Searching for the Phenolic Receptor(s) of Agrobacterium Tumefaciens: Developing a Chiral Molecule to be Used in a Novel Mutant Selection
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Authors
Marti, Erin
Issue Date
1999
Type
Thesis
Language
en_US
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Abstract
Conclusive evidence that a specific xenognostic receptor exists in Agrobacterium
tumefaciens has been presented through the testing of structurally varying phenols and
the development of a novel genetic screen to isolate mutants which exhibit a
hypersensitive response to the highly active inducer, acetosyringone. It has also been
demonstrated that only a' single enantiomer of the chiral inducers, (-)-transdehydroferulate
dimethylester and (+)-trans- cyclopropyl cinnamyl alcohol (CCA), are
active, thus indicating the presence of an enantioselective receptor. Attempts to identify
this receptor via another novel genetic screen that would employ the inactive (-)-trans-
CCA would be unsuccessful as a result of this compound's relatively low inducing
activity and the toxicity of phenolic compounds in general. It is well established that
dimethoxy phenols have significantly higher activities than their monomethoxy
counterparts and herin the synthesis of the dimethoxy version of trans-CCA, trans-4-
hydroxy-3,5-dimethoxy cyclopropyl cinnamyl alcohol (DCP), is presented. The activity
of the active (S,S)-trans-DCP, determined by a f3-galactosidase assay, is compared to that
of the active (S,S)-trans-CCA and indeed it possesses notably higher activity such that
the utilization of its inactive form, (R,R)-trans-DCP, for a novel mutant selection appears
promising. Comparison of the activities of both enantiomers of trans-DCP to ensure a
significant difference in activity will confirm the feasibility of this novel genetic screen
for the isolation of mutants. The mutants would most likely exhibit a difference in the
region of the xenognositc receptor that recognizes the chirality in the inducing phenol,
thus providing specific structural as well as genetic information on the receptor.
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