A composite method for mapping quantitative trait loci without interference of female achiasmatic and gender effects in silkworm,Bombyx mori

Abstract

The silkworm, Bombyx mori, is an economically important insect that was domesticated more than 5000 years ago. Its major economic traits focused on by breeders are quantitative traits, and an accurate and efficient QTL mapping method is necessary to explore their genetic architecture. However, current widely used QTL mapping models are not well suited for silkworm because they ignore female achiasmate and gender effects. In this study, we propose a composite method combining rational population selection and special mapping methods to map QTL in silkworm. By determining QTL for cocoon shell weight (CSW), we demonstrated the effectiveness of this method. In the CSW mapping process, only 56 markers were used and five loci or chromosomes were detected, more than in previous studies. Additionally, loci on chromosomes 1 and 11 dominated and accounted for 35.10% and 15.03% of the phenotypic variance respectively. Unlike previous studies, epistasis was detected between loci on chromosomes 11 and 22. These mapping results demonstrate the power and convenience of this method for QTL mapping in silkworm, and this method may inspire the development of similar approaches for other species with special genetic characteristics.

A Comparison of Co-expression Networks in Silk Gland Reveals the Causes of Silk Yield Increase During Silkworm Domestication

“…During the past few decades, the genes encoding silk fibroin (Fib-H, Fib-L, and P25) and sericin (Sericin1, Sericin2, and Sericin3) have been identified and cloned (Gamo, 1982;Chevillard et al, 1986;Michaille et al, 1986;Yamaguchi et al, 1989;Zhou et al, 2000). Although the genetic loci underlying the variation of silk yield among different domestic silkworm strains have been mapped, the candidate genes responsible for silk yield remain to be identified (Zhan et al, 2009;Li et al, 2013Li et al, , 2015Li C. et al, 2017). Later, the comparative analysis of transcriptomes among the domestic silkworm strains with different silk yields was used to identify the genes associated with silk yield (Li et al, 2016;Luan et al, 2018).…”

Role of microsatellites in genetic analysis of Bombyx mori silkworm: a review

“…Linkage maps with microsatellites have allowed us to advance in the knowledge of characteristics of economic interest in B. mori, as well as in the Lepidoptera genetic architecture. However, Xu et al 68 and Li et al 69 indicate that the most used models have not been adjusted according to the particular genetic characteristics of the silkworm, because they ignore the effects of gender and the presence of aquiasmatic meiosis, a process that implies the absence of chromosomal cross-linking in the germinal line of the females. As a result, these authors have proposed models that allow correcting the potential biases and lack of precision of the most used methods for mapping QTLs in B. mori.…”

“…As a result, these authors have proposed models that allow correcting the potential biases and lack of precision of the most used methods for mapping QTLs in B. mori. Xu et al 68 propose a statistical model to analyze QTLs in F2 populations, while Li et al 69 focus their method on the use of backcrossing and the rational selection of mapping populations to first identify the chromosomes with QTLs and subsequently their position.…”

A comparison of co-expression networks in silk gland reveals the causes of silk yield increase during silkworm domestication

“…During the past few decades, the genes encoding silk fibroin (Fib-H, Fib-L, and P25) and sericin (Sericin1, Sericin2, and Sericin3) have been identified and cloned [7][8][9][10][11]. The genetic loci underlying the variation of silk yield among the strains of the domestic silkworm have been mapped although the candidate genes responsible for silk yield remain to be identified [12][13][14][15]. Later, the comparative analysis of transcriptomes among the domestic silkworm strains with different silk yields was used to identify the genes associated with silk yield [16,17].…”