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Abstract
An active maize Adhl-F gene, a Ds-induced mutant of this gene, and two independent Ac-induced revertant alleles have been isolated. The Ds mutant differs from the progenitor allele in having a 405-base pair insertion flanked by a direct repeat of 8 bp. The repeat is a duplication of the 8 bp existing at the point of insertion in the 5' untranslated region of the gene. The insertion sequence is AT-rich (A, adenine; T, thymine) and has 11-bp inverted repeat sequences at its termini. In the revertants the insertion with its inverted repeats is deleted, but the 8-bp direct repeats remain in modified form. These results establish that the 405-bp sequence is a Ds element. The Adh1 messenger RNA level is low in the Ds mutant, and it appears that new sites for transcription initiation or RNA processing or both are used. There are at least 30 sequences in the maize genome related to the Ds element.
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2
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Abstract
Replication patterns of four classes of heterochromatin in the chromosomes of maize were analyzed. Centromeric heterochromatin, distal heterochromatin of the B chromosomes, and knob heterochromatin all have asynchronous late replication, knob heterochromatin being the last chromosomal DNA to complete replication. Nucleolus organizer heterochromatin replicates during the period of euchromatin DNA replication. The proportion of the S period involved in asynchronous late replication is directly dependent on the amount of heterochromatin in the nucleus. Both additional knob and B-chromosome heterochromatin participate in this effect. Each additional B chromosome produces an increment in the proportion of nuclei with asynchronous replication; in nuclei with 12 B chromosomes, the proportion of the S phase showing asynchronous late replication is more than 3 times greater than that in nuclei without B chromosomes. The data are consistent with the hypothesis that delayed DNA replication of knob heterochromatin is responsible, in some genotypes, for the loss of chromosome segments and for B-chromosome nondisjunction in the second pollen grain mitosis.
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Affiliation(s)
- A Pryor
- Commonwealth Scientific and Industrial Research Organisation, Division of Plant Industry, P.O. Box 1600, Canberra City, Australian Capital Territory, Australia 2601
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3
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Walker JC, Howard EA, Dennis ES, Peacock WJ. DNA sequences required for anaerobic expression of the maize alcohol dehydrogenase 1 gene. Proc Natl Acad Sci U S A 2010; 84:6624-8. [PMID: 16578816 PMCID: PMC299135 DOI: 10.1073/pnas.84.19.6624] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Expression of the maize alcohol dehydrogenase 1 (Adh1) gene is transcriptionally regulated under conditions of anaerobic stress. DNA sequences required for the expression of Adh1 have been identified by a functional analysis of in vitro constructed hybrid genes consisting of the Adh1 promoter fused to the chloramphenicol acetyltransferase coding region. A series of 5' deletions, 3' deletions, hybrid promoters, and linker scanning mutants of the Adh-CAT hybrid gene were introduced into maize protoplasts by electroporation and assayed for chloramphenicol acetyltransferase activity after incubation of the protoplasts under different oxygen tensions. The results indicate that a 40-base-pair DNA sequence within the Adh1 promoter is required for anaerobically regulated expression of the hybrid gene. Clustered point mutations in this sequence show that it is composed of two essential regions, each approximately 15 base pairs, separated by a 10-base-pair DNA sequence that does not appear to be important for anaerobic expression. Attachment of this 40-base-pair element to an unrelated promoter shows that this DNA sequence is both necessary and sufficient for induction of gene expression by low oxygen stress.
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Affiliation(s)
- J C Walker
- Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, GPO Box 1600, Canberra, ACT 2601, Australia
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4
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Peacock WJ, Dennis ES, Rhoades MM, Pryor AJ. Highly repeated DNA sequence limited to knob heterochromatin in maize. Proc Natl Acad Sci U S A 2010; 78:4490-4. [PMID: 16593063 PMCID: PMC319817 DOI: 10.1073/pnas.78.7.4490] [Citation(s) in RCA: 229] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A highly repeated DNA sequence has been isolated from the maize genome as a satellite in actinomycin D/CsCl gradients. By using maize stocks differing in their heterochromatin content we have established that the sequence is a major constituent of one class of heterochromatin, knob heterochromatin, which can occur at 23 locations in the chromosome complement. The repeating unit, of 185 base pairs, has been cloned in plasmid pBR322 and its nucleotide sequence has been determined. The presence of this DNA sequence in knob heterochromatin and its absence from centromeric, nucleolar, and B chromosome heterochromatin parallels the cytogenetic differentiation previously described for these classes of heterochromatin in maize. Because knob heterochromatin has a distinctive cytological appearance and is unique in showing neocentric activity at meiosis, its association with a particular repeated DNA sequence may reflect a functional role for the sequence in the cell cycle.
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Affiliation(s)
- W J Peacock
- Division of Plant Industry, Commonwealth Scientific and Industrial Research Organisation, P.O. Box 1600, Canberra City, ACT, Australia
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5
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Gerlach WL, Pryor AJ, Dennis ES, Ferl RJ, Sachs MM, Peacock WJ. cDNA cloning and induction of the alcohol dehydrogenase gene (Adh1) of maize. Proc Natl Acad Sci U S A 2010; 79:2981-5. [PMID: 16593188 PMCID: PMC346332 DOI: 10.1073/pnas.79.9.2981] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
cDNA clones of Adh1, one of two genes encoding alcohol dehydrogenase (ADH; alcohol:NAD(+) oxidoreductase, EC 1.1.1.1) in the maize genome, have been isolated. They were derived from mRNA extracted from anaerobically treated roots of maize seedlings. Identification was initially made on the basis of molecular weight and electrophoretic properties of the in vitro polypeptide obtained in hybridization-release-translation experiments. The identification was confirmed by antibody precipitation and by the use of maize stocks having different genetic constitutions at the Adh1 locus. The sequence of the longest cDNA segment, approximately 900 base pairs, was determined and appears to code for 168 COOH-terminal amino acids and to have a 3' nontranslated region of 364 base pairs. Reverse Southern hybridizations established that two different Adh1-S stocks produce a mRNA of 1,650 nucleotides, whereas an additional mRNA of 1,750 nucleotides is produced in three Adh1-F stocks. A 50-fold increase in Adh1 mRNA level occurs during anaerobiosis, reaching a maximum at 5 hr. Return to aerobic conditions indicates a half-life of more than 18 hr for the anaerobically induced Adh1 mRNA.
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Affiliation(s)
- W L Gerlach
- Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, P.O. Box 1600, Canberra City, A.C.T. 2601, Australia
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6
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Luo M, Platten D, Chaudhury A, Peacock WJ, Dennis ES. Expression, imprinting, and evolution of rice homologs of the polycomb group genes. Mol Plant 2009; 2:711-723. [PMID: 19825651 DOI: 10.1093/mp/ssp036] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Polycomb group proteins (PcG) play important roles in epigenetic regulation of gene expression. Some core PcG proteins, such as Enhancer of Zeste (E(z)), Suppressor of Zeste (12) (Su(z)12), and Extra Sex Combs (ESC), are conserved in plants. The rice genome contains two E(z)-like genes, OsiEZ1 and OsCLF, two homologs of Su(z)12, OsEMF2a and OsEMF2b, and two ESC-like genes, OsFIE1 and OsFIE2. OsFIE1 is expressed only in endosperm; the maternal copy is expressed while the paternal copy is not active. Other rice PcG genes are expressed in a wide range of tissues and are not imprinted in the endosperm. The two E(z)-like genes appear to have duplicated before the separation of the dicots and monocots; the two homologs of Su(z)12 possibly duplicated during the evolution of the Gramineae and the two ESC-like genes are likely to have duplicated in the ancestor of the grasses. No homologs of the Arabidopsis seed-expressed PcG genes MEA and FIS2 were identified in the rice genome. We have isolated T-DNA insertion lines in the rice homologs of three PcG genes. There is no autonomous endosperm development in these T-DNA insertion lines. One line with a T-DNA insertion in OsEMF2b displays pleiotropic phenotypes including altered flowering time and abnormal flower organs, suggesting important roles in rice development for this gene.
