Source-sink interactions shape herbivore-induced defense responses in Arabidopsis thaliana
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Plant tissues are not attacked uniformly, nor are they uniformly responsive to insect herbivores, in part because they are modular organisms made up of source and sink tissues. This results in complex patterns of defense that may vary spatially and temporally. My dissertation evaluates the importance of source-sink interactions and sink competition in shaping plant defense responses in Arabidopsis thaliana to feeding by two chewing lepidopterans--Pieris rapae (dietary specialist) and Spodoptera exigua (dietary generalist)--and in response to simulated herbivory with the defense elicitor, methyl-jasmonate. I investigated whether the presence of competing sinks naturally occurring during plant development (e.g. reproductive sinks and roots) facilitates or constrains the induction of defense metabolites (glucosinolates and phenolics) by altering whole-plant distribution and metabolic utilization of carbon. The use of short-lived radio-isotopes 11C (t1/2=20.4 min)as 11CO2, and 18F (t1/2= 110 min) as 2-[18F]fluoro-2-deoxy-D-glucose, provides new insight into the roles that plant architecture and competition between sinks play in determining how newly acquired carbon resources are used by plants in their defense against insect herbivory.
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