Molecular basis and the role of phenotypic plasticity in thermal adaptation

Understanding the mechanisms that generate phenotypic variation and their impact on evolutionary processes is central in modern biology.

When faced with adverse environmental conditions populations survive through two distinct processes: phenotypic plasticity (i.e. mechanism in which one genotype produces several different phenotypes depending on the environment) or evolutionary adaptation (i.e. pertinent allele frequency changes in population).

While numerous studies have expanded our knowledge of evolutionary principles, the molecular basis and the relative contribution of these two processes to the adaptation is still unknown.

Here I propose to tackle this key question by performing experimental evolution and exposing wild-caught D.melanogaster populations to four temperature selection regimes: constant cold temperature, constant hot temperature, fluctuating between hot and cold and optimal temperature as a control.

To determine the genetic targets of selection behind the change in thermal tolerance I will perform pooled whole population sequencing of both ancestral and evolved populations.

The alleles that increase in frequencies between the ancestral and evolved populations will be further validated to determine their effect on the thermal tolerance.

To understand the contribution of phenotypic plasticity to the process of adaptation, I will transfer the evolved populations into a non-selective environment and determine the relative change in thermal tolerance that occurred upon the transfer.

Furthermore, to unravel the gene regulatory changes associated with plastic response, I will perform ATAC-seq (chromatin accessibility assay) and RNA-seq (changes in gene expression) of evolved individuals before and after the transfer to the non-selective environment.

The inclusion of epigenomic and transcriptomic analysis of the evolved populations will enable us to construct a more holistic picture of adaptation.