Fig. 6. Loss of Poxm and ectopic Poxm change the number of adult muscle precursors. (A-C) Expression of Twi in abdominal hemisegments of wild-type (A), Poxm^R361 (B), and 24BGal4/UAS-Poxm (C) stage 14 embryos was visualized by staining with an anti-Twi antiserum (anterior to the left and dorsal up). Only precursors of adult muscles and the alary cells express Twi at this stage [alary cells, marked by black arrows, are located on the segment margins in the dorsal and dorsolateral region; see Bate et al. (Bate et al., 1991)]. The adult muscle precursors are arranged in dorsal (D), dorsolateral (DL), lateral (L) and ventral (V) groups. The staining of the trachea is caused by a crossreactivity of the anti-Twi antiserum. (D) Analysis of number of adult muscle precursors in embryos mutant for Poxm or expressing ubiquitous mesodermal Poxm. The number of adult muscle precursors was analyzed in 90 hemisegments each of Poxm^R361 and 24BGal4/UAS-Poxm embryos. The total numbers for 90 hemisegments are shown for the dorsal (DaP), dorsolateral (DLaP), lateral (LaP) and ventral (VaP) group of adult muscle precursors with the numbers expected for wild-type embryos in parentheses.