The PIWI-interacting RNA (piRNA) pathway is a conserved defense system that protects the genome integrity of the animal germline from deleterious transposable elements. Targets of silencing are recognized by small noncoding piRNAs that are processed from long precursor molecules. Although piRNAs and other classes of small noncoding RNAs, such as miRNAs and small interfering (si)RNAs, interact with members of the same family of Argonaute (Ago) proteins and their function in target repression is similar, the biogenesis of piRNAs differs from those of the other two small RNAs. Recently, many aspects of piRNA biogenesis have been revealed in Drosophila melanogaster. In this review, we elaborate on piRNA biogenesis in Drosophila somatic and germline cells. We focus on the mechanisms by which piRNA precursor transcription is regulated and highlight recent work that has advanced our understanding of piRNA precursor processing to mature piRNAs. We finish by discussing current models to the still unresolved question of how piRNA precursors are selected and channeled into the processing machinery.

PIWI相互作用RNA（piRNA）途径是一种保守的防御系统，可保护动物种系的基因组完整性免受有害的转座因子的侵害。沉默的靶标是由较长的前体分子加工而成的小型非编码piRNA识别的。尽管piRNA和其他类型的小型非编码RNA（例如miRNA和小型干扰（si）RNA）与同一Argonaute（Ago）蛋白家族的成员相互作用，并且它们在靶标阻遏中的功能相似，但piRNA的生物发生机理却与之不同。其他两个小RNA中的一个。最近，在果蝇中已经揭示了piRNA生物发生的许多方面。在这篇综述中，我们详细阐述了果蝇中的piRNA生物发生。体细胞和种系细胞。我们专注于piRNA前体转录受调控的机制，并着重介绍了最近的工作，这些工作已经使我们对piRNA前体加工成成熟piRNA有了更深的了解。我们通过讨论当前模型来解决尚未解决的有关如何选择piRNA前体并将其导入加工设备的问题。