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Affiliation(s)
- Ming Luo
- CSIRO Plant Industry, GPO BOX 1600, ACT 2601, Australia.
| | - Damien Platten
- CSIRO Plant Industry, GPO BOX 1600, ACT 2601, Australia; Vitagrain, Uttara Model Town, Dhaka, Bangladesh
| | - Abed Chaudhury
- CSIRO Plant Industry, GPO BOX 1600, ACT 2601, Australia; IRRI, Los Banos, Laguna 4031, Philippines
| | - W J Peacock
- CSIRO Plant Industry, GPO BOX 1600, ACT 2601, Australia
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7
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Peacock WJ. Recombinant DNA Research: Its Methods, Achievements and Prospects. AUST J FORENSIC SCI 2009. [DOI: 10.1080/00450617709413231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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8
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Abstract
The acceleration of flowering by prolonged low temperature treatment (vernalization) has unique properties including the floral transition occurring at a time separate from the vernalization treatment. This implies the vernalization condition is inherited through mitotic divisions, but this vernalized state is not inherited from one generation to the next. FLC, the key gene mediating this response in the Arabidopsis is repressed by histone modifications involving the VRN2 protein complex. Other protein complexes participate in activating the gene. While many plant species depend on vernalization for optimising flowering time, the genes involved differ between dicot and monocot plants in both Arabidopsis and cereals, vernalization regulates photoperiod control of flowering by preventing the induction of the floral promoter FT by long days in autumn but allowing induction of FT in spring and hence flowering occurs at an optimal time in the annual life cycle.
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Affiliation(s)
- E S Dennis
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
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9
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Hunt PW, Klok EJ, Trevaskis B, Watts RA, Ellis MH, Peacock WJ, Dennis ES. Increased level of hemoglobin 1 enhances survival of hypoxic stress and promotes early growth in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2002; 99:17197-202. [PMID: 12486248 PMCID: PMC139292 DOI: 10.1073/pnas.212648799] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Overexpression of a class 1 Hb (GLB1) protects Arabidopsis thaliana plants from the effects of severe hypoxia. Overexpression of the bifunctional symbiotic Hb (GLB1S) from Parasponia andersonii in A. thaliana also increases survival after hypoxia. Plants overexpressing the Hb 1 protein, mutated to have a low oxygen affinity, are as susceptible to hypoxia as WT plants, suggesting that the protection against hypoxia depends on the ability of the Hb to bind ligands, such as oxygen, with high affinity. A mild hypoxia pretreatment (5%) induces the Hb gene and increases the survival of plants after severe hypoxic treatment (0.1%). These results with Hb 1 show that plant Hbs have a role other than in nitrogen-fixing root nodules. Plants overexpressing the GLB1 protein show early vigorous growth in nonhypoxic conditions and are 50% larger in weight than the controls at 14 days. The constitutive expression of GLB1 also resulted in a reduced number of root hairs and increased number of laterals in the root system.
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Affiliation(s)
- P W Hunt
- Commonwealth Scientific and Industrial Research Organization Plant Industry, G.P.O. Box 1600, Canberra ACT 2601, Australia
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10
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Abstract
Seed development requires coordinated expression of embryo and endosperm and has contributions from both sporophytic and male and female gametophytic genes. Genetic and molecular analyses in recent years have started to illuminate how products of these multiple genes interact to initiate seed development. Imprinting or differential expression of paternal and maternal genes seems to be involved in controlling seed development, presumably by controlling gene expression in developing endosperm. Epigenetic processes such as chromatin remodeling and DNA methylation affect imprinting of key seed-specific genes; however, the identity of many of these genes remains unknown. The discovery of FIS genes has illuminated control of autonomous endosperm development, a component of apomixis, which is an important developmental and agronomic trait. FIS genes are targets of imprinting, and the genes they control in developing endosperm are also regulated by DNA methylation and chromatin remodeling genes. These results define some exciting future areas of research in seed development.
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Affiliation(s)
- A M Chaudhury
- CSIRO Plant Industry, GPO BOX 1600, ACT 2601, Australia.
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11
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Abstract
FLOWERING LOCUS C (FLC) in Arabidopsis encodes a dosage dependent repressor of flowering. We isolated five FLC-related sequences from Brassica napus (BnFLC1-5). Expression of each of the five sequences in Arabidopsis delayed flowering significantly, with the delay in flowering time ranging from 3 weeks to more than 7 months, relative to the flowering time of 3 weeks in untransformed Ler. In the reciprocal experiment, expression of Arabidopsis FLC (AtFLC) in an early flowering B. napus cultivar delayed flowering by 2-6 weeks, confirming the requirement of this gene for floral repression. In B. napus, we show that late flowering and responsiveness to vernalization correlate with the level of BnFLC mRNA expression. The different BnFLC genes show differential expression in leaves, stems and shoot tips, but expression is not detectable in roots. Vernalization dramatically reduces the level of BnFLC transcript and restores early flowering in the winter cultivar Colombus. We conclude that BnFLC genes confer winter requirement in B. napus and account for the major vernalization-responsive flowering time differences in the different cultivars of B. napus in a manner analogous to that of AtFLC in Arabidopsis ecotypes.
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Affiliation(s)
- M Tadege
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, GPO BOX 1600, Canberra, ACT, 2601, Australia
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12
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Hunt PW, Watts RA, Trevaskis B, Llewelyn DJ, Burnell J, Dennis ES, Peacock WJ. Expression and evolution of functionally distinct haemoglobin genes in plants. Plant Mol Biol 2001; 47:677-92. [PMID: 11725952 DOI: 10.1023/a:1012440926982] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Haemoglobin genes have been found in a number of plant species, but the number of genes known has been too small to allow effective evolutionary inferences. We present nine new non-symbiotic haemoglobin sequences from a range of plants, including class 1 haemoglobins from cotton, Citrus and tomato, class 2 haemoglobins from cotton, tomato, sugar beet and canola and two haemoglobins from the non-vascular plants, Marchantia polymorpha (a liverwort) and Physcomitrella patens (a moss). Our molecular phylogenetic analysis of all currently known non-symbiotic haemoglobin genes and a selection of symbiotic haemoglobins have confirmed the existence of two distinct classes of haemoglobin genes in the dicots. It is likely that all dicots have both class 1 and class 2 non-symbiotic haemoglobin genes whereas in monocots we have detected only class 1 genes. The symbiotic haemoglobins from legumes and Casuarina are related to the class 2 non-symbiotic haemoglobins, whilst the symbiotic haemoglobin from Parasponia groups with the class 1 non-symbiotic genes. Probably, there have been two independent recruitments of symbiotic haemoglobins. Although the functions of the two non-symbiotic haemoglobins remain unknown, their patterns of expression within plants suggest different functions. We examined the expression in transgenic plants of the two non-symbiotic haemoglobins from Arabidopsis using promoter fusions to a GUS reporter gene. The Arabidopsis GLB1 and GLB2 genes are likely to be functionally distinct. The class 2 haemoglobin gene (GLB2) is expressed in the roots, leaves and inflorescence and can be induced in young plants by cytokinin treatment in contrast to the class 1 gene (GLB1) which is active in germinating seedlings and can be induced by hypoxia and increased sucrose supply, but not by cytokinin treatment.
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MESH Headings
- Adenine/analogs & derivatives
- Adenine/pharmacology
- Arabidopsis/genetics
- Arabidopsis/growth & development
- Brassica napus/genetics
- Cytokinins/pharmacology
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Plant/chemistry
- DNA, Plant/genetics
- Databases, Nucleic Acid
- Evolution, Molecular
- Gene Expression Regulation, Plant/drug effects
- Genes, Plant/genetics
- Glucuronidase/genetics
- Glucuronidase/metabolism
- Gossypium/genetics
- Hemoglobins/genetics
- Hemoglobins/physiology
- Isopentenyladenosine
- Molecular Sequence Data
- Phylogeny
- Plants/genetics
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/growth & development
- Promoter Regions, Genetic/genetics
- Protein Isoforms/genetics
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Sequence Analysis, DNA
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Affiliation(s)
- P W Hunt
- CSIRO Division of Plant Industry, Black Mountain, Canberra, ACT, Australia
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13
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Helliwell CA, Sullivan JA, Mould RM, Gray JC, Peacock WJ, Dennis ES. A plastid envelope location of Arabidopsis ent-kaurene oxidase links the plastid and endoplasmic reticulum steps of the gibberellin biosynthesis pathway. Plant J 2001; 28:201-8. [PMID: 11722763 DOI: 10.1046/j.1365-313x.2001.01150.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We have used fusions of gibberellin biosynthesis enzymes to green fluorescent protein (GFP) to determine the subcellular localization of the early steps of the pathway. Gibberellin biosynthesis from geranylgeranyl diphosphate is catalysed by enzymes of the terpene cyclase, cytochrome P450 mono-oxygenase and 2-oxoglutarate-dependent dioxygenase classes. We show that the N-terminal pre-sequences of the Arabidopsis thaliana terpene cyclases copalyl diphosphate synthase (AtCPS1) and ent-kaurene synthase (AtKS1) direct GFP to chloroplasts in transient assays following microprojectile bombardment of tobacco leaves. The AtKS1-GFP fusion is also imported by isolated pea chloroplasts. The N-terminal portion of the cytochrome P450 protein ent-kaurene oxidase (AtKO1) directs GFP to chloroplasts in tobacco leaf transient assays. Chloroplast import assays with 35S-labelled AtKO1 protein show that it is targeted to the outer face of the chloroplast envelope. The leader sequences of the two ent-kaurenoic acid oxidases (AtKAO1 and AtKAO2) from Arabidopsis direct GFP to the endoplasmic reticulum. These data suggest that the AtKO1 protein links the plastid- and endoplasmic reticulum-located steps of the gibberellin biosynthesis pathway by association with the outer envelope of the plastid.
