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Last results for Polyploidy in Brassica


> Contact: Karine ALIX (alix_at_moulon.inra.fr)
Philippe Brabant, Catherine Damerval, Pierre Gérard,
Agnès Rousselet, Clémentine Vitte

1. Polyploidy and regulation of gene expression

  • By comparing root and stem proteomes of resynthesized B. napus allotetraploids (AACC) with the proteomes of their diploid progenitors (B. rapa AA and B. oleracea CC), we identified numerous deviations from the additivity hypothesis (predicting a mid-parent proteome for the allotetraploids) (Albertin et al. 2006). Identification of non additive proteins by mass spectrometry demonstrated that the differential regulation of gene products was not related to functional properties of the proteins (Albertin et al. 2007). To determine the timing of the regulation of protein expression, we assayed the accumulation of the transcripts of more than 100 genes encoding non additive proteins, by semi-quantitative and real-time quantitative RT-PCR. We found that two-thirds of them had additive transcript levels, indicating that most of the differential protein regulation is not explained by transcriptional changes. Our data suggest that protein regulation is mainly governed by post-transcriptional modifications (Marmagne et al. 2010): we currently investigate the small RNA pathway as a putative molecular mechanism for the post-transcriptional control of gene expression of the resynthesized oilseed rapes.

2. Evolutionary dynamics of transposable elements in Brassica

  • Isolation and molecular characterization of a C genome-specific CACTA transposon, designated Bot1, indicated that this class II TE played a major role in the recent A and C genome divergence (Alix et al. 2008). Recently, using molecular and bioinformatics tools, we characterized BraSto, a Stowaway MITE, and showed that the recently active copies of this MITE preferentially accumulate in the B. rapa gene space (Sarilar et al. 2011). As previous studies suggest that TEs may be involved in the structural and functional regulation of allopolyploid genomes (Parisod et al. 2010), we have undertaken a SSAP approach to identify insertion polymorphisms for these two TE families and an Athila-like retrotransposon (Alix et al. 2005) in the resynthesized B. napus allotetraploids, in comparison with the parental SSAP profiles. In order to characterize the polymorphism observed and to reveal new insertion / excision events, analysis of non additive SSAP bands by cloning and sequencing is in progress.

 

> Collaborators GQE – Le Moulon
Matthieu Falque, Johann Joets

> External collaborations
Hélène Bergès (CNRGV, Toulouse), Anne-Marie Chèvre (IGEPP, Rennes), Martin Crespi et Christine Lelandais (ISV, Gif-sur-Yvette), Pat Heslop-Harrison (University of Leicester, UK), Eric Jenczewski (IJPB, Versailles), Anne Marmagne (IJPB, Versailles), Mark Tepfer (IJPB, Versailles)

> Where are they now?

Nadeem KHAN, Postdoctorant Post-doctorant (2009-2010)
Anne MARMAGNE, Ingénieur de Recherche Post-doctorante (2006-2008)
Pauline PALACIO-MARTINEZ, Postdoctorante PhD student
Véronique SARILAR, Postdoctorante Stagiaire M2 (2006), Doctorante (2008-2011)
Marion TAPIE, Responsable du laboratoire de culture in vitro
des Pépinières Martaillac

Aurélie VAURIJOUX, Doctorante Stagiaire M2 (2012)
Laëtitia VIRLOUVET, Postdoctorante Post-doctorante

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