The Drosophila spermatogenesis has the renewal of germline stem cells, meiosis of spermatocytes, and morphological transformation of spermatids into mature sperm. We previously demonstrated that Ocnus (ocn) plays an essential role in spermatogenesis. ValRS-m (Valyl-tRNA synthetase, mito-chondrial) gene was downregulated in ocn RNAi testes. By hatchability testing, we found that ValRS-m-knockdown induced complete sterility of male flies. We also concluded that ValRS-m-knockdown inhibited the transition from spermatogonia to spermatocytes and caused accumulated spermatogonia in testes. To understand the intrinsic reason for this destruction, we further conducted transcriptome sequencing analysis in ValRS-m RNAi testes. A total of 7710 dif-ferentially expressed genes (DEGs) were identified to have at least a 2-fold change with a p-value of