CRISPR-Cas13-mediated RNA editing in the silkworm Bombyx mori

The RNA-guided CRISPR-Cas13 system has been recently developed as a highly efficient and stable RNA editing technique. Although the CRISPR-Cas13 system has been utilized in several insects, its application in lepidopteran insects has not yet been reported. In the present study, we evaluated RNA cleavage activity of the CRISPR-Cas13 system in the silkworm <i>Bombyx mori</i> as a lepidopteran model insect, both <i>ex vivo</i> and <i>in vivo</i>. We established two silkworm BmE cell lines that stably express PspCas13b and CasRx, respectively. Subsequent analysis showed that PspCas13b and CasRx could efficiently downregulate the transcription of exogenously-introduced target and endogenous genes in BmE cells. In addition, we generated two transgenic silkworm strains expressing CasRx and an RNA-guided crRNA targeting <i>Sex combs reduced</i> (<i>Scr</i>), respectively. Further crossing experiments showed that CasRx could induce a downregulation of the <i>Scr</i> transcription in the silkworm, which thereby retarded systemic growth of silkworm larvae. Our study reveals that the CRISPR-Cas13 RNA editing system works efficiently in the silkworm and provides an alternative approach for RNA manipulation in the silkworm, even other lepidopteran insects.