Gene regulatory evolution in flycatchers: statistical approaches for the analysis of allele-specific expression

Sammanfattning: Understanding the molecular mechanisms underlying evolutionary changes in gene expression is a major research topic in biology. While a powerful approach to study this is the analysis of allele-specific expression (ASE), most of previously published methods can only be applied to lab organisms. In this thesis, to enable the analysis of ASE in natural organisms, I developed two methods for ASE detection. The first one was Bayesian negative binomial approach, and the second one was Read-backed Phasing-based ASE approach. Both methods performed well in simulations and comparisons. By applying those methods, I found that ASE was prevalent in natural flycatcher species. Combining the analyses of differential gene expression and ASE, I found a widespread cis-trans compensation and a critical role of tissue-specific regulatory mechanism during gene expression evolution. Moreover, for cis-regulatory sequences, there was a larger proportion of slightly deleterious mutations and weaker signatures of positive selection for genes with ASE than genes without ASE. For coding sequence, no such difference was observed. These results indicated that the evolution of gene expression and coding sequences could be uncoupled and occurred independently.