chromatin; histone modifications; chromosome organisation; reprogramming; gamete; endosperm; sexual reproduction; clonal propagation; Arabidopsis; Rice
Wenjing She, Célia Baroux (2015), Chromatin dynamics in pollen mother cells underpin a common scenario at the somatic-to-reproductive fate transition of both the male and female lineages in Arabidopsis, in Frontiers in Plant Sciences
, 28, 294-301.
Wenjing She, Celia Baroux (2014), Chromatin dynamics during plant sexual reproduction, in Frontiers in Plant Sciences
, 5, 354-370.
She Wenjing, Grimanelli Daniel, Rutowicz Kinga, Whitehead Marek W J, Puzio Marcin, Kotlinski Maciej, Jerzmanowski Andrzej, Baroux Célia (2013), Chromatin reprogramming during the somatic-to-reproductive cell fate transition in plants., in Development (Cambridge, England)
, 140(19), 4008-19.
Raissig Michael T, Gagliardini Valeria, Jaenisch Johan, Grossniklaus Ueli, Baroux Célia (2013), Efficient and rapid isolation of early-stage embryos from Arabidopsis thaliana seeds., in Journal of visualized experiments : JoVE
, (76), x-x.
Baroux Célia, Raissig Michael T, Grossniklaus Ueli (2011), Epigenetic regulation and reprogramming during gamete formation in plants., in Current opinion in genetics & development
, 21(2), 124-33.
Wenjing She, Daniel Grimanelli, Célia Baroux, An efficient method for quantitative, single-cell analysis of chromatin modification and nuclear architecture in whole-mount ovules in Arabidopsis thaliana, in Journal of Vizualised Experiments (JoVE)
1.Summary 1.1BackgroundThe plant genome harbors an extraordinary plasticity: fully differentiated plant cells can be re-programmed to produce new individuals either sexually (via the production of gametes in flower organs) or clonally (via the production of clonal sprouts from vegetative tissues). This is in stark contrast to animals that must set aside a lineage of undifferentiated cells for reproduction (germ cells) and cannot naturally regenerate from body parts. Recent studies suggest that plant ge-nome plasticity may be supported by specific chromatin organization and composition. But the precise events and control mechanisms of large-scale chromatin remodeling and chromosome organization in reprogramming processes, as described above, are barely explored. 1.2Hypothesis (a) Sexual reproduction in plants involves double fertilization. The two female gametes are clo-nally derived in a multicellular structure but have distinct post-fertilization fates. We hypothesize that distinct epigenetic chromatin signatures are established early during gametogenesis to mark their cell fate. (b) Reproductive success relies on the endosperm, an extra-embryonic nurse tissue produced at fertilization. The dosage of paternally vs maternally-derived products is crucial for its devel-opment; alteration can result in seed abortion and hybridization failure. We discovered a specific heterochromatin fraction which responds to ploidy alterations in a parent-of-origin-dependent manner (Baroux et al, 2007). We hypothesize that parental dosage is mediated, in part, by genes regulated in this heterochromatin fraction.(c) During clonal propagation, somatic cells de-differentiate under appropriate stimuli and become totipotent. Progeny is produced via somatic embryogenesis or organogenesis. We hypo-thesize that this genome-wide reprogramming involves specific large-scale chromatin modifications.1.3Specific AimsTo answer the above questions, we will:(a) Identify gametic chromatin signatures and analyze their role in cell fate determination.(b) Investigate the role, control, and nature of endosperm-specific heterochromatin in parental dosage regulation and the hybridization barrier.(c) Describe the chromatin dynamics accompanying reprogramming in an experimental case of clonal propagation.1.4Experimental approach(a) Chromatin organization and dynamics will be described in developing gametophytes of Ara-bidopsis using whole-mount immunolabelling, FISH, and GFP-tagged proteins. Mutant analysis will uncover the role of candidate signatures. We will investigate the conservation of the signatures in rice. (b) Quantitative and qualitative alteration of the endosperm-specific heterochromatin in hybrids and mutants will uncover its significance and molecular control, respectively. The presence of candidate genes within this fraction will be tested by FISH. For (c) a simple experimental system is chosen where somatic embryos can be induced at high efficiency from Brassica microspores.1.5SignificanceThis research will significantly contribute to elucidating the mechanistic basis of the extraordinary plasticity of plant cells and the acquisition of cell fate. Understanding parental dosage control in nonviable vs viable hybrid seeds could potentially feed applications in hybrid plant production.