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Fig. 1 | BMC Developmental Biology

Fig. 1

From: Electrochemical patterns during Drosophila oogenesis: ion-transport mechanisms generate stage-specific gradients of pH and membrane potential in the follicle-cell epithelium

Fig. 1

Development of pHi-gradients in the FCE during S8–12 (CFDA; SIM). a Types of germ-line and somatic cells of the Drosophila follicle. At stage 10b (S10b), the oocyte (Oo, posterior) constitutes almost one half of the follicle’s volume. The anterior half is formed by 15 nurse cells (NC). The 16 germ-line cells (Oo and NC) are covered by a single-layered somatic follicle-cell epithelium (FCE). The columnar FCE surrounding the oocyte is subdivided into three follicle-cell (FC) populations: centripetally migrating FC (cFC), mainbody FC (mbFC) and posterior FC (pFC). The dorsal FCE (dFC) is thicker than the ventral FCE (vFC). Squamous FC surround the NC population. The oocyte nucleus and the border cells, a cluster of migratory follicle cells, lie close to each other near the dorsal side (DIC image). b Schematic drawing of an ovariole showing pHi in the analysed stages S8–12 (cf. Additional file 1: Figure S1 for examples; Ger, germarium). c In S8, anterior FC (aFC) are more alkaline compared to pFC. During S9–12, an antero-posterior (a-p) gradient establishes with relatively acidic cFC and relatively alkaline pFC. From S9 and, in particular, from S10b onwards, a dorso-ventral (d-v) gradient with relatively alkaline vFC and relatively acidic dFC develops. To analyse the a-p and d-v gradients, the fluorescence intensities of the different FC types (3 < n < 46 follicles per stage) were measured and normalised using the fluorescence intensity in the whole FCE of the respective follicle (relative intensity). Mean values, shown with their standard deviation (cf. Additional file 2: Table S1), were compared using an unpaired t-test (* p < 0.05; ** p < 0.01; *** p < 0.001). d Optical median sections of a CFDA-stained S10b-follicle. Inset shows a pseudocolour image of the same section. Low fluorescence intensity (blue) indicates lower pHi (relatively acidic) while high fluorescence intensity (pink) indicates higher pHi (relatively alkaline). Asterisk, oocyte nucleus (dorsal)

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