rst mRNA is first detected at low levels in early pupae, peaks at 24% APF and then returns to basal levels by 43% APF.

rst transcripts are found predominantly within the interommatidial cell at 24 hours APF.

rst transcript is expressed from embryonic stage 4-14. Embryonic stage 4 expression is initially in a pattern of seven stripes, which soon fades. Subsequently, rst is expressed in dorsally in the procephalic region and in the amnioserosa anlage. At stage 8, rst is expressed in mesectodermal cells in a segmental pattern. At stage 9, rst is expressed at the dorsal midline and in mesodermal cells. Dorsal midline expression intensifies during stage 10-11, as expression begins in visceral muscle progenitors. At stage 12, rst has strong expression in most mesodermal cells as dorsal midline expression fades. At stages 13-14, expression is in muscle founder cells, and in fusion-competent myoblasts.

rst transcripts are expressed throughout development with peaks in embryonic and pupal stages. In late stage 11 embryos, transcripts are detected in lateral mesodermal cell clusters, in the midline, in cell clusters in the mandibular, maxillary, and labial buds, and in the clypeolabrum. In late third instar larvae, strong signal is observed in the imaginal discs and in the outer optic anlagen. In the eye disc, expression starts just in front of the morphogenetic furrow. In pupae, expression is observed in the lamina and in subpopulations of medullar cells. At 36hr, retinal expression is restricted to cells between the ommatidiial clusters (ie. to presumptive secondary and tertiary pigment cells and to cells of the bristle complex). Expression is then down-regulated in the retina and transcripts can no longer be detected 72hr after puparium formation.

rst and rst are observed primarily in interommatidial cells in a pattern complementary to sns and hbs.

In late third instar larvae salivary glands, strong rst immunoreactivity is observed at cell boundaries and in an internal lace-like pattern that appears to show colocalization with tubulin. No expression is observed in the luminal region of the gland. A few hours later, no staining is seen and then signal is observed again at 3 hours APF but in a reorganized intracellular pattern. Expression persists until 10 hours APF.

rst protein is expressed in pupal eye discs in the interommatidial precursor cells and most strongly in primary pigment cells. In pupal brains, rst protein localizes to a distinct layer in the neuropil of the distal medulla, where is overlaps with X11L expression. It is also expressed in well-defined layers of the lamina, the proximal medulla, and the lobula complex. In ommatidial cells, rst is clearly associated with cell membranes.

rst exhibits dynamic expression from larval through pupal development. High levels are seen at the border between two primary pigment cells and between neighboring interommatidial cells in pupal cells from 24-42 hours APF.

rst protein is localised along the border between secondary and tertiary pigment cells,