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Affiliation(s)
- C A Helliwell
- CSIRO Plant Industry, GPO Box 1600, ACT 2601, Australia.
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14
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Abstract
Hemispherectomy is a valuable procedure in the management of seizure disorders caused by unilateral hemispheric disease. Modifications to anatomical hemispherectomy have been proposed to reduce the incidence of superficial cerebral hemosiderosis and hydrocephalus while still achieving seizure control. We report on the modification of a previously described disconnective form of hemispherectomy. We used this procedure on 2 children, with the aid of stereotactic navigation in 1 of the 2 cases. This disconnection was achieved via a transventricular route with minimal cortical resection or disruption of the blood supply. Over the 20 months of follow-up, 1 patient achieved complete seizure control, and 1 patient achieved control of previously incapacitating seizures with few minor seizures persisting. Motor function and speech significantly improved in both patients. Blood loss during the two procedures was significantly less than that reported for anatomical hemispherectomy, and so far there have been no signs of postoperative complications. The hospital stay was limited to 7-14 days after surgery.
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Affiliation(s)
- M Danielpour
- Department of Pediatric Neurosurgery, Cedars-Sinai Medical Center, Los Angeles, Calif, USA
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15
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Watts RA, Hunt PW, Hvitved AN, Hargrove MS, Peacock WJ, Dennis ES. A hemoglobin from plants homologous to truncated hemoglobins of microorganisms. Proc Natl Acad Sci U S A 2001; 98:10119-24. [PMID: 11526234 PMCID: PMC56925 DOI: 10.1073/pnas.191349198] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have identified a nuclear-encoded Hb from plants (GLB3) that has a central domain similar to the "truncated" Hbs of bacteria, protozoa, and algae. The three-dimensional structure of these Hbs is a 2-on-2 arrangement of alpha-helices, distinct from the 3-on-3 arrangement of the standard globin fold [Pesce, A., Couture, M., Dewilde, S., Guertin, M., Yamauchi, K., Ascenzi, P., Moens, L. & Bolognesi, M. (2000) EMBO J. 19, 2424-2434]. GLB3-like genes are not found in animals or yeast, but our analysis reveals that they are present in a wide range of Angiosperms and a Bryophyte. Although cyanobacteria and Chlamydomonas have 2-on-2 Hbs (GLBN), GLB3 is more likely related to GLBO-type 2-on-2 Hbs from bacteria. Consequently, GLB3 is unlikely to have arisen from a horizontal transfer between the chloroplast and nuclear genomes. Arabidopsis thaliana GLB3 protein exhibits unusual concentration-independent binding of O(2) and CO. The absorbance spectrum of deoxy-GLB3 is unique; the protein forms a transient six-coordinate structure after reduction and deoxygenation, which slowly converts to a five-coordinate structure. In A. thaliana, GLB3 is expressed throughout the plant but responds to none of the treatments that induce plant 3-on-3 Hbs. Our analysis of the sequence, ligand interactions, and expression profile of GLB3 indicates that this protein has unique biochemical properties, evolutionary history, and, most likely, a function distinct from those of other plant Hbs.
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Affiliation(s)
- R A Watts
- CSIRO Plant Industry, Canberra, ACT 2601, Australia
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16
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Abstract
Spasticity occurs in children and adults due to a wide range of conditions, including cerebral palsy, head and spinal cord trauma, cerebrovascular accidents and multiple sclerosis. Multiple treatment options have been described, including medical and surgical treatments. Medical treatments include intramuscular botulinum A toxin, oral baclofen and supportive bracing. Surgical approaches include selective posterior rhizotomy, intrathecal baclofen and orthopedic procedures to address deformities. Many reports have been published on these different treatment options, but rarely has a comparison been made between them. Therefore, this review is aimed at comparing selective posterior rhizotomy and intrathecal baclofen injection for spasticity due to cerebral palsy, especially in children.
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Affiliation(s)
- C S von Koch
- Department of Neurological Surgery, University of California San Francisco, 505 Parnassus Avenue, San Francisco, CA 94143-0112, USA.
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17
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Abstract
Pediatric epilepsy surgery patients are different than adult epilepsy surgery patients by having a higher proportion of extratemporal than temporal lobe lesions, and by having cortical dysplasia as the most frequent pathology. We analyzed 111 pediatric epilepsy patients who received lobar or multilobar resections at the University of California, Los Angeles, between the years 1986 and 2000 to determine if there were differences in seizure outcome by lobe of resection and tissue pathology. Results showed that temporal lobe resection patients had lower pre- and postoperative seizure frequencies compared with extratemporal single lobe resection patients (p < 0.05). Furthermore, single lobe resection patients from any brain region had lower pre- and postoperative seizure frequencies compared with multilobar resection patients (p < 0.05), an effect which was due to the better seizure outcomes in temporal lobe resection cases. Patients with mass lesions had the best postoperative seizure control, followed by cortical dysplasia patients and other pathologies (p < 0.05). In all patient groups, there was a significant reduction in pre- to postoperative seizure frequencies (p < 0.0001). These results indicate that postsurgery seizure outcomes in pediatric epilepsy surgery patients vary by lesion location and pathology, with the best outcomes in temporal lobe patients with mass lesions. However, surgical resections of epileptogenic lesions, regardless of lobe, were associated with significant postoperative improvements in seizure frequency.
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Affiliation(s)
- J W Leiphart
- Division of Neurosurgery, Mental Retardation Research Center and Brain Research Institute, University of California, Los Angeles, CA, USA
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18
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Chaudhury A, Koltunow A, Dennis ES, Peacock WJ. Apomixis. eLS 2001. [DOI: 10.1038/npg.els.0002035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
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19
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Danielpour M, Peacock WJ. Epilepsy surgery in children. Clin Neurosurg 2001; 47:400-21. [PMID: 11197714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- M Danielpour
- Department of Neurological Surgery, University of California, San Francisco, California, USA
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20
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Helliwell CA, Chandler PM, Poole A, Dennis ES, Peacock WJ. The CYP88A cytochrome P450, ent-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway. Proc Natl Acad Sci U S A 2001; 98:2065-70. [PMID: 11172076 PMCID: PMC29382 DOI: 10.1073/pnas.98.4.2065] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have shown that ent-kaurenoic acid oxidase, a member of the CYP88A subfamily of cytochrome P450 enzymes, catalyzes the three steps of the gibberellin biosynthetic pathway from ent-kaurenoic acid to GA(12). A gibberellin-responsive barley mutant, grd5, accumulates ent-kaurenoic acid in developing grains. Three independent grd5 mutants contain mutations in a gene encoding a member of the CYP88A subfamily of cytochrome P450 enzymes, defined by the maize Dwarf3 protein. Mutation of the Dwarf3 gene gives rise to a gibberellin-responsive dwarf phenotype, but the lesion in the gibberellin biosynthesis pathway has not been identified. Arabidopsis thaliana has two CYP88A genes, both of which are expressed. Yeast strains expressing cDNAs encoding each of the two Arabidopsis and the barley CYP88A enzymes catalyze the three steps of the GA biosynthesis pathway from ent-kaurenoic acid to GA(12). Sequence comparison suggests that the maize Dwarf3 locus also encodes ent-kaurenoic acid oxidase.
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Affiliation(s)
- C A Helliwell
- CSIRO Plant Industry, GPO Box 1600, Canberra 2601, Australia.
