Carotenoid silk coloration is controlled by a carotenoid-binding protein, a product of the Yellow blood gene

Abstract

Mechanisms for the uptake and transport of carotenoids, essential nutrients for humans, are not well understood in any animal system. The Y (Yellow blood) gene, a critical cocoon color determinant in the silkworm Bombyx mori, controls the uptake of carotenoids into the intestinal mucosa and the silk gland. Here we provide evidence that the Y gene corresponds to the intracellular carotenoid-binding protein (CBP) gene. In the Y recessive strain, the absence of an exon, likely due to an incorrect mRNA splicing caused by a transposon-associated genomic deletion, generates a nonfunctional CBP mRNA, resulting in colorless hemolymph and white cocoons. Enhancement of carotenoid uptake and coloration of the white cocoon was achieved by germ-line transformation with the CBP gene. This study demonstrates the existence of a genetically facilitated intracellular process beyond passive diffusion for carotenoid uptake in the animal phyla, and paves the way for modulating silk color and lipid content through genetic engineering.carotenoid transport ͉ cocoon color ͉ transgenic silkworm

Repression of tyrosine hydroxylase is responsible for the sex-linked chocolate mutation of the silkworm, Bombyx mori

“…Nevertheless, we observed a barely detectable expression in the sch l mutant, resulting in the lethality of sch l at room temperature. Among B. mori mutants, TE-mediated gene disruption has also been reported for the Yellow blood and distinct translucent genes (42,43). In the revised B. mori genome datasets, Tc1-mariner type transposons and non-LTR retrotransposons comprise about 13.8 and 2.7% of the genome sequence, respectively (44).…”

The silkworm Green b locus encodes a quercetin 5- O -glucosyltransferase that produces green cocoons with UV-shielding properties

“…Yellow and pinkish colors are produced from carotenoids (4,7), and green colors are the products of flavonoids (8,9). Inheritance for the carotenoid cocoon has been well established and basically follows a classical Mendelian pattern (2,3,5,7). However, the inheritance pattern for the flavonoid cocoon is much more complicated and largely unknown (5).…”

“…Silkworm cocoon colors are determined by two main pigments, carotenoids (4) and flavonoids (5), which are derived from mulberry leaves (6). Yellow and pinkish colors are produced from carotenoids (4,7), and green colors are the products of flavonoids (8,9). Inheritance for the carotenoid cocoon has been well established and basically follows a classical Mendelian pattern (2,3,5,7).…”

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

“…A carotenoid binding protein (CBP) was isolated from the silk gland of the fifth instar Bombyx larvae [2]. CBP can be only found in Y gene dominant strains (Y/Y) with yellow cocoons rather than recessive strains (+ Y /+ Y ) with white cocoons [3][4][5][6]. RFLP analysis of the genes showed that CBP and the Y-gene were at the same chromosome locus and they may correspond to each other [7].…”

“…The domestic silkworm (Bombyx mori L.), an important economic species, is proposed as an animal model to elucidate this mechanism benefited from the research progress of carotenoid binding protein (CBP) [2,3] .…”