Abstract
The wild silkworm Bombyx mandarina is widely believed to be an ancestor of the domesticated silkworm, Bombyx mori. Silkworms are often used as a model for studying the mechanism of species domestication. Here, we performed transcriptome sequencing of the wild silkworm using an Illumina HiSeq2000 platform. We produced 100,004,078 high-quality reads and assembled them into 50,773 contigs with an N50 length of 1764 bp and a mean length of 941.62 bp. A total of 33,759 unigenes were identified, with 12,805 annotated in the Nr database, 8273 in the Pfam database, and 9093 in the Swiss-Prot database. Expression profile analysis found significant differential expression of 1308 unigenes between the middle silk gland (MSG) and posterior silk gland (PSG). Three sericin genes (sericin 1, sericin 2, and sericin 3) were expressed specifically in the MSG and three fibroin genes (fibroin-H, fibroin-L, and fibroin/P25) were expressed specifically in the PSG. In addition, 32,297 Single-nucleotide polymorphisms (SNPs) and 361 insertion-deletions (INDELs) were detected. Comparison with the domesticated silkworm p50/Dazao identified 5,295 orthologous genes, among which 400 might have experienced or to be experiencing positive selection by Ka/Ks analysis. These data and analyses presented here provide insights into silkworm domestication and an invaluable resource for wild silkworm genomics research.
Highlights
The wild silkworm Bombyx mandarina belongs to Lepidoptera Bombycidae
Despite the short domestication history, many traits are different between B. mandarina and B. mori including body size and color in the larval stage, size and silk quality of cocoons, fight behavior and egg laying in the adult stage
We performed de novo transcriptome sequencing for B. mandarina using Illumina HiSeq2000 sequencing platform
Summary
The wild silkworm Bombyx mandarina belongs to Lepidoptera Bombycidae. It is widely accepted as that B. mandarina is widely accepted as an ancestor of the domesticated silkworm, Bombyx mori. B. mandarina have been domesticated for at least 5000 years to increase and improve cocoon yield. Despite the short domestication history, many traits are different between B. mandarina and B. mori including body size and color in the larval stage, size and silk quality of cocoons, fight behavior and egg laying in the adult stage. B. mandarina and B. mori are good models for studying species domestication. Based on next-generation sequencing results, some studies have found that phenotypic changes are involved in genetic divergences.
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