The first comprehensive sequencing of the genome of the silkworm
Silk is one of the strongest natural fibers, as its thread is stronger than a steel filament of the same diameter, and it has high flexibility when stretched, and it restores its original dimensions when the tensile force affecting it is removed.
It can absorb moisture, and has the ability to withstand high temperatures. It can even be heated at 140 degrees Celsius without decomposing, but it begins to decompose at 170 degrees Celsius.
Silkworms excrete fibroin protein ( silk ) through small holes in their jaws (two salivary glands) in the form of a connected thread.
Because of silk's importance, high value and multiple uses, a systematic analysis of the genetic basis of domestication and selection of breed improvement has become necessary to solve unresolved problems in sericulture.
The Chinese company BGI Genomics, in collaboration with Southwest University, State Key Laboratory of Silkworm Genome Biology and other partners, has built the pangenome dataset for the silkworm.
The paper, which provides genetic insights into artificial selection (domestication and breeding) and environmental adaptation, was published on September 24 in Nature Communications.
The genetic sequence of the silkworm
The study's press release , published on Eurek Alert on September 30, states that this is the first-ever research to digitize the silkworm gene pool and create a "digital silkworm" which greatly facilitates functional genomic research, promotes controlled breeding, and thus enables Additional cases of silk use.
The team sequenced the genomes of thousands of several species of silkworms, generating a huge amount of genomic data. This comprehensive genome dataset contains the most comprehensive information on the genomes of both domestic and wild silkworms, and is the world's largest long-read comprehensive genome of plants and animals to date.
Meanwhile, in-depth studies were conducted on the different genetic variations, artificial selection, environmental adaptations and economic traits of the silkworm, which yielded fruitful results.
The material in this study represents the richest genetic diversity from all major silkworm breeding regions in the world, in which the team identified 468 genes associated with domestication and 198 genes associated with improvement, of which 264 and 185 genes, respectively, were newly identified.
These genes will be important candidate targets for the molecular improvement of the silkworm. At the same time, the team found that the beneficial Chinese and Japanese species shared less than 3% of the improvement sites. This not only reveals the relatively independent breeding history of each Chinese and Japanese strain, but also explains why it provides This common genetic basis has such hybrid advantages for both species, and this finding sheds new insights into the future reproduction of the silkworm.
Economic features of sericulture
The press release states that silk production and quality have often been targeted as key economic criteria for artificial selection of the silkworm, yet - to date - little is known about how genes and their locations on the DNA strand control these quantitative traits, and a "comprehensive genome" was needed to be The "closest bridge" between phenotypes (the physical phenotype of an organism) and especially complex traits.
One example is the regulation of silk production by the cell cycle-associated transcription factor BmE2F1 revealed by selection signals and structural variation.
The CRISPR-cas9 gene clipper technique reduces the number of silk gland cells by 7.68% and silk production by 22%, and on the contrary, the overexpression of BME2F1 increases the number of silk gland cells by 23% and silk production by 16%.
It is worth noting that fine silk has unique applications and higher economic value, but the genetic basis for the fineness of the fibers was previously unknown, and analysis of rare variants in the genomes of slender species led to the identification of the gene that controls silk fineness.
It can be highly detected in fine cultivars, and by inactivating it via genetic scissors technique improved the fineness of the coarse silk produced by local (Chinese) silkworms, indicating that this gene plays a major role in determining the fineness of silk.
Accordingly, this study opens the door to artificial selection and environmental adaptation. “Through comprehensive sampling and dataset combined with a variety of experiments to identify genes, this study opens the door to artificial selection and environmental adaptation,” said Shuaishuai Tai, co-author and senior researcher in genomics at BGI. With which the silkworms are likely to be studied in the future, we hope to speed up the silkworm's pre-planned molecular reproduction process."
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