Advisory Committee Chair
Karolina Mukhtar
Advisory Committee Members
Zsuzsanna Bebok
Melissa Harris
Shahid Mukhtar
Jeanmarie Verchot
Document Type
Dissertation
Date of Award
2023
Degree Name by School
Doctor of Philosophy (PhD) College of Arts and Sciences
Abstract
Given their immobility, plants have various survival strategies, including the critical ability to recognize and respond to stressors. Exposure to different environmental and intracellular signals triggers significant modifications in stress response regulators' expression. These changes often occur in the endoplasmic reticulum (ER), where a rise in protein synthesis can overwhelm the system, accumulating misfolded proteins and activating a mechanism known as the unfolded protein response (UPR). UPR is a complex regulatory network with three primary branches in eukaryotic systems. The IRE1-mediated pathway is the most conserved among UPR signaling branches. In Arabidopsis, IRE1 splices bZIP60 mRNA and produces a functional transcription factor, activating cytoprotective genes and maintaining cellular homeostasis. One of my project's findings indicated that different Arabidopsis accessions have single nucleotide polymorphisms (SNPs) in the promoter regions of IRE1. These SNPs affect IRE1 expression, and its regulatory network under different stresses. The various natural accessions demonstrated varying levels of promoter activity for both IRE1a and IRE1b (the two homologs of IRE1), as well as distinct expression patterns for IRE1a and IRE1b and differential downstream cascade when subjected to heat stress, tunicamycin, and salicylic acid treatment. One of IRE1’s primary roles is to activate the pro-survival pathway by splicing the bZIP60 mRNA. When plants are subjected to acute ER stress, the pro-survival iv pathway switches to the pro-death pathway. However, the critical regulator which acts as the molecular switch has not been discovered yet. In my final chapter, I propose a microRNA, miR5658, which acts as a novel molecular switch and activates the pro-death pathway. Furthermore, long non-coding natural antisense transcripts (lncNAT) play critical roles in maintaining ER homeostasis, which must be studied more deeply. In summary, my thesis dissected the crucial roles of the IRE1a/bZIP60 pathway in managing the ER stress response. Additionally, it highlighted the vital functions of the miR5658 in determining cell fate by regulating the IRE1a/bZIP60 pathway during acute ER stress. Understanding the role of miR5658 on bZIP60 mRNA target is very critical to agricultural industries as it will be able to create novel options for biotechnologists to alleviate the ER stress for quality crop production.
Recommended Citation
Afrin, Taiaba, "Exploring the Regulatory Mechanisms of IRE1 Signaling in Biotic and Abiotic Stress Responses in Arabidopsis" (2023). All ETDs from UAB. 452.
https://digitalcommons.library.uab.edu/etd-collection/452
