title: Multifunctional warheads: diversification of the toxin arsenal of centipedes via novel multidomain transcripts.
abstract: Arthropod toxins are almost invariably encoded by transcripts encoding prepropeptides that are posttranslationally processed to yield a single mature toxin. In striking contrast to this paradigm, we used a complementary transcriptomic, proteomic and MALDI-imaging approach to identify four classes of multidomain centipede-toxin transcripts that each encodes multiple mature toxins. These multifunctional warheads comprise either: (1) repeats of linear peptides; (2) linear peptides preceding cysteine-rich peptides; (3) cysteine-rich peptides preceding linear peptides; or (4) repeats of linear peptides preceding cysteine-rich peptides. MALDI imaging of centipede venom glands revealed that these peptides are posttranslationally liberated from the original gene product in the venom gland and not by proteases following venom secretion. These multidomain transcripts exhibit a remarkable conservation of coding sequences, in striking contrast to monodomain toxin transcripts from related centipede species, and we demonstrate that they represent a rare class of predatory toxins that have evolved under strong negative selection. We hypothesize that the peptide toxins liberated from multidomain precursors might have synergistic modes of action, thereby allowing negative selection to dominate as the toxins encoded by the same transcript become increasingly interdependent.
  
  
  CONCLUSIONS
  These results have direct implications for understanding the evolution of centipede venoms, and highlight the importance of taking a multidisciplinary approach for the investigation of novel venoms. The potential synergistic actions of the mature peptides are also of relevance to the growing biodiscovery efforts aimed at centipede venom. We also demonstrate the application of MALDI imaging in providing a greater understanding of toxin production in venom glands. This is the first MALDI imaging data of any venom gland.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Eivind A B
authors.initials: EA
authors.lastname: Undheim
authors.affiliation: Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CIIMAR/CIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas 289, P 4050-123 Porto, Portugal.
authors.forename: Kartik
authors.initials: K
authors.lastname: Sunagar
authors.affiliation: OMICS, Pathology Department, Mater Health Services, South Brisbane, QLD 4101, Australia.
authors.forename: Brett R
authors.initials: BR
authors.lastname: Hamilton
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Alun
authors.initials: A
authors.lastname: Jones
authors.affiliation: OMICS, Pathology Department, Mater Health Services, South Brisbane, QLD 4101, Australia; School of Medicine, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Deon J
authors.initials: DJ
authors.lastname: Venter
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia. Electronic address: bgfry@uq.edu.au.
authors.forename: Bryan G
authors.initials: BG
authors.lastname: Fry
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia. Electronic address: glenn.king@imb.uq.edu.au.
authors.forename: Glenn F
authors.initials: GF
authors.lastname: King
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001180:Arthropod Venoms / Q000737:chemistry*; D001181:Arthropods / Q000737:chemistry*; D002853:Chromatography, Liquid; D019143:Evolution, Molecular; D015723:Gene Library; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D020543:Proteome; D040901:Proteomics; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D059467:Transcriptome
chemical_list: D001180:Arthropod Venoms; D010455:Peptides; D020543:Proteome
keywords: Centipede venom; Evolution; MALDI imaging; Multidomain transcript; Posttranslational modification