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Research Interests
- Plant Reproduction, Convergence of reproductive strategies between plants and mammals
- Chromatin remodeling, Role played by Polycomb group pathways and Retinoblastoma related pathways
- Regulation of imprinting
Research Projects
We are studying the regulation of developmental timing during reproduction. Such regulation comprises the creation and the maintenance of cellular memory involving chromatin remodeling. Namely, we focus our work on the impact of chromatin remodeling by methylation of histones and of DNA on reproduction in the model plant Arabidopsis. We are interested in all aspects of reproduction including gametogenesis, fertilization and development of the two components of the seed, the embryo and the endosperm.
MSI1, a conserved retinoblastoma binding protein, participates to several chromatin remodeling complexes including the Polycomb Group Fertilisation Independent Seed (FIS) (Guitton et al., 2004). We have shown that loss-of-function of MSI1 causes autonomous parthenogenetic development of the embryo and the endosperm from unfertilised embryo sacs (the plant female reproductive structure) (Guitton et al., 2005). This phenotype may result either from deregulation of the cell cycle or from temporal deregulation of female gametogenesis. We are currently exploring the links between the different pathways, which involve MSI1 during male and female gametogenesis and fertilization.
MSI1 and related pathways appear to control embryo development and we are interested to understand the role played by chromatin remodeling in embryo patterning.
The endosperm controls the supply of maternally provided nutrients to the embryo during seed development. Temporal aspects endosperm development are regulated by the FIS Polycomb group complex (Ingouff, Haseloff et al., 2005). The FIS complex also regulates expression of the formin AtFH5, an actin nucleator involved in cytokinesis. Deregulation of the FIS pathway thus causes a pleiotropic endosperm phenotype including prevention of cytokinesis (Ingouff, FitzGerald et al., 2005) and preservation of juvenile characters (Ingouff, Haseloff et al., 2005). We are exploring further the link between the FIS pathway and AtFH5.
Genes subjected to parental genomic imprinting are expressed from one of the two parental alleles. Parental genomic imprinting was originally identified in mammals and the FIS gene MEDEA was the first example of genomic imprinting in plants. We are studying the regulation of imprinting, which involves DNA methylation and histone methylation by Polycomb Group activity. Only five loci are currently known as imprinted in Arabidopsis although imprinting probably affects several unknown other genes involved in the control of endosperm growth and seed size. We wish to isolate these genes and aim to isolate cis-elements and new trans-acting factors essential for imprinting in plants.
Imprinting regulation shares strikingly similar controls in mammals and plants. We propose that such similarities result from evolutionary convergence and wish to explore its origin. |