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21
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Adcock GJ, Dennis ES, Easteal S, Huttley GA, Jermiin LS, Peacock WJ, Thorne A. Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins. Proc Natl Acad Sci U S A 2001; 98:537-42. [PMID: 11209053 PMCID: PMC14622 DOI: 10.1073/pnas.98.2.537] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2000] [Indexed: 11/18/2022] Open
Abstract
DNA from ancient human remains provides perspectives on the origin of our species and the relationship between molecular and morphological variation. We report analysis of mtDNA from the remains of 10 ancient Australians. These include the morphologically gracile Lake Mungo 3 [ approximately 60 thousand years (ka) before present] and three other gracile individuals from Holocene deposits at Willandra Lakes (<10 ka), all within the skeletal range of living Australians, and six Pleistocene/early Holocene individuals (15 to <8 ka) from Kow Swamp with robust morphologies outside the skeletal range of contemporary indigenous Australians. Lake Mungo 3 is the oldest (Pleistocene) "anatomically modern" human from whom DNA has been recovered. His mtDNA belonged to a lineage that only survives as a segment inserted into chromosome 11 of the nuclear genome, which is now widespread among human populations. This lineage probably diverged before the most recent common ancestor of contemporary human mitochondrial genomes. This timing of divergence implies that the deepest known mtDNA lineage from an anatomically modern human occurred in Australia; analysis restricted to living humans places the deepest branches in East Africa. The other ancient Australian individuals we examined have mtDNA sequences descended from the most recent common ancestor of living humans. Our results indicate that anatomically modern humans were present in Australia before the complete fixation of the mtDNA lineage now found in all living people. Sequences from additional ancient humans may further challenge current concepts of modern human origins.
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MESH Headings
- Africa, Eastern
- Animals
- Australia
- Base Sequence
- Biological Evolution
- Chromosomes, Human, Pair 11/genetics
- DNA, Mitochondrial/genetics
- Evolution, Molecular
- Extrachromosomal Inheritance/genetics
- Female
- Fossils
- Gene Frequency
- Genetics, Population
- Hominidae/classification
- Hominidae/genetics
- Humans
- Likelihood Functions
- Male
- Models, Biological
- Molecular Sequence Data
- Mutagenesis, Insertional
- Native Hawaiian or Other Pacific Islander/genetics
- Pan paniscus/genetics
- Pan troglodytes/genetics
- Phylogeny
- Selection, Genetic
- Sequence Alignment
- Sequence Homology, Nucleic Acid
- Species Specificity
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Affiliation(s)
- G J Adcock
- Research School of Pacific and Asian Studies and John Curtin School of Medical Research, Australian National University, Canberra ACT 0200, Australia
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22
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Sheldon CC, Finnegan EJ, Rouse DT, Tadege M, Bagnall DJ, Helliwell CA, Peacock WJ, Dennis ES. The control of flowering by vernalization. Curr Opin Plant Biol 2000; 3:418-22. [PMID: 11019811 DOI: 10.1016/s1369-5266(00)00106-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The process by which vernalization, the exposure of a germinating seed or a juvenile plant to a prolonged period of low temperature, promotes flowering in the adult plant has remained a mystery for many years. The recent isolation of one of the key genes involved in vernalization, FLOWERING LOCUS C, has now provided an insight into the molecular mechanism involved, including the role of DNA methylation.
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Affiliation(s)
- C C Sheldon
- Commonwealth Scientific and Industrial Research Organisation, Plant Industry, Canberra, Australian Capital Territory
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23
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Luo M, Bilodeau P, Dennis ES, Peacock WJ, Chaudhury A. Expression and parent-of-origin effects for FIS2, MEA, and FIE in the endosperm and embryo of developing Arabidopsis seeds. Proc Natl Acad Sci U S A 2000; 97:10637-42. [PMID: 10962025 PMCID: PMC27077 DOI: 10.1073/pnas.170292997] [Citation(s) in RCA: 365] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2000] [Indexed: 11/18/2022] Open
Abstract
The promoters of MEA (FIS1), FIS2, and FIE (FIS3), genes that repress seed development in the absence of pollination, were fused to beta-glucuronidase (GUS) to study their activity pattern. The FIS2GUS product is found in the embryo sac, in each of the polar cell nuclei, and in the central cell nucleus. After pollination, the maternally derived FIS2GUS protein occurs in the nuclei of the cenocytic endosperm. Before cellularization of the endosperm, activity is terminated in the micropylar and central nuclei of the endosperm and subsequently in the nuclei of the chalazal cyst. MEAGUS has a pattern of activity similar to that of FIS2GUS, but FIEGUS protein is found in many tissues, including the prepollination embryo sac, and in embryo and endosperm postpollination. The similarity in mutant phenotypes; the activity of FIE, MEA, and FIS2 in the same cells in the embryo sac; and the fact that MEA and FIE proteins interact in a yeast two-hybrid system suggest that these proteins operate in the same system of control of seed development. Maternal and not paternal FIS2GUS, MEAGUS, and FIEGUS show activity in early endosperm, so these genes may be imprinted. When fis2, mea, and fie mutants are pollinated, seed development is arrested at the heart embryo stage. The seed arrest of mea and fis2 is avoided when they are fertilized by a low methylation parent. The wild-type alleles of MEA or FIS2 are not required. The parent-of-origin-determined differential activity of MEA, FIS2, and FIE is not dependent on DNA methylation, but methylation does control some gene(s) that have key roles in seed development.
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Affiliation(s)
- M Luo
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, G.P.O. Box 1600, Canberra ACT 2601, Australia
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24
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Abstract
Recent research has demonstrated that DNA methylation plays an integral role in regulating the timing of flowering and in endosperm development. The identification of key genes controlling these processes, the expression of which is altered in plants with low methylation, opens the way to understanding how DNA methylation regulates plant development.
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Affiliation(s)
- E J Finnegan
- Commonwealth Scientific and Industrial Research Organisation, Plant Industry, PO Box 1600, Canberra, 2601, Australia. j.finnegan@pi. csiro.au
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25
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Sheldon CC, Rouse DT, Finnegan EJ, Peacock WJ, Dennis ES. The molecular basis of vernalization: The central role of FLOWERING LOCUS C (FLC). Proc Natl Acad Sci U S A 2000; 97:3753-8. [PMID: 10716723 PMCID: PMC16312 DOI: 10.1073/pnas.97.7.3753] [Citation(s) in RCA: 355] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
In Arabidopsis, the MADS-box protein encoded by FLOWERING LOCUS C (FLC) is a repressor of flowering. Vernalization, which promotes flowering in the late-flowering ecotypes and many late-flowering mutants, decreases the level of FLC transcript and protein in the plant. This vernalization-induced reduction in FLC transcript levels is mitotically stable and occurs in all tissues. FLC activity is restored in each generation, as is the requirement of a low-temperature exposure for the promotion of flowering. The level of FLC determines the extent of the vernalization response in the promotion of flowering, and there is a quantitative relationship between the duration of cold treatment and the extent of down-regulation of FLC activity. We conclude that FLC is the central regulator of the induction of flowering by vernalization. Other vernalization-responsive late-flowering mutants, which are disrupted in genes that encode regulators of FLC, are late-flowering as a consequence of their elevated levels of FLC.
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Affiliation(s)
- C C Sheldon
- Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, G.P.O. Box 1600, Canberra, ACT 2600, Australia
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26
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Abstract
Many neurosurgical procedures have been designed for or applied to the treatment of spasticity arising from different disorders, including cerebral palsy; traumatic, ischemic, or hypoxic brain injury, multiple sclerosis, and spinal cord injury. Neurosurgical procedures are primarily aimed at reducing spasticity by interrupting the stretch reflex at various sites along the spinal reflex arc or attempting to increase the centrally mediated inhibitory influence on the pool of motor neurons in the anterior horn. Surgical interventions for spasticity can be classified into peripheral ablative procedures, such as rhizotomy or peripheral neurectomy, and central ablative procedures, such as cordectomy, myelotomy, or stereotactic procedures. Non-ablative procedures include peripheral nerve or motor point blocks, the implantation of cerebellar or spinal stimulators, and the implantation of subdural catheters for infusion of pharmacologic agents to increase inhibitory activity. Several proposed mechanisms for spasticity are reviewed so that the rationale for the various surgical interventions for spasticity described may be better understood.
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Affiliation(s)
- M D Smyth
- Department of Neurological Surgery, Room M-779, Box 0112, University of California San Francisco, 505 Parnassus Avenue, San Francisco, California 94143-0112, USA.
