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Global patterns of natural variation in Drosophila melanogaster's immune genes

Grant number: 17/06374-0
Support type:Scholarships abroad - Research Internship - Master's degree
Effective date (Start): August 07, 2017
Effective date (End): February 06, 2018
Field of knowledge:Biological Sciences - Genetics
Principal researcher:Rodrigo Cogni
Grantee:Murillo Fernando Rodrigues
Supervisor abroad: John Pool
Home Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Research place: University of Wisconsin-Madison (UW-Madison), United States  
Associated to the scholarship:16/01354-9 - Clinal variation in immune-related genes of Drosophila melanogaster, BP.MS

Abstract

The question "Are immunity genes more subject to selection than other genes?" has been widely addressed, especially in Drosophila melanogaster. The studies differ in the methods used for detecting selection: while some methods recover what happened in a recent past, others reveal selection in the million-years timescale. Investigating natural selection over a long timescale, Obbard et al. (2009) found that immunity genes have double the adaptive rate than other genes. However, the signature of natural selection was heterogeneous among immune classes, with RNAi being the class that showed the strongest adaptive changes. I've been addressing the same question in my MSc thesis, but over a very recent timescale. My preliminary analyses, suggest that immunity genes are more subject to natural selection than other genes in this recent timescale. RNAi is the class that showed the stronger sign of selection, similar to what was found in the long timescale. A very recently published study performed a scan for adaptive evolution in D. melanogaster immune system since D. melanogaster global expansion, but no signatures of natural selection in immunity genes, or even in RNAi genes, was uncovered. The study suffered from low statistical power to detect differences between immunity and non-immunity genes. Therefore, we propose to further investigate the evolution of D. melanogaster's immune system in this intermediate timescale. We are going to take advantage of the Drosophila Genome Nexus, a resource with over 1000 genomes from around the world. We will estimate FST for each polymorphism in immunity genes and compare with nearby non-immunity genes. Furthermore, we will compare the FST for all the immune classes. Our expectation is that immunity genes will show stronger signatures of adaptive change, with RNAi being the class in which selection acted more intensely.