[
International Worm Meeting,
2021]
The PIWI/piRNA pathway is a highly conserved small RNA pathway. Central to the pathway is an RNA silencing complex made of an Argonaute protein of the PIWI clade and PIWI-interacting RNAs (piRNAs), which target transposons in animal germlines. In C. elegans, piRNAs also target endogenous protein-coding genes, making the PIWI/piRNA pathway an important regulator of gene expression. C. elegans piRNAs are referred to as 21U RNAs since they are 21 nucleotides long and have a 5' bias for uridine monophosphate. We recently identified a protein complex driving 21U RNA biogenesis, which we named PETISCO (Cordeiro Rodrigues et al., 2019). However, we found that PETISCO can have different functions depending on whether it interacts with the proteins PID-1 (PiRNA Induced silencing Defective) or TOST-1 (Twenty-One U antagoniST). PETISCO:PID-1 complex participates in the 21U RNA biogenesis by interaction and stabilization of the 21U RNA precursors. While being important for gene regulation, the loss of PID-1 is not embryonic lethal. In contrast, PETISCO:TOST-1 is not involved in 21U RNA biogenesis but is nevertheless essential for embryonic development of the subsequent generation (Cordeiro Rodrigues et al., 2019; Zeng et al., 2019). The molecular function of this complex as well as the observed lethality effect is not yet understood. Based on preliminary data, we hypothesize that the PETISCO:TOST-1 complex regulates replication-dependent histones mRNA expression. In this study we want to characterize the PETISCO::TOST-1 complex and dissect its role in embryogenesis. This study would highlight the role of 21U RNA pathway factors in gene expression and C. elegans embryonic development.