Regulation of Silk Genes by Hox and Homeodomain Proteins in the Terminal Differentiated Silk Gland of the Silkworm Bombyx mori.

Takuya Tsubota,Shigeharu Takiya,Mai Kimoto

doi:10.3390/jdb4020019

Abstract

The silk gland of the silkworm Bombyx mori is a long tubular organ that is divided into several subparts along its anteroposterior (AP) axis. As a trait of terminal differentiation of the silk gland, several silk protein genes are expressed with unique regional specificities. Most of the Hox and some of the homeobox genes are also expressed in the differentiated silk gland with regional specificities. The expression patterns of Hox genes in the silk gland roughly correspond to those in embryogenesis showing “colinearity”. The central Hox class protein Antennapedia (Antp) directly regulates the expression of several middle silk gland–specific silk genes, whereas the Lin-1/Isl-1/Mec3 (LIM)-homeodomain transcriptional factor Arrowhead (Awh) regulates the expression of posterior silk gland–specific genes for silk fiber proteins. We summarize our results and discuss the usefulness of the silk gland of Bombyx mori for analyzing the function of Hox genes. Further analyses of the regulatory mechanisms underlying the region-specific expression of silk genes will provide novel insights into the molecular bases for target-gene selection and regulation by Hox and homeodomain proteins.

Highlights

The pioneering genetic studies on homeotic mutations in the silkworm Bombyx mori, which change the identity of the larval thoracic segments and abdominal segments, were mostly carried out in the first half of the 20th century [1,2,3] and therein
Bombyx mori was directly regulated by several homeodomain-containing the regional expression of silk protein genes in the fully differentiated silk gland of the transcriptional factors including the. Identified their regulatory elements silkworm Bombyx mori was directly regulated by several homeodomain-containing transcriptional recognized by these proteins
We found that the70 region of the ser1 promoter was essential for its middle silk gland (MSG)-specific expression [50]

Summary

Introduction

The pioneering genetic studies on homeotic mutations in the silkworm Bombyx mori, which change the identity of the larval thoracic segments and abdominal segments, were mostly carried out in the first half of the 20th century [1,2,3] and therein. Identification of more target genesregulation and their steps in addition to DNA-binding-independent stepsThe appear to be involved in the functional regulatory elements that are recognized by. The identification of more target genes and their regulatory elements moreare clearly the molecular underlying in be vivouseful functions of Hox proteins. We clearly previously that recognizedbases by Hox proteinsthe will for understanding more the reported that the regional specific expression of silk protein genes in the fully differentiated silk molecular bases underlying the in vivo functions of Hox proteins. We previously reported that gland of the specific silkworm Antp, and identified their regulatory elements silkworm Bombyx mori was directly regulated by several homeodomain-containing transcriptional recognized by these proteins [46,47,48,49,50,51].

Schematic

Region-Specific Expression of Silk Genes in the Silk Gland

Antp Regulates the MSG-Specific Expression of ser1

Antp Activates Other MSG-Specific Silk Genes

Perspective