Honors Theses
Date of Award
Spring 5-8-2022
Document Type
Undergraduate Thesis
Department
Biology
First Advisor
Yongjian Qiu
Relational Format
Dissertation/Thesis
Abstract
The plant stem grows against the gravitational force, a phenomenon called negative gravitropism. In the model dicotyledonous plant Arabidopsis thaliana, gravity is sensed by starch-filled amyloplasts, which trigger the shoot gravitropic response through the action of a growth hormone called auxin. In the darkness, a group of transcription factors named PHYTOCHROME-INTERACTING FACTORS (PIFs) promote stem negative gravitropism by inhibiting the starch metabolism in the endodermal amyloplasts. Red light promotes starch metabolism and converts amyloplasts into other types of plastids (e.g., chloroplasts) through the red/far-red light photoreceptors—phytochromes. Consequently, red-light-grown seedlings lose starch granules in amyloplasts and exhibit agravitropic growth. However, the detailed molecular mechanism by which starch metabolism is triggered in red light is still not well understood. Here, an Arabidopsis mutant that showed hypocotyl negative gravitropic growth in red light was identified. Interestingly, we observed that its negative gravitropism phenotype was also temperature dependent—specifically, stronger gravitropic response at warmer temperatures. Genetic analyses further demonstrated that PIFs are required for the mutant’s unique negative gravitropic phenotype in red light. The gene that was mutated encodes a key component involved in the microRNA pathway, suggesting a previously unknown role of small RNAs in regulating shoot negative gravitropism.
Recommended Citation
Lott, Julia, "Investigating the Role of Small RNA Pathways in Arabidopsis Shoot Gravitropism" (2022). Honors Theses. 2558.
https://egrove.olemiss.edu/hon_thesis/2558
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