| 1. |
- Barlier, I, et al.
(författare)
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The SUR2 gene of Arabidopsis thaliana encodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis.
- 2000
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 97:26
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Tidskriftsartikel (refereegranskat)abstract
- Genetic screens have been performed to identify mutants with altered auxin homeostasis in Arabidopsis. A tagged allele of the auxin-overproducing mutant sur2 was identified within a transposon mutagenized population. The SUR2 gene was cloned and shown to encode the CYP83B1 protein, which belongs to the large family of the P450-dependent monooxygenases. SUR2 expression is up-regulated in sur1 mutants and induced by exogenous auxin in the wild type. Analysis of indole-3-acetic acid (IAA) synthesis and metabolism in sur2 plants indicates that the mutation causes a conditional increase in the pool size of IAA through up-regulation of IAA synthesis.
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| 2. |
- Baud, Sébastien, et al.
(författare)
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gurke and pasticcino3 mutants affected in embryo development are impaired in acetyl-CoA carboxylase.
- 2004
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Ingår i: EMBO Reports. - : EMBO. - 1469-221X .- 1469-3178. ; 5:5
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Tidskriftsartikel (refereegranskat)abstract
- Normal embryo development is required for correct seedling formation. The Arabidopsis gurke and pasticcino3 mutants were isolated from different developmental screens and the corresponding embryos exhibit severe defects in their apical region, affecting bilateral symmetry. We have recently identified lethal acc1 mutants affected in acetyl-CoA carboxylase 1 (ACCase 1) that display a similar embryo phenotype. A series of crosses showed that gk and pas3 are allelic to acc1 mutants, and direct sequencing of the ACC1 gene revealed point mutations in these new alleles. The isolation of leaky acc1 alleles demonstrated that ACCase 1 is essential for correct plant development and that mutations in ACCase affect cellular division in plants, as is the case in yeast. Interestingly, significant metabolic complementation of the mutant phenotype was obtained by exogenous supply of malonate, suggesting that the lack of cytosolic malonyl-CoA is likely to be the initial factor leading to abnormal development in the acc1 mutants.
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| 3. |
- Bellec, Y., et al.
(författare)
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Pasticcino2 is a protein tyrosine phosphatase-like involved in cell proliferation and differentiation in Arabidopsis
- 2002
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 32:5, s. 713-722
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Tidskriftsartikel (refereegranskat)abstract
- The pasticcino2 (pas2) mutant shows impaired embryo and seedling development associated with cell dedifferentiation and proliferation. This process is specifically enhanced in presence of cytokinins leading to callus-like structure of the apical part of the seedling. Cell proliferation concerns localized and stochastic nodules of dividing cells. In absence of cytokinins, cell proliferation leads to small calli on stems but, most often, cell proliferation is associated with post-genital organ fusion. The PAS2 gene was identified by positional cloning. PAS2 expression was found in every plant organ and was not regulated by PAS1 and PAS3 genes. PAS2 encodes the Arabidopsis member of the protein tyrosine phosphatase-like (Ptpl) family, a new PTP family originally described in mice and humans and characterized by a mutated PTP active site. This family of proteins has a yeast homolog that is essential for cell viability. The absence of yeast PAS2 homolog can be functionally replaced by the Arabidopsis PAS2 protein, demonstrating that PAS2 function is conserved between higher and lower eukaryotes.
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| 4. |
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| 5. |
- Camilleri, C., et al.
(författare)
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The Arabidopsis TONNEAU2 gene encodes a putative novel protein phosphatase 2A regulatory subunit essential for the control of the cortical cytoskeleton
- 2002
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Ingår i: Plant Cell. - 1040-4651 .- 1532-298X. ; 14:4, s. 833-845
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Tidskriftsartikel (refereegranskat)abstract
- In Arabidopsis ton2 mutants, abnormalities of the cortical microtubular cytoskeleton, such as disorganization of the interphase microtubule array and lack of the preprophase band before mitosis, markedly affect cell shape and arrangement as well as overall plant morphology. We present the molecular isolation of the TON2 gene, which is highly conserved in higher plants and has a vertebrate homolog of unknown function. It encodes a protein similar in its C-terminal part to B" regulatory subunits of type 2A protein phosphatases (PP2As). We show that the TON2 protein interacts with an Arabidopsis type A subunit of PP2A in the yeast two-hybrid system and thus likely defines a novel subclass of PP2A subunits that are possibly involved in the control of cytoskeletal structures in plants., ISSN = 1040-4651, DOI = 10.1105/tpc.010402, url = ://WOS:000175350100008, year = 2002, type = Journal Article
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| 6. |
- Carol, R. J., et al.
