How Chinese scientists are unravelling the secrets of the silkworm – one gene at a time
- Researchers sequence more than 1,000 domestic and wild samples to find the answers to silk yield and fineness
- The results also give insight into the insect’s origins, study says
In the study, the researchers sequenced more than 1,000 domestic and wild silkworms to create a digital silkworm gene pool.
The pool is the world’s largest pan-genome data set for a plant or animal to date, according to the study led by researchers from Southwest University in Chongqing, the Chinese Academy of Sciences and BGI Genomics in Shenzhen.
The study was published in the peer-reviewed journal Nature Communications on September 24.
“This ushers in a new era for silkworm basic research and molecular breeding and provides guidelines for the large-scale pan-genome research of other species,” the authors said.
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The silkworm was domesticated from its wild ancestor about 5,000 years ago, but due to the scarcity of wild silkworms and technical limitations, the origin of the domesticated silkworm has long been an open question.
Through the sequencing process, the researchers found that the insect was domesticated from the lower and middle reaches of the Yellow River in China.
Their finding is further supported by archaeological evidence, including a half cocoon unearthed at Xia county in Shanxi province in 1926 and a silkworm fossil excavated at the county in 2019, according to the authors.
The researchers compared local and improved strains to identify breeding-associated genes. They found that silkworms from China and Japan only shared around 3 per cent of the improvement-associated genes, indicating that breeding proceeded independently in the two countries.
The finding also has important implications for future breeding of silkworms, according to the study.
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They also identified two genes responsible for silk yield and silk fineness – important qualities in breeding silkworms.
Little has been known about the key genes responsible for these traits but the authors found one gene, called BmE2F1, played a critical role in silk yield.
They used a gene-editing tool to knock out the gene and found the silk yield was reduced by 22 per cent. Conversely, the overexpression of BmE2F1 increased silk yield by 16 per cent, according to the study.
Similarly, they identified one gene that determined silk fineness after performing gene-sequencing and analysing 40 differentially expressed genes.
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In addition, the researchers decoded adaptation-related genes linked to a kind of dormancy known as diapause.
Some animals delay development during tough environmental times but it is not well understood how they do this in the embryo stage.
In the study, the authors identified the BmTret1-like gene as a “critical embryonic diapause determinant after fertilisation”, the first time it has been identified in an insect, according to BGI Genomics.
“Our results show that the generated pan-genome … provides resources for high throughput and accurate assessment of valuable alleles for silkworm functional genomics research and breeding,” the study concluded.
Tai Shuaishuai, study co-author and a senior researcher with BGI Genomics, said one of the goals was to improve breeding of the insect.
“With comprehensive sampling and data set combined with a variety of experiments to identify genes for future potential study, we hope to accelerate the process of silkworm molecular design breeding,” Tai said.
