Fig. 4. Silencer activity is necessary for germline stem cell maintenance. (A-D) Ovarioles from females expressing Bam inappropriately in GSCs. A and C are DIC images, whereas B and D are DAPI-stained fluorescent micrographs. The ovariole in A and B was taken from a female expressing Bam:GFP from a nos promoter. The ovariole in C and D is from a female carrying 2 copies of a transgene expressing Bam:GFP from a (–799/+4) bam promoter fragment that lacks the sequences required for GSC silencer activity. Note that in both examples, the ovariole contains well-developed cysts with nurse cells but the germarium (arrow) is shriveled.