines were obtained that had the phenotype of the parental Landsberg erecta line and expressed the chimeric gene, as indicated by detection of its mRNA by reverse transcriptase-polymerase chain reaction. The results indicate that Synechocystis sp. PCC 6803 heme oxygenase encoded by ho1 can substitute for the defective HY1 gene product and that the only required enzyme activity of the HY1 gene product is heme oxygenase.

Amino Acid Sequence↗
PubMed2000

Interactions between hy1 and gun mutants of Arabidopsis, and their implications for plastid/nuclear signalling.

Lhcb and other nuclear genes for chloroplastic proteins are regulated by several signals. Among them, light and retrograde signals from the plastid itself appear to act through closely related mechanisms. To investigate this interaction, we analysed an Arabidopsis mutant, hy1, deficient in plastidic heme oxygenase. hy1 is defective in phytochrome chromophore biosynthesis, which has other indirect effects on tetrapyrrole metabolism. We generated double mutants between hy1-6.2, genetically a null mutation, and three known gun (genome uncoupled) mutants, defective in retrograde plastid signalling. Recent molecular evidence shows GUN5 to be involved in tetrapyrrole metabolism (N. Mochizuki and J. Chory, manuscript in preparation). We observed hy1gun4 to be semi-albino plants, and hy1gun5 albino lethal, in a high-light-sensitive manner. Both double mutants showed defective greening and chloroplast development, and expressed Lhcb at reduced levels specifically in high light. Their degree of 'genome uncoupling' (Lhcb expression in the absence of functional chloroplasts) was similar to that observed in single mutants. These results can be interpreted as a metabolic (rather than genetic) interaction between HY1 and GUN4 or GUN5, and this in turn supports the involvement of tetrapyrroles as plastid signals. The tetrapyrrole precursor 5-aminolevulinic acid (ALA) inhibited Lhcb expression in hy1. Surprisingly, ALA also rescued photomorphogenesis of hy1. We speculate that either one tetrapyrrole intermediate, which can accumulate anomalously in hy1, or an altered ratio between two intermediates, plays a role as a repressor of Lhcb expression. gun1 did not exacerbate the plastid or Lhcb expression phenotype of hy1. This can be interpreted as a role for gun1 strictly on the same pathway as hy1 or, more likely, as evidence for the existence of at least one separate, non-tetrapyrrole related plastid signal.

Aminolevulinic Acid↗
PubMed2000

Activation tagging in Arabidopsis.

Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.

Arabidopsis↗
PubMed2000

Brassinosteroid-insensitive-1 is a ubiquitously expressed leucine-rich repeat receptor serine/threonine kinase.

Brassinosteroid (BR) mutants of Arabidopsis have pleiotropic phenotypes and provide evidence that BRs function throughout the life of the plant from seedling development to senescence. Screens for BR signaling mutants identified one locus, BRI1, which encodes a protein with homology to leucine-rich repeat receptor serine (Ser)/threonine (Thr) kinases. Twenty-seven alleles of this putative BR receptor have been isolated to date, and we present here the identification of the molecular lesions of 14 recessive alleles that represent five new mutations. BR-insensitive-1 (BRI1) is expressed at high levels in the meristem, root, shoot, and hypocotyl of seedlings and at lower levels later in development. Confocal microscopy analysis of full-length BRI1 fused to green fluorescent protein indicates that BRI1 is localized in the plasma membrane, and an in vitro kinase assay indicates that BRI1 is a functional Ser/Thr kinase. Among the bri1 mutants identified are mutants in the kinase domain, and we demonstrate that one of these mutations severely impairs BRI1 kinase activity. Therefore, we conclude that BRI1 is a ubiquitously expressed leucine-rich repeat receptor that plays a role in BR signaling through Ser/Thr phosphorylation.

Arabidopsis↗
PubMed2000

RSF1, an Arabidopsis locus implicated in phytochrome A signaling.

In Arabidopsis, phytochrome A (phyA) is the major photoreceptor both for high irradiance responses to far-red light and broad spectrum very low fluence responses, but little is known of its signaling pathway(s). rsf1 was isolated as a recessive mutant with reduced sensitivity to far-red inhibition of hypocotyl elongation. At the seedling stage rsf1 mutants are affected, to various degrees, in all described phyA-mediated responses. However, in adult rsf1 plants, the photoperiodic flowering response is normal. The rsf1 mutant has wild-type levels of phyA suggesting that RSF1 is required for phyA signaling rather than phyA stability or biosynthesis. RSF1 thus appears to be a major phyA signaling component in seedlings, but not in adult, Arabidopsis plants.

