The vanO operator DNA sequence is specifically bound by the DNA-binding domain of the vanR gene of Caulobacter vibrioides. This property can be utilized to form a binary expression system to control the spatial and temporal expression of a gene of interest: a transgene or modified endogenous locus in which the target gene of interest is downstream of vanO sequences can be combined with a transgene or modified endogenous locus encoding any 'driver' that includes the vanR DNA-binding domain plus a transcriptional activation sequence (PMID:22187155).