(författare)
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PASTICCINO1 (AtFKBP70) is a nuclear-localised immunophilin required during Arabidopsis thaliana embryogenesis
- 2001
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Ingår i: Plant Science. - : Elsevier BV. - 0168-9452 .- 1873-2259. ; 161:3, s. 527-535
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Tidskriftsartikel (refereegranskat)abstract
- The PASTICCINO1 (PAS1) gene of Arabidopsis thaliana encodes a protein with homology to the FK506-binding protein (FKBP) class of immunophilins. To begin to understand more about the possible function of PAS1, we tested some properties of recombinant PAS1 protein and analysed the expression of the gene in Arabidopsis embryos and cell cultures and in tobacco cells. In pas1-1/+ heterozygote embryos the pas1-1 allele is expressed at very low levels in all cells, but it is misexpressed in the pas1-1 homozygote mutant at the same stage. Anti-PAS1 affinity-purified antibodies recognise a 70 kDa protein from dividing cell cultures of Arabidopsis. In indirect immunofluorescence, the same antibodies label the nuclei of dividing tobacco BY-2 cells. In a protease-coupled assay, recombinant PAS1 protein has low peptidylprolyl cis-trans isomerase (PPIase) activity, which is inhibited by the immunosuppressive drugs FK506 and rapamycin, but not by cyclosporin. PAS1 also binds calmodulin in vitro. This data suggests the importance of the correctly regulated production of functional PAS1 protein, a likely nuclear-localised FKBP, for the correct development of the plant embryo. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.
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| 7. |
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| 8. |
- Descamps, D, et al.
(författare)
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Extreme ultraviolet interferometry measurements with high-order harmonics
- 2000
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Ingår i: Optics Letters. - 0146-9592. ; 25:2, s. 135-137
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that high-order harmonics generated by short, intense laser pulses in gases provide an interesting radiation source for extreme ultraviolet interferometry, since they are tunable, coherent, of short pulse duration, and simple to manipulate. Harmonics from the 9th to the 15th are used to measure the thickness of an aluminum layer. The 11th harmonic is used to determine the spatial distribution of the electron density of a plasma produced by a 300-ps laser. Electronic densities higher than 2-10(20) electrons/cm(3) are measured. (C) 2000 Optical Society of America. OCIS codes: 190.0190, 190.4160, 190.7110, 120.3180, 140.7240, 350.4500.
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| 9. |
- Fagard, M, et al.
(författare)
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AGO1, QDE-2, and RDE-1 are related proteins required for post-transcriptional gene silencing in plants, quelling in fungi, and RNA interference in animals.
- 2000
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 97:21
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Tidskriftsartikel (refereegranskat)abstract
- Introduction of transgene DNA may lead to specific degradation of RNAs that are homologous to the transgene transcribed sequence through phenomena named post-transcriptional gene silencing (PTGS) in plants, quelling in fungi, and RNA interference (RNAi) in animals. It was shown previously that PTGS, quelling, and RNAi require a set of related proteins (SGS2, QDE-1, and EGO-1, respectively). Here we report the isolation of Arabidopsis mutants impaired in PTGS which are affected at the Argonaute1 (AGO1) locus. AGO1 is similar to QDE-2 required for quelling and RDE-1 required for RNAi. Sequencing of ago1 mutants revealed one amino acid essential for PTGS that is also present in QDE-2 and RDE-1 in a highly conserved motif. Taken together, these results confirm the hypothesis that these processes derive from a common ancestral mechanism that controls expression of invading nucleic acid molecules at the post-transcriptional level. As opposed to rde-1 and qde-2 mutants, which are viable, ago1 mutants display several developmental abnormalities, including sterility. These results raise the possibility that PTGS, or at least some of its elements, could participate in the regulation of gene expression during development in plants.
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| 10. |
- Ghetti, Roberta, et al.
(författare)
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Calibration of a neutron time-of-flight multidetector system for an intensity interferometry experiment
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 516:2-3, s. 492-501
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Tidskriftsartikel (refereegranskat)abstract
- We present the details of an experiment on light particle interferometry. In particular, we focus on a time-of-flight technique which uses a cyclotron RF signal as a start and a liquid scintillator time signal as a stop, to measure neutron energy in the range of En approximate to 1.8-150 MeV. This dynamic range (up to 300 ns) is much larger than the beam bunch separation (54 ns) of the AGOR cyclotron (KVI). However, the problem of a short burst period is overcome by using the time information obtained from a fast projectile fragment phoswich detector. The complete analysis procedure to extract the final neutron kinetic energy spectra, is discussed. (C) 2003 Elsevier B.V. All rights reserved.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Ghetti, R., et al.
