Tj controls the morphogenetic behavior and specification of cap cells.

<p>Yellow arrowheads mark the germarium/TF boundary. (<b>A-G</b>) GSC niches of adult ovaries. LamC identifies TF and cap cells. In the control (wt) (A,C,E), cap cells form a cluster inside the germarium and TF cells form a stalk outside the germarium. In ovaries of <i>tj</i><sup><i>39</i></sup>/<i>tj</i><sup><i>eo2</i></sup> (<i>tj</i><sup>hypo</sup>) (B) and <i>tj</i><sup>null</sup> mutants (<i>tj</i><sup><i>eo2</i></sup><i>/tj</i><sup><i>eo2</i></sup> in D, <i>tj</i><sup><i>eo2</i></sup><i>/tj</i><sup><i>Df1</i></sup> in F,G), the cluster is missing and the stalk is abnormally long. (B) In a <i>tj</i><sup>hypo</sup> ovary, the basal cells of the elongated stalk (between arrow and arrowhead) express markers in a cap cell-specific manner (strong Bab2 and <i>1444-lacZ</i> signals), in contrast to distal cells in the stalk. (D,F,G) In <i>tj</i><sup>null</sup> ovaries, all cells in the elongated stalks express markers similar to normal TFs (weak and strong expression of Bab2 (D,F) and <i>LB27-lacZ</i> (F,G), respectively, and no detection of <i>1444-lacZ</i> (D). (<b>H,I</b>) Adult GSC niches with <i>tj</i><sup><i>z4735</i></sup> mutant cell clones. <i>tj</i><sup><i>z4735</i></sup> mutant cap cells, which only express the non-functional isoform of Tj (red) and lack GFP (green), are located in the TF (above the arrowhead) and display the flat shape of TF cells (asterisks), whereas control cap cells, which co-express Tj and GFP, are located in the germarium (below the arrowhead). (<b>J-M</b>) Prepupal ovaries. TFs are longer in <i>tj</i><sup>null</sup> ovaries (<i>tj</i><sup><i>eo2</i></sup><i>/tj</i><sup><i>eo2</i></sup> in K, <i>tj</i><sup><i>z4735</i></sup><i>/tj</i><sup><i>eo2</i></sup> in M) than in control ovaries (J,L). (J,K) <i>B1-lacZ</i> (red) labels cap and TF cells. LamC (green), which is only seen in the distal half of TFs in the control ovary, is present in all <i>B1-lacZ</i>-positive cells of the <i>tj</i><sup>null</sup> ovary. The germ cell population, marked by Vasa (blue), is not divided into ovarioles in the <i>tj</i><sup>null</sup> ovary in contrast to the control. (L,M) <i>1444-lacZ</i> (red), which labels nascent cap cells in the control ovary is not detected in the <i>tj</i><sup>null</sup> ovary. Tj (blue) is seen in cap cells but not in TFs in the control ovary. In the <i>tj</i><sup>null</sup> ovary, which expresses a mutant Tj isoform, Tj is seen in the basal portion of the elongated TFs (between arrowhead and arrow). Genotypic markers: <i>1444-lacZ/+</i> (A,B,L,M) or <i>1444-lacZ</i> (C,D), <i>LB27-lacZ/+</i> (E-G), <i>Ubi-GFP</i> (H,I), and <i>B1-lacZ</i> (J,K). Anterior is up. Scale bars: 10 μm in A-F,H-M; 50 μm in G.</p>