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27
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Dennis ES, Bilodeau P, Burn J, Finnegan EJ, Genger R, Helliwell C, Kang BJ, Sheldon CC, Peacock WJ. Methylation controls the low temperature induction of flowering in Arabidopsis. Symp Soc Exp Biol 2000; 51:97-103. [PMID: 10645430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Control of the transition to flowering is critical for reproductive success of a plant. Studies in Arabidopsis have led us to suggest how this species has harnessed the environmental cue of a period of low temperature to ensure flowering occurs at an appropriate time. We propose that Arabidopsis has both vernalization-independent and vernalization-dependent pathways for the initiation of inflorescence development in the shoot apex. The vernalization-independent pathway may be concerned with the supply of carbohydrate to the shoot apex. In late flowering ecotypes which respond to vernalization the vernalization-independent pathway is blocked by the action of two dominant repressors of flowering, FRI and FLC, which interact to produce very late flowering plants which respond strongly to vernalization. We have isolated a gene which may correspond to FLC. We suggest the vernalization-dependent pathway, which may be concerned with apical GA biosynthesis, is blocked by methylation of a gene critical for flowering. This gene may correspond to that encoding kaurenoic acid hydroxylase (KAH), an enzyme catalysing a step in the GA biosynthetic pathway. Under this scheme vernalization causes unblocking of this pathway by demethylation possibly of the KAH gene and consequent biosynthesis of active GAs in the apex.
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Affiliation(s)
- E S Dennis
- CSIRO Plant Industry, Canberra, Australia
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28
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Dennis ES, Dolferus R, Ellis M, Rahman M, Wu Y, Hoeren FU, Grover A, Ismond KP, Good AG, Peacock WJ. Molecular strategies for improving waterlogging tolerance in plants. J Exp Bot 2000; 51:89-97. [PMID: 10938799 DOI: 10.1093/jexbot/51.342.89] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Plants, like animals, are obligate aerobes, but due to their inability to move, have evolved adaptation mechanisms that enable them to survive short periods of low oxygen supply, such as those occurring after heavy rain or flooding. Crop plants are often grown on soils subject to waterlogging and many are sensitive to waterlogging of the root zone. The combination of unfavourable weather conditions and suboptimal soil and irrigation techniques can result in severe yield losses. The molecular basis of the adaptation to transient low oxygen conditions has not been completely characterized, but progress has been made towards identifying genes and gene products induced during low oxygen conditions. Promoter elements and transcription factors involved in the regulation of anaerobically induced genes have been characterized. In this paper an account is presented of the molecular strategies that have been used in an attempt to increase flooding tolerance of crop plants.
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Affiliation(s)
- E S Dennis
- CSIRO Plant Industry, Canberra ACT, Australia.
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29
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Mathern GW, Giza CC, Yudovin S, Vinters HV, Peacock WJ, Shewmon DA, Shields WD. Postoperative seizure control and antiepileptic drug use in pediatric epilepsy surgery patients: the UCLA experience, 1986-1997. Epilepsia 1999; 40:1740-9. [PMID: 10612338 DOI: 10.1111/j.1528-1157.1999.tb01592.x] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Young children with refractory symptomatic epilepsy are at risk for developing neurologic and cognitive disabilities. Stopping the seizures may prevent these disabilities, but it is unclear whether resective surgery is associated with adequate long-term seizure control. METHODS This study determined pre- and postsurgery seizure frequency and antiepileptic drug (AED) use (6 months to 10 years) in children with symptomatic seizures from unilateral cortical dysplasia (CD; n = 64) and non-CD etiologies (i.e., ischemia, infection; n = 71), and compared them with older temporal lobe epilepsy (TLE; n = 31) patients with complex partial seizures. RESULTS Compared with presurgery, postsurgery seizure frequencies were decreased for CD, non-CD, and TLE patients (p < 0.002), and there were no differences between the three groups from 6 to 24 months after surgery (p > 0.12). At 5 years after surgery, seizure frequencies were greater in CD compared with TLE cases (p = 0.009). Compared with presurgery, the number of AEDs declined after surgery in all three groups (p < 0.002), and positively correlated with seizure frequencies (p = 0.0001). CONCLUSIONS This study indicates that seizure relief and AED use after resective surgery for symptomatic CD and non-CD etiologies was comparable with complex partial TLE cases up to 2 years after surgery. Furthermore, at 5 years after surgery, CD patients had outcomes better than those before surgery, but worse than TLE cases. In young children, these findings support the concept that early removal of symptomatic pathologic substrates is associated with seizure control and reduced AED use, similar to that noted in older TLE cases up to 2 years after surgery. Seizure control may reduce the risk of developing the seizure-related encephalopathy associated with severe symptomatic early-onset childhood epilepsy.
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Affiliation(s)
- G W Mathern
- Division of Neurosurgery, The Mental Retardation Research Center, University of California, Los Angeles, USA.
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30
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Cepeda C, Li Z, Cromwell HC, Altemus KL, Crawford CA, Nansen EA, Ariano MA, Sibley DR, Peacock WJ, Mathern GW, Levine MS. Electrophysiological and morphological analyses of cortical neurons obtained from children with catastrophic epilepsy: dopamine receptor modulation of glutamatergic responses. Dev Neurosci 1999; 21:223-35. [PMID: 10575246 DOI: 10.1159/000017402] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The present study examined the electrophysiological effects produced by activation of specific dopamine (DA) receptors and the distribution of DA receptor subtypes and glutamate receptor subunits [N-methyl-D-aspartate (NMDAR1) and GluR1] in cortical tissue samples obtained from children (ages 3 months to 16 years) undergoing epilepsy surgery. DA receptor activation produced differential effects depending on the receptor subtype that was activated. D1 receptor family agonists generally enhanced cortical excitability and favored the emergence of epileptogenic activity. In contrast, D2 receptor family agonists had more variable effects on cortical excitability and the expression of epileptiform discharges. Activation of D1 or D2 receptors decreased the amplitude of non-NMDA-mediated excitatory postsynaptic potentials. In contrast, DA and D1 agonists increased the amplitude of NMDA-mediated potentials. Immunohistochemical analysis showed that the DA receptor subtypes and glutamate receptor subunits examined were present in all cortical layers and areas throughout development. Whole-cell voltage clamp recordings of pyramidal neurons visualized with differential interference contrast optics and infrared videomicroscopy indicated that these neurons displayed a persistent Na(+) current, followed by an outward current. DA reduced the outward current but had little effect on the persistent Na(+) current. These results suggest a dual role for DA's actions in the human cerebral cortex. Activation of D2 receptors or antagonism of D1 receptors may help control seizures in children.
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Affiliation(s)
- C Cepeda
- Mental Retardation Research Center, UCLA, Los Angeles, CA 90024, USA
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31
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Abstract
OBJECTIVE To increase awareness about the treatment of adult patients with shunt-nonresponsive hydrocephalus--a state characterized by marked ventriculomegaly, low intracranial pressure, and a patent cerebrospinal fluid diversionary shunt. DESIGN Retrospective analysis of hospital and outpatient records. PATIENTS Four patients with symptomatic ventriculomegaly and patent ventriculoperitoneal shunts treated with a protocol of progressive ventricular hypotension induced by external cerebrospinal fluid drainage. RESULTS Severe clinical manifestations exhibited by the patients, including parkinsonian features, Parinaud syndrome, and extensor posturing, completely reversed once a normalization of ventricular size was achieved. External ventricular drainage pressures as low as -30 cm H2O were required to reduce ventricular size. All patients finally received a shunt incorporating a standard medium differential pressure valve with no antisiphon device. CONCLUSIONS Shunt siphoning may be an essential mechanism by which cerebrospinal fluid shunting is effective in many patients with adult hydrocephalus. Cerebrospinal fluid shunts that contain an antisiphon device are ineffective in these patients, despite the attainment of "physiologic" intracranial pressures. Based on reported experimental and clinical evidence, it seems that the cause of this condition may be related to abnormally high intracranial compliance.
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Affiliation(s)
- M Bergsneider
- Division of Neurosurgery, Brain Research Institute, University of California at Los Angeles School of Medicine, 90095-7039, USA.
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32
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Abstract
UNLABELLED The most appropriate time to consider cortical resection to treat medically intractable infantile spasms has not been clearly defined. The risks that need to be reconciled to make this decision are: What is the risk of loss of developmental potential if surgery is delayed too long versus what is the risk of unnecessary surgery if it is done too soon. We propose that, in addition to evaluation of seizures, developmental assessment is a key factor in the surgical decision. The case report illustrates this concept. CASE REPORT HC had onset of seizures at 9 days of age and developed infantile spasms due to mild right hemimegancephaly. At 19 months, she was having up to 50 seizures/day and was evaluated and approved for right hemispherectomy but surgery was delayed. Despite the seizures, her development had been much better than most patients with hemimegencephaly and infantile spasms. At 25 months her seizure control was much improved but she had several seizures/week. EcoG at the time of surgery did not demonstrate the usual abnormalities so no resection was performed. She has had only 5 seizures in the 2(1/2) year since. CONCLUSIONS (a) Hemimegalencephaly is not always associated with severe mental retardation; (b) normal or near-normal development may, in some cases, indicate the possibility of medical control of seizures as the child grows; (c) a localized developmental brain abnormality in a child with intractable seizures should not necessarily lead to cortical resection; and (d) when a child meets developmental milestones, it may be appropriate to delay surgical intervention.
