Figure 6. Hh-decorated cytonemes are required for GSC maintenance.

(A and F) Germaria from females grown at 18°C and transferred to 31°C for 5 d upon eclosion. (A and B) Ovaries stained with anti-Hh (red) to mark cytonemes and anti-Hts (green) to label the spectrosomes and fusomes of germline cells. (A) Control germarium from a tub-Gal80^ts/+; UAS-dia ^CA/+ female displaying a short cytoneme (yellow arrow). (B) Experimental germarium from a tub-Gal80^ts/+; bab1-Gal4/UAS-dia ^CA female. In this condition, the percentage of germaria showing short cytonemes and the number of GSCs per germarium are significantly lower than in controls. (C and D) Bar charts representing the mean number of GSCs (± s.d.) per germarium (C) or the percentage of germaria showing short cytonemes (D) in control tub-Gal80^ts/+; UAS-wasp ^Myr (or UAS-dia ^CA)/+ and in experimental tub-Gal80^ts/+; bab1-Gal4/UAS-wasp ^Myr (Wasp^Myr) and tub-Gal80^ts/+; bab1-Gal4/UAS-dia ^CA (Dia^CA) germaria. The number of germaria analysed for each experiment (n) is shown. Black triangles indicate a statistically significant difference between the given experimental condition and the control (Student's t test, p<0.01). The percentages of experimental germaria containing cytonemes were significantly different from controls with a probability of 95% (Chi-square test). (E and F) The overexpression of Dia^CA largely abrogates the activation of the Hh pathway in ECs, as shown by the absence of ptc-lacZ expression—a target of the pathway—in experimental germaria. Asteriks, GSCs; red open arrowheads, ECs showing ptc-lacZ expression; yellow dashed lines, CpC clusters; white dashed lines, GSCs in (A) and (E) and differentiating cysts within the niche in (B) and (F). Scale bars: 10 µm.