Arabidopsis↗
PubMed2000

Cloning of the Arabidopsis RSF1 gene by using a mapping strategy based on high-density DNA arrays and denaturing high-performance liquid chromatography.

Mapping genes by chromosome walking is a widely used technique applicable to cloning virtually any gene that is identifiable by mutagenesis. We isolated the gene responsible for the recessive mutation rsf1 (for reduced sensitivity to far-red light) in the Arabidopsis Columbia accession by using classical genetic analysis and two recently developed technologies: genotyping high-density oligonucleotide DNA array and denaturing high-performance liquid chromatography (DHPLC). The Arabidopsis AT412 genotyping array and 32 F(2) plants were used to map the rsf1 mutation close to the top of chromosome 1 to an interval of approximately 500 kb. Using DHPLC, we found and genotyped additional markers for fine mapping, shortening the interval to approximately 50 kb. The mutant gene was directly identified by DHPLC by comparing amplicons generated separately from the rsf1 mutant and the parent strain Columbia. DHPLC analysis yielded polymorphic profiles in two overlapping polymorphic amplicons attributable to a 13-bp deletion in the third of five exons of a gene encoding a 292-amino acid protein with a basic helix-loop-helix (bHLH) domain. The mutation in rsf1 results in a truncated protein consisting of the first 129 amino acids but lacking the bHLH domain. Cloning the RSF1 gene strongly suggests that numerous phytochrome A-mediated responses require a bHLH class transcription factor.

Alleles↗
PubMed1999

BAS1: A gene regulating brassinosteroid levels and light responsiveness in Arabidopsis.

The Arabidopsis bas1-D mutation suppresses the long hypocotyl phenotype caused by mutations in the photoreceptor phytochrome B (phyB). The adult phenotype of bas1-D phyB-4 double mutants mimics that of brassinosteroid biosynthetic and response mutants. bas1-D phyB-4 has reduced levels of brassinosteroids and accumulates 26-hydroxybrassinolide in feeding experiments. The basis for the mutant phenotype is the enhanced expression of a cytochrome P450 (CYP72B1). bas1-D suppresses a phyB-null allele, but not a phyA-null mutation, and partially suppresses a cryptochrome-null mutation. Seedlings with reduced BAS1 expression are hyperresponsive to brassinosteroids in a light-dependent manner and display reduced sensitivity to light under a variety of conditions. Thus, BAS1 represents one of the control points between multiple photoreceptor systems and brassinosteroid signal transduction.

Arabidopsis↗
PubMed1999

The Arabidopsis det3 mutant reveals a central role for the vacuolar H(+)-ATPase in plant growth and development.

In all multicellular organisms growth and morphogenesis must be coordinated, but for higher plants, this is of particular importance because the timing of organogenesis is not fixed but occurs in response to environmental constraints. One particularly dramatic developmental juncture is the response of dicotyledonous seedlings to light. The det3 mutant of Arabidopsis develops morphologically as a light-grown plant even when it is grown in the dark. In addition, it shows organ-specific defects in cell elongation and has a reduced response to brassinosteroids (BRs). We have isolated the DET3 gene by positional cloning and provide functional and biochemical evidence that it encodes subunit C of the vacuolar H(+)-ATPase (V-ATPase). We show that the hypocotyl elongation defect in the det3 mutant is conditional and provide evidence that this is due to an alternative mechanism of V-ATPase assembly. Together with the expression pattern of the DET3 gene revealed by GFP fluorescence, our data provide in vivo evidence for a role for the V-ATPase in the control of cell elongation and in the regulation of meristem activity.

Amino Acid Sequence↗
PubMed1999

Activation tagging of the floral inducer FT.

FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. Like LFY, FT acts partially downstream of CONSTANS (CO), which promotes flowering in response to long days. Unlike many other floral regulators, the deduced sequence of the FT protein does not suggest that it directly controls transcription or transcript processing. Instead, it is similar to the sequence of TERMINAL FLOWER 1 (TFL1), an inhibitor of flowering that also shares sequence similarity with membrane-associated mammalian proteins.

Alleles↗
PubMed1999

PKS1, a substrate phosphorylated by phytochrome that modulates light signaling in Arabidopsis.

Plants constantly monitor their light environment in order to grow and develop optimally, in part through use of the phytochromes, which sense red/far-red light. A phytochrome binding protein, PKS1 (phytochrome kinase substrate 1), was identified that is a substrate for light-regulated phytochrome kinase activity in vitro. In vivo experiments suggest that PKS1 is phosphorylated in a phytochrome-dependent manner and negatively regulates phytochrome signaling. The data suggest that phytochromes signal by serine-threonine phosphorylation.

