The 20bp VAS1 DNA sequence (TAGTCGACCCCGCGGGTAGT) is an artificial sequence designed to be specifically and robustly bound by the TALE repeat present in the TALE1::VP64 driver. VAS1 and TALE1::VP64 thus form a binary expression system that can be used to control the spatial and temporal expression of a gene of interest: a transgene or modified endogenous locus carrying the target gene of interest downstream of VAS1 sequences is combined with a second transgene or modified endogenous locus encoding the TALE1::VP64 driver expressed in the required expression pattern (FBrf0237269).