title: Sequential origin in the high performance properties of orb spider dragline silk.
abstract: Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers.
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325-3908, USA. blackledge@uakron.edu
authors.forename: Todd A
authors.initials: TA
authors.lastname: Blackledge
authors.forename: José
authors.initials: J
authors.lastname: Pérez-Rigueiro
authors.forename: Gustavo R
authors.initials: GR
authors.lastname: Plaza
authors.forename: Belén
authors.initials: B
authors.lastname: Perea
authors.forename: Andrés
authors.initials: A
authors.lastname: Navarro
authors.forename: Gustavo V
authors.initials: GV
authors.lastname: Guinea
authors.forename: Manuel
authors.initials: M
authors.lastname: Elices
mesh_terms: D000818:Animals; D055595:Mechanical Phenomena; D010802:Phylogeny; D047011:Silk / Q000737:chemistry* / Q000235:genetics; D013112:Spiders / Q000737:chemistry* / Q000235:genetics
chemical_list: D047011:Silk