References of "Motte, Patrick"
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See detailTumoral and choroidal vascularization: differential cellular mechanisms involving plasminogen activator inhibitor type I.
Jost, Maud; Maillard, Catherine ULg; Lecomte, Julie ULg et al

in American Journal of Pathology (2007), 171(4), 1369-80

An adequate balance between serine proteases and their plasminogen activator inhibitor-1 (PAI-1) is critical for pathological angiogenesis. PAI-1 deficiency in mice is associated with impaired choroidal ... [more ▼]

An adequate balance between serine proteases and their plasminogen activator inhibitor-1 (PAI-1) is critical for pathological angiogenesis. PAI-1 deficiency in mice is associated with impaired choroidal neovascularization (CNV) and tumoral angiogenesis. In the present work, we demonstrate unexpected differences in the contribution of bone marrow (BM)-derived cells in these two processes regulated by PAI-1. PAI-1(-/-) mice grafted with BM-derived from wild-type mice were able to support laser-induced CNV formation but not skin carcinoma vascularization. Engraftment of irradiated wild-type mice with PAI-1(-/-) BM prevented CNV formation, demonstrating the crucial role of PAI-1 delivered by BM-derived cells. In contrast, the transient infiltration of tumor transplants by local PAI-1-producing host cells rather than by BM cells was sufficient to rescue tumor growth and angiogenesis in PAI-1-deficient mice. These data identify PAI-1 as a molecular determinant of a local permissive soil for tumor angiogenesis. Altogether, the present study demonstrates that different cellular mechanisms contribute to PAI-1-regulated tumoral and CNV. PAI-1 contributes to BM-dependent choroidal vascularization and to BM-independent tumor growth and angiogenesis. [less ▲]

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See detailGene regulation in Arabidopsis halleri, a model system to understand zinc homeostasis in plants.
Hanikenne, Marc ULg; Talke, Ina N.; Lanz, Christa et al

Conference (2006, December 18)

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See detailInsights into nuclear organization in plants as revealed by the dynamic distribution of Arabidopsis SR splicing factors
Tillemans, Vinciane ULg; Leponce, Isabelle ULg; Rausin, Glwadys ULg et al

in Plant Cell (2006), 18(11), 3218-3234

Serine/arginine-rich (SR) proteins are splicing regulators that share a modular structure consisting of one or two N-terminal RNA recognition motif domains and a C-terminal RS-rich domain. We investigated ... [more ▼]

Serine/arginine-rich (SR) proteins are splicing regulators that share a modular structure consisting of one or two N-terminal RNA recognition motif domains and a C-terminal RS-rich domain. We investigated the dynamic localization of the Arabidopsis thaliana SR protein RSZp22, which, as we showed previously, distributes in predominant speckle-like structures and in the nucleolus. To determine the role of RSZp22 diverse domains in its nucleolar distribution, we investigated the subnuclear localization of domain-deleted mutant proteins. Our results suggest that the nucleolar localization of RSZp22 does not depend on a single targeting signal but likely involves different domains/motifs. Photobleaching experiments demonstrated the unrestricted dynamics of RSZp22 between nuclear compartments. Selective inhibitor experiments of ongoing cellular phosphorylation influenced the rates of exchange of RSZp22 between the different nuclear territories, indicating that SR protein mobility is dependent on the phosphorylation state of the cell. Furthermore, based on a leptomycin B- and fluorescence loss in photobleaching-based sensitive assay, we suggest that RSZp22 is a nucleocytoplasmic shuttling protein. Finally, with electron microscopy, we confirmed that RSp31, a plant-specific SR protein, is dynamically distributed in nucleolar cap-like structures upon phosphorylation inhibition. Our findings emphasize the high mobility of Arabidopsis SR splicing factors and provide insights into the dynamic relationships between the different nuclear compartments. [less ▲]

