University of Cambridge
The Role of Epigenetics in the Regulation of Meiotic Recombination in Triticum aestivum and Arabidopsis thaliana
Abstract
dc:description.abstractMeiosis is a highly conserved specialized cell division unique to eukaryotes that functions to increase genetic diversity in offspring. Crossover formation is an outcome of the process of meiotic recombination, a cascading series of events during which homologous chromosomes undergo pairing and reciprocal exchange of genetic information. During meiotic recombination, meiotic DSB formation and crossover localization is negative correlated in plant species with high levels of heterochromatic features such as H3K9me2, DNA methylation, and nucleosome density. In plant species, maintenance of heterochromatin is controlled via the concerted efforts CHROMOMETHYLASE 3 (CMT3) and KRYPTONITE/SUVH5/SUVH6 (KSS), and mutation of these features can remodel recombination events to previously suppressed regions of the genome. Remodelling of crossovers to cold regions is of particular interest to crop breeders, who seek to unlock genomic regions to crossovers to identify novel, beneficial allelic combinations. To further characterize the meiotic recombination landscape in bread wheat, I have analyzed the genome wide distribution of the meiotic axis protein, ASY1, and the meiotic recombinase, DMC1 via Chromatin-Immunoprecipitation and sequencing (ChIP-seq). Consistent with crossover distribution, I have observed enrichment of both factors in the distal, highly recombining regions of the genome, correlating with facultative heterochromatin, signatures of adaption, and defense response genes (i.e. NLR containing gene families). I have also generated homozygous mutant lines for kryptonite and suvh5/6 orthologues in wheat, and also characterized a CMT3 related, cmt6S-ε mutant. Here, I have observed reduction of heterochromatin, resulting in reduced fertility and high prevalence of homoeologous recombination events in metaphase I chromosomes in cmt6S-ε, similar to Ph1 locus mutant phenotypes. This confirms an intimate relationship with early meiotic recombination events and crossovers in bread wheat and presents a novel function for epigenetic regulation of homoeologous recombination. In addition, I present the ChIP-seq analysis of DMC1 in Arabidopsis thaliana in wildtype versus cmt3 and kss mutants. DMC1 in wildtype is enriched strikingly in regions flanking meiotic DSB sites, however this pattern is remodelled to the DSB sites themselves in cmt3 and kss mutants. This presents a novel function for DNA methylation in determining the fine-scale distributions of recombinases in Arabidopsis meiosis. Together, these results advance the understanding of epigenetic regulation of meiotic processes in plants.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2023
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Holland, Daniel
- Advisor dc:contributor.advisor
-
- Henderson, Ian
Subjects
dc:subject × 3Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.96958
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/350431