Evolution of Crassulacean Acid Metabolism (CAM) in Neotropical Orchids: Linking Gene Expression with Susceptibility to Extinction by Drought

EPA Grant Number: F07D60205
Title: Evolution of Crassulacean Acid Metabolism (CAM) in Neotropical Orchids: Linking Gene Expression with Susceptibility to Extinction by Drought
Investigators: Silvera, Katia
Institution: University of Nevada - Reno
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2007 through September 1, 2010
RFA: GRO Fellowships for Graduate Environmental Study (2007) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Molecular Biology/Genetics


This study focuses on the evolution of Crassulacean acid metabolism (CAM) in neotropical orchids by elucidating the molecular mechanisms needed for CAM function. CAM is a specialized form of photosynthesis that minimizes water loss by limiting CO2 uptake from the atmosphere at night, thus improving the ability to acquire carbon in water and CO2-limited environments. Orchid CAM distribution can be used to predict susceptibility of extinction by drought under current global climate change because orchids excel in a wide variety of tropical ecosystems through the expression of a continuum of C3 to CAM photosynthetic pathways. This project is designed to test the hypothesis that at least three major changes have occurred during evolution to adapt CAM progenitor genes for function in CAM plants: 1) CAM isoform genes in orchids have evolved highly expressed mRNA expression patterns; 2) Leaf preferential (or specific) expression patterns; and 3) Circadian clock control expression patterns. The results of this project will help understand photosynthetic plasticity in plants and how changes in gene expression may explain adaptation to changing climatic conditions.


A combination of approaches will be used to decipher the basic molecular mechanisms of CAM function. The occurrence of CAM (determined by stable carbon isotope and titratable acidity) will be mapped onto an orchid phylogeny (Subtribe Oncidiinae) tracing the evolution of gene expression within closely related species. CAM expression will then be linked with quantitative and qualitative molecular diagnostic indicators of CAM, so that the molecular mechanisms necessary to evolve from a C3 species to a CAM species can be understood.

Expected Results:

CAM-specific gene recruitment and expression in orchids is expected to be linked with patterns of evolutionary history of drought resistance mechanisms in tropical ecosystems. This work will elucidate the mechanisms of how plants can cope with drought under current trends of global climate change, and help refine predictions of whether endangered species are more prone to extinction.

Supplemental Keywords:

Climate Change, Crassulacean Acid Metabolism (CAM), CITES, Drought, Epiphytes, Molecular Genetics, Molecular Markers, Orchids, Photosynthetic Pathways, Subtribe Oncidiinae, Endangered species,, RFA, Air, climate change, Air Pollution Effects, Atmosphere

Progress and Final Reports:

  • 2008
  • 2009
  • Final