<i>Robo2</i> transcription levels in the testis depend on JAK-STAT signaling.

<p>(A–D) Whole testis in situ hybridization of <i>robo2</i> mRNA. Hubs are marked with an asterisk. In (A) temperature sensitive Stat92E flies (<i>Stat92E^ts</i>) and (C) <i>hs-Upd</i> flies at 18°C, <i>robo2</i> is expressed in the hub and surrounding early CySCs and daughters, consistent with the wild type <i>robo2</i> mRNA expression pattern (not shown). (B) In <i>Stat92E^ts</i> flies shifted to the restrictive temperature (29°C) for 24 hours, <i>robo2</i> expression is abolished. (D) In <i>hs-Upd</i> flies heat shocked for 45 minutes at 37°C, <i>robo2</i> expression expands throughout the testis apex. (E–F) Confocal sections of testes containing the <i>Robo2-GFP</i> enhancer trap with Zfh-1 staining CySCs and early cyst cell daughters (red) and GFP reporting <i>robo2</i> expression (green). Fewer GFP⁺ cyst lineage cells are found in (E) <i>Robo2-GFP</i> testes than in (F) <i>Robo2-GFP</i> testes overexpressing Upd. Hubs outlined in white, DAPI stains DNA (blue), scale bars = 10 µm.