torso-like expression in Delta RNAi. Wildtype (A) and Delta (B) RNAi ovarioles stained for tubulin (green) and tsl mRNA (red). (A) In wildtype tsl is expressed in the interfollicular stalk (arrowheads) and in putative stalk precursor cells (arrow). (B) Upon Delta RNAi, tsl mRNA in stalk cells is severely reduced (arrowheads), while it is absent in the stalk precursors (arrow). Still some residual differentiated stalk cells remain (red arrow).