Abstract
Mechanisms that regulate silk protein synthesis provide the basis for silkworm variety breeding and silk gland bioreactor optimization. Here, using the pooling sequencing-based methodology, we deciphered the genetic basis for the varied silk production in different silkworm strains. We identified 8 SNPs, with 6 on chromosome 11 and 1 each on chromosomes 22 and 23, that were linked with silk production. After conducting an association analysis between gene expression pattern, silk gland development and cocoon shell weight (CSW), BMGN011620 was found to be regulating silk production. BMGN011620 encodes the 60S ribosomal protein, L18, which is an indispensable component of the 60S ribosomal subunit; therefore we named it BmRPL18. Moreover, the clustering of linked SNPs on chromosome 11 and the analysis of differentially expressed genes reported in previous Omics studies indicated that the genes regulating silk protein synthesis may exhibit a clustering distribution in the silkworm genome. These results collectively advance our understanding of the regulation of silk production, including the role of ribosomal proteins and the clustered distribution of genes involved in silk protein synthesis.
Highlights
The ability of silkworm to synthesize silk proteins has laid the foundation for the sericulture industry that has contributed greatly to the economy of different countries such as China, Brazil and India[1]
The silkworm strains with huge variations in silk synthesis were selected as parents to produce the F1 generation, and the F1 males were backcrossed with the parent strain yielding lower silk to produce the mapping population (BC1M)
Since silk is synthesized in the silk glands, genes with EST representation in silk gland were selected for the association analysis of expression pattern to identify the genes associated with silk synthesis regulation
Summary
The ability of silkworm to synthesize silk proteins has laid the foundation for the sericulture industry that has contributed greatly to the economy of different countries such as China, Brazil and India[1]. Understanding the regulatory mechanism and identifying genes controlling silk protein synthesis will be of great significance to breed silkworm strains that yield high quantities of silk and to optimize bioreactor parameters. Cocoon related traits, such as cocoon shell weight (CSW) and cocoon shell ratio (CSR) are the main phenotypes that reveal the ability of a silkworm strain to synthesize the main silk proteins, fibroins and sericins. We combined generation sequencing and bulked segregation analysis (BSA) to identify the genes that control silk protein synthesis This methodology, termed as pooling-sequencing, is a newly developed protocol to identify genes with high efficiency by combining individuals with similar phenotypes for high coverage sequencing of genes or regions associated with traits of interest[14,15]. Based on a comprehensive analysis of this study and previous Omics data, we propose for the first time that genes regulating silk protein synthesis may be distributed in clusters in the silkworm genome
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