Papers by Christian Dumas
Journal of Cell Science, 1989
Recently developed techniques for the isolation of sex cells of flowering plants represent an imp... more Recently developed techniques for the isolation of sex cells of flowering plants represent an important first step toward eventual detailed cytological and biochemical analyses and experimental manipulations of higher plant gametes that was not previously possible. In the present investigation we have analysed a population of isolated viable male gametes from the standpoint of qualitative and quantitative ultrastructure in order to elucidate the process of double fertilization in angiosperms. The vast majority of the Zea mays sperm cells were found to be structurally intact spherical cells. Morphometric analysis of 400 isolated sperm cells indicates that the average cell is 7.66 μm in diameter, has volume and surface areas of 235.3μm3 and 184.3μm2, respectively, and contains a variously shaped, often curved nucleus, which occupies 38.5% of the cell volume. Other cell constituents and their relative volumes (expressed as percentages of the protoplasm) included in the analysis are: va...
Proceedings of the National Academy of Sciences, Jan 22, 2013
The COP9 (Constitutive photomorphogenesis 9) signalosome (CSN), a large multiprotein complex that... more The COP9 (Constitutive photomorphogenesis 9) signalosome (CSN), a large multiprotein complex that resembles the 19S lid of the 26S proteasome, plays a central role in the regulation of the E3-cullin RING ubiquitin ligases (CRLs). The catalytic activity of the CSN complex, carried by subunit 5 (CSN5/Jab1), resides in the deneddylation of the CRLs that is the hydrolysis of the cullin-neural precursor cell expressed developmentally downregulated gene 8 (Nedd8) isopeptide bond. Whereas CSN-dependent CSN5 ...
Acta Agronomica Hungarica, 1998
Planta, 1987
The quality of Cucurbita pepo L. pollen was studied using field pollinations and the fluorochroma... more The quality of Cucurbita pepo L. pollen was studied using field pollinations and the fluorochromatic-reaction test. The extreme sensitivity of this pollen to dehydration and ageing is demonstrated. Controlled stress applied to mature pollen leads to the development of seedless fruits. Molecular signals seem to be involved in the induction of this parthenocarpy. These results indicate the existence of distinct sequences involved in the completion of the fertilization program of pollen. With pollen altered by stress, the fertilization process may be stopped at different stages of its completion. We bring evidence that Cucurbita pepo plants have developed special adaptations in order to compensate for the poor viability of their pollen.
Journal of Biological Chemistry, 2000
Within the large Brassica S gene family, SLG (S locus glycoprotein) and SRK (S locus receptor kin... more Within the large Brassica S gene family, SLG (S locus glycoprotein) and SRK (S locus receptor kinase) participate to the control of pollen-stigma self-incompatibility. In the self-compatible species maize, S gene family members are predominantly expressed in vegetative organs but are also expressed to a lesser extent in the stigma (silk). To determine if the expression of any S gene family members correlates with female receptivity, we analyzed their expression in developing maize silks. We show that a large family of maize S transcripts is expressed in developing silks. Surprisingly, we isolated a cDNA complementary to a large portion of the antisense strand of the maize receptor kinase S domain. Rapid amplification of cDNA ends (RACE)-polymerase chain reaction, RNase protection, and Northern hybridization with single-stranded riboprobes confirmed that natural antisense S transcripts exist in leaves and seedling shoots and in all sexual tissues tested except mature pollen. These natural antisense S transcripts co-exist with several less abundant sense S transcripts. The accumulation of sense and antisense S transcripts is differentially regulated during pollen and silk development. Thus, these results support a role for S gene family members in sexual tissue development and/or compatible pollination and reveal a new level of complexity in the regulation and function of the S gene family in maize.
Journal of Biological Chemistry, 2000
The nef gene is required for optimal viral spread of human and simian immunodeficiency viruses. H... more The nef gene is required for optimal viral spread of human and simian immunodeficiency viruses. However, the molecular mechanisms underlying the action of the Nef proteins may not be identical for all viral families. Here we investigate the interaction between the Nef protein of human and simian immunodeficiency viruses and SH3 domains from Src family kinases. Using the yeast two-hybrid system and immunoblotting we show that, in contrast to HIV-1 Nef, SIV and HIV-2 Nef poorly interact with Hck SH3 but bind to Src and Fyn SH3 domains. The molecular basis of these differences in SH3 targeting was revealed by sequence analysis and homology modeling of the putative SH3-Nef structures. Three amino acids (Trp-113, Thr-117, and Gln-118) that localize in a "hydrophobic pocket" implicated in SH3 binding of HIV-1 Nef, are systematically substituted in SIV/HIV-2 alleles (by Tyr, Glu, and Glu, respectively). We demonstrate that site-directed mutagenesis of these residues in SIV mac239 Nef suffices to restore Hck SH3 binding and co-immunoprecipitation with full-length Hck from transfected cells. Our findings identify fundamental mechanistic differences in targeting of Src family kinases by HIV and SIV Nef. The herein described mechanism of SH3 selection by Nef via a "pocket" proximal to the canonical proline-rich motif may be a common feature for SH3 recognition by their natural ligands.
Canadian Journal of Botany, 1975
Teratological floral parts corresponding to petals and stamens capped by stigmatoid lobes are fou... more Teratological floral parts corresponding to petals and stamens capped by stigmatoid lobes are found in double male flowers. These abnormal structures are quite comparable with normal stigmas in their morphology, histology, and histochemistry. Like the stigmas, the stigmatoid formations present a glandular activity and release an essentially hydrophobic exsudate. Fundamental differences between normal stigmas and stigmatoid formations cannot be demonstrated by the methods used.
