Christiana Merrywell

Chemical Genomics: Forging Complementation at the Interface of Chemistry, Engineering, Computational Sciences and Cell Biology
University of California, Riverside


I received my Bachelors degree in Chemistry from the University of Southern California in 2004 and went on to the University of California-Riverside to pursue a Ph.D. in Analytical Chemistry under the guidance of Professors Cynthia Larive of the Chemistry Department and Natasha Raikhel of the Center for Plant Cell Biology (CEPCEB). My research interests are focused in the field of metabonomics in which the levels of endogenous metabolites are profiled in response to some stressor. Because the stressors I am interested in are xenobiotic compounds, I am also interested in understanding how they are metabolized. As a second year student, I began the IGERT program at UCR in Chemical Genomics (Chemical Genomics: Forging Complementation at the Interface of Chemistry, Engineering, Computational Sciences and Cell Biology). Our program seeks to screen combinatorial libraries of chemical compounds for specific effects in plants and fungi, with the majority of studies focusing on the model plant Arabidopsis thaliana. Two compounds that caused severe defects in vacuolar morphology and protein sorting were identified by members of the Raikhel lab in a screen of approximately 5,000 compounds. These two compounds are now referred to as Sortin1 and Sortin2 (sorting inhibitors). While the phenotype induced by these compounds has been well characterized, little detail is known about the metabolic effects of the compounds.

My goals are to use high resolution nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) to investigate the effects of the Sortins in Arabidopsis thaliana. Our lab houses modern state-of-the-art instruments for performing these types of analyses. Both instruments are capable of being coupled to liquid chromatography, in which analytes are separated prior to analysis by NMR and MS. This reduces the complexity of the resulting spectrum and facilitates the identification and quantification of a greater number of metabolites. Arabidopsis thaliana seedlings are grown in nutrient agar containing increasing concentrations of the Sortins. Seedling metabolites are extracted into a buffer containing deuterated acetonitrile and water prior to NMR analysis. Following NMR analysis, the samples are then analyzed by MS. Pattern recognition software is used to analyze the large amounts of data generated for each sample. Thus far the primary method of statistical analysis used is principle components analysis (PCA). PCA is a multivariate statistical technique in which variance between data sets, as well as the variables responsible for the variance, is calculated and the resulting plots can be used to identify which metabolites are most affected by the compound.

All my experiments thus far have focused on the wild-type plant. More recently, hypersensitive and resistant mutant strains of Arabidopsis thaliana have been identified in the Raikhel lab. The next step will be to characterize the metabolic profiles of these mutant strains in response to the Sortins. The expectations are that these kinds of studies will further aid in the identification of the biological targets of the Sortins.

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