Drosophila males differentially express small proteins regulating stem cell division frequency in response to mating
: The germline stem cells (GSCs) in the male gonad of Drosophila can increase their division frequency in response to a demand for more sperm caused by repeated mating.  However, the molecules and mechanisms regulating and mediating this response have yet to be fully explored. Here, we present the results of a transcriptome analysis comparing expression from the testis tips from non-mated and mated males. An overlapping set of 18 differentially expressed genes (DEGs) from two independent wild-type (wt) strains revealed that the majority of the DEGs encode secreted proteins, which suggests roles for them in cell-cell interactions. Consistent with a role for secretion in regulating GSC divisions, knocking down Signal Recognition Particle (SRP) components within the germline cells using RNA Interference (RNAi), prevented the increase in GSC division frequency in response to mating. The major class of DEGs encodes polypeptides below the size of 250 amino acids, also known as small proteins. Upon reducing germline expression of small proteins, males no longer increased GSC division frequency after repeated mating. We hypothesize that mating induces cellular interactions via small proteins to ensure continued GSC divisions for the production of sperm. Overall design: mRNA expression comparison of apical testis tissue collected from mated and unmated Canton S1 and Oregon R flies in triplicate.