The molecular basis for adaptations could rely on mutations in genes encoding proteins, changes in how genes are expressed, or a combination of both. One way to evaluate the molecular basis for adaptation is to examine the genetic architecture underlying cases of convergent evolution, the independent evolution of similar phenotypes in distantly related organisms. The independent evolution of silk production in multiple arthropod lineages provides an ideal model system to examine convergent molecular evolution. With an initial focus on spiders and moths, the databases and analytical methods developed here will lay the groundwork for future comparative work on arthropod silk production, through the achievement of the following goals. (1) Candidate genes specifically involved in spider silk production will be identified by generating ESTs from multiple tissue types of the black widow spider. A novel statistical method will be applied to identify differentially expressed genes and these candidate genes will be tested for silk gland specific expression using experimental methods, dramatically improving our understanding of spider silk production. (2) Expression patterns of the domesticated silkworm and black widow silk glands will be compared to determine if convergence in gene expression can, in part, explain convergent evolution of silk production. New statistical methods will be applied to evaluate the similarity of expression patterns from divergently related species. These findings will contribute to the understanding of the molecular mechanisms of convergent evolution and adaptation. (3) Putative regulatory regions of spider silk genes will be identified using phylogenetic footprinting. Binding motifs for transcription factors known to be important in silkworm silk expression will be specifically targeted. In combination with Goals 1 &2, these results will provide insights into the evolution of tissue specific expression of gene family members. Relevance: The proposed research will broaden the current understanding of gene expression in arthropods, a group of animals that are well known for being disease vectors but also possess many beneficial applications for humans. Additionally, this research will add an unexplored dimension to the production of artificial silk by identifying chaperones and other silk-associated proteins that may be required for accurately mimicking native spider silk. These artificial silks can then be used in biomedical applications, such as artificial ligaments or tendons and incredibly thin but strong sutures.
