Recurrent evolution of adhesive defence systems in amphibians by parallel shifts in gene expression.

Natural selection can drive organisms to strikingly similar adaptive solutions, but the underlying molecular mechanisms often remain unknown. Several amphibians have independently evolved highly adhesive skin secretions (glues) that support a highly effective antipredator defence mechanism. Here we demonstrate that the glue of the Madagascan tomato frog, Dyscophus guineti, relies on two interacting proteins: a highly derived member of a widespread glycoprotein family and a galectin.

Diversity and Evolution of Frog Visual Opsins: Spectral Tuning and Adaptation to Distinct Light Environments.

Visual systems adapt to different light environments through several avenues including optical changes to the eye and neurological changes in how light signals are processed and interpreted. Spectral sensitivity can evolve via changes to visual pigments housed in the retinal photoreceptors through gene duplication and loss, differential and coexpression, and sequence evolution. Frogs provide an excellent, yet understudied, system for visual evolution research due to their diversity of ecologies (including biphasic aquatic-terrestrial life cycles) that we hypothesize imposed different selective pressures leading to adaptive evolution of the visual system, notably the opsins that encode the protein component of the visual pigments responsible for the first step in visual perception.

Diversity and Molecular Evolution of Antimicrobial Peptides in Caecilian Amphibians.

Antimicrobial peptides (AMPs) are key molecules in the innate immune defence of vertebrates with rapid action, broad antimicrobial spectrum, and ability to evade pathogen resistance mechanisms. To date, amphibians are the major group of vertebrates from which most AMPs have been characterised, but most studies have focused on the bioactive skin secretions of anurans (frogs and toads). In this study, we have analysed the complete genomes and/or transcriptomes of eight species of caecilian amphibians (order Gymnophiona) and characterised the diversity, molecular evolution, and antimicrobial potential of the AMP repertoire of this order of amphibians.

Q586B2 is a crucial virulence factor during the early stages of Trypanosoma brucei infection that is conserved amongst trypanosomatids.

Human African trypanosomiasis or sleeping sickness, caused by the protozoan parasite Trypanosoma brucei, is characterized by the manipulation of the host's immune response to ensure parasite invasion and persistence. Uncovering key molecules that support parasite establishment is a prerequisite to interfere with this process. We identified Q586B2 as a T.

Resistance Is Not Futile: Widespread Convergent Evolution of Resistance to Alpha-Neurotoxic Snake Venoms in Caecilians (Amphibia: Gymnophiona).

Predatory innovations impose reciprocal selection pressures upon prey. The evolution of snake venom alpha-neurotoxins has triggered the corresponding evolution of resistance in the post-synaptic nicotinic acetylcholine receptors of prey in a complex chemical arms race. All other things being equal, animals like caecilians (an Order of legless amphibians) are quite vulnerable to predation by fossorial elapid snakes and their powerful alpha-neurotoxic venoms; thus, they are under strong selective pressure.

Odorant-binding proteins in canine anal sac glands indicate an evolutionarily conserved role in mammalian chemical communication.

Background: Chemical communication is an important aspect of the behavioural ecology of a wide range of mammals. In dogs and other carnivores, anal sac glands are thought to convey information to conspecifics by secreting a pallet of small volatile molecules produced by symbiotic bacteria. Because these glands are unique to carnivores, it is unclear how their secretions relate to those of other placental mammals that make use of different tissues and secretions for chemical communication.

A New Family of Diverse Skin Peptides from the Microhylid Frog Genus .

A wide range of frogs produce skin poisons composed of bioactive peptides for defence against pathogens, parasites and predators. While several frog families have been thoroughly screened for skin-secreted peptides, others, like the Microhylidae, have remained mostly unexplored. Previous studies of microhylids found no evidence of peptide secretion, suggesting that this defence adaptation was evolutionarily lost.

Multiple Independent Recruitment of Sodefrin Precursor-Like Factors in Anuran Sexually Dimorphic Glands.

Chemical signaling in animals often plays a central role in eliciting a variety of responses during reproductive interactions between males and females. One of the best-known vertebrate courtship pheromone systems is sodefrin precursor-like factors (SPFs), a family of two-domain three-finger proteins with a female-receptivity enhancing function, currently only known from salamanders. The oldest divergence between active components in a single salamander species dates back to the Late Paleozoic, indicating that these proteins potentially gained a pheromone function earlier in amphibian evolution.

The anuran skin peptide bradykinin mediates its own absorption across epithelial barriers of the digestive tract.

When faced with a potential predator, a wide range of frog species secrete a mixture of peptide toxins from their skin to defend themselves. We have recently shown that antimicrobial peptides (AMPs) in a frog's defensive poison enhance the uptake of these peptides across epithelia, thereby speeding up the process of predator intoxication. This study provides evidence that bradykinin, a widespread peptide toxin in anurans (frogs), is capable to pass through epithelial barriers independent of this delivery system.

Reprint of: The non-mammalian MIF superfamily.

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule.

The non-mammalian MIF superfamily.

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule.

An orthologue of the host-defense protein psoriasin (S100A7) is expressed in frog skin.

Host-defense peptides and proteins are vital for first line protection against bacteria. Most host-defense peptides and proteins common in vertebrates have been studied primarily in mammals, while their orthologues in non-mammalian vertebrates received less attention. We found that the European Common Frog Rana temporaria expresses a protein in its skin that is evolutionarily related to the host-defense protein S100A7.

