Fig. 5.

ARF1–GTP regulates Asrij expression in hemocytes. (A–F) Third instar larval hemocytes showing expression of Asrij (green) and ARF1 (red) in controls (A, C, and E) and (B) arf1 knockdown and (D and F) ARF1-GTP perturbed conditions in (D) garz knockdown and (F) arf1GAP overexpression. Genotypes are as labeled. Right panels are merged images. [Scale bar, 5 μm (A–F).] (G) Proposed model for the role of ARF1 in lymph gland hematopoiesis. ARF1 cycles between GDP- and GTP-bound states depending on the activity of its GAP (Gap69c) and GEF (Garz), respectively. ARF–GDP does not support niche maintenance and promotes premature differentiation possibly due to absence of Asrij interaction. ARF–GTP interacts with and stabilizes Asrij thereby supporting maintenance of blood cell homeostasis by Asrij.