bab gene functions contribute to regulation of Engrailed/Invected accumulation in Terminal Filament cells but not in Cap Cells.

(A-C') Prepupal ovaries immunostained for detection of GFP (green) and Engrailed/Invected (En/Inv) (grey in A’ and red in B’,C’). F-actin labeling is shown in red (A) and grey (B-C'). Anterior is up, medial is left. Scale bars: 10 μm. (A-A', B') Green and yellow brackets indicate Terminal Filament (TF) cells and Cap Cells (CCs), respectively. (C-C') The cluster of medial hhG+ cells depleted of Bab1 and Bab2 is encircled (pink dotted line). Green and yellow arrowheads indicate the anterior- and posterior-most hhG+ cells, respectively. (A-A’) Niche region of a mosaic ovary (hs-FLP; FRT-bab^AR07/FRT-GFP) containing mitotic cell clones homozygous for the bab^AR07 mutation that are marked by absence of GFP (green and yellow arrowheads). In bab^AR07 mutant TF cells (green arrowheads), the signal for En/Inv is lower than that in wild type TF cells (green brackets). However, in bab^AR07 mutant Cap Cells (CCs) in contact with GCs (yellow arrowheads), the level of En/Inv is similar to its endogenous level in wild type CCs (yellow bracket). (B,C) Prepupal ovaries expressing GFP in hhG+ cells (hhG>GFP), and in C, RNAi transgenes against bab1 and bab2 (hhG>GFP, bab1^IR, bab2^IR) as well. (B’,C’) Higher magnifications of the regions framed with dotted lines in (B,C). The anterior-most cells hhG+ cells of hhG>GFP, bab1^IR, bab2^IR ovaries (C’, green arrowheads) present lower levels of En/Inv (C’, green arrowheads) than TF cells in the control (B’, green brackets). The posterior-most hhG+ cells depleted of Bab1 and Bab2 (C', yellow arrowheads) show a similar level of En/Inv than in control CCs (B’, yellow brackets). (D) Graph comparing the fluorescence intensity (arbitrary units) of En/Inv in control niche and bab^AR07 clonal cells. In bab^AR07 mutant TF cells (hs-FLP, bab^AR07), the En/Inv fluorescence intensity is more than 2-fold lower than in adjacent control TF cells (hs-FLP, GFP). However, in bab^AR07 mutant CCs, the En/Inv fluorescence intensity is similar to that in adjacent control CCs. (E) Graph comparing the fluorescence intensity (arbitrary units) of En/Inv in CCs in the control (B', yellow brackets) and in posterior-most hhG+ cells knocked down for bab1 and bab2 using RNAi (C', yellow arrowheads). Values are presented as means +s.d. p-values are calculated using a Kruskal-Wallis (D) or Mann-Whitney (E) test. n: sample size; NS: Not Significant (p>0.05); **** p<0.0001).