Hox transcription factor Antp regulates sericin-1 gene expression in the terminal differentiated silk gland of Bombyx mori

• Published in: Developmental biology Vol. 386; no. 1; pp. 64 - 71
• Main Authors: Kimoto, Mai, Tsubota, Takuya, Uchino, Keiro, Sezutsu, Hideki, Takiya, Shigeharu
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2014
• Subjects: Animals; Animals, Genetically Modified; Antp; Base Sequence; Bombyx - genetics; Bombyx - metabolism; Bombyx mori; Cell Differentiation; Cloning, Molecular; Female; Gene Expression Profiling; Gene Expression Regulation, Developmental; Homeodomain Proteins - metabolism; In Situ Hybridization; Larva; Male; Molecular Sequence Data; Promoter Regions, Genetic; Recombinant Proteins - metabolism; RNA Splicing; Sericin-1; Sericins - metabolism; Silk - metabolism; Silk gland; Tissue Distribution; Transgenes; Transgenic; Transgenic; Bombyx mori; Silk gland; Sericin-1; Antp
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2013.12.002

Hox genes are well-known master regulators in developmental morphogenesis along the anteroposterior axis of animals. However, the molecular mechanisms by which Hox proteins regulate their target genes and determine cell fates are not fully understood. The silk gland of Bombyx mori is a tubular tissue divided into several subparts along the anteroposterior axis, and the silk genes are expressed with specific patterns. The sericin-1 gene (ser1) is expressed in the middle silk gland (MSG) with sublocal specificity. Here we show that the Hox protein Antp is a component of the middle silk gland-specific complex, MIC (MSG–intermolt-specific complex), binds to the essential promoter element of ser1, and activates its expression. Ectopic expression of Antp in transgenic silkworms induced the expression of ser1 in the posterior silk gland (PSG), but not in the anterior part of MSG (MSG-A). Correspondingly, a MIC-like complex was formed by the addition of recombinant Antp in extracts from PSG with its cofactors Exd and Hth, but not in extracts from MSG-A. Splicing patterns of ser1 mRNA induced by the ectopic expression of Antp in PSG were almost the same as those in MSG at the fifth instar and altered depending on the induction timing of Antp. Other Hox genes were expressed with sublocal specificity in the silk gland. The Bombyx silk gland might provide a useful system for understanding how Hox proteins select and regulate their target genes.
•Hox genes are expressed with characteristic patterns in the larval silk gland.•Antp is expressed specifically in the middle silk gland (MSG).•Antp binds to the essential promoter element of ser1 expressed specifically in MSG.•Misexpression of Antp induces ectopic expression of ser1 in the posterior silk gland (PSG).•Antp makes an activator complex of ser1 with its cofactors Exd and Hth.