Population genomics of Arabidopsis arenosa

 

Adaptation to whole genome duplication:
Autotetraploids arise from within‐species genome duplication and carry four rather than two homologous copies of each chromosome. This is a game‐changing mutation; newly formed polyploid lineages face challenges to genome stability, gene regulation and chromosome segregation, and may show epigenetic and structural instability, extensive chromatin remodeling, and even chromosome gain or loss (aneuploidy). Most established polyploid species do not suffer the instabilities observed in young polyploids, suggesting that selection can stabilize duplicated genomes. Though there has been extensive work on the cytology of polyploids, and several genes for meiotic stabilization have been mapped (and one has been characterized - the Ph1 gene in allohexaploid wheat), little is known about the proteins that promote meiotic adaptation in autopolyploids.

 

We have been using a genome scanning approach to begin to understand the molecular basis of adaptation to whole genome duplication. Our first efforts, to scan for selection in the tetraploid genome, is currently in press at PLoS Genetics, revealed numerous interesting candidate genes, including factors important for chromosome synapsis, homologous recombination and DNA repair. Additional cellular and physiological processes are also implicated, including cell cycle genes, chromatin remodeling genes, and cell size and shape regulators. We are currently also sequencing and analyzing diploid A. arenosa to compare to the tetraploid and analyze genetic divergence. This is in collaboration with Levi Yant and Jesse Hollister.

 

Population genomics:
We are also using RADseq and low pass population resequencing to study the history and biogeography of diploid and tetraploid A. arenosa. We are especially interested to understand how and when the tetraploids formed, how they spread across the landscape and how they subsequently adapted to novel habitats.

 

 

A tetraploid Arabidopsis arenosa plant growing on a limestone rock outcrop in southwest Germany (in the Upper Danube Valley region, near the town of Hausen im Tal; photo, K Bomblies).