Scholar: Leticia Rodriguez
Faculty Mentor: Dr. John Cushman
Research Topic: "Mechanisms Of The Evolutionary Origins Of Crassulacean Acid Metabolism In Tropical Orchids"
Abstract: Neotropical orchids have adjusted to the environment in order to prevent water loss by evolving a photosynthetic pathway to help cope with the carbon uptake and water loss. This photosynthetic pathway is termed crassulacean acid metabolism (CAM). The metabolic reactions required for CAM in plants are well understood, but the evolution of this pathway remains uncharacterized. This research focuses on the understanding of the evolutionary mechanisms of CAM within neotropical orchids by developing molecular markers for tracing CAM evolution. I focused on the phosphoenolpyruvate carboxylase (PEPC) gene family because it is widely conserved in plants, and specific members of the family are differentially expressed in plants performing CAM. PEPC was used to trace the evolutionary progression from C3, weak CAM, to strong CAM. Based on stable carbon isotope, night titratable acidity, and leaf thickness measurements, orchid species were identified as either CAM, weak CAM, or C3. Sequence analysis of DNA obtained from CAM species Oncidium ampliatum, Oncidium nanum, Oncidium carthagenense, and Rossioglossum insleyi indicated that three different PEPC isoforms were present in each species. Based upon sequence alignments and relative frequency of sampled cDNA clones, isoforms with the highest relative frequencies appeared to be related to other known CAM specific PEPC isoforms present in the National Center for Biotechnology Information (NCBI) database. The other isoforms present in each orchid species were found to have high homology to C3 PEPC isoforms. A phylogenetic tree of nucleotide sequences resulted in the grouping of two distinct groups one of Ppc1, the CAM specific isoform, and the other Ppc2 and Ppc3. Understanding the molecular mechanism responsible for CAM expression will be important to our understanding of species survival in the face of current global climate change and of arid land area expansion worldwide.
Graduated With Baccalaureate Degree: Spring 2008
Masters or Doctoral Program Update: Received a masters in Biotechnology from the University of Nevada, Reno in spring 2008. Accepted into the Doctoral Program in Pharmaceutical Sciences at the University of Texas, Austin.