A snRNA:U6:96Ac (U6:3) promoter drives expression of a quintuple-gRNA comprising a gRNA targeting comt, a gRNA targeting Nsf2, a second gRNA targeting Nsf2, a second gRNA targeting comt, and a final gRNA targeting BFP, each separated by a tRNA-Gln (Q). The 2.1 gRNA scaffold (which includes an additional extension of the second stem loop compared to the (F+E) gRNA scaffold described in FBrf0241409) is used.