Figure 9.

Antagonistic interaction of pnr and L is crucial for DV patterning during second instar of larval eye development: (A) Schematic for the conditional blocking of pnr activity by overexpression of ush in the eye by ey-GAL4 (ey>ush). Temperature sensitivity of GAL4 drivers was used to control the time window of expression of Ush. Cultures were shifted to 29° to induce ush expression in a specific time window. Cultures were otherwise maintained at 18°. (A) Five different experimental conditions listed as 1–5 were used to block pnr activity. (B) Control showing overexpression of ush in the eye. ey>ush (A, experiment 1) throughout eye development showed no eye in 80% of the eye discs observed. ELAV was used as a marker for eye fate. (C) Overexpression of ush in the L²/+ eye (L²/+; ey>ush) throughout development completely eliminates eye field in nearly 100% of flies observed (A, experiment 2). (D) Blocking pnr activity by ush overexpression in L²/+ background during first or third instar of larval eye development results in loss of the ventral eye (A, experiments 3 and 4), a phenotype similar to that of the L²/+ mutant eye. (E) Blocking pnr activity during second instar of larval eye development by overexpression of ush results in rescue of the L mutant's ventral eye phenotype (A, experiment 5).