PubMed Health⌕ Search

Biomedical subjects

E M Meyerowitz

Publications and source records attributed to E M Meyerowitz.

At least 19 recordsLinked to original sources
PubMed1995

Role of SUPERMAN in maintaining Arabidopsis floral whorl boundaries.

The Arabidopsis gene SUPERMAN (SUP) is necessary for the proper spatial development of reproductive floral tissues. Recessive mutations cause extra stamens to form interior to the normal third whorl stamens, at the expense of fourth whorl carpel development. The mutant phenotype is associated with the ectopic expression of the B function genes, AP3 and PI, in the altered floral region, closer to the centre of the flower than in the wild type, and ap3 sup and pi sup double mutants exhibit a phenotype similar to ap3 and pi single mutants. These findings led to SUP being interpreted as an upstream negative regulator of the B function organ-identity genes, acting in the fourth whorl, to establish a boundary between stamen and carpel whorls. Here we show, using molecular cloning and analysis, that it is expressed in the third whorl and acts to maintain this boundary in developing flowers. The putative SUPERMAN protein contains one zinc-finger and a region resembling a basic leucine zipper motif, suggesting a function in transcriptional regulation.

Amino Acid Sequence↗
PubMed1995

Ethylene insensitivity conferred by Arabidopsis ERS gene.

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.

Amino Acid Sequence↗
PubMed1995

UFO: an Arabidopsis gene involved in both floral meristem and floral organ development.

We describe the role of the UNUSUAL FLORAL ORGANS (UFO) gene in Arabidopsis floral development based on a genetic and molecular characterization of the phenotypes of nine ufo alleles. UFO is required for the proper identity of the floral meristem and acts in three different aspects of the process that distinguishes flowers from shoots. UFO is involved in establishing the whorled pattern of floral organs, controlling the determinacy of the floral meristem, and activating the APETALA3 and PISTILLATA genes required for petal and stamen identity. In many respects, UFO acts in a manner similar to LEAFY, but the ufo mutant phenotype also suggests an additional role for UFO in defining boundaries within the floral primordia or controlling cell proliferation during floral organ growth. Finally, genetic interactions that prevent flower formation and lead to the generation of filamentous structures implicate UFO as a member of a new, large, and diverse class of genes in Arabidopsis necessary for flower formation.

Arabidopsis↗
PubMed1995

Genetic separation of third and fourth whorl functions of AGAMOUS.

AGAMOUS (AG) is an Arabidopsis MADS box gene required for normal development of the third and fourth whorls of the flower. In previously described ag mutants, the third whorl stamens are replaced by petals, and the fourth whorl is replaced by another (mutant) flower. We describe two new ag alleles, ag-4 and AG-Met205, retaining partial AG activity. Both produce flowers with stamens in the third whorl and indeterminate floral meristems; however, ag-4 flowers contain sepals in the fourth whorl, and AG-Met205 produces carpels. The ag-4 mutation results in partial loss of the C terminus of the K domain, a putative coiled coil, and AG-Met205 contains a site-directed mutation that causes a single amino acid change in this same region of the K box. Two models that might explain how these changes in AG result in the separation of different AG activities are discussed.

AGAMOUS Protein, Arabidopsis↗
PubMed1995

LEUNIG regulates AGAMOUS expression in Arabidopsis flowers.

LEUNIG was identified in a genetic screen designed to isolate second-site enhancer mutations of the floral homeotic mutant apetala2-1. leunig mutations not only enhance apetala2, but by themselves cause a similar but less-pronounced homeotic transformation than apetala2 mutations. leunig flowers have sepals that are transformed toward stamens and carpels, and petals that are either staminoid or absent. In situ hybridization experiments with leunig mutants revealed altered expression pattern of the floral homeotic genes APETALA1, APETALA3, PISTILLATA, and AGAMOUS. Double mutants of leunig and agamous exhibited a phenotype similar to agamous single mutants, indicating that agamous is epistatic to leunig. Our analysis suggests that a key role of LEUNIG is to negatively regulate AGAMOUS expression in the first two whorls of the Arabidopsis flower.

Arabidopsis↗
PubMed1992

Manipulation of flower structure in transgenic tobacco.

Genetic studies suggest that three homeotic functions, designated A, B, and C, act alone and together to specify the fate of floral organ primordia in distantly related dicotyledonous plant species. To test the genetic model, we have generated transgenic tobacco plants that ectopically express the AGAMOUS gene from Brassica napus, which is necessary for the C function. Flowers on the resulting plants showed homeotic transformations of sepals into carpels and petals into stamens. These phenotypes are consistent with predictions from the genetic model, show that expression of AGAMOUS is sufficient to provide ectopic C function, and demonstrate that the structure of flowers can be manipulated in a predictable manner by altering the expression of a single regulatory gene. Furthermore, the generation of the predicted transformations by ectopic expression of the Brassica gene in transgenic tobacco indicates that gene functions are interchangeable between phylogenetically distant species.

