Scientists have uncovered the genes responsible for silk and venom production in black widow spiders (Latrodectus hesperus). This could help develop medicines based on the venom proteins, and new silk-like spidey substances, which are light and stretchy, but durable as bulletproof vests.
Two articles published in the open access journal BMC Genomics describe the use of next generation sequencing to expand the number of known genes involved in the processes from less than ten for either, to 647 for silk, and 695 for venom.
As well as their unusual love life, black widows are known for their strong silk and deadly venom. To understand and mimic the properties of these substances, scientists need to know the proteins used to make them. The researchers found the genes active in the spiders' silk and venom glands, and cephalothorax. They compared these to identify genes only activated in the glands and, therefore, involved in producing the silk and venom.
Black widows produce seven types of silk which are stretchy, but tougher than most man-made materials. The silks are made up mostly of fibrous proteins called spidroins, some of which have been produced in genetically modified organisms. However, no experiments have successfully produced a material that mimics black widow silk's qualities.
When scientists used traditional sequencing to find the genes involved in silk production, the six known spidroins swamped traces of all others. Using next generation sequencing, however, the researchers on the first paper identified 647 proteins produced at far higher rates in the silk glands than other tissues. Identifying these could illuminate crucial stages and components in silk production and move current experiments towards real application in new materials or glues.
Nadia Ayoub from Washington and Lee University says: "We were able to identify all the known silk components plus increase the potential silk gene toolkit one hundred fold. What was most exciting was the ability to determine not only specific genes, but whole functional classes of proteins that are far more abundant in silk glands than other tissues."
Thomas Clarke, also of Washington and Lee University, says: "The ecological success of the spiders depends on silk and venom. Examining the changes in gene expression from all the involved proteins, rather than just a few, will give a holistic view of the consequences of changing environments on these important phenotypes."
Latrotoxins in the venom of black widows cause its prey's neurons to fire, immobilizing them. The second paper identified 695 proteins specific to the venom glands. They used mass spectrometry to identify 61 proteins in the venom, and compared them to the 695 produced in the glands. The fact that the glands produce many proteins that don't make it into the final venom suggests that these make or package toxins, or protect the spider from its own venom. Understanding the proteins in the venom itself could improve antivenoms to combat all its different properties.
Jessica Garb, from the University of Massachusetts Lowell says: "Our work shows that black widow venom is dominated by unique toxins, suggesting that it is the product of dramatic evolutionary change. These toxins may yield novel pharmaceutical leads."
Robert Haney, also of the University of Massachusetts Lowell, says: "This work has revealed that other toxin types than latrotoxins also occur in widow venom, together with a number of putative unknown toxins, or unique toxins developed from molecules that have other functions in the nervous system. How these components interact to generate the toxicity of venom is a fascinating question."
Cheryl Hayashi, from University of California, Riverside says: "We've shed light on how to make two of the most amazing natural materials in the world. These discoveries will fuel follow-up studies for years to come. No matter how much we discover about them, black widow spiders are still alluring."
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Notes to Editor
1. Multi-tissue transcriptomics of the black widow spider reveals expansions, co-options, and functional processes of the silk gland gene toolkit
Thomas H Clarke III, Jessica E Garb, Cheryl Y Hayashi, Robert A Haney, Alexander K Lancaster, Susan Corbett and Nadia A Ayoub
BMC Genomics 15:365
Article available at journal website
Dramatic expansion of the black widow toxin arsenal uncovered by multi-tissue transcriptomics and venom proteomics
Robert A. Haney, Nadia A. Ayoub, Thomas H. Clarke, Cheryl Y. Hayashi and Jessica E. Garb
BMC Genomics 15: 366
Article available at journal website
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2. BMC Genomics is an open access, peer-reviewed journal that considers articles on all aspects of genome-scale analysis, functional genomics, and proteomics.
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