Date of Award

Winter 12-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Molecular Genetics & Genomics)

Degree Name

Doctor of Philosophy (PhD)

Degree Type



The phytohormone auxin acts as an essential regulator of plant growth and development through its mediation of cell division, elongation, and differentiation. Proper spatiotemporal distribution of auxin within a plant is regulated on a cellular level and is critical to ensuring precise organ morphogenesis and physiology. The proper level and distribution of active auxin (indole-3-acetic acid, IAA) is tightly regulated via de novo synthesis, transport, and conversion from its conjugated forms and precursors. Studies in Arabidopsis have revealed the importance of one such precursor, indole-3-butyric acid (IBA), in regulation of auxin homeostasis. Unlike IAA, the mechanism for IBA transport and metabolism is not well defined. In this work, we describe the studies we undertook to demonstrate and identify novel roles for factors involved in modulating IBA contributions to the active auxin pool via IBA transport or regulation of IBA conjugation. First, an IBA transporter was identified and characterized for its roles in regulating root apical meristem length and leaf size. Next, an E3-ubiquitin ligase F-Box protein and its putative targets were examined for their previously undefined roles in regulating auxin homeostasis through modulation of IBA contributions to the active auxin pool via degradation of IBA conjugating enzymes. Together, this work uncovers previously uncharacterized mechanisms governing IBA transport and metabolism in Arabidopsis and provides a stronger understanding of the roles and significance of IBA transport and IBA contributions to the active auxin pool to influence auxin homeostasis.


English (en)

Chair and Committee

Lucia Strader

Committee Members

Michael Nonet


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Available for download on Wednesday, August 18, 2032