Abstract
Wild silk moths produce a variety of cocoons and silks. Given our interest in both the evolution and material properties of silk, we analyzed the silk genes of the saturniid moths Antheraea pernyi, Antheraea yamamai, Samia cynthia ricini, Samia cynthia pryeri, Rhodinia fugax, Saturnia
japonica, and Cricula trifenestrata by sequencing clones of genomic DNA libraries and/or cDNA libraries from silk glands. We also analyzed the silk genes of a spider (Araneus ventricosus) and a hornet (Vespa simillima xanthoptera) using cDNA libraries. In saturniid species, the deduced amino acid sequences of fibroins, the major components of silk, consist primarily of repetitive units (motifs) containing polyalanine blocks. Each type of motif was conserved within species, but extreme sequence diversity was observed between species. Polyalanine-containing motifs were common in spider fibroins, although the fibroin of the domesticated silkworm Bombyx mori lacked polyalanine-containing motifs. Hornet silk was composed of four major fibroins with a complex of alanine-rich and serinerich sequences. We have been attempting to introduce fragments of fibroin genes from wild silk moths and spiders into B. mori using transgenic techniques. These studies will enable us to understand the dynamic evolution
of silk genes and produce genetically engineered silks.
