Abstract EN:

Diatoms are early divergent ubiquitous unicellular brown alga. Diatoms are one of the most lineage rich eukaryotes and are a major group of phytoplankton. In the past decade, efforts have been made to understand the incredible success of diatoms in modern oceans. The methylation of carbon 5 of cytosine is an epigenetic mark involved in the repression of transposable elements, the establishment and maintenance of genomic imprinting and the inactivation of the X chromosome in mammals. However, questions remained about its role in diatoms. This manuscript provides profound insights into the DNA methylation machinery of the divergent Stramenopile-Alevolates-Rhizaria lineages. We also demonstrate for the very first time that the DNMT5 enzyme is required for the propagation of DNA methylation patterns and the repression of transposable elements in the model diatom Phaeodactylum tricornutum. Recent advances in high throughput sequencing technologies revealed that allelic effects are more widespread than previously thought in diploid organisms. Here we formally report random monoallelic expression in Phaeodactylum tricornutum, its extent and potential epigenetic control mechanisms involved in its regulation. This manuscript, contributes to the emergence of Phaeopdactylum tricontum as a model species for the study of epigenetic mechanisms in eukaryotes.