Speciation in flowering mustard plant driven by alleles adapted to local conditions

HudsonAlpha faculty investigator part of team that identified chromosomal inversion

On the slopes of the Northern Rocky Mountains, the flowering mustard plant Boechera stricta is undergoing a quiet transformation – that is, evolving into a fitter species better adapted to its local environment. HudsonAlpha faculty investigator Jeremy Schmutz was part of a team led by Thomas Mitchell-Olds of Duke University who analyzed the mechanisms by which Boechera stricta living in a hybrid zone in the Northern Rocky Mountains experienced positive directional selection. Their study was published in Nature Ecology and Evolution in April 2017.

“Here, in Boechera stricta we are capturing that moment of selection – the moment when the subpopulation with the inversion takes over from the pre-inversion genotype and outcompetes it,” said DOE JGI Plant Program Head Jeremy Schmutz, a co-author on the study. “The inversion fixes a set of alleles in the population. Here the set of fixed alleles improves survivability over the previous genotypes.” Schmutz is also the co-director of the HudsonAlpha Genome Sequencing Center.

As part of the DOE JGI’s Community Science Program and Emerging Technologies Opportunity Program, the researchers who worked on the project sequenced and analyzed the genome of Boechera stricta, a relative of the model plant Arabidopsis. With the genome in hand, they used techniques including gene mapping and chromosome painting methods to identify a major chromosomal inversion that controls ecologically important traits in the plant. They tested for QTLs—regions of the genome where the DNA codes for genetic traits—in Boechera stricta’s chromosomal inversion. They found several linked QTLs that changed ecologically important characteristics of the plant such as flowering time and plant size, enabling it to adapt to its local environment, which in turn increased its fitness.

The knowledge gained from this study “gives evolutionary biologists experimental evidence showing how chromosomal changes contribute to adaptation and speciation,” said senior author and DOE JGI collaborator Thomas Mitchell-Olds of Duke University. “Furthermore, the genome sequence will help us understand how Boechera species are able to reproduce asexually by seeds, a process that can be used by farmers to speed up crop improvement practices.”