A comprehensive analysis of the chorion locus in silkmoth

Abstract

Despite more than 40 years of intense study, essential features of the silkmoth chorion (eggshell) are still not fully understood. To determine the precise structure of the chorion locus, we performed extensive EST analysis, constructed a bacterial artificial chromosome (BAC) contig, and obtained a continuous genomic sequence of 871,711 base pairs. We annotated 127 chorion genes in two segments interrupted by a 164 kb region with 5 non-chorion genes, orthologs of which were on chorion bearing scaffolds in 4 ditrysian families. Detailed transcriptome analysis revealed expression throughout choriogenesis of most chorion genes originally categorized as “middle”, and evidence for diverse regulatory mechanisms including cis-elements, alternative splicing and promoter utilization, and antisense RNA. Phylogenetic analysis revealed multigene family associations and faster evolution of early chorion genes and transcriptionally active pseudogenes. Proteomics analysis identified 99 chorion proteins in the eggshell and micropyle localization of 1 early and 6 Hc chorion proteins.

Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta

“…The DNOP of genes share a common <400 bp promoter region and the two genes are transcribed in opposite orientations. In B. mori DNOP genes are clustered into a single genetic locus (Kafatos et al, 1995; Chen et al, 2015a,b). With rare exceptions, each DNOP consists of a gene for a class A chorion protein and a gene for a class B chorion protein.…”

“…This locus is split into two distinct chorion gene clusters which are separated by a 197 kb region where 4 non-chorion genes are located. Syntenic analysis shows that orthologs of these non-chorion genes are neighbors of chorion genes in 4 ditrysian families (Chen et al, 2015a,b). Another (possibly only partially) sequenced lepidopteran chorion locus is a region which may exceed 1170 kb, in H. melpomene .…”

Identification of silkworm hemocyte subsets and analysis of their response to BmNPV infection based on single-cell RNA sequencing

“…Clusters 17 and 18, which are the least abundant, clearly represent terminally differentiated cells because of the very high induction of a subset of genes (9 and 16 genes with log2FC > 8, respectively). Interestingly, the gene with the highest differential expression in cluster 18 encodes one of the early class “CA” chorion proteins, which were thought to be exclusively expressed in the ovary and are constituents of the eggshell (Chen et al, 2015). Early chorion proteins are proposed to form an initial scaffold during the first steps of chorion assembly and their expression in cluster 18 hemocytes may reflect a similar role in the assembly of another protective layer, the cuticle.…”

Identification and functional analysis of a novel chorion protein essential for egg maturation in the brown planthopper

“…RNAi revealed that a novel chorion protein, Femcoat, is required for endochorion formation (Kim et al, 2002). In moths, chorion proteins are classified into families of early A, early B, middle A, middle B, late high-cysteine A and late high-cysteine B (Regier et al, 1978;Chen et al, 2015). Spatially restricted components of silkmoth eggshell were described, and 23 proteins were found entirely or predominantly in the aeropyle crown or stripe regions (Regier et al, 1980).…”