Immunostaining with Caspase 3 in the cyst assembly towards to the terminal epithelium region, where the mature sperms are released into the testis lumen and then pass into the seminal vesicle, the signal was not detectable in the WT (Fig. S6A), but obvious in Pif1A1 mutants (Fig. S6B). Here, CASP3 is linked to cyst.