library_construction_protocol: 15-20 embryos were collected per sample and resuspended in 8 uL of low input lysis buffer of the NEBNext Single Cell/Low input cDNA Synthesis & Amplification module (#E6421S). Whole cells were processed with the "NEBNext Single Cell/Low Input RNA Library Prep" kit (NEB #E6420) by following manufacturer instructions. Double stranded cDNA production was performed by limited-cycle PCR. Sequencing libraries were completed with the "NEBNext Ultra II FS DNA Library Prep Kit for Illumina" (NEB #E7805) and subsequently analysed on an Illumina instrument by following manufacturer's protocols. ultra-low input RNA-seq