UMBC postdoctoral fellow Sarah Stellwagen and co-author Rebecca Renberg at the Army Research Lab have published the first-ever complete sequences of two genes that allow spiders to produce glue — a sticky, modified version of spider silk that keeps a spider’s prey stuck in its web.
Before Stellwagen and Renberg’s work, which was funded by the Army Research Lab, the longest silk gene sequenced was about 20,000 base pairs. When she started this project, Stellwagen was expecting to sequence the glue genes quickly and then move on, building on what she learned from the sequence. Instead, it took her and Renberg two years just to finalize the sequence.
“It ended up being this behemoth of a gene that’s more than twice as large as the previous largest silk gene,” Stellwagen says. It was a long, hard road to the day she found Renberg in the lab and said, “I think our gene is 42,000 bases long. I think we finished it.” And in the end, it was taking a risk on a cutting-edge technique that finally yielded the complete sequence.
Not only was the gene exceptionally long, but, like spider silk genes, it has many repetitions of the same sequence of bases — A, T, G, and C — in the middle. Modern sequencing techniques (called “next generation sequencing”) work by generating DNA sequences for all of an organism’s genes, but chopped up in little pieces. Then, like solving a puzzle, scientists must match up the overlapping ends of the short sections to determine the entire sequence.
Sarah D. Stellwagen, Rebecca L. Renberg. Towards Spider Glue: Long Read Scaffolding for Extreme Length and Repetitious Silk Family Genes AgSp1 and AgSp2 with Insights into Functional Adaptation. G3: Genes|Genomes|Genetics, 2019; g3.400065.2019 DOI: 10.1534/g3.119.400065