DNA methylation has been associated with transcriptional repression of transposable elements. Here we describe the first DNA methylation deficient cell line of a diatom by generating DNMT5:KOs in Phaeodactylum tricornutum. These data show the extend of the loss of DNA methylation in DNMT5:KOs compared to the reference strain. All DNA methylation is lost in DNMT5:KOs. Overall design: 3 conditions - 2 independent DNMT5:KOs -> DNMT5:KO line M23 DNMT5:KO line M25 + 1 reference strain "WT" Pt18.6. 1 replicate per condition.