The evolutionary road from wild moth to domestic silkworm

Abstract

The Silk Road, which derives its name from the trade of silk produced by the domestic silkworm Bombyx mori, was an important episode in the development and interaction of human civilizations. However, the detailed history behind silkworm domestication remains ambiguous, and little is known about the underlying genetics with respect to important aspects of its domestication. Here, we reconstruct the domestication processes and identify selective sweeps by sequencing 137 representative silkworm strains. The results present an evolutionary scenario in which silkworms may have been initially domesticated in China as trimoulting lines, then subjected to independent spreads along the Silk Road that gave rise to the development of most local strains, and further improved for modern silk production in Japan and China, having descended from diverse ancestral sources. We find that genes with key roles in nitrogen and amino acid metabolism may have contributed to the promotion of silk production, and that circadian-related genes are generally selected for their adaptation. We additionally identify associations between several candidate genes and important breeding traits, thereby advancing the applicable value of our resources.

Gut microbiota metabolic potential correlates with body size between mulberry‐feeding lepidopteran pest species

“…The larvae of several lepidopteran insects are major pests of mulberry in the field, including the large dagger moth Acronicta major (Lepidoptera: Noctuidae), brown‐tail moth Euproctis similis (Lepidoptera: Lymantriidae) and mulberry pyralid Glyphodes pyloalis (Lepidoptera: Pyralidae). Considering that mulberry leaves are the sole food source for silkworms, the silkworm could also be seen as a mulberry specialist pest . Using this model organism, we observed abundant gut bacteria in silkworms in a previous study; however, the potential metabolic functions of the microbial community are still unknown.…”

“…Considering that mulberry leaves are the sole food source for silkworms, the silkworm could also be seen as a mulberry specialist pest. 3 Using this model organism, we observed abundant gut bacteria in silkworms in a previous study 4 ; however, the potential metabolic functions of the microbial community are still unknown.…”

The hormone neuroparsin seems essential in Lepidoptera but not in domesticated silkworms

“…Therefore this mutation makes it impossible for the neuroendocrine cells expressing this mutated neuroparsin gene to secrete this neurohormone. Over time a large number of different silkworm strains have been sequenced, in order to analyze the domestication of the silkworm and and its underlying evolutionary process (Xia et al, 2009;Xiang et al, 2018). Sequences for still other lines are available at silkbase (http://silkbase.ab.a.utokyo.ac.jp).…”

“…It is indeed surprising, that while in virtually all Lepidopteran genomes a neuroparsin gene can be detected that seems to be functional, it is only in some domesticated Bombyx strains that this gene has apparently become superfluous. It is well documented that domestication leads to significant changes in the genome of a species and this also occurred in the silkworm (Xiang et al, 2018). As this mutated gene is only present in some but not all domesticated silkworms it is clearly not a mutation that facilitated domestication, it is rather a gene that domesticated silkworms can do without, while remaining essential in wild moths.…”

Artificial Selection onStorage Protein 1Contributes to Increase of Hatchability during Silkworm Domestication

“…However, during domestication, there might be other factors that contributes to 245 improved hatchability, that is, improved amide and peptide biosynthesis and activated 246 ribosome activities in the ovarian. Methionine-rich SP1 seems to be of special interest, since methionine is reported to be Given that in those cocoon-producing silk moths, another nitrogen utilization 272 system such as gluminate/glutamine cycle system were reported to be vital in 273 metamorphosis silk-cocoon production [1,4,27], we suspect that strategy of nitrogen Notably, increased hatchability during domestication may not be solely attributed 311 to increased expression of SP1 and the associated downstream genes, given that 312 artificial selection acts on hundreds of gene loci in silkworm genome [1,36] and that 313 ova comparative transcriptome between wild and domestic silkworm identified much 314 more genes than that between SP1 mutant and wild type silkworm. We factually (Table 4).…”