tld expression is detected on the dorsal surface of cellular blastoderm embryos. It is detected in a similar pattern to that of tok but is detected at least 40 min. earlier. In third instar larvae, tld is expressed in a complex pattern in all imaginal discs and in the proliferative regions of the optic lobes. With the exception of its lack of expression in the ring gland, the pattern of tld is very similar to that of tok in larval tissues but tld is expressed at a significantly lower level.

tld transcripts are observed in 0-12 hr embryos on northern blots. Transcripts are first detected by in situ hybridization at nuclear cycle 10-11 in dorsally located nuclei in the central portion of the embryo and in dorsally and ventrally positioned nuclei at the poles. The pattern extends and amplifies until at cycle 13, tld staining encompasses the dorsal-most 50% of the embryo. By the end of cellularization, four distinct bands of expression are observed. In late stage 8 to stage 9, a new pattern is seen. tld expression is observed in three lateral patches of cells in the emerging gnathal segments and more weakly in patches of cells in more posterior segments. At stage 11, the most intense staining is seen in a series of epidermal cells located ventral to each tracheal pit that are shaped like parentheses. Weaker staining is seen in cells encircling the tracheal pits and in patches of cells in the neurogenic ectoderm.