RESUMEN
Insect developmental transitions are precisely coordinated by ecdysone and juvenile hormone (JH). We previously revealed that accumulated H3K27 trimethylation (H3K27me3) at the locus encoding JH signal transducer Hairy is involved in the larval-pupal transition in insects, but the underlying mechanism remains to be fully defined. Here, we show in Drosophila and Bombyx that Rpd3-mediated H3K27 deacetylation in the prothoracic gland during the last larval instar promotes ecdysone biosynthesis and the larval-pupal transition by enabling H3K27me3 accumulation at the Hairy locus to induce its transcriptional repression. Importantly, we find that the homeodomain transcription factor Schlank acts to switch active H3K27 acetylation (H3K27ac) to repressive H3K27me3 at the Hairy locus by directly binding to the Hairy promoter and then recruiting the histone deacetylase Rpd3 and the histone methyltransferase PRC2 component Su(z)12 through physical interactions. Moreover, Schlank inhibits Hairy transcription to facilitate the larval-pupal transition, and the Schlank signaling cascade is suppressed by JH but regulated in a positive feedback manner by ecdysone. Together, our data uncover that Schlank mediates epigenetic reprogramming of H3K27 modifications in hormone actions during insect developmental transition.
Asunto(s)
Proteínas de Drosophila , Ecdisona , Regulación del Desarrollo de la Expresión Génica , Histonas , Larva , Animales , Histonas/metabolismo , Acetilación , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Ecdisona/metabolismo , Larva/metabolismo , Larva/crecimiento & desarrollo , Larva/genética , Bombyx/metabolismo , Bombyx/genética , Bombyx/crecimiento & desarrollo , Hormonas Juveniles/metabolismo , Metilación , Drosophila melanogaster/metabolismo , Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/genética , Transducción de Señal , Pupa/metabolismo , Pupa/crecimiento & desarrollo , Pupa/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Histona Desacetilasas/metabolismo , Histona Desacetilasas/genética , Proteínas de Insectos/metabolismo , Proteínas de Insectos/genética , Proteínas Represoras , Factores de Transcripción con Motivo Hélice-Asa-Hélice BásicoRESUMEN
The CRISPR-Cas13 system, an RNA-guided editing tool, has emerged as a highly efficient and stable RNA editing technique. Although the CRISPR-Cas13 system has been developed in several insect species, its application in lepidopterans has not yet been reported. In the present study, we evaluated the RNA cleavage activity of the CRISPR-Cas13 system in the silkworm ( Bombyx mori), a model lepidopteran insect, both ex vivo and in vivo. We established two stable silkworm BmE cell lines expressing PspCas13b and CasRx, respectively. Further analysis demonstrated that both PspCas13b and CasRx effectively down-regulated the transcription of exogenously-introduced target and endogenous genes in these cell lines. In addition, we generated two transgenic silkworm strains, one expressing CasRx and the other expressing RNA-guided CRISPR RNA targeting Sex combs reduced ( Scr). Further crossing experiments showed that CasRx induced a down-regulation of Scr transcription in silkworms, which impaired systemic growth of larvae. Overall, this study demonstrated that the CRISPR-Cas13 RNA editing system works efficiently in the silkworm, providing a potential alternative approach for RNA manipulation in lepidopteran insects.