UC Santa Barbara

Our understanding of the molecular mechanisms governing plant traits and development is largely restricted to a few model taxa which represent a small fraction of plant biodiversity. As such, these model systems lack the variation necessary to investigate many traits, especially adaptations to extreme environmental conditions. A suite of traits is common among high alpine plants which allow them to mitigate environmental stressors, including dwarfism and the production of stomata on both sides of a leaf (amphistomaty). The blue limestone columbine (Aquilegia jonesii) exemplifies both of these traits. The ability to cross this species with a non-alpine relative, along with an annotated reference genome, gives us an opportunity to fill a significant gap in our understanding of these adaptations at the genetic level. In addition, A. jonesii is unique among columbine species by having lost an otherwise novel floral organ, staminodes, which allows us to dissect aspects of their development.

In this dissertation, I present my research investigating the genetic basis and phenotypic nuance of these three exceptional traits in A. jonesii using Quantitative Trait Locus (QTL) analysis. My results demonstrate that staminode loss is not complete in A. jonesii, and the genetic basis of its partial loss is complex. Dwarfism in A. jonesii is similarly complex, likely involving multiple hormonal pathways, in contrast to model taxa where dwarfism is most often caused by a single gene. In contrast, amphistomaty is controlled primarily by a single major-effect QTL. I will show that this QTL is very likely due to cis-regulatory variation at the ortholog of a master stomatal development gene (AqSPEECHLESS). These studies together demonstrate the varying levels of complexity in the mechanisms by which nature selects for adaptive traits.