PLENA and FARINELLI: redundancy and regulatory interactions between two Antirrhinum MADS-box factors controlling flower development.
; Motte, Patrick ; 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 ▲]Detailed reference viewed: 4 (0 ULg)
STYLOSA and FISTULATA: regulatory components of the homeotic control of Antirrhinum floral organogenesis.
Motte, Patrick ; ;
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 ▲]Detailed reference viewed: 9 (1 ULg)
Divergence of function and regulation of class B floral organ identity genes.
; ; Motte, Patrick 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 ▲]Detailed reference viewed: 4 (0 ULg)
Functional analysis of the Antirrhinum floral homeotic DEFICIENS gene in vivo and in vitro by using a temperature-sensitive mutant.
; ; Motte, Patrick 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 ▲]Detailed reference viewed: 10 (2 ULg)
FIL2, an extracellular Leucine-Rich Repeat protein, is specifically expressed in Antirrhinum flowers.
; Motte, Patrick ; 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 ▲]Detailed reference viewed: 8 (0 ULg)
GLOBOSA: a homeotic gene which interacts with DEFICIENS in the control of Antirrhinum floral organogenesis.
; ; Motte, Patrick 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 ▲]Detailed reference viewed: 10 (3 ULg)
Three-dimensional electron microscopy of ribosomal chromatin in two higher plants: a cytochemical, immunocytochemical, and in situ hybridization approach.
Motte, Patrick ; Loppes, Roland ; 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 ▲]Detailed reference viewed: 15 (2 ULg)
The Nucleolonema of Plant and Animal Cells: A Comparison
Deltour, Roger ; Motte, Patrick
in Biology of the Cell (1990), 68(1), 5-11
Depending on the author and the animal or plant origin of the material under study, the term "nucleolonema" is used in different contexts and thus indicates nucleolar ultrastructures that are different ... [more ▼]
Depending on the author and the animal or plant origin of the material under study, the term "nucleolonema" is used in different contexts and thus indicates nucleolar ultrastructures that are different. In this paper, we attempt to clarify this state of affairs and to propose a definition for the plant cell nucleolonema. [less ▲]Detailed reference viewed: 14 (1 ULg)