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See detailExpression of the somatolactin beta gene during zebrafish embryonic development
Lopez, Mauricio; Nica, G.; Motte, Patrick ULg et al

in Gene Expression Patterns (2006), 6(2), 156-161

Somatolactin (Sl) is a pituitary hormone closely related to prolactin (Prl) and growth hormone that was until now only found in various fish species. We isolated the cDNA coding for zebrafish Sl beta and ... [more ▼]

Somatolactin (Sl) is a pituitary hormone closely related to prolactin (Prl) and growth hormone that was until now only found in various fish species. We isolated the cDNA coding for zebrafish Sl beta and we identified the gene encoding this hormone. We also obtained a 1 kb genomic fragment corresponding to the sl beta upstream promoter region. Furthermore, the sl beta expression pattern was examined during zebrafish embryogenesis using whole-mount in situ hybridization. Sl beta mRNA is first detected in a single cell at the anterior border of the neural plate starting at 23 h post fertilization (hpf). Sl beta-expressing cells also express the transcription factor pit1 and are located close to prl-expressing cells. Using combined fluorescent in situ hybridization, we show that sl beta- and prl-expressing cells are clearly distinct at 29 hpf. Starting at 30 hpf, the number of sl beta positive cells increases and their location becomes more clearly distinct from lactotrope cells, in a more posterior position. At later stages (48 hpf), sl beta expression was observed posterior to growth hormone expression, again in a distinct cell type. We show that zebrafish mutants aal, as well as mutants in the pit1 gene, are deficient in sl beta expression. In conclusion, sl beta expression defines a new, additional cell type in zebrafish pituitary that depends on pit1 and aal for its differentiation. (C) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailPlasminogen activator inhibitor type I (PAI-1) controls bone marrow-dependent and independent vascularization
Jost, M.; Maillard, Catherine ULg; Lambert, Vincent ULg et al

in Acta Clinica Belgica (2006), 61(2, MAR-APR), 87

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See detailFunctional distribution and dynamics of Arabidopsis SR splicing factors in living plant cells
Tillemans, Vinciane ULg; Dispa, Laurence ULg; Remacle, Claire ULg et al

in Plant Journal (The) (2005), 41(4), 567-582

Serine/arginine-rich (SR) proteins constitute an important class of splicing regulators in higher eukaryotes that share a modular structure consisting of one or two N-terminal RNA recognition motif (RRM ... [more ▼]

Serine/arginine-rich (SR) proteins constitute an important class of splicing regulators in higher eukaryotes that share a modular structure consisting of one or two N-terminal RNA recognition motif (RRM) domains and a C-terminal RS-rich domain. Herein, we have investigated the in vivo functional distribution of Arabidopsis SR factors. Agrobacterium-mediated transient transformation revealed nuclear speckled distribution and the overall colocalization of fluorescent protein (FP)-tagged SR factors in both tobacco and Arabidopsis cells. Their overall colocalization in larger nucleoplasmic domains was further observed after transcriptional and phosphorylation/dephosphorylation inhibition, indicating a close functional association between SR factors, independent of their phosphorylation state. Furthermore, we demonstrated in vivo the conserved role of the RS and RRM domains in the efficient targeting of Arabidopsis SR proteins to nuclear speckles by using a series of structural domain-deleted mutants of atRSp31 and atRSZp22. We suggest additional roles of RS domain such as the shuttling of atRSZp22 between nucleoplasm and nucleolus through its phosphorylation level. The coexpression of deletion mutants with wild-type SR proteins revealed potential complex associations between them. Fluorescence recovery after photobleaching demonstrated similar dynamic properties of SR factors in both tobacco transiently expressing cells and Arabidopsis transgenics. Cell cycle phase-dependent organization of FP-tagged SR proteins was observed in living tobacco BY-2 cells. We showed that atRSp31 is degraded at metaphase by fluorescence quantification. SR proteins also localized within small foci at anaphase. These results demonstrate interesting related features as well as potentially important differences between plant and animal SR proteins. [less ▲]