(författare)
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Influence of multiple sources on the two-neutron correlation function in Ni-induced, intermediate energy, heavy ion reactions
- 2001
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 64:1
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Tidskriftsartikel (refereegranskat)abstract
- The strength of the neutron-neutron correlation function from the E=45AMeV58Ni+27Al, natNi, and 197Au reactions depends on the neutron parallel velocity. This indicates the presence of multiple sources of neutron emission. We find these sources consistent with a dissipative, binary reaction mechanism as it is described by, e.g., Boltzmann-Uehling-Uhlenbeck calculations.
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| 15. |
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| 16. |
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| 17. |
- Ghetti, Roberta, et al.
(författare)
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Isospin effects on two-particle correlation functions in E/A=61 MeV Ar-36+Sn-112,Sn-124 reactions
- 2004
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:3
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Tidskriftsartikel (refereegranskat)abstract
- Small-angle, two-particle correlation functions have been measured for Ar-36+Sn-112,Sn-124 collisions at E/A=61 MeV. Total momentum gated neutron-proton (np) and proton-proton (pp) correlations are stronger for the Sn-124 target. Some of the correlation functions for particle pairs involving deuterons or tritons (nd, pt, and nt) also show a dependence on the isospin of the emitting source.
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| 18. |
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| 19. |
- Harrar, Y., et al.
(författare)
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FKBPs : at the crossroads of folding and transduction
- 2001
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Ingår i: Trends in Plant Science. - : Elsevier BV. - 1360-1385 .- 1878-4372. ; 6:9, s. 426-431
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Forskningsöversikt (refereegranskat)abstract
- FK506-binding proteins (FKBPs) belong to the large family of peptidyl-prolyl cis-trans isomerases, which are known to be involved in many cellular processes, such as cell signalling, protein trafficking and transcription. FKBPs associate into protein complexes, although the involvement and precise role of their foldase activity remain to be elucidated. FKBPs represent a large gene family in plants that is involved in growth and development. Disruption of genes encoding FKBPs in plants and animals has underlined the importance of this family of proteins in the regulation of cell division and differentiation.
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| 20. |
- Harrar, Y., et al.
(författare)
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Hormonal control of cell proliferation requires PASTICCINO genes
- 2003
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 132:3, s. 1217-1227
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Tidskriftsartikel (refereegranskat)abstract
- PASTICCINO (PAS) genes are required for coordinated cell division and differentiation during plant development. In loss-of-function pas mutants, plant aerial tissues showed ectopic cell division that was specifically enhanced by cytokinins, leading to disorganized tumor-like tissue. To determine the role of the PAS genes in controlling cell proliferation, we first analyzed the expression profiles of several genes involved in cell division and meristem function. Differentiated and meristematic cells of the pas mutants were more competent for cell division as illustrated by the ectopic and enlarged expression profiles of CYCLIN-DEPENDENT KINASE A and CYCLIN B1. The expression of meristematic homeobox genes KNOTTED-LIKE IN ARABIDOPSIS (KNAT2, KNAT6), and SHOOT MERISTEMLESS was also increased in pas mutants. Moreover, the loss of meristem function caused by shoot meristemless mutation can be suppressed by pas2. The KNAT2 expression pattern defines an enlarged meristematic zone in pas mutants that can be mimicked in wild type by cytokinin treatment. Cytokinin induction of the primary cytokinin response markers, ARABIDOPSIS RESPONSE REGULATOR (ARR5 and ARR6), was enhanced and lasted longer in pas mutants, suggesting that PAS genes in wild type repress cytokinin responses. The expression of the cytokinin-regulated cyclin D, cyclin D3.1, was nonetheless not modified in pas mutants. However, primary auxin response genes were down-regulated in pas mutants, as shown by a lower auxin induction of IAA4 and IAA1 genes, demonstrating that the auxin response was also modified. Altogether, our results suggest that PAS genes are involved in the hormonal control of cell division and differentiation.
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| 21. |
- Hergott, JF, et al.
(författare)
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XUV interferometry using high-order harmonics: Application to plasma diagnostics
- 2001
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 19:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present and compare the two different XUV interferometric techniques using high-order harmonics that have been developed so far. The first scheme is based on the interference between two spatially separated phase-locked harmonic sources while the second uses two temporally separated harmonic sources. These techniques have been applied to plasma diagnostics in feasibility experiments where electron densities up to a few 1020 e[minus sign/cm3 have been measured with a temporal resolution of 200 fs. We present the main characteristics of each technique and discuss their respective potentials and limitations.
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| 22. |
- Merdji, H., et al.
