SEARCH AND CHARACTERIZATION OF GENES INVOLVED IN THE DEPOSITION OF HISTONE MARKS DURING DNA REPLICATION

OLDRA, MARÍA BELÉN; FRANCISCO M. IGLESIAS; CERDAN, PABLO DIEGO

Rosario

Simposio; Simposio Genómica Funcional de Plantas; 2017

IBR-CEFOBI-UNR-CONICET

In our laboratory we have identified a thermosensitive allele of the catalytic subunit of DNA polymerase δ from Arabidopsis thaliana, which was named gis5 and is the first viable allele identified in multicellular eukaryotes. When grown under permissive temperatures (18 °C), mutants are very similar to WT plants. However,under restrictive temperatures (24°C), the mutants show early flowering and curly leaves.We have strong evidence that there is an increase in the trimethylation of lysine 4 of histone 3 ( H3K4me3 ) in the locus SEP, which correlated with ectopic expression of SEP3. These data indicate that when DNA replication fails (at least in the ?lagging strand?) H3K4me3 deposition is deregulated. This increase of H3K4me3 in the gis5 mutant is also induced by raising the temperature to 24°C. These results suggest that the DNA polymerase δ is required for the proper establishment of transcriptionally active epigenetic marks which, if disturbed, might lead to devolpmental deffects due to the effects in the the epigenetic control of master genes. Hence, we have a system that, by manipulating ambient will allow us to study the relationship between DNA replication and the establishment of epigenetic marks.The thermosensitiveness of the gis5 allele is easy to follow. Leaves curl upwards along their axis and flowering occurs earlier at 18°C, but not at 24°C. With these easy to follow penotypes we decided to perform a suppresor genetic screening searching for mutants with plain leaves and/or WT flowering. We have already found 10 suppressor mutants that were confirmed in a secondary screening and mapping is underway We hope that these mutants will allow us to find genes involved in the connection between DNA replication and the deposition of H3K4me3