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See detailsox4b is a key player of pancreatic alpha cell differentiation in zebrafish
Mavropoulos, A.; Devos, Nathalie; Biemar, Frédéric et al

in Developmental Biology (2005), 285(1), 211-23

Pancreas development relies on a network of transcription factors belonging mainly to the Homeodomain and basic Helix-Loop-Helix families. We show in this study that, in zebrafish, sox4, a member of the ... [more ▼]

Pancreas development relies on a network of transcription factors belonging mainly to the Homeodomain and basic Helix-Loop-Helix families. We show in this study that, in zebrafish, sox4, a member of the SRY-like HMG-box (SOX) family, is required for proper endocrine cell differentiation. We found that two genes orthologous to mammalian Sox4 are present in zebrafish and that only one of them, sox4b, is strongly expressed in the pancreatic anlage. Transcripts of sox4b were detected in mid-trunk endoderm from the 5-somite stage, well before the onset of expression of the early pancreatic gene pdx-1. Furthermore, by fluorescent double in situ hybridization, we found that expression of sox4b is mostly restricted to precursors of the endocrine compartment. This expression is not maintained in differentiated cells although transient expression can be detected in alpha cells and some beta cells. That sox4b-expressing cells belong to the endocrine lineage is further illustrated by their absence from the pancreata of slow-muscle-omitted mutant embryos, which specifically lack all early endocrine markers while retaining expression of exocrine markers. The involvement of sox4b in cell differentiation is suggested firstly by its up-regulation in mind bomb mutant embryos displaying accelerated pancreatic cell differentiation. In addition, sox4b knock-down leads to a drastic reduction in glucagon expression, while other pancreatic markers including insulin, somatostatin, and trypsin are not significantly affected. This disruption of alpha cell differentiation is due to down-regulation of the homeobox arx gene specifically in the pancreas. Taken together, these data demonstrate that, in zebrafish, sox4b is expressed transiently during endocrine cell differentiation and plays a crucial role in the generation of alpha endocrine cells. [less ▲]

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See detailA mitochondrial half-size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii
Hanikenne, Marc ULg; Motte, Patrick ULg; Wu, Madeline C.S. et al

in Plant Cell and Environment (2005), 28(7), 863-873

Five cadmium-sensitive insertional mutants, all affected at the CDS1 ('cadmium-sensitive 1') locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe ... [more ▼]

Five cadmium-sensitive insertional mutants, all affected at the CDS1 ('cadmium-sensitive 1') locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half-size ABC transporters. This subfamily includes both vacuolar HMT-type proteins transporting phytochelatin-cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM-type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Delta sphmt1 cadmium-sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT-type transporter, the cds1 mutant accumulates a high amount of phytochelatin-cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of 'free' iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM-like transporter plays a major role in tolerance to cadmium. [less ▲]

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See detailADAMTS-2, a metalloproteinase containing a disintegrin domain and thrombospondin type I repeats, a new regulator of angiogenesis
Dubail, Johanne ULg; Kesteloot, Frédéric ULg; Motte, Patrick ULg et al

in Journal of Vascular Research (2005), 42(Suppl. 2), 76

Enzymes of the ADAMTS family are closely related to MMPs and ADAMs. They further contain specific domains, such as the “ThromboSpondin type I” (TSP1) repeats able to strongly repress angiogenesis. The ... [more ▼]

