Date Approved

11-30-2022

Graduate Degree Type

Thesis

Degree Name

Cell and Molecular Biology (M.S.)

Degree Program

Cell and Molecular Biology

First Advisor

Dr. Matthew Christians

Second Advisor

Dr. Mark Staves

Third Advisor

Dr. Sheila Blackman

Fourth Advisor

Dr. Dawn Hart

Academic Year

2022/2023

Abstract

The ability of plants to absorb light through photoreceptors is essential for successful plant development. Phytochromes are important plant photoreceptors that detect and absorb red and far-red light and must function properly for plant survival. The Light Response BTB proteins (LRB) play an important role in a plant’s response to red light by degrading phytochrome B (PhyB) via the ubiquitin proteasome system (UPS). Although there has been a successful investigation into understanding the function of the LRBs, the function of a few regions within LRB proteins remains unknown, including a portion located on the N-terminal end of the protein, termed Region 2. This study assessed the function of Region 2 by studying the red-light response that occurs when Region 2 is genetically mutated in Arabidopsis thaliana. A mutant gene that has deleted portions of Region 2 (LRB-R2D) was created using site directed mutagenesis techniques and transformed into A. thaliana lrb1-1 lrb2-1 mutants. The function of the LRB-R2D proteins were assessed via plant growth when exposed to a red light environment. It was found that lrb1-1 lrb2-1 plants containing LRB-R2D reverted back to the wild type phenotype. These results suggest that the function of Region 2 may not play a role in some red light responses. Although the function of Region 2 has yet to be determined, future studies searching for interacting factors with Region 2 may reveal possible functions. This study has ruled out red light responses being important for Region 2, but the methodology can be applied to other regions within the LRB protein such as Region 1 or Region 3. Further understanding of Region 2 and other regions of LRB can enhance the comprehension of this protein and its effects on plant development, which could impact agricultural practices in the future.

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