Amino Acid Sequence↗
PubMed1992

Vectors for plant transformation and cosmid libraries.

A series of vectors has been constructed for the purpose of introducing cloned DNAs into plant genomes, using Agrobacterium tumefaciens-mediated transformation methods. One of these vectors, pCIT20, is a plasmid that contains a multiple cloning site (MCS), and a marker (Hph) that confers hygromycin resistance to plant cells. The others are all cosmid vectors which allow insertion of up to 46 kb of plant genomic DNA, and which also contain all of the necessary sequences for A. tumefaciens-mediated plant transformation. The cosmid vectors either contain a Hph marker (pCIT30), or a kanamycin-resistance marker (pCIT101-104). Three of the cosmid vectors (pCIT30, pCIT101, and pCIT103) carry bacteriophage T7 and SP6 promoters flanking the cloning Bg/II site, for synthesis of end-specific RNAs. The end-specific RNAs may be used as probes when labeled with radioactive or biotinylated nucleotides, for example, in a chromosome-walking experiment. The other two cosmid vectors (pCIT102 and pCIT104) carry restriction sites flanking the insertion site (XhoI) for convenient release of the insert by restriction digests. These sites, in combination with sites internal to the insert, allow the generation of end fragments for subcloning or labeling probes. These vectors should be valuable for isolation and analysis of plant genes, using transformation, library screening, and chromosome-walking approaches.

Agrobacterium tumefaciens↗
PubMed1992

LEAFY controls floral meristem identity in Arabidopsis.

The first step in flower development is the generation of a floral meristem by the inflorescence meristem. We have analyzed how this process is affected by mutant alleles of the Arabidopsis gene LEAFY. We show that LEAFY interacts with another floral control gene, APETALA1, to promote the transition from inflorescence to floral meristem. We have cloned the LEAFY gene, and, consistent with the mutant phenotype, we find that LEAFY RNA is expressed strongly in young flower primordia. LEAFY expression procedes expression of the homeotic genes AGAMOUS and APETALA3, which specify organ identify within the flower. Furthermore, we demonstrate that LEAFY is the Arabidopsis homolog of the FLORICAULA gene, which controls floral meristem identity in the distantly related species Antirrhinum majus.

Amino Acid Sequence↗
PubMed1992

The homeotic gene APETALA3 of Arabidopsis thaliana encodes a MADS box and is expressed in petals and stamens.

Mutations in the APETALA3 (AP3) gene of A. thaliana result in homeotic transformations of petals to sepals and stamens to carpels. We have cloned the AP3 gene from Arabidopsis based on its homology to the homeotic flower gene deficiens (DEFA) from the distantly related plant Antirrhinum majus. The sequence of four ap3 mutant alleles and genetic mapping analysis prove that the DEFA homolog is AP3. Like several other plant homeotic genes, the AP3 gene contains a MADS box and likely acts as a transcription factor. The region-specific spatial expression pattern of AP3 rules out certain types of sequential models of flower development and argues in favor of a spatial model based on positional information. Since DEFA and AP3 have very similar protein products, mutant phenotypes, and spatial expression patterns, it is likely that these genes are cognate homologs.

Alleles↗
PubMed1992

The TMK1 gene from Arabidopsis codes for a protein with structural and biochemical characteristics of a receptor protein kinase.

Genomic and cDNA clones that code for a protein with structural and biochemical properties similar to the receptor protein kinases from animals were obtained from Arabidopsis. Structural features of the predicted polypeptide include an amino-terminal membrane targeting signal sequence, a region containing blocks of leucine-rich repeat elements, a single putative membrane spanning domain, and a characteristic serine/threonine-specific protein kinase domain. The gene coding for this receptor-like transmembrane kinase was designated TMK1. Portions of the TMK1 gene were expressed in Escherichia coli, and antibodies were raised against the recombinant polypeptides. These antibodies immunodecorated a 120-kD polypeptide present in crude extracts and membrane preparations. The immunodetectable band was present in extracts from leaf, stem, root, and floral tissues. The kinase domain of TMK1 was expressed as a fusion protein in E. coli, and the purified fusion protein was found capable of autophosphorylation on serine and threonine residues. The possible role of the TMK1 gene product in transmembrane signaling is discussed.

Amino Acid Sequence↗
PubMed1992

SUPERMAN, a regulator of floral homeotic genes in Arabidopsis.