Enzymes of the ADAMTS family are closely related to MMPs and ADAMs. They further contain specific domains, such as the “ThromboSpondin type I” (TSP1) repeats able to strongly repress angiogenesis. The primary function of ADAMTS-2 is to process procollagen type I, II, III and V into mature molecules by excising the amino-propeptide. We further hypothesized that it could modulate angiogenesis through its TSP1 repeats. Recombinant ADAMTS-2 induced morphological changes in HUVEC and HMEC cultured on gelatin, collagen and fibronectin. It also significantly reduced their proliferation, attachment and spreading. Similar effects were observed when using inactive ADAMTS-2 mutated at the Zn++-binding catalytic site. ADAMTS-2 did not alter the initial steps of formation of capillary-like structures by HUVEC in vitro. However, these structures appeared more rapidly disrupted in presence of ADAMTS-2 than in control conditions. Immunostaining with monoclonal antibodies against ADAMTS-2 indicate that it is tightly immobilized at the endothelial cell surface by an heparin-sensitive binding. With the aim to identify mechanism(s)leading to the modulation of angiogenesis by ADAMTS-2, we investigated various signalling pathways critical for EC. Phosphorylation status of FAK was not altered by ADAMTS-2 while a downregulation of phosphorylation of p42/44 MAPK was observed. Our data suggest that ADAMTS-2 reduces angiogenesis by regulating endothelial cell adhesion and proliferation, and by alteration of the stability of the capillary-like structures. These effects do not seem to be mediated by an integrin-dependent signaling pathway. Choroidal neovascularization induced in TS2+/+ or TS2-/- mice by LASER burns was used as in vivo model. Several genes involved in the healing and angiogenesis processes (fibrillar collagens, VEGF, TGF, CTGF, …) were not differently regulated in TS2+/+ and TS2-/- mice 5 days after the LASER impact. Wound capillaries visualized by confocal microscopy after FITC-conjugated dextran injection, were significantly increased (p<0,05) in TS2-/- mice suggesting an increased angiogenic response in the KO animals. The results obtained in in vivo and in vitro models indicate that ADAMTS-2 is involved in the control of angiogenesis. Additional investigations are being performed to determine which domain(s) of the molecule is (are) antiangiogenic and to identify the mechanism(s) underlying this regulatory function. [less ▲]

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See detailNuclear bodies and compartmentalization of pre-mRNA splicing factors in higher plants
Docquier, Sarah; Tillemans, Vinciane ULg; Deltour, Roger et al

in Chromosoma (2004), 112(5), 255-266

We studied the fine structural organization of nuclear bodies in the root meristem during germination of maize and Arabidopsis thaliana using electron microscopy (EM). Cajal bodies (CBs) were observed in ... [more ▼]

We studied the fine structural organization of nuclear bodies in the root meristem during germination of maize and Arabidopsis thaliana using electron microscopy (EM). Cajal bodies (CBs) were observed in quiescent embryos as well as germinating cells in both species. The number and distribution of CBs were investigated. To characterize the nuclear splicing domains, immunofluorescence labelling with antibodies against splicing factors (U2B" and m3G-snRNAs) and in situ hybridisation (with U1/U6 antisense probes) were performed combined with confocal microscopy. Antibodies specific to the Arabidopsis SR splicing factor atRSp31 were produced. AtRSp31 was detected in quiescent nuclei and in germinating cells. This study revealed an unexpected nuclear speckled organization of atRSp31 in root epidermal cells where micro clusters of interchromatin granules were also observed by EM. Therefore, we examined the distribution of green fluorescent protein (GFP)-tagged atRSp31 in living cells after Agrobacterium-mediated transient expression. When expressed transiently, atRSp31-GFP exhibited a speckled distribution in leaf cells. Treatments with -amanitin, okadaic acid, staurosporine or heat-shock induced the speckles to reorganize. Furthermore, we have generated stable Arabidopsis transgenics expressing atRSp31-GFP. The distribution of the fusion protein was identical to the endogenous atRSp31. Three-dimensional time-lapse confocal microscopy showed that speckles were highly dynamic domains over time. [less ▲]

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See detailEffect of ADAMTS-2, a metalloproteinase containing a disintegrin domain and thrombospondin type I repeats, during angiogenesis in vitro and in vivo
Dubail, Johanne ULg; Kesteloot, Frédéric ULg; Motte, Patrick ULg et al

in Angiogenesis (2004), 7(2), 172

Formation of new blood vessels (angiogenesis) is a key step during the development of various pathologies, including cancer. Enzymes of the ADAMTS family are closely related to MMPs and ADAMs. They ... [more ▼]

