(A) The Df(X)svb108 allele contains a deletion in the cis-regulatory of svb spanning three enhancers: DG2, DG3 and Z. Of those, only DG3 expresses on the ventral side. (B) Wild-type phenotype of trichomes along the A1 and A2 segments at 25°C. (C) At 25°C, the Df(X)svb108 deletion allele did not show a mutant phenotype along the A1 and A2 segments. (D) Zoomed out shot of the anterior region of a cuticle preparation of a wild-type (w1118) larva. (E) Zoomed out shot of the anterior region of a cuticle preparation of a larva carrying Df(X)svb108. The lack of trichomes along the T1 segment is a recessive marker used in subsequent experiments to select for embryos/larvae carrying this deletion allele. Even at 25°C, where the overall trichome numbers in A1 and A2 for the Df(X)svb108 deletion mutant is indistinguishable from wild-type svb, the trichomes at the side of the ventral stripe for A1 and A2 were lost, as marked by the black brackets. (F) Within the overall expression pattern of svb enhancers, DG3 provides exclusive coverage in the circled regions in segments A1 and A2. These regions correspond to the black brackets in panels D and E. (G) Wild-type phenotype of trichomes along the A1 and A2 segments at 32°C. (H) At 32°C, the Df(X)svb108 deletion allele showed a mutant phenotype. (I) A1 trichomes in the dashed boxes bounded by the two sensory cells, as indicated by the arrows, as shown in panels G and H, were counted. Deficiencies of the deletion allele only become clear when the animal is subjected to elevated temperature at 32°C, showing reduced trichome numbers in the A1 segment. The number of larvae counted was: 13 for wild-type at 25°C, 19 for Df(X)svb108 at 25°C, 14 for wild-type at 32°C and 30 for Df(X)svb108 at 32°C. Two-tailed t-test was applied for each individual comparison. In box plots, center line is the mean, upper and lower limits are standard deviation and whiskers show 95% confidence intervals.