So regulates <i>ey</i> expression through a binding site in an <i>ey</i> eye enhancer.

<p>(A–F) reporter expression in third instar discs; columns of Sens positive cells were counted to compare furrow progression at different times. (A–C) expression of <i>ey-dGFP</i> (green) and Sens (red) in early (one column of photoreceptors) (A), mid (12 columns of photoreceptors) (B) and late (20 columns of photoreceptors) (C) third instar eye imaginal discs; individual channels shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003731#pgen.1003731.s003" target="_blank">Figure S3</a>. (D–F) expression of <i>ey^mut-dGFP</i> (green) and Sens (red) in third instar eye imaginal discs; individual channels shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003731#pgen.1003731.s003" target="_blank">Figure S3</a>. (D) one column of photoreceptors, (E) 11 columns of photoreceptors, (F) 18 columns of photoreceptors. (G) <i>ey-dGFP</i> expression in <i>so³</i> null clone anterior (yellow arrow) and posterior (yellow arrowhead) to the morphogenetic furrow. (G′) Grayscale image of β-Galactosidase expression, magenta in G; loss of β-Galactosidase marks the clone (G″) Grayscale image of <i>ey-dGFP</i> expression, green in G (H–H″) Maximum projection of orthogonal sections through the posterior clone indicated by a yellow arrowhead in G–G″. (I) <i>ey^mut-dGFP</i> (green) expression in <i>so³</i> null clone marked by loss of β-Galactosidase expression (magenta) in a disc aged between panels D and E. The yellow arrowhead marks the furrow; the orange arrow indicates non-clone tissue, blue arrow indicates anterior clone; similar expression detected in and out of clone (I′) Grayscale image of β-Galactosidase expression, magenta in I. (I″) Grayscale image of <i>ey-dGFP</i> expression, green in I.