Formation of new blood vessels (angiogenesis) is a key step during the development of various pathologies, including cancer. Enzymes of the ADAMTS family are closely related to MMPs and ADAMs. They further contain specific domains, such as the ‘‘Thrombospondin type I’’ (TSP1) repeats, that are able to strongly repress angiogenesis, as described for thrombospondin-1 and -2, and for ADAMTS-1 and -8. The primary function of ADAMTS-2 is to process collagen type I, II and III precursors into mature molecules by excising the aminopropeptide. We further hypothesized that it could modulate angiogenesis through its TSP1 repeats. This hypothesis was investigated using different in vitro experimental models of angiogenesis. Recombinant ADAMTS-2 induced morphological changes in human umbilical vein endothelial cells (HUVEC) and human microvessel endothelial cells (HMEC), and significantly reduced their proliferation, attachment and spreading. Similar effects were observed when using inactive ADAMTS-2 mutated at the Zn2+-binding catalytic site. ADAMTS-2 did not alter the initial steps of formation of capillary-like structures by HUVEC in vitro. However, these structures appeared much less stable and were more rapidly disrupted in presence of ADAMTS-2 than in control conditions. ADAMTS-2 was also tested in an ex vivo angiogenesis model using aortic rings from rats and mice, wild type or KO for ADAMTS-2. Outgrowth of capillaries was slightly increased from aortas of ADAMTS-2 KO mice (TS2-/-) as compared to aortas from control animals (TS2+/+), while addition of full size recombinant ADAMTS-2 reduced the formation of capillary structures from rat aortas, suggesting its anti-angiogenic activity. Choroidal neovascularization induced in TS2+/+ or TS2-/- mice by LASER burns was used as in vivo model to confirm the in vitro and ex vivo results. Several genes involved in the healing and angiogenesis processes (fibrillar collagens, VEGF, TGF-beta and CTGF) were not differently regulated in TS2+/+ and TS2-/- mice at 5 days. [less ▲]

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See detailDopamine activates noradrenergic receptors in the preoptic area
Cornil, Charlotte ULg; Balthazart, Jacques ULg; Motte, Patrick ULg et al

in Journal of Neuroscience (2002), 22(21), 9320-9330

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate ... [more ▼]

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate that mediates the behavioral and endocrine effects of DA is poorly understood. Intracellular recordings showed that 100 muM DA hyperpolarizes most neurons in the medial preoptic nucleus (80%) by a direct effect, but depolarizes a few others (10%). DA-induced hyperpolarizations were not blocked by D1 or D2 antagonists (SCH-23390 and sulpiride). Extracellular recordings confirmed that DA inhibits the firing of most cells (52%) but excites a few others (24%). These effects also were not affected by DA antagonists (SCH-23390 and sulpiride) but were blocked by alpha(2)-(yohimbine) and alpha(1)-(prazosin) noradrenergic receptor antagonists, respectively. Two dopamine-beta-hydroxylase (DBH) inhibitors (cysteine and fusaric acid) did not block the DA-induced effects, indicating that DA is not converted into norepinephrine (NE) to produce its effects. The pK(B) of yohimbine for the receptor involved in the DA- and NE-induced inhibitions was similar, indicating that the two monoamines interact with the same receptor. Together, these results demonstrate that the effects of DA in the POA are mediated mostly by the activation of alpha(2) (inhibition) and alpha(1) (excitation) adrenoreceptors. This may explain why DA affects the expression of male sexual behavior through its action in the POA, which contains high densities of alpha(2)-noradrenergic but limited amounts of DA receptors. This study thus clearly demonstrates the existence of a cross talk within CNS catecholaminergic systems between a neurotransmitter and heterologous receptors. [less ▲]

