de la structure à la croissance cellulaire - Université Bordeaux 1

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122 M. Bourdon et al. Fig. 2 Molecular and functional analysis of genes involved in the control of endoreduplication during tomato fruit development. (a) Schemed profile of mRNA expression for the four tomato KRP genes. The stages of fruit development are indicated in days post-anthesis. MG: Mature Green. (b) Phenotypic and molecular analysis of tomato CCS52A down-regulated Pro35S: SlCCS52AAS plants. Mature fruits (red ripe stage) were compared with untransformed control
Endoreduplication and Growth of Fleshy Fruits 123 expression peaks during fruit maturation (Bisbis et al. 2006). Using quantitative PCR following reverse transcription (RT-qPCR), we showed that the four tomato KRPs display unique expression profiles during tomato fruit development (Fig. 2a). Interestingly, Solly;KRP4 is mostly expressed during the very early development of the fruit, i.e., when cell divisions predominantly drive fruit growth, while the expression of Solly;KRP3 increases at the latest stages of fruit development, i.e., when cell expansion predominantly accounts for fruit growth. These data suggest that these KRPs may display distinct physiological and functional roles during the cell cycle and eventually, during the endoreduplication cycle. During tomato fruit development, the large and hypervacuolarized cells constituting the jelly-like (gel) locular tissue undergo multiple rounds of endoreduplication. Within this particular tissue, mitosis is arrested after 20 DPA and only endoreduplication occurs until then concomitantly with a strong posttranslational inhibitory regulation of the CDKA activity (Joubès et al. 1999). The origin of this posttranslational regulatory mechanism resides in part in the accumulation of Solly; KRP1, which accounts for the inhibition of CDK/CYC kinase activity during the development of the gel tissue in tomato fruit (Bisbis et al. 2006). Role of CCS52 The ubiquitin-dependent proteolysis of mitotic cyclins requires the involvement of a specific E3-type ubiquitin ligase named the anaphase-promoting complex/ cyclosome (APC/C). In plants, the APC/C is activated by the CCS52A protein, homologous to the mammalian CDH1 and Drosophila FZR, which binds to cyclins to drive them towards the degradation process by the 26S proteasome (Capron et al. 2003). Like its eukaryotic counterparts, CCS52A was found to promote the onset and progression of endoreduplication (Cebolla et al. 1999; Vinardell et al. 2003). As far as the Arabidopsis CCS52A2 isoform is concerned, its transcriptional activity is under the control of the atypical E2Fe/DEL1 factor, which acts as a repressor of premature endocycle onset (Vlieghe et al. 2005; Lammens et al. 2008). We have investigated the functional role of CCS52 genes during tomato fruit development. Transgenic plants underexpressing SlCCS52A or SlCCS52B using the Fig. 2 (continued) (WT) of the same age. Fruit mass measurements of 25 DPA-fruits harvested from Slccs52A AS lines and WT. The corresponding transcript levels of 25 DPA-fruits were measured by real-time PCR, and the relative abundance of mRNA was normalized to Slbtubulin and SleiF4A. Data are mean standard deviation (n ¼ 3). The comparison of 25 DPA-pericarps from WT and Slccs52A AS fruits reveals an alteration in cell size induced by the down-regulation of SlCCS52A, together with a shift towards lower DNA ploidy levels. (c) Phenotypic and molecular analysis of Pro35S:SlCCS52AOE plants overexpressing tomato CCS52A. Mature fruits (red ripe stage) and fully developed leaves from line Pro35S:SlCCS52A OE3 were compared with untransformed control (WT). In line Pro35S:SlCCS52A OE3 DNA ploidy levels in leaves were shifted towards greater levels as a result of CCS52A overexpression. The growth kinetics of fruits harvested from WT plants and Pro35S:SlCCS52A OE < plants (lines OE1, OE25, OE27, OE29 and OE30) was established by measuring fruit mass daily up to 35 DPA
Page 1 and 2: UNIVERSITE BORDEAUX 1 Thèse souten
Page 3 and 4: Remerciements Ce travail a été r
Page 5 and 6: Sommaire Abréviations…………
Page 7 and 8: Abréviations Acides nucléiques et
Page 9 and 10: PARTIE 1 : Influence évolutive des
Page 11 and 12: Une autre hypothèse avancée pour
Page 13 and 14: nombre pair de chromosomes par rapp
Page 15 and 16: 1.3. Cycle cellulaire, endopolyplo
Page 17 and 18: exemples des cellules nourricières
Page 19 and 20: D’un point de vue évolutif, la m
Page 21 and 22: Cependant, l’implication de l’e
Page 23 and 24: Smith, A.V. and Orr-Weaver, T.L. (1
Page 25 and 26: Endoreduplication and Growth of Fle
Page 29 and 30: Table 1 Characteristics of fruit gr
Page 45: Endoreduplication and Growth of Fle
Page 57 and 58: PARTIE 3 : Endopolyploïdisation :
Page 59 and 60: l’oligomérisation du système ce
Page 61 and 62: d’expression génétique pouvaien