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Affiliation(s)
- W D Shields
- Division of Pediatric Neurology, UCLA Children's Hospital, Los Angeles, California 90095-1752, USA
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33
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Abstract
Methylation of plant DNA occurs at cytosines in any sequence context, and as the Arabidopsis methyltransferase, METI, preferentially methylates cytosines in CG dinucleotides, it is likely that Arabidopsis has other methyltransferases with different target specificities. We have identified five additional genes encoding putative DNA methyltransferases. Three of these genes are very similar to METI throughout the coding region; these genes probably arose by a series of gene duplication events, the most recent giving rise to METIIa and METIIb. METIIa and b are expressed at low levels in vegetative and floral organs and the level of transcripts is not affected by the introduction of a METI antisense transgene, nor do the METII enzymes substitute for the reduced activity of METI in methylating CG dinucleotides. METIII is not essential as it encodes a truncated protein. Two other genes encode a second class of DNA methyltransferase with the conserved motifs characteristic of cytosine methyltransferases, but with little homology to the METI-like methyltransferases through the remainder of the protein. These two methyltransferases are characterized by the presence of a chromodomain inserted within the methyltransferase domain, suggesting that they may be associated with heterochromatin. Both these genes are transcribed at low levels in vegetative and reproductive tissues.
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Affiliation(s)
- R K Genger
- CSIRO, Plant Industry, Canberra, ACT, Australia
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34
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Abstract
A ten-year-old healthy child presented with a right upper extremity focal seizure which secondarily generalized. Magnetic resonance imaging (MR) revealed a 1-cm area of abnormal signal intensity in the left posterior temporal lobe at the gray-white junction. This did not appear on all imaging sequences, raising the suspicion of an artifact. Repeat MR revealed no intracranial or extracranial pathology. This case illustrates MR 'wrap around' artifact that mimicked a temporal lobe abnormality in an epilepsy patient. The physics of MR are reviewed as they pertain to this artifact.
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Affiliation(s)
- P V Mummaneni
- Department of Neurosurgery, University of California, San Francisco, Calif. 94143-0112, USA.
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35
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Decroocq V, Zhu X, Kauffman M, Kyozuka J, Peacock WJ, Dennis ES, Llewellyn DJ. A TM3-like MADS-box gene from Eucalyptus expressed in both vegetative and reproductive tissues. Gene X 1999; 228:155-60. [PMID: 10072768 DOI: 10.1016/s0378-1119(98)00613-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
MADS-box genes in plants are a diverse class of transcription factors that are involved in regulating developmental processes, particularly meristem and organ identity during floral development. They are characterized by a highly conserved MADS-box domain of 59 amino acids that binds to specific DNA sequences. We report the characterization of a cDNA clone, ETL (Eucalyptus TM3 Like), from Eucalyptus globulus subspecies bicostata encoding a putative transcription factor of the MADS-box class that is strongly expressed in both vegetative and floral tissues, suggesting that it regulates processes other than floral development. The clone was isolated from a floral bud cDNA library with a probe generated from Eucalyptus genomic DNA by PCR using degenerate primers to the MADS-box of the floral regulatory gene APETALA 1. The ETL cDNA clone encodes a putative protein of 206 amino acids that contains an N-terminal MADS-box and a helical domain of approx. 60 amino acids predicted to form a coiled-coil (K-box). These structural features are characteristic of plant MADS-box proteins. The MADS-box domain contains all the signature residues of a class of MADS-box genes typified by the tomato gene TM3 and overall, ETL shows 56% amino acid identity to TM3. Like TM3, the ETL gene is expressed in both vegetative and reproductive organs, predominantly in root and shoot meristems and organ primordia, as well as in developing male and female floral organs.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Blotting, Northern
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA-Binding Proteins/genetics
- Eucalyptus/chemistry
- Eucalyptus/genetics
- Eucalyptus/growth & development
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Genes, Plant/genetics
- In Situ Hybridization
- MADS Domain Proteins
- Meristem/genetics
- Molecular Sequence Data
- Plant Proteins
- Plants, Medicinal
- RNA, Messenger/genetics
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transcription Factors/genetics
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Affiliation(s)
- V Decroocq
- CSIRO Plant Industry, P.O. Box 1600, Canberra, ACT 2601, Australia
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36
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Sheldon CC, Burn JE, Perez PP, Metzger J, Edwards JA, Peacock WJ, Dennis ES. The FLF MADS box gene: a repressor of flowering in Arabidopsis regulated by vernalization and methylation. Plant Cell 1999; 11:445-58. [PMID: 10072403 PMCID: PMC144185 DOI: 10.1105/tpc.11.3.445] [Citation(s) in RCA: 637] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A MADS box gene, FLF (for FLOWERING LOCUS F ), isolated from a late-flowering, T-DNA-tagged Arabidopsis mutant, is a semidominant gene encoding a repressor of flowering. The FLF gene appears to integrate the vernalization-dependent and autonomous flowering pathways because its expression is regulated by genes in both pathways. The level of FLF mRNA is downregulated by vernalization and by a decrease in genomic DNA methylation, which is consistent with our previous suggestion that vernalization acts to induce flowering through changes in gene activity that are mediated through a reduction in DNA methylation. The flf-1 mutant requires a greater than normal amount of an exogenous gibberellin (GA3) to decrease flowering time compared with the wild type or with vernalization-responsive late-flowering mutants, suggesting that the FLF gene product may block the promotion of flowering by GAs. FLF maps to a region on chromosome 5 near the FLOWERING LOCUS C gene, which is a semidominant repressor of flowering in late-flowering ecotypes of Arabidopsis.
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Affiliation(s)
- C C Sheldon
- Commonwealth Scientific and Industrial Research Organisation, Division of Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia
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37
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Sheldon CC, Burn JE, Perez PP, Metzger J, Edwards JA, Peacock WJ, Dennis ES. The FLF MADS box gene: a repressor of flowering in Arabidopsis regulated by vernalization and methylation. Plant Cell 1999. [PMID: 10072403 DOI: 10.2307/3870872] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A MADS box gene, FLF (for FLOWERING LOCUS F ), isolated from a late-flowering, T-DNA-tagged Arabidopsis mutant, is a semidominant gene encoding a repressor of flowering. The FLF gene appears to integrate the vernalization-dependent and autonomous flowering pathways because its expression is regulated by genes in both pathways. The level of FLF mRNA is downregulated by vernalization and by a decrease in genomic DNA methylation, which is consistent with our previous suggestion that vernalization acts to induce flowering through changes in gene activity that are mediated through a reduction in DNA methylation. The flf-1 mutant requires a greater than normal amount of an exogenous gibberellin (GA3) to decrease flowering time compared with the wild type or with vernalization-responsive late-flowering mutants, suggesting that the FLF gene product may block the promotion of flowering by GAs. FLF maps to a region on chromosome 5 near the FLOWERING LOCUS C gene, which is a semidominant repressor of flowering in late-flowering ecotypes of Arabidopsis.
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Affiliation(s)
- C C Sheldon
- Commonwealth Scientific and Industrial Research Organisation, Division of Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia
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38
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Wilkinson CC, Albanese CT, Jennings RW, Feldstein VA, Goldberg JD, Baehner FL, Farrell JA, Peacock WJ, Harrison MR. Fetal neurenteric cyst causing hydrops: case report and review of the literature. Prenat Diagn 1999; 19:118-21. [PMID: 10215067 DOI: 10.1002/(sici)1097-0223(199902)19:2<118::aid-pd478>3.0.co;2-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Routine prenatal ultrasound revealed a unilocular cystic mass associated with upper thoracic hemivertebrae that grew to 6 cm at 28 weeks and was associated with hydrops. A thoraco-amniotic shunt decompressed the cyst and resolved the hydrops, but the shunt occluded 17 days later. Preterm labour led to vaginal delivery at 31 2/7 weeks. Postnatally, the cyst was decompressed by thoracentesis due to respiratory distress. It was resected on day four of life. Severe tracheobronchomalacia was present post-operatively, presumably due to prenatal mass effect of the cyst. At one year of age, the child has recovered completely without adverse respiratory or neurological sequelae.