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See detailPLENA and FARINELLI: redundancy and regulatory interactions between two Antirrhinum MADS-box factors controlling flower development.
Davies, B.; Motte, Patrick ULg; Keck, E. et al

in EMBO Journal (1999), 18(14), 4023-34

We report the discovery of an Antirrhinum MADS-box gene, FARINELLI (FAR), and the isolation of far mutants by a reverse genetic screen. Despite striking similarities between FAR and the class C MADS-box ... [more ▼]

We report the discovery of an Antirrhinum MADS-box gene, FARINELLI (FAR), and the isolation of far mutants by a reverse genetic screen. Despite striking similarities between FAR and the class C MADS-box gene PLENA (PLE), the phenotypes of their respective mutants are dramatically different. Unlike ple mutants, which show homeotic conversion of reproductive organs to perianth organs and a loss of floral determinacy, far mutants have normal flowers which are partially male-sterile. Expression studies of PLE and FAR, in wild-type and mutant backgrounds, show complex interactions between the two genes. Double mutant analysis reveals an unexpected, redundant negative control over the B-function MADS-box genes. This feature of the two Antirrhinum C-function-like genes is markedly different from the control of the inner boundary of the B-function expression domain in Arabidopsis, and we propose and discuss a model to account for these differences. The difference in phenotypes of mutants in two highly related genes illustrates the importance of the position within the regulatory network in determining gene function. [less ▲]

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See detailSTYLOSA and FISTULATA: regulatory components of the homeotic control of Antirrhinum floral organogenesis.
Motte, Patrick ULg; Saedler, H.; Schwarz-Sommer, Z.

in Development (1998), 125(1), 71-84

The identity and developmental pattern of the four organ types constituting the flower is governed by three developmental functions, A, B and C, which are defined by homeotic genes and established in two ... [more ▼]

The identity and developmental pattern of the four organ types constituting the flower is governed by three developmental functions, A, B and C, which are defined by homeotic genes and established in two adjacent whorls. In this report we morphologically and genetically characterise mutants of two genes, STYLOSA (STY) and FISTULATA (FIS) which control floral homeotic meristem- and organ-identity genes and developmental events in all floral whorls. The morphology of the reproductive organs in the first and second whorls of sty fis double mutant flowers indicate that the two genes are part of the mechanism to prevent ectopic expression of the C-function in the perianth of wild-type flowers. This is verified by the detection of the expansion of the expression domain of the class C gene PLENA (PLE) towards the perianth. Interestingly, in the second whorl of sty and fis mutants, spatial differences in stamenoid features and in the pattern of ectopic expression of the PLE gene were observed. This suggests that, with respect to the negative control of PLE, petals are composed of two regions, a lateral and a central one. Mutation in ple is epistatic to most of the sty/fis-related homeotic defects. PLE, however, is not the primary target of STY/FIS control, because dramatic reduction of expression of FIMBRIATA, meristem identity genes (FLORICAULA and SQUAMOSA) and of class B organ identity genes (GLOBOSA) occur before changes in the PLE expression pattern. We propose that STY/FIS are hierarchically high-ranking genes that control cadastral component(s) of the A-function. SQUAMOSA as a potential target of this control is discussed. Retarded growth of second whorl organs, subdivision of third whorl primordia and the failure to initiate them in sty/fis mutants may be mediated by the FIMBRIATA gene. [less ▲]

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See detailDivergence of function and regulation of class B floral organ identity genes.
Samach, A.; Kohalmi, S. E.; Motte, Patrick ULg et al

in Plant Cell (1997), 9(4), 559-70

Regulatory mechanisms controlling basic aspects of floral morphogenesis seem to be highly conserved among plant species. The class B organ identity genes, which are required to establish the identity of ... [more ▼]

