Little is known about the processes by which organisms evolve and adapt to a broad range of environments, giving rise to the Earth's vast biological diversity (including >250,000 species of terrestrial plants). Occurrences of the rare and unusual serpentine (or ultra-mafic) rocks on the Earth's surface give rise to some of the most extreme terrestrial environments, characterized by high levels of toxic heavy metals such as nickel and chromium, and by extremely low levels of essential mineral nutrients such as calcium, nitrogen, phosphorus and potassium. The serpentine environment is also characterized by poor soil development and drought stress. Most plants are excluded from serpentine soils, but a very few plants have evolved remarkable tolerance to serpentine, providing a clear and compelling example of evolutionary adaptation to the environment. In order to study the genetic basis of serpentine tolerance we have developed a molecular-genetic experimental system based on the rare serpentine plant Caulanthus amplexicaulis var. barbarae and the closely related non-serpentine plant Caulanthus amplexicaulis var. amplexicaulis (both close relatives of the well-studied model plant Arabidopsis thaliana). Using this system, the number and chromosomal locations of genes that confer tolerance to serpentine will be estimated by quantitative trait locus (QTL) analysis. In the future, these genes can be identified and characterized by a comparative-genomics approach using information from Arabidopsis.
This project will yield insights into plant mineral nutrition and drought tolerance that may have significant implications for sustainable agricultural productivity in a changing global climate. In addition, greater understanding of the mechanisms of plant tolerance to toxic heavy metals is key to several strategies for bioremediation of metal-contaminated environments. Finally, this project will demonstrate how researchers can apply the genomic information gained from substantial public investments in a small number of model organisms toward understanding the world's biological diversity and adaptation to extreme and complex environments.
