RNA-Seq of urechis unicinctus : 2 cell
Total RNA was isolated from the embryo of the above samples using TRIZOL reagent (Invitrogen, Carlsbad, CA, USA) according to the manufacturer's instructions. The purity and integrity of the total RNA isolated from each embryo sample were examined   using a Nanodrop 2000C spectrophotometer (Thermo Scientific, Waltham, MA, USA) and Bioanalyzer 2100 (Agilent Technologies, Palo Alto CA, USA).