(A) The 23 E boxes present in the upstream sequence of arg-1 are indicated by arrows located between the stop site of F31A9.4 and the start site of arg-1. The asterisk (*) indicates the E box at position −6359 which was not included in the pZJ02 [−6240 to −1] gfp construct. (B) Four sets of successively smaller bi-directional deletion constructs derived from pZJ02 [−6240 to −1] in addition to a construct with no insert (pKKMCS) are shown. The smallest construct that retained full expression activity was pZJ19 [−436 to −1]. The gfp vector used for each construct was pKKMCS which contains an egl-18 basal promoter (black box) in front of the gfp cDNA (empty box). Each construct was tested for activity in at least two independent transgenic lines. For each line, at least 20 adult transgenic animals were observed for expression of GFP in the head mesodermal cell (hmc), vm1 vulval muscles (vm1), intestinal muscles (mu ints), anal sphincter (mu sph) and anal depressor (mu anal). Activities of each DNA insert were assigned based on percentage of animals observed with GFP expression according to the following criteria: +++ (90–100%), ++ (60–89%), + (20–59%), ± (11–19%), and − (≤ 7%).