Project
Hedging your bets: do organisms adapt crossover positioning to favour localized recombination?
Sexual reproduction creates new combinations of genes through meiotic crossovers. There is evidence that crossovers are located at positions of the genome marked by RNA transcription, which is often itself regulated in response to the environment. As such, this project aims to test whether environmentally regulated genes undergo more crossovers when transcribed. Studies are being undertaken in Saccharomyces cerevisiae and proposed in Arabidopsis thaliana.
Background
Meiotic recombination is instrumental in generating genetic variation in Eukaryote organisms, and is widely considered to be conserved across the Domain. However, the evolutionary benefits of recombination are less clear, as there are many costs to sexual reproduction. These include recombination load, where beneficial combination of alleles are broken up by recombination. There is evidence suggesting that genomes are non-randomly organized, with environmentally regulated, functionally related genes clustering together. This increases the likelihood that these genes will be inherited as a unit beyond the meiotic division.
Studies show many factors associated to the positioning of meiotic crossovers, including epigenetic marks such as the histone methylation mark H3K4me3. This specific mark is deposited on histones bound to transcribed DNA. Furthermore, there is recent evidence that the recombination landscape is shaped by extrinsic factors, such as temperature and age.
This project aims to test whether the recombination rate at regulated gene clusters is modified by environmentally responsive transcription changes. Increases in local recombination rate would increase the diversity of local genotypes, allowing for efficient selection of the fittest combinations.
Project description
To test differences in recombination rate, we have performed an experiment sequencing the bulk meiotic progeny of Saccharomyces paradoxus, classifying sequenced reads into recombinant or parental background and estimating local recombination rates across the genome.
We are in the process of constructing a selective marker-assisted assay to quantify the number of recombinant progeny in Saccharomyces cerevisiae across ~10kB windows containing regulated gene clusters.
Further proposals include a project to observe recombination rates across local regions in A. thaliana using previously constructed, fluorescently marked lines.