Regulatory mechanisms controlling basic aspects of floral morphogenesis seem to be highly conserved among plant species. The class B organ identity genes, which are required to establish the identity of organs in the second (petals) and third (stamens) floral whorls, are a good example of such conservation. This work compares the function of two similar class B genes in the same genetic background. The DEFICIENS (DEF) gene from Antirrhinum, including its promoter, was transformed into Arabidopsis and compared in function and expression with the Arabidopsis class B genes APETALA3 (AP3) and PISTILLATA (PI). The DEF gene was expressed in the second, third, and fourth whorls, as was PI. Functionally, DEF could replace AP3 in making petals and stamens. The DEF gene's AP3-like function and PI-like expression caused transformation of fourth-whorl carpels to stamens. Like AP3, all aspects of DEF function in Arabidopsis required a functional PI protein. Surprisingly, DEF could not replace the AP3 protein in properly maintaining AP3 transcripts (autoregulation). Our data allow us to revise the current model for class B autoregulation and propose a hypothesis for the evolution of class B gene expression in dicotyledonous plants. [less ▲]

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See detailFunctional analysis of the Antirrhinum floral homeotic DEFICIENS gene in vivo and in vitro by using a temperature-sensitive mutant.
Zachgo, S.; Silva, E de A; Motte, Patrick ULg et al

in Development (1995), 121(9), 2861-75

Flowers of the temperature-sensitive DEFICIENS (DEF) mutant, def-101, display sepaloid petals and carpelloid stamens when grown at 26 degrees C, the non-permissive temperature. In contrast, when ... [more ▼]

Flowers of the temperature-sensitive DEFICIENS (DEF) mutant, def-101, display sepaloid petals and carpelloid stamens when grown at 26 degrees C, the non-permissive temperature. In contrast, when cultivated under permissive conditions at 15 degrees C, the morphology of def-101 flowers resembles that of the wild type. Temperature shift experiments during early and late phases of flower development revealed that second and third whorl organ development is differentially sensitive to changes in DEF expression. In addition, early DEF expression seems to control the spatially correct initiation of fourth whorl organ development. Reduction of the def-101 gene dosage differentially affects organogenesis in adjacent whorls: at the lower temperature development of petals in the second whorl and initiation of carpels in the centre of the flower is not affected while third whorl organogenesis follows the mutant (carpelloid) pattern. The possible contribution of accessory factors to organ-specific DEF functions is discussed. In situ analyses of mRNA and protein expression patterns during def-101 flower development at 15 degrees C and at 26 degrees C support previously proposed combinatorial regulatory interactions between the MADS-box proteins DEF and GLOBOSA (GLO), and provide evidence that the autoregulatory control of DEF and GLO expression by the DEF/GLO heterodimer starts after initiation of all organ primordia. Immunolocalisation revealed that both proteins are located in the nucleus. Interestingly, higher growth temperature affects the stability of both the DEF-101 and GLO proteins in vivo. In vitro DNA binding studies suggest that the temperature sensitivity of the def-101 mutant is due to an altered heterodimerisation/DNA-binding capability of the DEF-101 protein, conditioned by the deletion of one amino acid within the K-box, a protein region thought to be involved in protein-protein interaction. In addition, we introduce a mutant allele of GLO, glo-confusa, where insertion of one amino acid impairs the hydrophobic carboxy-terminal region of the MADS-box, but which confers no strong phenotypic changes to the flower. The strong mutant phenotype of flowers of def-101/glo-conf double mutants when grown in the cold represents genetic evidence for heterodimerisation between DEF and GLO in vivo. The potential to dissect structural and functional domains of MADS-box transcription factors is discussed. [less ▲]

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See detailFIL2, an extracellular Leucine-Rich Repeat protein, is specifically expressed in Antirrhinum flowers.
Steinmayr, M.; Motte, Patrick ULg; Sommer, H. et al

in Plant Journal (The) (1994), 5(4), 459-67

The expression of the Antirrhinum gene FIL2 is affected in mutants of the homeotic transcription factor DEFICIENS. Northern and Western blot analyses showed that FIL2 in wild-type Antirrhinum flowers is ... [more ▼]

