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Untangling spider silk evolution with spidroin terminal domains.
BMC Evol Biol. 2010 Aug 09; 10:243.BE

Abstract

BACKGROUND

Spidroins are a unique family of large, structural proteins that make up the bulk of spider silk fibers. Due to the highly variable nature of their repetitive sequences, spidroin evolutionary relationships have principally been determined from their non-repetitive carboxy (C)-terminal domains, though they offer limited character data. The few known spidroin amino (N)-terminal domains have been difficult to obtain, but potentially contain critical phylogenetic information for reconstructing the diversification of spider silks. Here we used silk gland expression data (ESTs) from highly divergent species to evaluate the functional significance and phylogenetic utility of spidroin N-terminal domains.

RESULTS

We report 11 additional spidroin N-termini found by sequencing approximately 1,900 silk gland cDNAs from nine spider species that shared a common ancestor > 240 million years ago. In contrast to their hyper-variable repetitive regions, spidroin N-terminal domains have retained striking similarities in sequence identity, predicted secondary structure, and hydrophobicity. Through separate and combined phylogenetic analyses of N-terminal domains and their corresponding C-termini, we find that combined analysis produces the most resolved trees and that N-termini contribute more support and less conflict than the C-termini. These analyses show that paralogs largely group by silk gland type, except for the major ampullate spidroins. Moreover, spidroin structural motifs associated with superior tensile strength arose early in the history of this gene family, whereas a motif conferring greater extensibility convergently evolved in two distantly related paralogs.

CONCLUSIONS

A non-repetitive N-terminal domain appears to be a universal attribute of spidroin proteins, likely retained from the origin of spider silk production. Since this time, spidroin N-termini have maintained several features, consistent with this domain playing a key role in silk assembly. Phylogenetic analyses of the conserved N- and C-terminal domains illustrate dramatic radiation of the spidroin gene family, involving extensive duplications, shifts in expression patterns and extreme diversification of repetitive structural sequences that endow spider silks with an unparalleled range of mechanical properties.

Authors+Show Affiliations

Department of Biology, University of California, Riverside, CA 92521, USA. Jessica_Garb@uml.eduNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

20696068

Citation

Garb, Jessica E., et al. "Untangling Spider Silk Evolution With Spidroin Terminal Domains." BMC Evolutionary Biology, vol. 10, 2010, p. 243.
Garb JE, Ayoub NA, Hayashi CY. Untangling spider silk evolution with spidroin terminal domains. BMC Evol Biol. 2010;10:243.
Garb, J. E., Ayoub, N. A., & Hayashi, C. Y. (2010). Untangling spider silk evolution with spidroin terminal domains. BMC Evolutionary Biology, 10, 243. https://doi.org/10.1186/1471-2148-10-243
Garb JE, Ayoub NA, Hayashi CY. Untangling Spider Silk Evolution With Spidroin Terminal Domains. BMC Evol Biol. 2010 Aug 9;10:243. PubMed PMID: 20696068.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Untangling spider silk evolution with spidroin terminal domains. AU - Garb,Jessica E, AU - Ayoub,Nadia A, AU - Hayashi,Cheryl Y, Y1 - 2010/08/09/ PY - 2010/04/12/received PY - 2010/08/09/accepted PY - 2010/8/11/entrez PY - 2010/8/11/pubmed PY - 2010/9/24/medline SP - 243 EP - 243 JF - BMC evolutionary biology JO - BMC Evol. Biol. VL - 10 N2 - BACKGROUND: Spidroins are a unique family of large, structural proteins that make up the bulk of spider silk fibers. Due to the highly variable nature of their repetitive sequences, spidroin evolutionary relationships have principally been determined from their non-repetitive carboxy (C)-terminal domains, though they offer limited character data. The few known spidroin amino (N)-terminal domains have been difficult to obtain, but potentially contain critical phylogenetic information for reconstructing the diversification of spider silks. Here we used silk gland expression data (ESTs) from highly divergent species to evaluate the functional significance and phylogenetic utility of spidroin N-terminal domains. RESULTS: We report 11 additional spidroin N-termini found by sequencing approximately 1,900 silk gland cDNAs from nine spider species that shared a common ancestor > 240 million years ago. In contrast to their hyper-variable repetitive regions, spidroin N-terminal domains have retained striking similarities in sequence identity, predicted secondary structure, and hydrophobicity. Through separate and combined phylogenetic analyses of N-terminal domains and their corresponding C-termini, we find that combined analysis produces the most resolved trees and that N-termini contribute more support and less conflict than the C-termini. These analyses show that paralogs largely group by silk gland type, except for the major ampullate spidroins. Moreover, spidroin structural motifs associated with superior tensile strength arose early in the history of this gene family, whereas a motif conferring greater extensibility convergently evolved in two distantly related paralogs. CONCLUSIONS: A non-repetitive N-terminal domain appears to be a universal attribute of spidroin proteins, likely retained from the origin of spider silk production. Since this time, spidroin N-termini have maintained several features, consistent with this domain playing a key role in silk assembly. Phylogenetic analyses of the conserved N- and C-terminal domains illustrate dramatic radiation of the spidroin gene family, involving extensive duplications, shifts in expression patterns and extreme diversification of repetitive structural sequences that endow spider silks with an unparalleled range of mechanical properties. SN - 1471-2148 UR - https://www.unboundmedicine.com/medline/citation/20696068/Untangling_spider_silk_evolution_with_spidroin_terminal_domains_ L2 - https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-10-243 DB - PRIME DP - Unbound Medicine ER -