Annealed oligonucleotides

The snail-primary-enhancer_MS2 transgene was obtained by amplification of the sna endogenous promoter and primary enhancer using the primers listed in Supplementary table 1. The 128XMS2 tag was inserted immediately upstream of the yellow reporter gene sequence of the pbphi-yellow plasmid (Ferraro et al. 2016 ). The transgenic construct was inserted in the VK0033 landing site (BL9750) using PhiC31 targeted insertion (Venken et al. 2006) .
The homology arms for the recombination template for CRISPR/Cas9 editing of scyl gene to generate scyl_24X-MS2_CRISPR were assembled with NEBuilder® HiFi DNA Assembly Master Mix (primers listed in Supplementary table 1) and inserted into pBluescript opened SpeI/AscI (for the 5' homology arm) or XmaI/NheI (for the 3' homology arm) containing the 24X-MS2 (as in (Dufourt et al. 2018 )) inserted after Not1 digestion. Guide RNA (Supplementary table 1) were cloned into pCFD3-dU6:3gRNA (Addgene 49410) digested by BbsI using annealed oligonucleotides (Integrated DNA Technology™). The recombination template and guide RNA plasmids were injected into BDSC#55821 (BestGene Inc.). Transformant flies were screened using a dsRed marker inserted downstream of the 3'UTR of the genes.