(författare)
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Coherence properties of high-order harmonics : Application to high-density laser-plasma diagnostic
- 2000
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 18:3, s. 495-502
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Tidskriftsartikel (refereegranskat)abstract
- We present two interferometry schemes in the extreme ultraviolet, based on either the wave-front division of a unique harmonic beam (1st scheme) or two spatially separated, phase-locked harmonic sources (2nd scheme). In the first scheme using a Fresnel bimirror interferometer, we measure the degree of spatial coherence of the 13 th harmonic generated in xenon, as a function of different parameters. A high degree of coherence, larger than 0.5, is found for the best conditions in almost the full section of the beam. Then, we demonstrate that the second scheme can be used for interferometry measurements with an ultrahigh time resolution. The 11th harmonic is used to study the spatial variation of the electron density of a laser-produced plasma. Electronic densities higher than 2.10 20 cm -3 are measured.
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| 23. |
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| 24. |
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| 25. |
- Schrick, K., et al.
(författare)
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FACKEL is a sterol C-14 reductase required for organized cell division and expansion in Arabidopsis embryogenesis
- 2000
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Ingår i: Genes & Development. - 0890-9369 .- 1549-5477. ; 14:12, s. 1471-1484
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Tidskriftsartikel (refereegranskat)abstract
- In flowering plants, the developing embryo consists of growing populations of cells whose fates are determined in a position-dependent manner to form the adult organism. Mutations in the FACKEL (FK) gene affect body organization of the Arabidopsis seedling. We report that FK is required for cell division and expansion and is involved in proper organization of the embryo. We isolated FK by positional cloning. Expression analysis in embryos revealed that FK mRNA becomes localized to meristematic zones. FK encodes a predicted integral membrane protein related to the vertebrate lamin B receptor and sterol reductases across species, including yeast sterol C-14 reductase ERG24. We provide functional evidence that FK encodes a sterol C-14 reductase by complementation of erg24. GC/MS analysis confirmed that fk mutations lead to accumulation of intermediates in the biosynthetic pathway preceding the C-14 reductase step. Although fk represents a sterol biosynthetic mutant, the phenotype was not rescued by feeding with brassinosteroids (BRs), the only plant sterol signaling molecules known so far. We propose that synthesis of sterol signals in addition to BRs is important in mediating regulated cell growth and organization during embryonic development. Our results indicate a novel role for sterols in the embryogenesis of plants.
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| 26. |
- Schrick, K., et al.
(författare)
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Interactions between sterol biosynthesis genes in embryonic development of Arabidopsis
- 2002
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 31:1, s. 61-73
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Tidskriftsartikel (refereegranskat)abstract
- The sterol biosynthesis pathway of Arabidopsis produces a large set of structurally related phytosterols including sitosterol and campesterol, the latter being the precursor of the brassinosteroids (BRs). While BRs are implicated as phytohormones in post-embryonic growth, the functions of other types of steroid molecules are not clear. Characterization of the fackel (fk) mutants provided the first hint that sterols play a role in plant embryogenesis. FK encodes a sterol C-14 reductase that acts upstream of all known enzymatic steps corresponding to BR biosynthesis mutants. Here we report that genetic screens for fk -like seedling and embryonic phenotypes have identified two additional genes coding for sterol biosynthesis enzymes: CEPHALOPOD (CPH), a C-24 sterol methyl transferase, and HYDRA1 (HYD1), a sterol C-8,7 isomerase. We describe genetic interactions between cph , hyd1 and fk , and studies with 15-azasterol, an inhibitor of sterol C-14 reductase. Our experiments reveal that FK and HYD1 act sequentially, whereas CPH acts independently of these genes to produce essential sterols. Similar experiments indicate that the BR biosynthesis gene DWF1 acts independently of FK , whereas BR receptor gene BRI1 acts downstream of FK to promote post-embryonic growth. We found embryonic patterning defects in cph mutants and describe a GC-MS analysis of cph tissues which suggests that steroid molecules in addition to BRs play critical roles during plant embryogenesis. Taken together, our results imply that the sterol biosynthesis pathway is not a simple linear pathway but a complex network of enzymes that produce essential steroid molecules for plant growth and development.
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| 27. |
- Urrata, M, et al.
(författare)
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Neutron-neutron Intensity Interferometry in E/A = 45 MeV 58Ni + 27Al, 58Ni and 197Au Reactions
- 2000
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Ingår i: Physical Review C. Nuclear Physics. - : American Institute of Physics (AIP). - 0556-2813 .- 1089-490X. ; 62
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Tidskriftsartikel (refereegranskat)abstract
- Small angle neutron-neutron correlations have been measured for the E/A=45 MeV 58Ni+27Al, natNi, and 197Au reactions. Two-neutron correlation functions, both integrated and gated on the total momentum of the neutron pair, have been constructed. In order to explain these data, a fraction of fast "dynamical" emission is needed in addition to slower evaporative emission. The overall emission time scale is shorter for the symmetric system, indicating that the dynamical component is stronger in this case.
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