Chromatin remodeling in plant development.

Plant development results from specific patterns of gene expression that are tightly regulated in a spatio-temporal manner. Chromatin remodeling plays a central role in establishing these expression patterns and maintaining epigenetic transcriptional states through successive rounds of mitosis that take place within a cell lineage. Plant epigenetic switches occur not only at the embryo stage, but also during postembryonic developmental transitions, suggesting that chromatin remodeling activities in plants can provide a higher degree of regulatory flexibility which probably underlies their developmental plasticity. Here, we highlight recent progress in the understanding of plant chromatin dynamic organization, facilitating the activation or repression of specific sets of genes involved in different developmental programs and integrating them with the response to environmental signals. Chromatin conformation controls gene expression both in actively dividing undifferentiated cells and in those already fate-determined. In this context, we first describe chromatin reorganization activities required to maintain meristem function stable through DNA replication and cell division. Organ initiation at the apex, with emphasis on reproductive development, is next discussed to uncover the chromatin events involved in the establishment and maintenance of expression patterns associated with differentiating cells; this is illustrated with the complex epigenetic regulation of the Arabidopsis floral repressor FLOWERING LOCUS C (FLC). Finally, we discuss the involvement of chromatin remodeling in plant responses to environmental cues and to different types of stress conditions.