The expression of the Antirrhinum gene FIL2 is affected in mutants of the homeotic transcription factor DEFICIENS. Northern and Western blot analyses showed that FIL2 in wild-type Antirrhinum flowers is expressed weakly in the petals and more abundantly in the reproductive organs; the gene is active in the filaments and anthers of stamens, and in the stigma and transmitting tissue of the carpels. The FIL2 protein is glycosylated with high mannose type glycan chains and is located in the middle lamella of the extracellular matrix. The amino acid sequence contains 10 tandem repeats, the composition of which is similar to the Leucine-Rich Repeat (LRR) motif found in mammals, Drosophila and yeast. The possibility that FIL2 might be a component of a cellular signalling mechanism, involving LRR-mediated protein-protein interactions is discussed. [less ▲]

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See detailGLOBOSA: a homeotic gene which interacts with DEFICIENS in the control of Antirrhinum floral organogenesis.
Trobner, W.; Ramirez, L.; Motte, Patrick ULg et al

in EMBO Journal (1992), 11(13), 4693-704

GLOBOSA (GLO) is a homeotic gene whose mutants show sepaloid petals and carpelloid stamens. The similarity of Glo mutants to those of the DEFICIENS (DEFA) gene suggests that the two genes have comparable ... [more ▼]

GLOBOSA (GLO) is a homeotic gene whose mutants show sepaloid petals and carpelloid stamens. The similarity of Glo mutants to those of the DEFICIENS (DEFA) gene suggests that the two genes have comparable functions in floral morphogenesis. The GLO cDNA has been cloned by virtue of its homology to the MADS-box, a conserved DNA-binding domain also contained in the DEFA gene. We have determined the structure of the wild type GLO gene as well as of several glo mutant alleles which contain transposable element insertions responsible for somatic and germinal instability of Glo mutants. Analyses of the temporal and spatial expression patterns of the DEFA and GLO genes during development of wild type flowers and in flowers of various stable and unstable defA and glo alleles indicate independent induction of DEFA and GLO transcription. In contrast, organ-specific up-regulation of the two genes in petals and stamens depends on expression of both DEFA and GLO. In vitro DNA-binding studies were used to demonstrate that the DEFA and GLO proteins specifically bind, as a heterodimer, to motifs in the promoters of both genes. A model is presented which proposes both combinatorial and cross-regulatory interactions between the DEFA and GLO genes during petal and stamen organogenesis in the second and third whorls of the flower. The function of the two genes controlling determinate growth of the floral meristem is also discussed. [less ▲]

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See detailThree-dimensional electron microscopy of ribosomal chromatin in two higher plants: a cytochemical, immunocytochemical, and in situ hybridization approach.
Motte, Patrick ULg; Loppes, Roland ULg; Menager, M. et al

in Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society (1991), 39(11), 1495-506

We report the 3-D arrangement of DNA within the nucleolar subcomponents from two evolutionary distant higher plants, Zea mays and Sinapis alba. These species are particularly convenient to study the ... [more ▼]

We report the 3-D arrangement of DNA within the nucleolar subcomponents from two evolutionary distant higher plants, Zea mays and Sinapis alba. These species are particularly convenient to study the spatial organization of plant intranucleolar DNA, since their nucleoli have been previously reconstructed in 3-D from serial ultra-thin sections. We used the osmium ammine-B complex (a specific DNA stain) on thick sections of Lowicryl-embedded root fragments. Immunocytochemical techniques using anti-DNA antibodies and rDNA/rDNA in situ hybridization were also applied on ultra-thin sections. We showed on tilted images that the OA-B stains DNA throughout the whole thickness of the section. In addition, very low quantities of cytoplasmic DNA were stained by this complex, which is now the best DNA stain used in electron microscopy. Within the nucleoli the DNA was localized in the fibrillar centers, where large clumps of dense chromatin were also visible. In the two plant species intranucleolar chromatin forms a complex network with strands partially linked to chromosomal nucleolar-organizing regions identified by in situ hybridization. This study describes for the first time the spatial arrangement of the intranucleolar chromatin in nucleoli of higher plants using high-resolution techniques. [less ▲]

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