Genome and silk transcriptome of Darwin's bark spider

Natural silks crafted by spiders comprise some of the most versatile materials known. Spider silks and bioinspired artificial silks might some day be utilized in commercial and medical applications.

To characterize the repertoire of protein sequences giving silks their biophysical properties and to determine the set of expressed genes across each unique silk gland contributing to the formation of natural silks, we report here draft genomic and transcriptomic assemblies of Darwin’s bark spider, Caerostris darwini, an orb-weaving spider whose dragline is the toughest known biomaterial on Earth.

We identify at least 31 putative spidroin genes, observe substantial sharing of spidroin repetitive sequence motifs between species, but also new motifs unique to C. darwini.

Also, it seems that silks emanating from a given gland represent composite materials to a greater extent than previously appreciated.

We hypothesize that the extraordinary toughness of C. darwini major ampullate dragline silk may relate to the unique protein composition of major ampullate spidroins, including relatively high expression of stretchy flagelliform spidroins whose union into a single fiber may be aided by novel motifs and cassettes that act as molecule-binding helices.