Figure 2. The role of the Wari insulator in the enhancer-blocking activity of scs and scs' insulators in transgenic lines.

Tests were conducted for the functional interaction of Wari with the scs insulator inserted in (A) direct or (B) reverse orientation and (C) with the scs' insulator. In the reductive scheme of the transgenic construct used in the assay, the white and yellow genes are shown as white and black boxes, respectively, with an arrow indicating the direction of transcription; the delta sign (Δ) indicates deletion of Wari located at the 3' end of the white gene; downward arrows indicate target sites for Flp recombinase (frt) or Cre recombinase (lox); the same sites in construct names are denoted by parentheses; the eye enhancer is shown as black oval; the yellow wing and body enhancers are shown as white ovals. The “white” column shows the number of transgenic lines with different levels of eye pigmentation. Arrows indicate the excision of an element to produce the derivative transgenic lines. Wild-type white expression determined the bright red eye color (R); in the absence of white expression, the eyes were white (W). Intermediate levels of pigmentation, with the eye color ranging from pale yellow (pY), through yellow (Y), dark yellow (dY), orange (Or), dark orange (dOr), and brown (Br) to brownish red (BrR), reflect the increasing levels of white expression. The “yellow” column shows the numbers of transgenic lines with the yellow pigmentation level in the abdominal cuticle (reflecting the activity of the body enhancer); in most of the lines, the pigmentation level in wing blades (reflecting the activity of the wing enhancer) closely correlated with these scores. The level of pigmentation (i.e., of y expression) was estimated on an arbitrary five-grade scale, with wild-type expression and the absence of expression assigned scores 5 and 1, respectively. N is the number of lines in which flies acquired a new white or yellow phenotype after deletion (Δ) of the specified DNA fragment; T is the total number of lines examined for each particular construct. Other designations are as in Figure 1.