title: House spider genome uncovers evolutionary shifts in the diversity and expression of black widow venom proteins associated with extreme toxicity.
abstract: Black widow spiders are infamous for their neurotoxic venom, which can cause extreme and long-lasting pain. This unusual venom is dominated by latrotoxins and latrodectins, two protein families virtually unknown outside of the black widow genus Latrodectus, that are difficult to study given the paucity of spider genomes. Using tissue-, sex- and stage-specific expression data, we analyzed the recently sequenced genome of the house spider (Parasteatoda tepidariorum), a close relative of black widows, to investigate latrotoxin and latrodectin diversity, expression and evolution.
  
  
  
  We discovered at least 47 latrotoxin genes in the house spider genome, many of which are tandem-arrayed. Latrotoxins vary extensively in predicted structural domains and expression, implying their significant functional diversification. Phylogenetic analyses show latrotoxins have substantially duplicated after the Latrodectus/Parasteatoda split and that they are also related to proteins found in endosymbiotic bacteria. Latrodectin genes are less numerous than latrotoxins, but analyses show their recruitment for venom function from neuropeptide hormone genes following duplication, inversion and domain truncation. While latrodectins and other peptides are highly expressed in house spider and black widow venom glands, latrotoxins account for a far smaller percentage of house spider venom gland expression.
  
  
  
  The house spider genome sequence provides novel insights into the evolution of venom toxins once considered unique to black widows. Our results greatly expand the size of the latrotoxin gene family, reinforce its narrow phylogenetic distribution, and provide additional evidence for the lateral transfer of latrotoxins between spiders and bacterial endosymbionts. Moreover, we strengthen the evidence for the evolution of latrodectin venom genes from the ecdysozoan Ion Transport Peptide (ITP)/Crustacean Hyperglycemic Hormone (CHH) neuropeptide superfamily. The lower expression of latrotoxins in house spiders relative to black widows, along with the absence of a vertebrate-targeting α-latrotoxin gene in the house spider genome, may account for the extreme potency of black widow venom.
authors.affiliation: Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, 01854, USA.|Department of Biological Sciences, Virginia Tech, Biocomplexity Institute, Blacksburg, VA, 24061, USA.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Gendreau
authors.affiliation: Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, 01854, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Haney
authors.affiliation: Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, 01854, USA.
authors.forename: Evelyn E
authors.initials: EE
authors.lastname: Schwager
authors.affiliation: Institut für Mathematik und Informatik, Ernst-Moritz-Arndt Universität Greifswald, Walther-Rathenau-Straße 47, 17487, Greifswald, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Wierschin
authors.affiliation: Institut für Mathematik und Informatik, Ernst-Moritz-Arndt Universität Greifswald, Walther-Rathenau-Straße 47, 17487, Greifswald, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Stanke
authors.affiliation: Human Genome Sequencing Center, Department of Human and Molecular Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Richards
authors.affiliation: Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, 01854, USA. Jessica_Garb@uml.edu.
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Garb
mesh_terms: D000818:Animals; D001740:Black Widow Spider; D044125:Coxiellaceae / Q000502:physiology; D019143:Evolution, Molecular; D005260:Female; D020869:Gene Expression Profiling; D014644:Genetic Variation; D023281:Genomics; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D008297:Male; D000072417:Protein Domains; D012727:Sex Characteristics; D013111:Spider Venoms / Q000235:genetics*; D013559:Symbiosis
chemical_list: D019476:Insect Proteins; D013111:Spider Venoms
keywords: Gene family evolution; Genomics; Latrodectus; RNA-Seq; Venom toxins