We describe a locus, SUPERMAN, mutations in which result in extra stamens developing at the expense of the central carpels in the Arabidopsis thaliana flower. The development of superman flowers, from initial primordium to mature flower, is described by scanning electron microscopy. The development of doubly and triply mutant strains, constructed with superman alleles and previously identified homeotic mutations that cause alterations in floral organ identity, is also described. Essentially additive phenotypes are observed in superman agamous and superman apetala2 double mutants. The epistatic relationships observed between either apetala3 or pistillata and superman alleles suggest that the SUPERMAN gene product could be a regulator of these floral homeotic genes. To test this, the expression patterns of AGAMOUS and APETALA3 were examined in superman flowers. In wild-type flowers, APETALA3 expression is restricted to the second and third whorls where it is required for the specification of petals and stamens. In contrast, in superman flowers, APETALA3 expression expands to include most of the cells that would normally constitute the fourth whorl. This ectopic APETALA3 expression is proposed to be one of the causes of the development of the extra stamens in superman flowers. The spatial pattern of AGAMOUS expression remains unaltered in superman flowers as compared to wild-type flowers. Taken together these data indicate that one of the functions of the wild-type SUPERMAN gene product is to negatively regulate APETALA3 in the fourth whorl of the flower. In addition, superman mutants exhibit a loss of determinacy of the floral meristem, an effect that appears to be mediated by the APETALA3 and PISTILLATA gene products.

Gene Expression Regulation↗
PubMed1991

The war of the whorls: genetic interactions controlling flower development.

The analysis of mutations affecting flower structure has led to the identification of some of the genes that direct flower development. Cloning of these genes has allowed the formulation of molecular models of how floral meristem and organ identity may be specified, and has shown that the distantly related flowering plants Arabidopsis thaliana and Antirrhinum majus use homologous mechanisms in floral pattern formation.

Cloning, Molecular↗
PubMed1991

Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.

We characterized the distribution of AGAMOUS (AG) RNA during early flower development in Arabidopsis. Mutations in this homeotic gene cause the transformation of stamens to petals in floral whorl 3 and of carpels to another ag flower in floral whorl 4. We found that AG RNA is present in the stamen and carpel primordia but is undetectable in sepal and petal primordia throughout early wild-type flower development, consistent with the mutant phenotype. We also analyzed the distribution of AG RNA in apetela2 (ap2) mutant flowers. AP2 is a floral homeotic gene that is necessary for the normal development of sepals and petals in floral whorls 1 and 2. In ap2 mutant flowers, AG RNA is present in the organ primordia of all floral whorls. These observations show that the expression patterns of the Arabidopsis floral homeotic genes are in part established by regulatory interactions between these genes.

DNA-Binding Proteins↗
PubMed1991

Dynamin-like protein encoded by the Drosophila shibire gene associated with vesicular traffic.

Temperature-sensitive paralysis is the most striking defect of adult Drosophila carrying the shibire mutation. This is believed to be due to a reversible block of endocytosis, which prevents membrane cycling and thus depletes synaptic vesicles. The shibire mutation also affects many tissues outside the nervous system. We have now mapped and characterized the shibire gene. A 275-kilobase yeast artificial chromosome was subcloned into cosmids, among which the gene was then located by analysing with restriction-fragment length polymorphisms. A 15-kilobase fragment of wild-type DNA rescues the mutant phenotype and the sequence of two mutant alleles show differences with wild type, demonstrating that we have isolated the shibire gene. The gene encodes a protein that is highly similar to rat dynamin, 69% of the amino-acid sequence is identical. Dynamin is a GTP-driven mechanochemical enzyme related to mammalian mx-proteins and to the yeast vps 1 gene product. Because the shibire gene product and dynamin have extensive similarity, we propose that they are cognate homologues. Dynamin causes microtubules to slide along each other in vitro and in extracts it is associated with a distinct, but so far uncharacterized, membrane fraction. In light of the shibire phenotype, we suggest that these proteins provide the motor for vesicular transport during endocytosis.

Amino Acid Sequence↗
PubMed1991

Large scale screen for transposon insertions into cloned genes.

We describe a method of screening for transposon insertions in or near Drosophila loci that correspond to cloned DNA sequences. We mobilize a modified P element transposon that carries a bacterial plasmid origin of replication and a drug-resistance marker. The genomic sequences flanking each transposon insertion site can then be rescued as a plasmid in Escherichia coli. Libraries of such plasmids, representing pools of transposon-mutagenized individuals, are used as hybridization probes against cloned sequences to determine whether a transposon has inserted next to a particular site in the genome. The number of loci that can be screened simultaneously by this procedure is quite large. We have screened an array of cDNA clones representing almost 700 distinct loci against libraries representing 760 mutagenized flies, and we obtained hybridization signals to 7 different cDNAs. Three of these events have been analyzed in detail and represent genuine insertions near genomic sequences that correspond to the cDNAs.

Animals↗
PubMed1991

Transposon-facilitated DNA sequencing.

We describe here a transposon-based DNA sequencing strategy that allows the introduction of sequencing priming sites throughout a target sequence by bacterial mating. A miniplasmid was designed to select against transposon insertions into the vector. Sites of transposon insertion are mapped by the polymerase chain reaction with bacterial overnight cultures providing the templates. A small set of plasmids with transposons spaced several hundred base pairs apart can then be sequenced. Sequencing primers corresponding to the transposon ends allow sequencing in both directions. Thus, the entire sequence of both strands can be easily determined.

Base Sequence↗