Convergent Molecular Evolution of Moth and Spider Silks

描述（由申请人提供）：适应性的分子基础可能依赖于编码蛋白质的基因突变，基因表达方式的变化，或两者的结合。评估适应的分子基础的一种方法是检查趋同进化案例的遗传结构，趋同进化是远亲生物中相似表型的独立进化。多节肢动物产丝的独立进化为研究趋同分子进化提供了一个理想的模型系统。通过实现以下目标，本文开发的数据库和分析方法将为今后节肢动物产丝的比较工作奠定基础。(1)通过从黑寡妇蜘蛛的多种组织类型中生成ESTs来鉴定特异性参与蛛丝生产的候选基因。我们将采用一种新的统计方法来鉴定差异表达基因，并利用实验方法对这些候选基因进行丝腺特异性表达测试，从而大大提高我们对蜘蛛丝生产的理解。(2)将家蚕和黑寡妇丝腺的表达模式进行比较，以确定基因表达的趋同是否可以部分解释产丝的趋同进化。新的统计方法将应用于评估不同亲缘物种表达模式的相似性。这些发现将有助于理解趋同进化和适应的分子机制。(3)利用系统发育足迹技术确定蛛丝基因的可能调控区域。已知在蚕丝表达中重要的转录因子结合基序将被特异性靶向。结合目标1和目标2，这些结果将为基因家族成员的组织特异性表达的进化提供见解。

DESCRIPTION (provided by applicant): 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.