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The Allelic Variation in Avian β-Defensin Genes in Dabbling Ducks: A Comparison Between Teals and Mallards
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Zoonotisk Ekologi och Epidemiologi (ZEE))
2016 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Studies considering the evolution of the immune system are of great importance and can, for example, reveal naturally occurring resistance alleles. This is knowledge that subsequently can be applied in fields such as medicine, conservation biology and animal breeding. One way to find naturally occurring resistance alleles is by detecting the existence of trans-species polymorphism (TSP), which has been well studied in the adaptive immune system. However, the innate immune system has gained less attention, and this is despite its importance as a first line of defence against pathogens. For this study, the allelic variation of five avian beta-defensin genes (AvBD3b, AvBD4, AvBD5, AvBD10 and AvBD13), a type of antimicrobial peptide in the innate immune system, was investigated in the dabbling duck, teal (Anas crecca) and compared with previously collected data from the closely related mallard (Anas platyrhynchos). Allelic variation in teals were slightly higher than in mallards, though, purifying selection was found to be the most common evolutionary pressure acting on β-defensin genes in both species. This study did not provide evidence for TSP. However, the most common amino acid allele at each locus, except AvBD3b, was shared between the two species. Hence, these alleles may be important resistance alleles among the AvBD genes. Presumably, these alleles have, at least to some extent, been shaped by common duck pathogens that are shared between the two species by driving the development and maintenance of alleles with the best ability to eliminate these pathogens. With respect to the presumed activity of these alleles against common duck pathogens, it would be interesting to investigate these further.

Abstract [sv]

Studier rörande immunsystemets evolution är av stor vikt eftersom man tack vare dessa kan upptäcka naturligt förekommande resistensalleler. Detta är kunskap som i sin tur kan appliceras inom områden som medicin, bevarandebiologi och djuruppfödning. Ett sätt att finna dessa resistensalleler är genom att detektera förekomsten av trans-species polymorphism (TSP), något som är väl studerat i det adaptiva immunförsvaret. Det medfödda immunsystemet har dock blivit mer förbisett, och detta trots att det utgör en viktig första barriär mot infektioner. I denna studie undersöktes allelvariationen hos fem olika β-defensingener (AvBD3b, AvBD4, AvBD5, AvBD10 och AvBD13), en typ av antimikrobiell peptid i det medfödda immunsystemet, hos simmanden kricka (Anas crecca) vilken sedan jämfördes med tidigare insamlad data rörande variationen hos den nära släktingen gräsanden (Anas platyrhynchos). Allelvariationen var överlag något högre hos krickan än hos gräsanden. Det dominerande evolutionära trycket på AvBD-generna var ändå negativ (purifying) selektion hos båda arterna. Trots att denna studie inte kunde påvisa någon förekomst av TSP, fann vi att den vanligaste aminosyra-allelen för respektive loci (utom AvBD3b) delades mellan de två arterna. Detta betyder att dessa kan utgöra viktiga resistensalleler bland AvBD-generna. Dessa har troligen, åtminstone till viss del, formats av vanliga and-patogener som också delas mellan krickan och gräsanden genom att pådriva utvecklingen och följaktligen bibehållandet av allelerna med bäst förmåga att eliminera dessa vanliga patogener. Med hänseende till att dessa alleler troligen är aktiva mot vanliga andpatogener vore det intressant att studera dessa mer djupgående. 

Place, publisher, year, edition, pages
2016. , 53 p.
Keyword [en]
Antimicrobial peptides, β-Defensins, Waterfowl, Teals, Mallards
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:lnu:diva-55078OAI: oai:DiVA.org:lnu-55078DiVA: diva2:950078
Subject / course
Biology
Educational program
Biology Programme, 180 credits
Supervisors
Examiners
Available from: 2016-08-01 Created: 2016-07-27 Last updated: 2016-08-01Bibliographically approved

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