Fig. 2
Typical dorsoventral electrochemical gradients, as observed in the wt FE beginning with S10B, are missing in grk. DiBAC staining (Vmem, a-l) and CFDA staining (pHi, m-x); median optical sections (SIM) of typical S8–12 follicles. a-l Pseudocolor images of DiBAC stained wt (a-f) and grk (g-l) follicles. Relative depolarisation of Vmem is indicated by stronger (red), relative hyperpolarisation by weaker (blue) fluorescence intensities (scale bars represent 100 μm; composed pictures show different regions of the same follicle; positions of the ON are marked with asterisks). m-x Pseudocolor images of CFDA stained wt (m-r) and grk (s-x) follicles. Relatively alkaline pHi is indicated by stronger (yellow), relatively acidic pHi by weaker (blue) fluorescence intensities. In early to mid-vitellogenic S8-10A (a-c, g-i, m-o, s-u), a-p gradients, but no d-v gradients, of both Vmem and pHi are detectable in the FE of both wt and grk. Compared to wt, the mFC in grk are less hyperpolarised relative to cFC, and the whole FE is more depolarised. More striking differences between wt and grk become obvious during S10B when d-v gradients (triangles indicate fluorescence-intensity gradients) of both Vmem and pHi are established in wt (d, p), but not in grk (j1, v). Some grk S10B follicles showed a transversal Vmem-gradient (j2), but such a gradient was never observed during later stages (k,l), in contrast to wt (e,f). For variability of follicles in S9 and S10B, see Additional file: Fig. S1; for numbers of analysed follicles, see Additional file: Table S3