Breeding of Chinese white-cocoon silkworm races lacking yellow-fluorescent substances in their cocoon shell

Abstract

Cocoon shells in some white-cocoon races of silkworms are known to emit yellowish-white, yellowish-green, or purple fluorescence under black light. Three-dimensional fluorescence analysis has revealed that a fluorescent flavonoid in white cocoon shells is probably responsible for yellow fluorescence, and on average, the intensity of this fluorescence is higher in the Chinese races than in the Japanese races. Recently, a recombinant protein production method using a transgenic silkworm has been developed; this was found to be useful for producing different types of recombinant proteins. Genetically modified silks have also been produced from transgenic silkworms. The fibroin H chain gene vector and ordinary breeding methods have been used for producing transgenic silkworm races that are adapted for the mass production of recombinant silks with fluorescent colors. However, strains containing fluorescent substances in the sericin layer are undesirable for breeding fluorescent silk. Therefore, we investigated the presence or absence of yellow fluorescence in commercial white-cocoon races and found that differences in fluorescence intensity among individuals in some strains. The Chinese silkworm races MCS3, MCS181, and MCS107, which lacked yellow fluorescence, were bred by selecting cocoons lacking yellow-fluorescent substances.