CAREER: Understanding the evolution and genetic basis of meiotic recombination rate

Meiotic recombination is an important source of genetic diversity and plays a key role in organismal adaptation. Meiotic recombination rate varies greatly at the individual, population, and species level. However, the genetic basis and evolution of recombination rate variation remains poorly understood. Using state-of-the-art genomic techniques such as single-cell sequencing and CRISPR-Cas9 gene editing, this project will identify the genes responsible for recombination rate variation and will illuminate whether recombination rate evolves due to natural selection. Moreover, this project will disseminate cutting-edge genomic knowledge through an innovative, inquiry-based undergraduate curriculum, engaging students of diverse backgrounds in research, and hosting public outreach events for K-12 students. This project will examine the evolution and genetic basis of meiotic recombination rate variation in the freshwater microcrustacean species Daphnia pulex and D. pulicaria, which experienced strong divergent selection during their divergence. Standard procedures for constructing genetic maps are laborious and difficult to scale up for population surveys. This project will develop a novel high throughput system for mapping based on single-sperm genomic sequencing with combinatorial indexing. This will enable the construction of hundreds of genetic maps in an economical and efficient manner. Using this approach, this project will perform comprehensive population genomic analyses of recombination rate variation both within- and between-species. It will also examine the genomic signatures of adaptive vs. neutral evolution of recombination rate. This will help bridge the gap between empirical data and evolutionary theory on recombination rate evolution. Lastly, this project will identify causal genes and genetic variants for recombination rate variation in Daphnia by combining association mapping analyses and CRISPR-Cas9 gene editing, thereby enhancing understanding of genetic regulation of meiotic recombination. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.