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Exhibition of Undergraduate Research and Creative Achievement (EURēCA) Abstract Submission Form 2013 Please submit electronically to your Division Representative and the Office of Research (email: [email protected]) no later than February 20, 2013. Student Name(s): Title of Presentation: Alissa Nathans Division of Entry: Interaction of two calcium sensors, CML38 and rgsCaM, with the SBP1 E3 ubiquitin ligase of Arabadopsis Faculty Advisor: Arts & Sciences Dr. Dan Roberts Abstract: (Type in 12 point font to fit the box below.) Post-transcriptional gene silencing is an important mechanism used for antiviral defense response in plants. However, it has also been found to play a key role in endogenous gene expression in normal plant development. In previous studies in Nicotiana tabacum, a calcium sensing protein was found to act as an endogenous suppressor of gene silencing. This protein, regulator of gene silencing calmodulin-like protein (rgsCaM), was shown to suppress gene silencing as well as reverse established silencing when overexpressed. An endogenous mechanism for the suppression the plant’s own gene silencing represents a novel mechanism to regulate gene expression. In an attempt to elucidate the mechanism behind this suppression of silencing, a yeast-two hybrid assay was performed to screen for rgsCaM interactions. One of these, the E3 Ligase S-RNase Binding Protein1 (SBP1), is of particular interest because it could serve in a mechanism in which calcium signaling activates rgsCaM, which, in accordance with the calmodulin paradigm, may bind and activate its target, SBP1. The SBP1-mediated protein degradation could represent an important step in the suppression of silencing. In support of this hypothesis, the Cterminal domain of SBP1 contains a predicted calmodulin-binding domain. To further these investigations, we will also use the more robust model plant Arabidopsis thaliana. The Arabidopsis homolog of rgsCaM, calmodulin-like protein 38 (CML38), retains the rgsCaM function. To confirm the interactions between SBP1 and both rgsCaM and CML38, a yeast-two hybrid assay was performed alongside in planta bimolecular fluorescence complementation. To test if the C-terminal domain of SBP1 is responsible for its interaction with CML38 and rgsCaM, the three domains of SBP1 were separately tested using a yeast-two hybrid assay.