Main area of research:

Chromatin-based mechanisms involved in plant development and adaptation to changes in environmental conditions.

Eukaryotic DNA is assembled into chromatin, in which it is packaged by histone proteins into nucleosomes. A complete nucleosome contains eight core histone molecules (two of each: H2A, H2B, H3 and H4) and one molecule of histone H1.

We focus on transcriptional activation and repression of plant genes through modulation of chromatin structure through active nucleosome remodeling, DNA and histone modifications and changes in stoichiometry of chromatin linker (H1) histone isoforms.

Chromatin remodeling projects:

As the packaging of the genome into chromatin restricts the access to DNA of the transcription factors and enzymes involved in DNA processing, the modification of chromatin structure by active ATP-dependent nucleosome remodeling has evolved as a key mechanism of gene regulation in eukaryotes. Chromatin remodeling is mediated by large multi-protein complexes which belong to several different classes. Our studies led to identification and functional characterization in Arabidopsis thaliana of BSH and AtSWI3 proteins, homologues of yeast SNF5 and SWI3, respectively, the core subunits of the Swi/Snf-type complex involved in chromatin remodeling. We also showed that Arabidopsis protein DDM1 (Decrease in DNA Methylation 1) involved in maintaining DNA methylation is a true ATP-dependent chromatin remodeling factor.

We are currently interested in functional and structural links between SWI/SNF chromatin remodeling and hormone signaling in Arabidopsis. We have recently revealed that Arabidopsis BRAHMA SWI/SNF ATPase directly controls several key genes of the gibberellin signaling pathway. By using advanced proteomics and genome-wide mapping of nucleosomes and chromatin epigenetic marks in wild-type and perturbed (mutants and stressed) plants we hope to unravel the network of genes the regulation of which is linked to chromatin remodeling.

Histone H1 projects:

Of all chromatin histones, those representing the H1 group remain the most mysterious. The gene knock-out experiments showed that in simpler unicellular eukaryotes these proteins are not essential for basic life functions. Most multi-cellular organisms express several different H1 variants in different cell types and during various developmental stages. We are interested in mechanisms underlying H1 function and in the H1 biological role. In the past, by using transgenic tobacco plants expressing only selected variants out of the native complement of tobacco H1 histones, we showed that the natural stoichiometry of H1 variants is required for correct chromosome separation during male meiotic division.

These data provided the first evidence of the physiological importance of the stoichiometry H1 histones in plants. The more recent results from our laboratory, based on the analysis of Arabidopsis mutants deprived of H1 histones, strongly suggest the involvement of these proteins in the system of cellular memory and perhaps in epigenetic inheritance. Our current efforts are focused on understanding in detail the molecular mechanisms by which H1 histones are involved in development and in short- and long-term adaptation of plants to environmental stresses.