Amino Acid Sequence↗
PubMed1999

Light receptor kinases in plants!

Plants must adapt to a capricious light environment, but the mechanism by which light signals are transmitted to cause changes in development has long eluded us. The search might be over, however, as two photoreceptors, phytochrome and NPH1, have been shown to autophosphorylate in a light-dependent fashion.

Arabidopsis Proteins↗
PubMed1999

Arabidopsis det2 is defective in the conversion of (24R)-24-methylcholest-4-En-3-one to (24R)-24-methyl-5alpha-cholestan-3-one in brassinosteroid biosynthesis.

Previously, we have shown that the Arabidopsis det2 (deetiolated2) mutant is defective in the biosynthesis of brassinosteroids (BR) and that DET2 (a steroid 5alpha-reductase) acts early in the proposed BR biosynthetic pathway. In this paper we present further biochemical characterization of det2. We have undertaken metabolic experiments with 2H-labeled substrates of intermediates involved in the formation of campestanol from campesterol, and quantitative analysis of intermediates in Arabidopsis wild type and det2. The results of these studies indicate the early operating steps of BR biosynthesis as: campesterol --> 4-en-3beta-ol --> 4-en-3-one --> 3-one --> campestanol in Arabidopsis, with det2 deficient in the conversion of 4-en-3-one to 3-one. We have also detected these intermediates in the formation of campestanol from campesterol and their metabolic conversions using cultured cells of Catharanthus roseus. These studies confirmed the biosynthetic sequence of events from campesterol to campestanol as was found in Arabidopsis. As such, the originally proposed biosynthetic pathway should be modified.

Arabidopsis↗
PubMed1999

The phosphoenolpyruvate/phosphate translocator is required for phenolic metabolism, palisade cell development, and plastid-dependent nuclear gene expression.

The Arabidopsis chlorophyll a/b binding protein (CAB) gene underexpressed 1 (cue1) mutant underexpresses light-regulated nuclear genes encoding chloroplast-localized proteins. cue1 also exhibits mesophyll-specific chloroplast and cellular defects, resulting in reticulate leaves. Both the gene underexpression and the leaf cell morphology phenotypes are dependent on light intensity. In this study, we determine that CUE1 encodes the plastid inner envelope phosphoenolpyruvate/phosphate translocator (PPT) and define amino acid residues that are critical for translocator function. The biosynthesis of aromatics is compromised in cue1, and the reticulate phenotype can be rescued by feeding aromatic amino acids. Determining that CUE1 encodes PPT indicates the in vivo role of the translocator in metabolic partitioning and reveals a mesophyll cell-specific requirement for the translocator in Arabidopsis leaves. The nuclear gene expression defects in cue1 suggest that a light intensity-dependent interorganellar signal is modulated through metabolites dependent on a plastid supply of phosphoenolpyruvate.

Arabidopsis↗
PubMed1998

An Arabidopsis mutant defective in the plastid general protein import apparatus.

Elaborate mechanisms have evolved for the translocation of nucleus-encoded proteins across the plastid envelope membrane. Although putative components of the import apparatus have been identified biochemically, their role in import remains to be proven in vivo. An Arabidopsis mutant lacking a new component of the import machinery [translocon at the outer envelope membrane of chloroplasts (Toc33), a 33-kilodalton protein] has been isolated. The functional similarity of Toc33 to another translocon component (Toc34) implies that multiple different translocon complexes are present in plastids. Processes that are mediated by Toc33 operate during the early stages of plastid and leaf development. The data demonstrate the in vivo role of a translocon component in plastid protein import.

Amino Acid Sequence↗
PubMed1998

dCAPS, a simple technique for the genetic analysis of single nucleotide polymorphisms: experimental applications in Arabidopsis thaliana genetics.

PCR-based detection of single nucleotide polymorphisms is a powerful tool for the plant geneticist. Cleaved amplified polymorphic sequence analysis is the most widely used approach for the detection of single nucleotide polymorphisms. However, this technique is limited to mutations which create or disrupt a restriction enzyme recognition site. This paper presents a modification of this technique where mismatches in a PCR primer are used to create a polymorphism based on the target mutation. This technique is useful for following known mutations in segregating populations and genetic mapping of isolated DNAs used for positional based cloning of new genes. In addition, a computer program has been developed that facilitates the design of these PCR primers.

Arabidopsis↗