Date of Award
Spring 5-2024
Document Type
Thesis (Undergraduate)
Department
Biological Sciences
First Advisor
Dr. G. Eric Schaller
Second Advisor
Dr. Thomas P. Jack
Third Advisor
Dr. Bing He
Abstract
The domestication and cultivation of plants was fundamental in the rise of human societies. Plants are critical to many industries, and therefore understanding how plant growth is controlled is of the utmost importance. This project aims to elucidate how the plant hormones ethylene and auxin control growth and development in the model plant Arabidopsis thaliana, with a focus on hypocotyl growth in dark-grown Arabidopsis seedlings. Data from the Schaller lab suggests that the noncanonical Aux/IAA repressor IAA20, a negative regulator of auxin signaling, is induced by ethylene. Additionally, a GCC box binding motif for ERF family transcription factors was identified in IAA20’ s promoter, further implying that IAA20 may be regulated by ethylene to control etiolated hypocotyl growth. To examine this hypothesis, ERF1 and IAA20 GFP fusion constructs were transformed into various Arabidopsis backgrounds and characterized for (i) transgenic mRNA expression, (ii) transgenic protein expression and localization, and (iii) the growth effects of mutating the IAA20 promoter GCC box or expressing IAA20 or ERF1 in the epidermis. This thesis establishes that IAA20 is expressed in the hypocotyl and root tip vasculature. Altering IAA20 expression through GCC box mutation or epidermal expression resulted in differential expression of the IAA20-GFP protein, increased seedling hypocotyl growth, and decreased growth sensitivity to auxin. Based upon a triple response assay, modifying IAA20 expression did not impact the ethylene sensitivity of seedlings, suggesting that IAA20 does not primarily mediate ethylene inhibition of hypocotyl growth. These data support a model for IAA20 function in the regulation of hypocotyl cell expansion, and suggest that the GCC box motif may be required for IAA20 expression in specific tissues at different developmental stages. This study has improved our understanding of plant growth control and generated hypotheses which provide avenues for further exploration.
Recommended Citation
Smith, Ian A., "Plant hormone signaling: the control of cell expansion in Arabidopsis thaliana" (2024). Biological Sciences Undergraduate Senior Theses. 3.
https://digitalcommons.dartmouth.edu/biology_senior_theses/3
Included in
Biology Commons, Botany Commons, Cell Biology Commons, Genetics Commons, Plant Biology Commons, Plant Breeding and Genetics Commons
