The Dioscorea genus is made up of a group of monocotyledonous plants comprising the "true yams”. Yam is an important staple crop, which is made up mainly of carbohydrates but also constitutes an important source of proteins which make up 1-3% of the fresh tubers (Gaidamashvili et al., 2004). This research uses Dioscorea alata, D. villosa, D. bulbifera, D. dodecaneura, and D. nipponica to determine the expression profile of the enzyme, carbonic anhydrase (CAH), in varying structural components of yams. This profile was determined by conducting PCR amplification of cDNA samples and analyzing them through gel electrophoresis and sequencing. Using the extracted CAH sequences from the Dioscorea species and CAH amino acid sequences from the international database, GenBank, of Arabidopsis thaliana and Oryza sativa, this project infers evolutionary relationships between the three taxa. Determining the evolutionary history of CAH allows for a better understanding of the evolution of the Dioscorea genus as a whole.

CAH expression was confirmed in the tubers of D. bulbifera and D. dodecaneura, and in the leaves of D. bulbifera. However, CAH absence was confirmed in the leaves of D. alata, D. villosa, D. dodecaneura, and D. nipponica, and in the shoot tips of all five species. The phylogenetic tree which was developed (see attached) shows that D. bulbifera leaf and tuber sequences contain the same version of the CAH gene, and a highly similar version to D. dodecaneura. Surprisingly, it also indicates that instead of each version of the CAH gene being more similar to corresponding versions in different taxa (orthologous relationships) as was expected, it is most similar to copies within its own taxa (paralogous relationships). These results indicate that the CAH gene replicated after speciation occurred in the three taxa (Dioscorea, Arabidopsis thaliana, and Oryza sativa) not before as was expected.
Establishing the expression of protein in the leaves of Dioscorea where it was previously believed undetectable shows that the plants could have nutritional value in places other than just the tuber. This could mean that every part of the D. bulbifera plant is edible, not just the tubers, and after engineering and refining this newly discovered protein, this project could be a new step in combating world hunge

This study is supported with funding from the Simons Foundation and the Department of Ecology and Evolution at SUNY Stony Brook.