A piRNA modulates the levels of 20-hydroxyecdysone in the ovary of the German cockroach

Abstract

The PIWI-interacting RNAs (piRNAs) are small non-coding RNAs ranging from 26 to 31 nucleotides. Initially, piRNA functions were associated with repressing transposable elements as part of a mechanism that maintains genomic stability across evolution. However, in the last years, new regulatory functions for piRNAs have been identified. Now, we investigated the regulatory role of piRNAs in insect oogenesis and embryo development. We studied the expression and function of piRNA-83679, one the most abundantly expressed piRNA in Blattella germanica adult ovaries. piRNA-83679 is expressed in germinal and somatic cells in adult ovaries during the gonadotropic cycle, and is maternally provided to the egg. Using an antisense oligonucleotide (ASO), we reduced piRNA-83679 levels in B. germanica adult females, enabling the study of its functions. piRNA-83679 depletion affected the expression of different ecdysone and chorion genes in the ovary, and the organization of the F-actin fibers in the basal pole of the follicle cells of the basal ovarian follicle. As a result, the eggs were not correctly encapsulated in the ootheca. Moreover, piRNA-83679 depletion delayed oviposition and affected embryo development, especially in the early stages.