This project will investigate genome evolution in cacti, the flowering plant family Cactaceae. The 1500 species of cacti are among the most spectacular and evolutionarily successful groups of succulent plants in arid and semi-arid regions of the Americas. Despite their remarkably diverse life forms and extreme physiological adaptations for life in arid, often hot habitats, genomic resources in Cactaceae are still very limited. This research team, with members from Arizona State University, the Desert Botanic Garden, and the University of Arizona, will provide fundamental genomic information and resources essential to our understanding of species diversity, ecology, photosynthesis and evolution of cacti, with expected impacts in basic science as well as horticultural and economic arenas. Undergraduates from underrepresented groups in science will be trained broadly in genomics, bioinformatics, computational, evolutionary and systematic biology techniques. Results from this project will be used to enhance an undergraduate genetics course and a biology education website at Arizona State University, and outreach programs at the Desert Botanical Garden. All data from the project will be deposited in public databases.
This project will focus on the unusual size and rearrangements of the plastid (i.e., chloroplast) genome within cacti, and in particular the loss of multiple genes critical to the process of photosynthesis observed in several large columnar North American species. The DNA sequence data generated will be used to produce complete plastid genomes, as well as identify multiple nuclear and mitochondrial genes, from a broad sampling of ecologically and morphologically diverse cactus species. This will enable an investigation of the distribution and pattern of specific structural genomic rearrangements and test hypotheses about the causes and consequences of these architectural changes. At the same time, the project will contribute data to generate a more robust phylogenetic framework for investigating the evolutionary relationships of specific groups of Cactaceae, as well as measuring rates of molecular evolution and mutation across the family. Reconstructing the history of gene losses and genome reconfigurations in this family of photosynthetic plants offers a system for studying genome variation and evolution under the selective pressures of life in the desert environment.