Project description: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.
Project description: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.
Project description: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.
Project description: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.
Project description:PIWI proteins and their guiding Piwi-interacting small RNAs (piRNAs) are crucial for fertility and transposon defense in the animal germline. In most species, the majority of piRNAs are produced from distinct large genomic loci, called piRNA clusters. It is assumed that germline-expressed piRNA clusters, particularly in Drosophila, act as master regulators to control the activity of transposons dispersed across the genome. Here, using synteny analysis, we show that large germline clusters are evolutionarily labile, arise at loci characterized by recurrent chromosomal rearrangements, and are mostly species-specific across the Drosophila genus. By engineering chromosomal deletions in D. melanogaster, we demonstrate that the three largest germline clusters, which the generation of >40% of all transposon-targeting piRNAs depend on, are neither required for fertility nor for the regulation of transposon activity in trans. We provide further evidence that dispersed active elements, rather than the regulatory action of large Drosophila germline clusters in trans, may be central for transposon defense.