20XUAS regulatory sequences are separated from sequence encoding tdTomato-tagged CsChrimson by a "SPARC2-S" module that comprises: an attP site of 34bp, a STOP cassette, a second attP site (60bp, full-length site), ribozyme sequence (to prevent leaky expression in the absence of phiC31:int) and an attB site. phiC31:int catalyzes irreversible recombination between the attB site and one of the two attP sites; if the attP site upstream of the STOP cassette is utilized, the STOP cassette is excised, permitting expression of tdTomato-tagged CsChrimson, while if the attP site downstream of the STOP cassette is utilized, the STOP cassette is preserved. The "SPARC2-S" module typically results in expression of the effector (in this case tdTomato-tagged CsChrimson) in approximately 5% of cells (recombination of the attB site with the full-length attP downstream of the STOP cassette is more likely than recombination with the shortened attP site upstream of the STOP cassette).