Pachytene piRNAs govern male meiosis I by spatial restriction of gene expression (siRNA)

Pachytene piRNAs control male fertility across metazoans, yet mechanisms through which they govern meiosis I in pachytene remain unclear. We demonstrate, in C. elegans, that homolog pairing, and crossover formation are compromised in the absence of piRNA function. We identify several protein coding genes as targets of piRNAs including Polo like kinase 3 (PLK-). Pachytene piRNAs spatially restrict and exclude PLK-3 expression from meiosis I. Expansion of PLK-3 expression into the pachytene region, upon loss of piRNAs, is reflected in meiotic defects, which are partially rescued by removal of ectopic PLK-3. Pachytene piRNAs regulate PLK-3 through both translational repression and post-transcriptional degradation establishing the spatiotemporal control of gene expression. Given the conserved role of pachytene piRNAs, we propose that these mechanisms may be applicable to mammals. Overall design: To identify differences in 22G siRNA levels mapping to protein-coding genes between wild type and prg-1 mutant adult male C. elegans, we profiled small RNA samples for piRNAs derived from animals of the following genotypes [replicates]: Wild Type [x3], prg-1(null) [x3].