Date of Award

Summer 8-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Plant & Microbial Biosciences)

Degree Name

Doctor of Philosophy (PhD)

Degree Type



Plants regulate cell division and cell expansion through the action of the phytohormone auxin.

Auxin is a vital small molecule whose effects on growth and development are conveyed through

the interactions and regulation of three protein families: TRANSPORT INHIBITOR


(ARF) transcription factors, and AUXIN/INDOLE 3-ACETIC ACID INDUCIBLE (Aux/IAA)

repressor proteins. Whereas the stability of and protein-protein interactions between the

TIR1/AFB and Aux/IAA protein families have been well studied, the interactions within the

ARF protein family and between the ARF and Aux/IAA protein families is less understood. Here, we describe the studies we undertook to determine the structure of an ARF interaction domain. We further characterize this domain using complementary biochemical, biophysical, and in planta approaches. We highlight the importance of conserved structural motifs within the domain that are necessary for auxin signaling and established a new binding model. Finally, we use a combination of forward genetics and cell biology approaches to identify a novel protein required for regulating the stability of ARF proteins. Taken together, this work highlights new insights into the importance of ARF•ARF and ARF•Aux/IAA protein-protein interactions, as well as a new understanding of both ARF protein stability and cellular localization.


English (en)

Chair and Committee

Lucia C Strader

Committee Members

Gaya Amarasinghe, Barbara Kunkel, Sona Pandey, Hani Zaher,


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