Low structural variation in the host-defense peptide repertoire of the dwarf clawed frog Hymenochirus boettgeri (Pipidae).

THE skin secretion of many amphibians contains peptides that are able to kill a broad range of microorganisms (antimicrobial peptides: AMPs) and potentially play a role in innate immune defense. Similar to the toxin arsenals of various animals, amphibian AMP repertoires typically show major structural variation, and previous studies have suggested that this may be the result of diversifying selection in adaptation to a diverse spectrum of pathogens. Here we report on transcriptome analyses that indicate a very different pattern in the dwarf clawed frog H.

Origin and functional diversification of an amphibian defense peptide arsenal.

The skin secretion of many amphibians contains an arsenal of bioactive molecules, including hormone-like peptides (HLPs) acting as defense toxins against predators, and antimicrobial peptides (AMPs) providing protection against infectious microorganisms. Several amphibian taxa seem to have independently acquired the genes to produce skin-secreted peptide arsenals, but it remains unknown how these originated from a non-defensive ancestral gene and evolved diverse defense functions against predators and pathogens. We conducted transcriptome, genome, peptidome and phylogenetic analyses to chart the full gene repertoire underlying the defense peptide arsenal of the frog Silurana tropicalis and reconstruct its evolutionary history.

Alternative interactions define gyrase specificity in the CcdB family.

Toxin-antitoxin (TA) modules are small operons associated with stress response of bacteria. F-plasmid CcdB(F) was the first TA toxin for which its target, gyrase, was identified. Plasmidic and chromosomal CcdBs belong to distinct families.

Anuran radiations and the evolution of tadpole morphospace.

Anurans (frogs and toads) are unique among land vertebrates in possessing a free-living larval stage that, parallel to adult frogs, diversified into an impressive range of ecomorphs. The tempo and mode at which tadpole morphology evolved through anuran history as well as its relationship to lineage diversification remain elusive. We used a molecular phylogenetic framework to examine patterns of morphological evolution in tadpoles in light of observed episodes of accelerated lineage diversification.

Functional and structural diversification of the Anguimorpha lizard venom system.

Venom has only been recently discovered to be a basal trait of the Anguimorpha lizards. Consequently, very little is known about the timings of toxin recruitment events, venom protein molecular evolution, or even the relative physical diversifications of the venom system itself. A multidisciplinary approach was used to examine the evolution across the full taxonomical range of this ∼130 million-year-old clade.

Gradual adaptation toward a range-expansion phenotype initiated the global radiation of toads.

Recent studies have identified range expansion as a potential driver of speciation. Yet it remains poorly understood how, under identical extrinsic settings, differential tendencies for geographic movement of taxa originate and subsequently affect diversification. We identified multiple traits that predict large distributional ranges in extant species of toads (Bufonidae) and used statistical methods to define and phylogenetically reconstruct an optimal range-expansion phenotype.

Identical skin toxins by convergent molecular adaptation in frogs.

The Tree of Life is rife with adaptive convergences at all scales and biological levels of complexity. However, natural selection is not likely to result in the independent evolution of identical gene products. Here we report such a striking example of evolutionary convergence in the toxic skin secretions of two distantly related frog lineages.

Novel venom proteins produced by differential domain-expression strategies in beaded lizards and gila monsters (genus Heloderma).

The origin and evolution of venom proteins in helodermatid lizards were investigated by multidisciplinary techniques. Our analyses elucidated novel toxin types resultant from three unique domain-expression processes: 1) The first full-length sequences of lethal toxin isoforms (helofensins) revealed this toxin type to be constructed by an ancestral monodomain, monoproduct gene (beta-defensin) that underwent three tandem domain duplications to encode a tetradomain, monoproduct with a possible novel protein fold; 2) an ancestral monodomain gene (encoding a natriuretic peptide) was medially extended to become a pentadomain, pentaproduct through the additional encoding of four tandemly repeated proline-rich peptides (helokinestatins), with the five discrete peptides liberated from each other by posttranslational proteolysis; and 3) an ancestral multidomain, multiproduct gene belonging to the vasoactive intestinal peptide (VIP)/glucagon family being mutated to encode for a monodomain, monoproduct (exendins) followed by duplication and diversification into two variant classes (exendins 1 and 2 and exendins 3 and 4). Bioactivity characterization of exendin and helokinestatin elucidated variable cardioactivity between isoforms within each class.

The toxicogenomic multiverse: convergent recruitment of proteins into animal venoms.

Throughout evolution, numerous proteins have been convergently recruited into the venoms of various animals, including centipedes, cephalopods, cone snails, fish, insects (several independent venom systems), platypus, scorpions, shrews, spiders, toxicoferan reptiles (lizards and snakes), and sea anemones. The protein scaffolds utilized convergently have included AVIT/colipase/prokineticin, CAP, chitinase, cystatin, defensins, hyaluronidase, Kunitz, lectin, lipocalin, natriuretic peptide, peptidase S1, phospholipase A(2), sphingomyelinase D, and SPRY. Many of these same venom protein types have also been convergently recruited for use in the hematophagous gland secretions of invertebrates (e.

A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus.

The predatory ecology of Varanus komodoensis (Komodo Dragon) has been a subject of long-standing interest and considerable conjecture. Here, we investigate the roles and potential interplay between cranial mechanics, toxic bacteria, and venom. Our analyses point to the presence of a sophisticated combined-arsenal killing apparatus.