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The silks of the common garden spider contain genetic elements that have remained the same since the Mesozoic era 125 million years ago, report two researchers from the University of California, Riverside in this week's (March 30) issue of Science.

Cheryl Hayashi, an assistant professor of biology at UCR, and John Gatesy, an assistant researcher in the same department, are experts on the genetic structure of spider silks. Their latest research shows that spider silks are created not just by the spinning process, but also by ancient protein structures handed down genetically over millions of years of evolutionary history.

"Spiders make up to seven different kinds of silk," said Hayashi, a newly hired faculty member at UCR. The stretchiness of the "capture silk" in the center of the web is perfect for catching insect prey. It can stretch up to three times its length before breaking. The silk called "dragline silk" forms the guy lines and spokes for the wheel-shaped web. It is stronger than capture silk but less flexible, and only one-fifth as elastic.

Spider silks are made from liquid proteins composed of repeating mosaics of amino acid sequences. Each type of silk has its own mosaic, a repeating pattern that is critical for determining the strength and flexibility of the silk strands. Modern genetic analysis shows that some of the amino acid motifs have been maintained for over 125 million years, since the time dinosaurs ruled the earth.

"My co-authors and I looked at a broad spectrum of spider types," Hayashi said. "That kind of conservation of the genetic material suggests that this is central to understanding the mechanical properties of orb weaver silks. It shows that more work needs to be done on spider silks so we can understand their exceptional properties."

Orb weaver spiders can be generally described as those that spin the classic wagon wheel shaped web. They include garden spiders, black widows, brown widows, golden silk spiders and thousands of other spider species, Hayashi said.

The paper, titled "Extreme Diversity, Conservation and Convergence of Spider Silk Fibroin Sequences," is authored by Gatesy, Hayashi and former colleagues at the University of Wyoming, Laramie: Dagmara Motriuk, Justin Woods and Randolph Lewis.

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The University of California, Riverside (www.ucr.edu) is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.

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