Genomic signatures of parasite-driven natural selection in north European Atlantic salmon (Salmo salar)

Abstract Understanding the genomic basis of host-parasite adaptation is important for predicting the long-term viability of species and developing successful management practices. However, in wild populations, identifying specific signatures of parasite-driven selection often presents a challenge, as it is difficult to unravel the molecular signatures of selection driven by different, but correlated, environmental factors. Furthermore, separating parasite-mediated selection from similar signatures due to genetic drift and population history can also be difficult. Populations of Atlantic salmon (Salmo salar L.) from northern Europe have pronounced differences in their reactions to the parasitic flatworm Gyrodactylus salaris Malmberg 1957 and are therefore a good model to search for specific genomic regions underlying inter-population differences in pathogen response. We used a dense Atlantic salmon SNP array, along with extensive sampling of 43 salmon populations representing the two G. salaris response extremes (extreme susceptibility vs resistant), to screen the salmon genome for signatures of directional selection while attempting to separate the parasite effect from other factors. After combining the results from two independent genome scan analyses, 57 candidate genes potentially under positive selection were identified, out of which 50 were functionally annotated. This candidate gene set was shown to be functionally enriched for lymph node development, focal adhesion genes and anti-viral response, which suggests that the regulation of both innate and acquired immunity might be an important mechanism for salmon response to G. salaris. Overall, our results offer insights into the apparently complex genetic basis of pathogen susceptibility in salmon and highlight methodological challenges for separating the effects of various environmental factors.Peer reviewe

Footprints of directional selection in wild atlantic salmon populations: Evidence for parasite-driven evolution?

Mechanisms of host-parasite co-adaptation have long been of interest in evolutionary biology; however, determining the genetic basis of parasite resistance has been challenging. Current advances in genome technologies provide new opportunities for obtaining a genome-scale view of the action of parasite-driven natural selection in wild populations and thus facilitate the search for specific genomic regions underlying inter-population differences in pathogen response. European populations of Atlantic salmon (Salmo salar L.) exhibit natural variance in susceptibility levels to the ectoparasite Gyrodactylus salaris Malmberg 1957, ranging from resistance to extreme susceptibility, and are therefore a good model for studying the evolution of virulence and resistance. However, distinguishing the molecular signatures of genetic drift and environment-associated selection in small populations such as land-locked Atlantic salmon populations presents a challenge, specifically in the search for pathogen-driven selection. We used a novel genome-scan analysis approach that enabled us to i) identify signals of selection in salmon populations affected by varying levels of genetic drift and ii) separate potentially selected loci into the categories of pathogen (G. salaris)-driven selection and selection acting upon other environmental characteristics. A total of 4631 single nucleotide polymorphisms (SNPs) were screened in Atlantic salmon from 12 different northern European populations. We identified three genomic regions potentially affected by parasite-driven selection, as well as three regions presumably affected by salinity-driven directional selection. Functional annotation of candidate SNPs is consistent with the role of the detected genomic regions in immune defence and, implicitly, in osmoregulation. These results provide new insights into the genetic basis of pathogen susceptibility in Atlantic salmon and will enable future searches for the specific genes involved

Sulphonamide inhibition studies of the beta-carbonic anhydrase GsaCA beta present in the salmon platyhelminth parasite Gyrodactylus salaris

Peer reviewe

Commencement Program, August (1966)

https://red.mnstate.edu/commencement/1105/thumbnail.jp

Cloning, purification, kinetic and anion inhibition studies of a recombinant beta-carbonic anhydrase from the Atlantic salmon parasite platyhelminth Gyrodactylus salaris

A beta-class carbonic anhydrase (CA, EC 4.2.1.1) was cloned from the genome of the Monogenean platyhelminth Gyrodactylus salaris, a parasite of Atlantic salmon. The new enzyme, GsaCA beta has a significant catalytic activity for the physiological reaction, CO2 + H2O (sic) HCO3- + H+ with a k(cat) of 1.1 x 10(5) s(-1) and a k(cat)/K-m of 7.58 x 10(6) M-1 x s(-1). This activity was inhibited by acetazolamide (K-I of 0.46 mu M), a sulphonamide in clinical use, as well as by selected inorganic anions and small molecules. Most tested anions inhibited GsaCA beta at millimolar concentrations, but sulfamide (K-I of 81 mu M), N,N-diethyldithiocarbamate (K-I of 67 mu M) and sulphamic acid (K-I of 6.2 mu M) showed a rather efficient inhibitory action. There are currently very few non-toxic agents effective in combating this parasite. GsaCA beta is subsequently proposed as a new drug target for which effective inhibitors can be designed.Peer reviewe

Cloning, purification, kinetic and anion inhibition studies of a recombinant β-carbonic anhydrase from the Atlantic salmon parasite platyhelminth Gyrodactylus salaris

A β-class carbonic anhydrase (CA, EC 4.2.1.1) was cloned from the genome of the Monogenean platyhelminth Gyrodactylus salaris, a parasite of Atlantic salmon. The new enzyme, GsaCAβ has a significant catalytic activity for the physiological reaction, CO2 + H2O ⇋ HCO3− + H+ with a kcat of 1.1 × 105 s−1 and a kcat/Km of 7.58 × 106 M−1 × s−1. This activity was inhibited by acetazolamide (KI of 0.46 µM), a sulphonamide in clinical use, as well as by selected inorganic anions and small molecules. Most tested anions inhibited GsaCAβ at millimolar concentrations, but sulfamide (KI of 81 µM), N,N-diethyldithiocarbamate (KI of 67 µM) and sulphamic acid (KI of 6.2 µM) showed a rather efficient inhibitory action. There are currently very few non-toxic agents effective in combating this parasite. GsaCAβ is subsequently proposed as a new drug target for which effective inhibitors can be designed.</p

Review: Insect Life - Cycle Polymorphism

Danks, H. V. (ed.) 1994: Insect Life-Cycle Polymorphism. - Kluwer Academic Publishers, Dordrecht, The Netherlands. ISBN 0-7923-2828-0

Sallan jääjärvi katosi 10 500 vuotta sitten, mutta muutamat reliktinieriäpopulaatiot ovat vielä elossa

Tämän tutkielman aiheena on kolme Suomen Metsä-Lapissa tunnettua, eristynyttä nieriä- eli rautupopulaatiota. Ne ovat jääkauden jälkeisiltä ajoilta jääneitä reliktejä ja yritämme artikkelissa hahmotella niiden asemaa sukunsa ja lajinsa edustajina. Ehdotamme myös hypoteesia populaatioiden reliktiluonteesta. Milloin ja miten ne ovat saapuneet lampiinsa, miksi ja miten ne ovat ovat säilyneet nykyaikaan, ja miten niiden käy tulevaisuudessa. Pienten eristyneiden reliktipopulaatioiden biologiassa täytyy olla jotain opittavaa tutkijalle, joka haluaa selvittää elossa pysymisen näkökohtia evoluutiossa. Nykyisen maailmankauden, antroposeenin, eliöpopulaatioiden ankarin evolutiivinen haaste on elinkykyisenä pysyminen. Populaatiot, joiden säilyminen nykyaikaan on suorastaan ihme, ovat mitä kiinnostavampia tutkimuskohteita. Ne ovat myös tärkeitä suojelukohteita. Jos populaatio on pysynyt elossa kymmenen tuhatta vuotta vastoin todennäköisyyden lakeja, sen säilyttäminen on meille eettinen velvollisuus