The LexA-lexAop system uses the LexA DNA-binding domain from a bacterial transcription factor that can be linked to the GAL4 activation domain or the VP16 activation domain. This adds the flexibility of having a GAL80-repressible (GAL4 activation domain) or independent (VP16) LexA driver. The LexA system is most often used in combination with GAL4 (Lai et al. 2006; Rodríguez et al. 2011). Transgenes expressing fluors under the control of lexAop promoter are listed below.