The beta-1, 4-N-acetylglucosaminidase 1 gene, selected by domestication and breeding, is involved in cocoon construction of Bombyx mori

Abstract

Holometabolous insects have distinct larval, pupal, and adult stages. The pupal stage is typically immobile and can be subject to predation, but cocoon offers pupal protection for many insect species. The cocoon provides a space in which the pupa to adult metamorphosis occurs. It also protects the pupa from weather, predators and parasitoids. Silk protein is a precursor of the silk used in cocoon construction. We used the silkworm as a model species to identify genes affecting silk protein synthesis and cocoon construction. We used quantitative genetic analysis to demonstrate that β-1 , 4-N-acetylglucosaminidase 1 ( BmGlcNase1 ) is associated with synthesis of sericin, the main composite of cocoon. BmGlcNase1 has an expression pattern coupled with silk gland development and cocoon shell weight (CSW) variation, and CSW is an index of the ability to synthesize silk protein. Up-regulated expression of BmGlcNase1 increased sericin content by 13.9% and 22.5% while down-regulation reduced sericin content by 41.2% and 27.3% in the cocoons of females and males, respectively. Genomic sequencing revealed that sequence variation upstream of the BmGlcNase1 transcriptional start site (TSS) is associated with the expression of BmGlcNase1 and CSW. Selective pressure analysis showed that GlcNase1 was differentially selected in insects with and without cocoons ( ω 1 = 0.044 vs. ω 2 = 0.154). This indicates that this gene has a conserved function in the cocooning process of insects. BmGlcNase1 appears to be involved in sericin synthesis and silkworm cocooning.

The Landscapes of Full-Length Transcripts and Splice Isoforms as Well as Transposons Exonization in the Lepidopteran Model System, Bombyx mori

“…B.mori is the only truly domesticated insect. Long-term artificial selection has resulted in significant differences between the domesticated silkworm and its ancestors (Bombyx mandarina) in traits such as silk yield, behavior, body color and so on ( Li, et al, 2020 ; Lu, et al, 2020 ; Wang, et al, 2020 ). Besides, more than 3,000 silkworm strains and >600 mutations with diverse phenotypes are available worldwide which are generated through spontaneous mutation, artificial mutagenesis, or breeding ( Nagaraju et al, 2000 ; Goldsmith, et al, 2005 ; Furdui, et al, 2014 ).…”

“…The Toll ligand Spz-3 controls the black stripe of each segment of the silkworm ( Kondo, et al, 2017 ). The BmGlcNase1 gene is involved in the synthesis of sericin ( Li, et al, 2020 ). However, a great number of control genes of the traits of domestication and mutation remain unclear.…”

“…Subsequently, population genomes and chromosome-level reference genome of the silkworm have been completed one after another (Xia, et al, 2008;Xia, et al, 2009;Xiang, et al, 2018;Kawamoto, et al, 2019). These genome resources play an important role in silkworm domestication history and functional genomics studies (Yang, et al, 2014;Xiang, et al, 2018;Zhu, et al, 2019;Li, et al, 2020;Wang, et al, 2020). Compared with the high-quality genome of the silkworm, the quality of transcripts is poor.…”

Gene mapping reveals the association between tyrosine protein kinase Abl1 and the silk yield of Bombyxmori

“…However, owing to the uncertainty of omics analysis, researchers are still trying to map the major genes through forward genetics. So far, only BmGlcNase1, which affects the synthesis of sericin, has been located on chromosome 11 (Li et al 2020). Therefore, mapping the major genes on the Z chromosome has great economic and scientific significance.…”

A Cluster of Genes at the Terminal Region of Chromosome 1 Contributes to Silk Yield in Bombyx Mori.

“…However, because the silkworm has complex genetic characteristics such as female complete linkage and other factors that could affect yield-related indicators, it is di cult to formulate suitable mapping materials and methods in forward genetic studies, making it di cult to research the genetic basis of silk yield. Therefore, over the past 100 years, only a few major genes have been detected, including BmGlcNase1 and BmAbl1 [11,12]. Since the inheritance of silk yield traits is dominated by additive effects [13] and the few identi ed genes have limited effects on molecular breeding, it is necessary to identify additional silk yield controlling genes.…”