Page 63 and 64: homologue. Chez les plantes, ce pro
Page 65 and 66: sur l’organisation du génome. Ce
Page 67 and 68: Partant de ce constat, l’endopoly
Page 69 and 70: L’étude de l’enveloppe nucléa
Page 71 and 72: (Schwacke et al. 2007) ont révél
Page 73 and 74: cellulaire et ainsi d’étudier fi
Page 75 and 76: endoreduplication and ploidy-depend
Page 77 and 78: Lee, H.-C., Chiou, D.-W., Chen, W.-
Page 79 and 80: Zybina, E.V. and Zybina, T.G. (2008
Page 81 and 82: PARTIE 1 : ARTICLE 1 In planta quan
Page 83 and 84: INTRODUCTION Endopolyploidy is a wi
Page 85 and 86: DNA content of individual cells fro
Page 87 and 88: 1, Figure S1). It was therefore not
Page 89 and 90: Since the shape of the nuclei is ve
Page 91 and 92: (D’Amato, 1984; Bourdon et al., 2
Page 93 and 94: appeared to be the best compromise
Page 95 and 96: unambiguously despite its localizat
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Figure 7. Ploidy mapping on tomato
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that the cell layers located in the
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CONCLUSION Despite the widespread o
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µm thick) were made on a Reichert
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Image analysis The surface of the s
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step was realized in a moist chambe
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SUPPORTING INFORMATION Figure S1. D
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Figure S4. FISH on interphase nucle
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Grandjean, O., Vernoux, T., Laufs,
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PARTIE 2 : ARTICLE 2 Structural ana
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INTRODUCTION Endopolyploidy is a wi
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cellular and nuclear modifications
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2a-d). Second we used transmission
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exchange ability. On the contrary,
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We next calculated the ratio of mit
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As shown in Figure 5a, the 5.8S rRN
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Endoreduplication triggers the form
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linked to the endoreduplication-ass
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EXPERIMENTAL PROCEDURES Plant mater
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DIG labeling efficiency was then ch
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Mitochondria staining All steps wer
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enclosed invaginations. Counting of
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REFERENCES Anisimov, A.P. (2005) En
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Hernandez-Verdun, D. (2006) Nucleol
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Schauer, N., Semel, Y., Roessner, U
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comparer des lignées de tomate sig
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- gros fruits : 35 familles. - peti
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Figure 3. Distribution des valeurs
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ornes. Sur les 62 familles analysé
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Chaque donnée de la génération B
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Figure 9. Structure des demi-fruits
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- 153 -
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nous pensons qu’une partie de la
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noyaux à 512 C (Figure 7). Le fait
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observé ans cette famille serait a
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moyen des fruits sauvages de Micro-
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Bünger-Kibler, S. and Bangerth, F.
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CHAPITRE 3 : DISCUSSION - CONCLUSIO
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- 167 -
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division à différents stades de d
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presse) ont montré que l’intégr
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intermédiaire), le gain d’énerg
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nucléaire, un avantage non néglig
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dans l’espace via ces zones d’a
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REFERENCES DISCUSSION - CONCLUSION
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PRODUCTION SCIENTIFIQUE Revues à c
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