Molecular physiology of pumiliotoxin sequestration in a poison frog

Abstract

Poison frogs bioaccumulate alkaloids for chemical defense from their arthropod diet. These small molecules are sequestered from their gastrointestinal tract and transported to the skin for storage. Although many alkaloids are accumulated without modification, some poison frog species can metabolize pumiliotoxin (PTX 251D) into the more potent allopumiliotoxin (aPTX 267A). Despite extensive research characterizing the chemical arsenal of poison frogs, the physiological mechanisms involved in the sequestration and metabolism of individual alkaloids is unknown. We performed a feeding experiment with the Dyeing poison frog (Dendrobates tinctorius) to ask if this species can metabolize PTX 251D into aPTX 267A and what gene expression changes are associated with PTX 251D exposure in the intestines, liver, and skin. We found that D. tinctorius can metabolize PTX 251D into aPTX 267A, and that PTX 251D exposure changed the expression of genes involved in immune system function and small molecule metabolism and transport. These results show that individual alkaloids can modify gene expression across poison frog tissues and suggest that different alkaloid classes in wild diets may induce specific physiological changes for accumulation and metabolism.

Poison frog dietary preference depends on prey type and alkaloid load

“…The following week, frogs were retested in a final preference trial. Previous work has established this alkaloid-feeding paradigm as appropriate in creating low and high DHQ groups (30,31).…”

“…We first analyzed frog secretions using GC/MS as described above and did not detect DHQ. We then used liquid chromatography / mass spectrometry (LC/MS) as previously described [30,31] given this method is more sensitive. The preliminary LC/MS data is consistent with an increase in DHQ with longer feeding times.…”

“…The following week, female frogs were retested in a final preference trial. Previous work has established this alkaloid-feeding paradigm as appropriate in creating low and high DHQ groups [30,31]. Each female frog was assayed once for dietary preference between ants, beetles, flies and larvae at each toxicity level for a total of three trials.…”

State of the Amphibia 2020: A review of five years of amphibian research and existing resources

“…Research on many other amphibian genera has made notable historical contributions to biology: e.g., Plethodon cinereus in behavioral ecology and development (Dent 1942;Heatwole 1962;Kleeberger and Werner 1982;Wyman and Hawksley-Lescault 1987;Kerney 2011;Kerney et al 2012); Engystomops in sexual selection (Ryan et al, 1990); Rana in cloning (Briggs and King, 1952); Rana and (Lefcort et al, 1998;Hopkins et al, 2000;Bridges, 2000;Pollet and Bendell-Young, 2000) Acris (Fleming et al, 1982;Clark et al, 1998;Reeder et al, 1998) in community ecology and toxicology. New tools have since promoted the emergence of more model systems from classically "non-model" species and systems, such as dendrobatid poison frogs for the neurobiology of parental care (Roland and O'Connell, 2015;O'Connell, 2020) and the molecular evolution of chemical defense (Saporito et al, 2012;Tarvin et al, 2017;Caty et al, 2019;Alvarez-Buylla et al, 2022), toxic salamanders and resistant garter snakes for co-evolution (Geffeney et al, 2005;Bucciarelli et al, 2022), Spea for phenotypic plasticity and life-history evolution (Levis et al, 2015(Levis et al, , 2020, and Nanorana parkeri for adaptation to high elevation (Sun et al, 2015(Sun et al, , 2018Wang et al, 2018). As we will highlight here, the growing availability of amphibian genomes and other molecular resources poises amphibian researchers to further develop other amphibians as new "model" species.…”

State of the Amphibia 2020: A Review of Five Years of Amphibian Research and Existing Resources

“…Research on many other amphibian genera has made notable historical contributions to biology: e.g., Plethodon cinereus in behavioral ecology and development (Dent, 1942;Heatwole, 1962;Kleeberger and Werner, 1982;Wyman and Hawksley-Lescault, 1987;Kerney, 2011;Kerney et al, 2012); Engystomops in sexual selection (Ryan et al, 1990); Rana in cloning (Briggs and King, 1952); Rana (Lefcort et al, 1998;Bridges, 2000;Hopkins et al, 2000;Pollet and Bendell-Young, 2000) and Acris (Fleming et al, 1982;Clark et al, 1998;Reeder et al, 1998) in community ecology and toxicology. New tools have since promoted the emergence of more model systems from classically ''non-model'' species and systems, such as dendrobatid poison frogs for the neurobiology of parental care (Roland and O'Connell, 2015;O'Connell, 2020) and the molecular evolution of chemical defense (Saporito et al, 2012;Tarvin et al, 2017;Caty et al, 2019;Alvarez-Buylla et al, 2022), toxic salamanders and resistant garter snakes for coevolution (Geffeney et al, 2005;Bucciarelli et al, 2022), Spea for phenotypic plasticity and life-history evolution (Levis et al, 2015(Levis et al, , 2020, and Nanorana parkeri for adaptation to high elevation (Sun et al, 2015(Sun et al, , 2018Wang et al, 2018). As we will highlight here, the growing availability of amphibian genomes and other molecular resources poises amphibian researchers to further develop other amphibians as new ''model'' species.…”