No extraction was done prior to library construction. For each technical replicate, 10~20 pairs of testes from < 1 day old male flies were dissected in PBS on ice, and immediately digested for 8 minutes at room temperature in 0.5mg/ml of dispase (Worthington LS02109) and 0.5mg/ml of collagenase XI (Sigma C7657) dissolved in PBS with 0.3mM of CaCl2. Testis were washed once in cold PBS and broken open by pipetting 7 ~ 10 times in 50ul of cold PBS. Cells were spun down at 2000rpm for 1min, cold lysis buffer (Buenrostro et al. 2015) added, and the pellet gently resuspended by flicking the tube. After another 2000rpm 2min spin, 20ul of transposase mix from the Nextera Kit (Illumina, cat. no. FC-121-1030) was added and the pellet gently resuspended by flicking the tube. The reaction was incubated at 30oC for 25min with the tube flicked once during incubation. The DNA was purified using Qiagen MinElute column (Qiagen 28004) and the entire sample used for PCR with NEBNext (NEB M0541S) for a total of 8~9 amplification cycles.