Abstract
BackgroundOrb-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.ResultsWe 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.ConclusionsMiSp 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.
Highlights
Orb-web weaving spiders and their relatives use multiple types of task-specific silks
Our goals were to determine the extent of variation in minor ampullate spidroins (MiSp) sequences and minor ampullate silk properties within cobweb weaving spiders, compare this variation to that found in orb-web weaving spiders, and identify any relationship between sequence and material property variation across both groups
Multiple loci encode MiSp in cobweb weavers We employed a series of molecular experiments to identify MiSp-encoding sequences in our five species of cobweb weavers
Summary
Orb-web weaving spiders and their relatives use multiple types of task-specific silks. Minor ampullate silks of orb-web weaving spiders are as tough as draglines, due to their higher extensibility despite lower strength. Despite making architecturally distinct prey-capture webs (Fig. 1), orb-web and cobweb weaving araneoid spiders possess homologous gland types, most of which produce silks with homologous functions. The consistency of minor ampullate silks’ mechanical properties when wet or dry, as well as their increased extensibility relative to draglines and greater variability among species, could allow for different applications of minor ampullate silk that would not be feasible for major ampullate silk. The material properties of minor ampullate silks made by cobweb weavers have yet to be measured, but given the different functions of this silk in cobweb weavers compared to in orb-web weavers, we predict divergence in the mechanical performance of these fibers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
