Research profile

Main area of research: Chromatin-based mechanisms involved in plant development.

Our laboratory is interested in mechanisms of transcriptional activation and repression of plant genes through remodeling of chromatin structure and in the biological functions of linker (H1) histones.

Chromatin remodeling projects:
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. 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 nucleosome remodeling has evolved as a key mechanism of gene regulation in eukaryotes. Chromatin remodeling is mediated by the 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 interested in isolation and biochemical characterization of plant remodeling complexes and in analysis of mutants defective in their key subunits. To this end we have engaged in purifying different remodeling complexes from Arabidopsis and are currently involved in determining the identity of their subunits using advanced methods of proteomics. Once the subunits are known, transgenic plants with insertions in respective genes and/or with the respective genes suppressed by RNAi technology will be analyzed. By studying the effects of mutations on the level of transcriptosome, we hope to unravel the network of developmental genes the regulation of which is linked to chromatin remodeling. We are interested in applying bioinformatics to study the interactions and the internal organization of such a network.

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. 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 H1 histones. 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. Our current efforts are focused on understanding in detail the molecular mechanisms by which H1 histones are involved in the control of physiological processes in multicellular organisms.

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