Meeting Abstract
The expansive spider Family Theridiidae currently contains close to 2400 species, several of medical importance due to human envenomations. Among these are the notorious black widows of the genus Latrodectus and the closely related false widows of the genus Steatoda. We identified sets of venom gland specific transcripts (VSTs) from three widow spider species (L. hesperus, L. geometricus and S. grossa) using RNA-Seq data from replicates of three tissue types. The three species share a toxic arsenal consisting of atypically large neurotoxins (latrotoxins), small inhibitory cystine knot (ICK) toxins, CRISPs, enzymes with toxic potential and putatively novel toxins. Venom gland transcriptome evolution may proceed by changes in the number of transcripts of a given type due to duplication of the encoding genes, or by changes in the primary sequence of expressed proteins including those driven by adaptive evolution, or via changes in the magnitude or spatial pattern of expression of its component transcripts through regulatory mechanisms. We explore each of these potential avenues. We test whether venom gland specific expression has led to increased orthogroup size. We explore to what extent transcripts exhibit conserved patterns of venom gland biased expression across species, or whether recruitment to venom gland specific expression is a dynamic process in widow spiders. We test whether orthogroups with VSTs are more rapidly evolving at the sequence level or undergo more positive selection than those with more broadly expressed genes. We define lineage specific orthogroups and transcripts and test for lineage specific upregulation of transcripts in the venom gland, all of which may contribute to species-specific venom phenotypes.
