Diversity in Copy Number and Structure of a Silkworm Morphogenetic Gene as a Result of Domestication

Abstract

The carotenoid-binding protein (CBP) of the domesticated silkworm, Bombyx mori, a major determinant of cocoon color, is likely to have been substantially influenced by domestication of this species. We analyzed the structure of the CBP gene in multiple strains of B. mori, in multiple individuals of the wild silkworm, B. mandarina (the putative wild ancestor of B. mori), and in a number of other lepidopterans. We found the CBP gene copy number in genomic DNA to vary widely among B. mori strains, ranging from 1 to 20. The copies of CBP are of several types, based on the presence of a retrotransposon or partial deletion of the coding sequence. In contrast to B. mori, B. mandarina was found to possess a single copy of CBP without the retrotransposon insertion, regardless of habitat. Several other lepidopterans were found to contain sequences homologous to CBP, revealing that this gene is evolutionarily conserved in the lepidopteran lineage. Thus, domestication can generate significant diversity of gene copy number and structure over a relatively short evolutionary time.

Structural Variants in the Soybean Genome Localize to Clusters of Biotic Stress-Response Genes

“…Domesticated animal species, including dog, cow, and silkworm, have also been the focus of recent investigations of SV (Chen et al, 2009;Nicholas et al, 2009Nicholas et al, , 2011Liu et al, 2010;Sakudoh et al, 2011;Clop et al, 2012). CNV have been identified within genes and gene families associated with specific biological functions, such as immunity.…”

Polymorphism identification of carotenoid binding protein gene transcription in the silkworm, <i>Bombyx mori</i>

“…In our data, the cDNA clones for [8,9], which was found substantially different from A/B/C-type. There was no exon 2 or intron 2, but two new intron sequences lie downstream of exon 1 and exon 3 accordingly.…”

“…Sequence composition beyond these reshuffled domains was postulated to be the same among different gene structures. Afterwards, a unique CBP gene structure (de-signated as D-type) was identified from the well-accepted genome sequencing strain Dazao (p50T) [8,9]. Like white cocoon strains, Dazao strain could not absorb carotenoids possibly due to the lack of CBP production [9,10], although the cocoon color was green.…”

“…Also, CBP expression level in male tissues was often higher than that in female counterparts. Since Y-a type CBP gene was disclosed to exist as a single copy, and Y-b had three copies in strain N4 [9], it is worth investigating whether transcription activity of these two genes are actually different or not.…”

CD36 homolog divergence is responsible for the selectivity of carotenoid species migration to the silk gland of the silkworm Bombyx mori

“…(I) Genotyping of SCRB15 by genomic PCR in multiple strains of B. mori and multiple individuals of B. mandarina , the putative wild ancestor of B. mori ( 33 ). Details of the geographical location of the sampling area of B. mandarina are as described previously ( 50 ). The different band from strain c11 obtained with Primer-25 and Primer-24 was an artifact unrelated to SCRB15 that was amplifi ed with Primer-24 as both sense and antisense primers (data not shown).…”