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Affiliation(s)
- C C Wilkinson
- Fetal Treatment Center, University of California, San Francisco 94143-0570, USA
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39
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Mathern GW, Mendoza D, Lozada A, Pretorius JK, Dehnes Y, Danbolt NC, Nelson N, Leite JP, Chimelli L, Born DE, Sakamoto AC, Assirati JA, Fried I, Peacock WJ, Ojemann GA, Adelson PD. Hippocampal GABA and glutamate transporter immunoreactivity in patients with temporal lobe epilepsy. Neurology 1999; 52:453-72. [PMID: 10025773 DOI: 10.1212/wnl.52.3.453] [Citation(s) in RCA: 232] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Sodium-coupled transporters remove extracellular neurotransmitters and alterations in their function could enhance or suppress synaptic transmission and seizures. This study determined hippocampal gamma-aminobutyric acid (GABA) and glutamate transporter immunoreactivity (IR) in temporal lobe epilepsy (TLE) patients. METHODS Hippocampal sclerosis (HS) patients (n = 25) and non-HS cases (mass lesion and cryptogenic; n = 20) were compared with nonseizure autopsies (n = 8). Hippocampal sections were studied for neuron densities along with IR for glutamate decarboxylase (GAD; presynaptic GABA terminals), GABA transporter-1 (GAT-1; presynaptic GABA transporter), GAT-3 (astrocytic GABA transporter), excitatory amino acid transporter 3 (EAAT3; postsynaptic glutamate transporter), and EAAT2-1 (glial glutamate transporters). RESULTS Compared with autopsies, non-HS cases with similar neuron counts showed: 1) increased GAD IR gray values (GV) in the fascia dentata outer molecular layer (OML), hilus, and stratum radiatum; 2) increased GAT-1 OML GVs; 3) increased astrocytic GAT-3 GVs in the hilus and Ammon's horn; and 4) no IR differences for EAAT3-1. HS patients with decreased neuron densities demonstrated: 1) increased OML and inner molecular layer GAD puncta; 2) decreased GAT-1 puncta relative to GAD in the stratum granulosum and pyramidale; 3) increased GAT-1 OML GVs; 4) decreased GAT-3 GVs; 5) increased EAAT3 IR on remaining granule cells and pyramids; 6) decreased glial EAAT2 GVs in the hilus and CA1 stratum radiatum associated with neuron loss; and 7) increased glial EAAT1 GVs in CA2/3 stratum radiatum. CONCLUSIONS Hippocampal GABA and glutamate transporter IR differ in TLE patients compared with autopsies. These data support the hypothesis that excitatory and inhibitory neurotransmission and seizure susceptibility could be altered by neuronal and glial transporters in TLE patients.
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Affiliation(s)
- G W Mathern
- Division of Neurosurgery, University of California, Los Angeles, USA.
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Helliwell CA, Poole A, Peacock WJ, Dennis ES. Arabidopsis ent-kaurene oxidase catalyzes three steps of gibberellin biosynthesis. Plant Physiol 1999; 119:507-10. [PMID: 9952446 PMCID: PMC32127 DOI: 10.1104/pp.119.2.507] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/1998] [Accepted: 11/03/1998] [Indexed: 05/19/2023]
Abstract
The Arabidopsis GA3 cDNA was expressed in yeast (Saccharomyces cerevisiae) and the ability of the transformed yeast cells to metabolize ent-kaurene was tested. We show by full-scan gas chromatography-mass spectrometry that the transformed cells produce ent-kaurenoic acid, and demonstrate that the single enzyme GA3 (ent-kaurene oxidase) catalyzes the three steps of gibberellin biosynthesis from ent-kaurene to ent-kaurenoic acid.
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Affiliation(s)
- C A Helliwell
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, G.P.O. Box 1600, Canberra, ACT 2601, Australia.
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41
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Luo M, Bilodeau P, Koltunow A, Dennis ES, Peacock WJ, Chaudhury AM. Genes controlling fertilization-independent seed development in Arabidopsis thaliana. Proc Natl Acad Sci U S A 1999; 96:296-301. [PMID: 9874812 PMCID: PMC15133 DOI: 10.1073/pnas.96.1.296] [Citation(s) in RCA: 327] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have cloned two genes, FIS1 and FIS2, that control both fertilization independent seed development and postpollination embryo development in Arabidopsis. These genes confer female gametophytic phenotypes. FIS2 encodes a protein with a C2H2 zinc-finger motif and three putative nuclear localization signals, indicating that it is likely to be a transcription factor. FIS1 encodes a protein with homology to the Drosophila Polycomb group gene Enhancer-of-zeste and is identical to the recently described Arabidopsis gene MEDEA. FIS1 is a protein with a number of putative functional domains, including the SET domain present in Enhancer-of-zeste-related proteins. Comparison of the position of the lesions in the fis1 and medea mutant alleles indicates that fis1 is a null allele producing a truncated polypeptide lacking all the protein domains whereas the deduced protein from medea lacks only the SET domain. We present a model of the role of FIS1 and FIS2 gene products in seed development.
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Affiliation(s)
- M Luo
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
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42
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Ellis MH, Dennis ES, Peacock WJ. Arabidopsis roots and shoots have different mechanisms for hypoxic stress tolerance. Plant Physiol 1999; 119:57-64. [PMID: 9880346 PMCID: PMC32242 DOI: 10.1104/pp.119.1.57] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/1998] [Accepted: 10/11/1998] [Indexed: 05/18/2023]
Abstract
Arabidopsis has inducible responses for tolerance of O2 deficiency. Plants previously exposed to 5% O2 were more tolerant than the controls to hypoxic stress (0.1% O2 for 48 h) in both roots and shoots, but hypoxic acclimation did not improve tolerance to anoxia (0% O2). The acclimation of shoots was not dependent on the roots: increased shoot tolerance was observed when the roots of the plants were removed. An adh (alcohol dehydrogenase) null mutant did not show acclimation of the roots but retained the shoot survival response. Abscisic acid treatment also differentiated the root and shoot responses; pretreatment induced root survival in hypoxic stress conditions (0.1% O2) but did not induce any increase in the survival of shoots. Cycloheximide blocked both root and shoot acclimation, indicating that both acclimation mechanisms are dependent on protein synthesis.
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Affiliation(s)
- M H Ellis
- Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, G.P.O. Box 1600, Canberra ACT 2601, Australia
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43
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Mathern GW, Pretorius JK, Kornblum HI, Mendoza D, Lozada A, Leite JP, Chimelli L, Born DE, Fried I, Sakamoto AC, Assirati JA, Peacock WJ, Ojemann GA, Adelson PD. Altered hippocampal kainate-receptor mRNA levels in temporal lobe epilepsy patients. Neurobiol Dis 1998; 5:151-76. [PMID: 9848088 DOI: 10.1006/nbdi.1998.0200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study determined whether hippocampal kainate (KA) receptor mRNA levels were increased or decreased in temporal lobe epilepsy patients compared with nonseizure autopsies. Hippocampal sclerosis (HS; n = 17), nonsclerosis (non-HS; n = 11), and autopsy hippocampi (n = 9) were studied for KA1-2 and GluR5-7 mRNA levels using semiquantitative in situ hybridization techniques, along with neuron densities. Compared with autopsy hippocampi, HS and non-HS cases showed decreased GluR5 and GluR6 hybridization densities per CA2 and/or CA3 pyramid. Furthermore, HS patients demonstrated increased KA2 and GluR5 hybridization densities per granule cell compared with autopsy hippocampi. These findings indicate that chronic temporal lobe seizures were associated with differential changes in hippocampal KA1-2 and GluR5-7 hybridization densities that vary by subfield and pathology group. In temporal lobe epilepsy patients, these results support the hypothesis that pyramidal cell GluR5 and GluR6 mRNA levels are decreased as a consequence of seizures, and in HS patients granule cell KA2 and GluR5 mRNA levels are increased in association with aberrant fascia dentata mossy fiber sprouting and/or hippocampal neuronal loss.
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Affiliation(s)
- G W Mathern
- Division of Neurosurgery, University of California, Los Angeles 90095, USA
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44
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Southerton SG, Strauss SH, Olive MR, Harcourt RL, Decroocq V, Zhu X, Llewellyn DJ, Peacock WJ, Dennis ES. Eucalyptus has a functional equivalent of the Arabidopsis floral meristem identity gene LEAFY. Plant Mol Biol 1998; 37:897-910. [PMID: 9700063 DOI: 10.1023/a:1006056014079] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Two genes cloned from Eucalyptus globulus, Eucalyptus LeaFy (ELF1 and ELF2), have sequence homology to the floral meristem identity genes LEAFY from Arabidopsis and FLORICAULA from Antirrhinum. ELF1 is expressed in the developing eucalypt floral organs in a pattern similar to LEAFY while ELF2 appears to be a pseudo gene. ELF1 is expressed strongly in the early floral primordium and then successively in the primordia of sepals, petals, stamens and carpels. It is also expressed in the leaf primordia and young leaves and adult and juvenile trees. The ELF1 promoter coupled to a GUS reporter gene directs expression in transgenic Arabidopsis in a temporal and tissue-specific pattern similar to an equivalent Arabidopsis LEAFY promoter construct. Strong expression is seen in young flower buds and then later in sepals and petals. No expression was seen in rosette leaves or roots of flowering plants or in any non-flowering plants grown under long days. Furthermore, ectopic expression of the ELF1 gene in transgenic Arabidopsis causes the premature conversion of shoots into flowers, as does an equivalent 35S-LFY construct. These data suggest that ELF1 plays a similar role to LFY in flower development and that the basic mechanisms involved in flower initiation and development in Eucalyptus are similar to those in Arabidopsis.
