Density fractionation system

L1 larvae were grown as described above. Animals were liquid nitrogen flash frozen in polysome lysis buffer as described (Arribere et al., 2016 (link)) and ground in liquid nitrogen (with mortar and pestle). L1 staged cross progeny of (My14 males and N2 (tra-2(q122) females or N2 males (mIn1) and My14 hermaphrodites)) (Goodwin et al., 1993 (link)) were mixed with a C. brenneri lysate (staged L4), which was used as a carrier. The frozen worm powder was thawed on ice and solubilized in polysome lysis buffer that was supplemented with 5 mM DTT, 15 mM ribonucleoside vanadyl complexes (Sigma Aldrich). Lysates were loaded onto 10–60% sucrose gradients and spun for 3.5 hours at 35,000 rpm using SW41 Ti rotor in an ultracentrifugation system (Beckman Coulter). RNA from monosome and polysome peaks was isolated using a density fractionation system (Brandel), and RNA-seq libraries were prepared as described above from equivalent amount of input RNA without an initial rRNA depletion step. The data was used for the analysis in Figure 1C.