XVI International Botanical Congess

Transcriptional inactivation of transgenes often correlates with DNAhypermethylation and chromatin condensation. We've characterized a de novo methylation sequence that destabilizes expression of an adjacent marker gene. A protein (RPS-BP1) that binds to this sequence is similar to yeast and Drosophila chromatin proteins, suggesting that RPS-BP1 initiates assembly of repressive chromatin complexes.To test Drosophila chromatin proteins for function in plants we expressed the Drosophila Polycomb (Pc) and Heterochromatin Protein 1 (HP1) chromodomains in tobacco. HP1-expressing plants were normal but plants expressing the Pc chromo-domain showed pleiotropic mutant phenotypes and altered expression of at least one homeodomain gene. Our results suggest that chromodomains exert related functions in Drosophila and plants.