Large scale transposon co-option in the Caenorhabditis germline regulatory network [ATAC-seq]

The movement of repetitive elements in the germline creates widespread genomic alterations and pressure for resolution. Here we show that the Caenorhabditis clade took advantage of two transposon expansions by integrating hundreds of elements into its germline transcriptional network. We find that about one-third of C. elegans germline-specific promoters have been co-opted from CERP2 and CELE2 MITE elements and are regulated by HIM-17, a THAP domain-containing transcription factor related to a transposase. An ancestral CERP2 expansion took place in the common Caenorhabditis ancestor, concurrently with mutations in HIM-17 fixed by positive selection, whereas CELE2 expanded only in C. elegans. Through comparative analyses in C. briggsae, we find conservation as well as species-specific CERP2 co-option. Our work reveals the emergence of a novel transcriptional network driven by TE co-option and its impact on regulatory evolution. 4 single-end ATAC-seq libraries from C. briggsae strains (wt and glp-1 mutant)