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: eureca@utsp.tennessee.edu) 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.