LAUSR

Sex determination has been studied in the model lepidopteran species Bombyx mori, but it remains poorly understood in lepidopteran pests. In the present study, we identified and characterized the Masculinizer (Masc) gene in a Noctuidae pest species, Agrotis ipsilon. Sequence analysis revealed that AiMasc encodes a protein of 658 amino acids that has two CCCH‐type zinc finger domains and two conserved cysteine residues (Cys‐277 and Cys‐280). We assessed the masculinizing activity of AiMasc in BmN cells and found that AiMasc induced expression of the male‐specific doublesex isoform. Disruption of Masc via clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) in A. ipsilon caused abnormalities in abdominal segments and external genitalia, resulting in male‐specific sterility. These results suggest that Masc participates in the process of sex determination in A. ipsilon. Successful identification of sex‐determination gene in a pest species may enable the development of novel genetic approaches for pest control.