Date of Award


Document Type


Degree Name

Master of Science (MS)


College of Science and Mathematics



Thesis Sponsor/Dissertation Chair/Project Chair

James Campanella

Committee Member

Dirk Vanderklein

Committee Member

Scott Kight


Auxin (indole-3-acetic acid) was the first phytohormone to be discovered, and today is still regarded as one of the most widely understood plant hormones. Auxin has the ability to stimulate, promote, delay, or inhibit many of a plant’s physiological processes. The concentration of the hormone within in a plant is critical; low concentrations of IAA positively impact plants’ physiological processes, but high concentrations of IAA are inhibitory and toxic to plants. For this reason, auxin metabolism must be tightly regulated. Plants can regulate their endogenous concentration of auxin via conjugation to sugars, amino acids, or peptides. Indole-3-acetic acid is active when it is in its free state, and presumably inactive when it is in its conjugated form. Indole-3-acetic acid can exist in its inactive, conjugated form within a plant until it is needed, where it can then undergo hydrolysis from its conjugate via a hydrolase gene and become available for use within the plant. In an effort to better understand the IAA conjugation auxin metabolism strategy of plants, hydrolase genes have been identified, isolated, and studied in a variety of species. Hydrolases are enzymes that cleave the bond between IAA and its amide or ester conjugate, thereby releasing free active auxin that is available for use within the plant. Given the conservation of auxin regulation metabolism, we have become interested in investigating the conservation of hydrolase genes. Hydrolase genes have been identified in numerous tracheophyte species, but we are interested in tracing these genes as far back as possible in evolutionary time. We have isolated, characterized the enzymatic activity, and investigated the evolutionary implications of several newly identified bryophyte hydrolases from the moss species Physcomitrella patens and the liverwort species Marchantia polymorpha.

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