miRNA-1-3p, is an early embryonic male sex-determining factor in the Oriental fruit fly, Bactrocera dorsalis

Authors: PENG, WEI - Huazhong Agricultural University; YU, SHUNING - Huazhong Agricultural University; Handler, Alfred - Al; TU, ZHIJIAN - Virginia Polytechnic Institution & State University; SACCONE, GIUSEPPE - The University Of Naples Federico Ii; XI, ZHIYONG - Michigan State University; ZHANG, HONGYU - Huazhong Agricultural University

Submitted to: Nature Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2019
Publication Date: 2/18/2020
Citation: Peng, W., Yu, S., Handler, A.M., Tu, Z., Saccone, G., Xi, Z., Zhang, H. 2020. miRNA-1-3p, is an early embryonic male sex-determining factor in the Oriental fruit fly, Bactrocera dorsalis. Nature Communications. 11:932. https://doi.org/10.1038/s41467-020-14622-4.
DOI: https://doi.org/10.1038/s41467-020-14622-4

Interpretive Summary: The oriental fruit fly is a major invasive pest that has the potential to threaten numerous fruit and vegetable crops in the U.S. Analysis of the genetic mechanisms that control sexual differentiation in this insect is important to understanding its development and behavior, and may provide tools to create genetically modified strains for more effective biological control using the sterile insect technique (SIT). A major advance in developing an SIT program for the oriental fruit fly would be a system that genetically eliminates females early in embryonic development thus avoiding costs of rearing and the need to sterilize and release females along with sterile males. Scientists at Huazhong Agricultural University, PR China, Virginia Polytechnic Institute and State University, University Federico II of Naples, Italy, Michigan State University and USDA, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, collaborated on a project to discover and analyze a male-determining factor that could be used to select against females. The male-determining factor acts in males to suppress the activity of a gene that controls female-specific development. This study showed that the inappropriate expression of the male-determining factor in females results in a sex reversal of females into males and also causes them to be sterile. This genetic system establishes the basis for the production of a male-only sterile population which is ideal for use in developing an effective genetics-based SIT program for the oriental fruit fly.

Technical Abstract: Insects have evolved diverse mechanisms for sex determination, and among them the typically Y chromosome-linked male determining factor (M factor) has been recently identified in a few insects. However, the putative M factor remains unknown in most insect species including the oriental fruit fly, Bactrocera dorsalis (Hendel). By deep sequencing of B. dorsalis early embryonic small RNAs, we identified a male-biased microRNA, miR-1-3p, that has predicted target sites in the transformer gene (Bdtra) which is required for female development. We further demonstrate that miR-1-3p suppresses Bdtra both in vitro and in vivo. Injection of an miR-1-3p mimic in early embryos gave rise to up to 92% phenotypic males, while knock-down of miR-1-3p by an inhibitor produced up to 77% phenotypic females. CRISPR/Cas9-mediated knockout of miR-1-3p resulted in the expression of female-specific splice variants of Bdtra and doublesex (Bddsx), and induced complete sex reversal of males into phenotypic females. These results suggest that miR-1-3p is required for male sex determination in early embryogenesis in B. dorsalis, possibly functioning as an intermediate male determiner that may be activated by a Y-linked primary signal.