CRISPR/Cas9-Mediated Mutagenesis of Abdominal-A and Ultrabithorax in the Asian Corn Borer, Ostrinia furnacalis

SIMPLE SUMMARY: Homeotic genes encode transcription factors that coordinated the anatomical structure formation during the early embryonic development of organisms. In this study, we functionally characterized two homeotic genes, Abdominal-A (Abd-A) and Ultrabithorax (Ubx), in the Asian corn borer, Ostrinia furnacalis (a maize pest that has devastated the Asia-Pacific region) by using a CRISPR/Cas9 genome editing system. Our results show that the mutagenesis of OfAbd-A and OfUbx led to severe morphological defects in O. furnacalis, which included fused segments and segmental twist during the larval stage, and hollowed and incision-like segments during the pupal stage in OfAbd-A mutants, as well as defects in the wing-pad development in pupal and adult OfUbx mutants. Overall, knocking out Abd-A and Ubx in O. furnacalis resulted in the embryonic lethality to, and pleiotropic impact on, other homeotic genes. This study not only confirms the conserved body planning functions in OfAbd-A and OfUbx, but it also strengthens the control implications of these homeotic genes for lepidopteran pests. ABSTRACT: (1) Background: Abdominal-A (Abd-A) and Ultrabithorax (Ubx) are homeotic genes that determine the identity and morphology of the thorax and abdomen in insects. The Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Pyralidae), is a devastating maize pest throughout Asia, the Western Pacific, and Australia. Building on previous knowledge, we hypothesized that the knockout of Abd-A and Ubx would disrupt the abdominal body planning in O. furnacalis. (2) Methods: CRISPR/Cas9-targeted mutagenesis was employed to decipher the functions of these homeotic genes. (3) Results: Knockout insects demonstrated classical homeotic transformations. Specifically, the mutagenesis of OfAbd-A resulted in: (1) Fused segments and segmental twist during the larval stage; (2) Embryonic lethality; and (3) The pleiotropic upregulation of other homeotic genes, including Lab, Pd, Dfd, Antp, and Abd-B. The mutagenesis of OfUbx led to: (1) Severe defects in the wing pads, which limited the ability of the adults to fly and mate; (2) Female sterility; and (3) The pleiotropic upregulation of other homeotic genes, including Dfd, Abd-B, and Wnt1. (4) Conclusions: These combined results not only support our hypothesis, but they also strengthen the potential of using homeotic genes as molecular targets for the genetic control of this global insect pest.