Transgenic characterization of two testis‐specific promoters in the silkworm, <i> <scp>B</scp> ombyx mori </i>

<jats:title>Abstract</jats:title> <jats:p> Sex‐specific regulatory elements are key components for developing insect genetic sexing systems. The current insect genetic sexing system mainly uses a female‐specific modification system whereas little success was reported on male‐specific genetic modification. In the silkworm <jats:italic> <jats:styled-content style="fixed-case">B</jats:styled-content> ombyx mori </jats:italic> , a lepidopteran model insect with economic importance, a transgene‐based, female‐specific lethality system has been established based on sex‐specific alternative splicing factors and a female‐specific promoter <jats:italic>BmVgp</jats:italic> (vitellogenin promoter) has been identified. However, no male‐specific regulatory elements have yet been identified. Here we report the transgenic identification of two promoters that drive reporter gene expression in a testis‐specific manner in <jats:italic> <jats:styled-content style="fixed-case">B</jats:styled-content> . mori </jats:italic> . Putative promoter sequences from the <jats:italic> <jats:styled-content style="fixed-case">B</jats:styled-content> . mori Radial spoke head 1 </jats:italic> gene ( <jats:italic> <jats:styled-content style="fixed-case">BmR1</jats:styled-content> </jats:italic> ) and <jats:italic>beta‐tubulin 4</jats:italic> gene ( <jats:italic> <jats:styled-content style="fixed-case">Bmβ4</jats:styled-content> </jats:italic> ) were introduced using <jats:italic>piggybac</jats:italic> ‐based germline transformation. In transgenic silkworms, expression of the reporter gene enhanced green fluorescent protein ( <jats:styled-content style="fixed-case">EGFP)</jats:styled-content> directed by either <jats:italic>BmR1</jats:italic> promoter ( <jats:italic>BmR1p</jats:italic> ) or <jats:italic> <jats:styled-content style="fixed-case">Bmβ4p</jats:styled-content> </jats:italic> showed precisely testis‐specific manners from the larval to adult stage. Furthermore, EGFP expression of these two transgenic lines showed different localization in the testis, indicating that <jats:italic> <jats:styled-content style="fixed-case">BmR1p</jats:styled-content> </jats:italic> or <jats:italic> <jats:styled-content style="fixed-case">Bmβ4p</jats:styled-content> </jats:italic> might be used as distinct regulatory elements in directing testis‐specific gene expression. Identification of these testis‐specific promoters not only contributes to a better understanding of testis‐specific gene function in insects, but also has potential applications in sterile insect techniques for pest management. </jats:p>