pri / tal is expressed dynamically in imaginal discs. and C) pri/tal mRNA is detected in the R8 preclusters in eye discs (arrowhead in A) and in the chordotonal organ precursors in leg discs (C). (B and D) In ato1/Df(3R)p13mutants, pri/tal mRNA levels in the R8 clusters (B) and chordotonal organ precursors (D) are eliminated. (E) pri/tal mRNA is detected in the tarsal leg joints at 4-8 hr APF. T2-T4 mark the second to fourth tarsal segments. (F) pri/tal is expressed at the DV boundary (arrowheads) and in the precursors of anterior chemosensory organs (arrows). (G) No pri/tal mRNA is detected in the anterior chemosensory organ precursors in ac sc null mutants (sc10-1) (white arrows). (H) Wing disc of 0-4 hr APF. pri/tal mRNA is detected in the proveins of longitudinal veins L2-L5.