Evolutionary arms race with transposable elements has greatly diversified the sRNA pathways in individual species. This resonates in the GTSF-1 proteins, which are essential for sRNA pathways in many species but show evolutionary plasticity by acting at different steps of the pathway in different species. In D. melanogaster, GTSF-1 is a downstream factor where it binds a nuclear Ago and drive transcriptional silencing of transposons. However, in M. musculus, GTSF-1 acts upstream of the pathway by binding a cytoplasmic Ago and enabling the biogenesis of sRNAs. Surprisingly, in C. elegans, GTSF-1 is not involved in transposon silencing and does not bind Ago proteins. It instead forms a protein complex with an RNA Dependent RNA polymerase (RdRP) called RRF-3. Together they facilitate the biogenesis of siRNAs (26G RNAs), which ultimately targets pseudogenes and other recent gene duplications. This striking functional plasticity of GTSF-1 led us to hypothesize that even closely-related species have very customized sRNA populations. We are curious whether biochemical building blocks that together make a sRNA pathway can be differentially used to better meet the specific needs for genome defense in individual species To address this, we are studying GTSF-1 proteins in a set of nematodes i.e. C. inopinata, C. briggsae and P. pacificus. GTSF-1 is well conserved and these nematodes each carry a single homologous
gtsf-1 gene. We wish to characterize GTSF-1 in these nematodes using transgenic techniques, transcriptomics and proteomics. The study will describe a general molecular function of GTSF-1 like proteins in small RNA biology. Further, it will reveal how small RNA pathways have evolved during nematode evolution in relation to genome characteristics and gene-regulatory needs of the individual species.