Background: Orb-web weaving spiders and their relatives use multiple types of task-specific silks. The majority of spider silk studies have focused on the ultra-tough dragline silk synthesized in major ampullate glands, but other silk types have impressive material properties. For instance, minor ampullate silks of orb-web weaving spiders are as tough as draglines, due to their higher extensibility despite lower strength. Differences in material properties between silk types result from differences in their component proteins, particularly members of the spidroin (spider fibroin) gene family. However, the extent to which variation in material properties within a single silk type can be explained by variation in spidroin sequences is unknown. Here, we compare the minor ampullate spidroins (MiSp) of orb-weavers and cobweb weavers. Orb-web weavers use minor ampullate silk to form the auxiliary spiral of the orb-web while cobweb weavers use it to wrap prey, suggesting that selection pressures on minor ampullate spidroins (MiSp) may differ between the two groups. Results: We report complete or nearly complete MiSp sequences from five cobweb weaving spider species and measure material properties of minor ampullate silks in a subset of these species. We also compare MiSp sequences and silk properties of our cobweb weavers to published data for orb-web weavers. We demonstrate that all our cobweb weavers possess multiple MiSp loci and that one locus is more highly expressed in at least two species. We also find that the proportion of β-spiral-forming amino acid motifs in MiSp positively correlates with minor ampullate silk extensibility across orb-web and cobweb weavers. Conclusions: MiSp sequences vary dramatically within and among spider species, and have likely been subject to multiple rounds of gene duplication and concerted evolution, which have contributed to the diverse material properties of minor ampullate silks. Our sequences also provide templates for recombinant silk proteins with tailored properties.
|Original language||English (US)|
|Journal||BMC evolutionary biology|
|State||Published - Mar 14 2017|
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation (IOS-0951086 to NAA, IOS-0951061 to CYH), National Institutes of Health (F32 GM78875-1A to NAA; 1F32GM083661-01 and 1R15GM097714-01 to JEG), Army Research Office (W911NF-06-1-0455 and W911NF-11-1-0299 to CYH), and Washington and Lee University through Lenfest Summer Fellowships to NAA and Summer Research Scholarships to JVH and AKL. ERB was supported in part by a grant to Washington and Lee University from the Howard Hughes Medical Institute through the Precollege and Undergraduate Science Education Program (52007570).
© 2017 The Author(s).
- Gene expression
- Silk glands
- Silk proteins
- Spidroin gene family