Nature, 2001
The Seeker, the non-profit Citrus Research and Development Foundation, desires proposals for comp... more The Seeker, the non-profit Citrus Research and Development Foundation, desires proposals for compo
... The Seeker desires an improved synthesis of a specific nucleoside analogue. Specific details are p
... Correspondence to: Thierry Gaude Correspondence ...
The Plant Cell …, 1997
Martine Pastuglia,a Véronique Ruffio-Châble,b Valérie Delorme,all Thierry Gaude,a Christian Dumas... more Martine Pastuglia,a Véronique Ruffio-Châble,b Valérie Delorme,all Thierry Gaude,a Christian Dumas,a and J. Mark Cocka12 aReproduction et Développement des Plantes, UMR 9938 CNRS-INRA-ENSL, Ecole Normale Supérieure de Lyon, 46 allée d'ltalie, 69364 Lyon ...
Planta, 2000
Abstract. Egg cells were analysed cytologically during the female receptivity period in maize (Ze... more Abstract. Egg cells were analysed cytologically during the female receptivity period in maize (Zea mays L., line A 188). Three classes of egg cell were distinguished: type A ± small, non-vacuolated cells with a central nucleus; type B ± larger cells with small vacuoles surrounding the ...
Journal of bioenergetics and biomembranes, 2000
Three-dimensional structures are known from X-ray studies of the nucleoside diphosphate (NDP) kin... more Three-dimensional structures are known from X-ray studies of the nucleoside diphosphate (NDP) kinase of many organisms from bacteria to human. All NDP kinases have subunits of about 150 residues with a very similar fold based on the alphabeta sandwich or ferredoxin fold. This fold is found in many nucleotide or polynucleotide-binding proteins with no sequence relationship to NDP kinase. This common fold is augmented here with specific features: a surface alpha-helix hairpin, the Kpn loop, and the C-terminal extension. The alpha-helix hairpin and Kpn loop make up the nucleotide binding site, which is unique to NDP kinase and different from that of other kinases or ATPases. The Kpn loop and the C-terminal extension are also involved in the quaternary structure. Whereas all known eukaryotic NDP kinases, including mitochondral enzymes, are hexamers, some bacterial enzymes are tetramers. However, hexameric and tetrameric NDP kinases are built from the same dimer. The structural environme...
Genetics, 2001
The S locus receptor kinase and the S locus glycoproteins are encoded by genes located at the S l... more The S locus receptor kinase and the S locus glycoproteins are encoded by genes located at the S locus, which controls the self-incompatibility response in Brassica. In class II self-incompatibility haplotypes, S locus glycoproteins can be encoded by two different genes, SLGA and SLGB. In this study, we analyzed the sequences of these genes in several independently isolated plants, all of which carry the same S haplotype (S(2)). Two groups of S(2) haplotypes could be distinguished depending on whether SRK was associated with SLGA or SLGB. Surprisingly, SRK alleles from the two groups could be distinguished at the sequence level, suggesting that recombination rarely occurs between haplotypes of the two groups. An analysis of the distribution of polymorphisms along the S domain of SRK showed that hypervariable domains I and II tend to be conserved within haplotypes but to be highly variable between haplotypes. This is consistent with these domains playing a role in the determination of...
Plant molecular biology, 2001
The male component of the self-incompatibility response in Brassica has recently been shown to be... more The male component of the self-incompatibility response in Brassica has recently been shown to be encoded by the S locus cysteine-rich gene (SCR). SCR is related, at the sequence level, to the pollen coat protein (PCP) gene family whose members encode small, cysteine-rich proteins located in the proteo-lipidic surface layer (tryphine) of Brassica pollen grains. Here we show that the Arabidopsis genome includes two large gene families with homology to SCR and to the PCP gene family, respectively. These genes are poorly predicted by gene-identification algorithms and, with few exceptions, have been missed in previous annotations. Based on sequence comparison and an analysis of the expression patterns of several members of each family, we discuss the possible functions of these genes. In particular, we consider the possibility that SCR-related genes in Arabidopsis may encode ligands for the S gene family of receptor-like kinases in this species.
Structure (London, England : 1993), Jan 15, 1997
Human immunodeficiency virus (HIV) Nef protein accelerates virulent progression of acquired immun... more Human immunodeficiency virus (HIV) Nef protein accelerates virulent progression of acquired immunodeficiency syndrome (AIDS) by its interaction with specific cellular proteins involved in signal transduction and host cell activation. Nef has been shown to bind specifically to a subset of the Src family of kinases. The structures of free Nef and Nef bound to Src homology region 3 (SH3) domain are important for the elucidation of how the affinity and specificity for the Src kinase family SH3 domains are achieved, and also for the development of potential drugs and vaccines against AIDS. We have determined the crystal structures of the conserved core of HIV-1 Nef protein alone and in complex with the wild-type SH3 domain of the p59fyn protein tyrosine kinase (Fyn), at 3.0 A resolution. Comparison of the bound and unbound Nef structures revealed that a proline-rich motif (Pro-x-x-Pro), which is implicated in SH3 binding, is partially disordered in the absence of the binding partner; thi...
Acta Crystallographica Section D-biological Crystallography, 2004
Advances in Botanical Research, 1998
... Gametes, Fertilization and Early Embryogenesis in Flowering Plants CHRISTIAN DUMAS,FREDERIC B... more ... Gametes, Fertilization and Early Embryogenesis in Flowering Plants CHRISTIAN DUMAS,FREDERIC BERGER, JEAN-EMMANUEL FAURE and ELIZABETH MATTHYS-ROCHON Ecole Normale Supkrieure de Lyon, UMR 9938 CNRS-ha-ENS, 46 Allke d'ltalie, F-69364 LYON ...
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Papers by Christian Dumas