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Helliwell CA, Sheldon CC, Olive MR, Walker AR, Zeevaart JA, Peacock WJ, Dennis ES. Cloning of the Arabidopsis ent-kaurene oxidase gene GA3. Proc Natl Acad Sci U S A 1998; 95:9019-24. [PMID: 9671797 PMCID: PMC21195 DOI: 10.1073/pnas.95.15.9019] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The ga3 mutant of Arabidopsis is a gibberellin-responsive dwarf. We present data showing that the ga3-1 mutant is deficient in ent-kaurene oxidase activity, the first cytochrome P450-mediated step in the gibberellin biosynthetic pathway. By using a combination of conventional map-based cloning and random sequencing we identified a putative cytochrome P450 gene mapping to the same location as GA3. Relative to the progenitor line, two ga3 mutant alleles contained single base changes generating in-frame stop codons in the predicted amino acid sequence of the P450. A genomic clone spanning the P450 locus complemented the ga3-2 mutant. The deduced GA3 protein defines an additional class of cytochrome P450 enzymes. The GA3 gene was expressed in all tissues examined, RNA abundance being highest in inflorescence tissue.
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Affiliation(s)
- C A Helliwell
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
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46
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Affiliation(s)
- D V Vigil
- Department of Family Medicine, University of California, Los Angeles, USA
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47
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Abstract
Methylation of cytosine residues in DNA provides a mechanism of gene control. There are two classes of methyltransferase in Arabidopsis; one has a carboxy-terminal methyltransferase domain fused to an amino-terminal regulatory domain and is similar to mammalian methyltransferases. The second class apparently lacks an amino-terminal domain and is less well conserved. Methylcytosine can occur at any cytosine residue, but it is likely that clonal transmission of methylation patterns only occurs for cytosines in strand-symmetrical sequences CpG and CpNpG. In plants, as in mammals, DNA methylation has dual roles in defense against invading DNA and transposable elements and in gene regulation. Although originally reported as having no phenotypic consequence, reduced DNA methylation disrupts normal plant development.
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Affiliation(s)
- E. J. Finnegan
- 1Commonwealth Scientific and Industrial Research Organization, Plant Industry, P.O. Box 1600, Canberra, ACT 2601, Australia, Cooperative Research Centre for Plant Science, P.O. Box 475, Canberra, ACT 2601, Australia; e-mail: , 2Division of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
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Hoeren FU, Dolferus R, Wu Y, Peacock WJ, Dennis ES. Evidence for a role for AtMYB2 in the induction of the Arabidopsis alcohol dehydrogenase gene (ADH1) by low oxygen. Genetics 1998; 149:479-90. [PMID: 9611167 PMCID: PMC1460183 DOI: 10.1093/genetics/149.2.479] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The transcription factor AtMYB2 binds to two sequence motifs in the promoter of the Arabidopsis ADH1 gene. The binding to the GT-motif (5'-TGGTTT-3') is essential for induction of ADH1 by low oxygen, while binding to the second motif, MBS-2, is not essential for induction. We show that AtMYB2 is induced by hypoxia with kinetics compatible with a role in the regulation of ADH1. Like ADH1, AtMYB2 has root-limited expression. When driven by a constitutive promoter, AtMYB2 is able to transactivate ADH1 expression in transient assays in both Arabidopsis and Nicotiana plumbaginifolia protoplasts, and in particle bombardment of Pisum sativum leaves. Mutation of the GT-motif abolished binding of AtMYB2 and caused loss of activity of the ADH1 promoter in both transient assays and transgenic Arabidopsis plants. These results are consistent with AtMYB2 being a key regulatory factor in the induction of the ADH1 promoter by low oxygen.
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Affiliation(s)
- F U Hoeren
- C.S.I.R.O. Plant Industry, Canberra ACT 2601, Australia
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49
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Abstract
We have tested the hypothesis that the promotion of flowering by prolonged exposure to low temperatures (vernalization) is mediated by DNA demethylation [Burn, J. E., Bagnall, D. J., Metzger, J. M., Dennis, E. S. & Peacock, W. J. (1993) Proc. Natl. Acad. Sci. USA 90, 287-291]. Arabidopsis plants that have reduced levels of DNA methylation because of the presence of a methyltransferase (METI) antisense gene flowered earlier than untransformed control plants, without the need for a cold treatment. Decreased DNA methylation mutants (ddm1) also flowered earlier than the wild-type progenitor under conditions where they respond to vernalization. We conclude that demethylation of DNA is sufficient to cause early flowering, and we have found that the promotion of flowering is directly proportional to the decrease in methylation in METI antisense lines. The early-flowering phenotype was inherited in sexual progeny, even when the antisense transgene had been lost by segregation. Methyltransferase antisense plants with low DNA methylation levels responded to a low-temperature treatment by flowering even earlier than their untreated siblings indicating that the promotion of flowering by cold and by demethylation was additive when neither treatment saturated the early-flowering response. As in untransformed control plants, the cold-induced early-flowering signal was reset in progeny of METI antisense plants. These observations suggest that the demethylation brought about by a METI antisense can account for some properties of vernalization, but not for the need for revernalization in each generation.
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Affiliation(s)
- E J Finnegan
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, P.O. Box 1600, Canberra, ACT 2601, Australia.
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50
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Mathern GW, Pretorius JK, Kornblum HI, Mendoza D, Lozada A, Leite JP, Chimelli LM, Fried I, Sakamoto AC, Assirati JA, Lévesque MF, Adelson PD, Peacock WJ. Human hippocampal AMPA and NMDA mRNA levels in temporal lobe epilepsy patients. Brain 1997; 120 ( Pt 11):1937-59. [PMID: 9397013 DOI: 10.1093/brain/120.11.1937] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
This study was designed to determine whether hippocampal neuronal AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and NMDA (N-methyl-D-aspartate) mRNA levels were differentially increased in temporal lobe epilepsy patients compared with those measured in control tissue from non-seizure autopsies. Hippocampi from hippocampal sclerosis patients (n = 28) and temporal mass lesion cases (n = 12) were compared with those from the autopsies (n = 4), and studied for AMPA GluR1-3 and NMDAR1-2 mRNAs using semi-quantitative in situ hybridization, along with fascia dentata and Ammon's horn neuron densities. Compared with the autopsies, and without correction for neuron counts, the mass lesion cases with neuron densities similar to autopsies showed: (i) significantly increased NMDAR2 hybridization densities for fascia dentata granule cells; (ii) increased AMPA GluR3 mRNA densities for Ammon's horn pyramids; and (iii) similar or numerically increased mRNAs for all other subunits and hippocampal subfields. Compared with the autopsies, hippocampal sclerosis cases with decreased neuron densities showed: (i) significantly decreased AMPA GluR1-2 and NMDAR1-2 hybridization densities for Ammon's horn pyramids and (ii) similar or numerically decreased mRNAs for all other subunits and subfields. However, correcting for changes in neuron densities showed that hippocampal sclerosis patients had increased AMPA and NMDA mRNA levels per neuron compared with autopsies, and in the CA2 resistant sector GluR2 mRNA levels were numerically greater than autopsies and mass lesion cases. Furthermore, relative to autopsies both sclerosis and mass lesion hippocampi showed that, in the stratum granulosum, the greatest mRNA increases were in AMPA GluR1 and NMDAR2 compared with the other mRNAs. In chronic temporal lobe seizure patients these results indicate that mass lesion and sclerosis cases show differential increases in hippocampal AMPA and NMDA mRNA levels per neuron compared with autopsies, especially for AMPA GluR1 and NMDAR2 in fascia dentata granule cells. These findings support the hypothesis that temporal lobe seizures are associated with increased ionotropic glutamate receptor mRNA levels and alterations in receptor subunit composition that probably contribute to neuronal hyperexcitability, synchronization and seizure generation.
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Affiliation(s)
- G W Mathern
- Department of Neurology, University of California, USA
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