THE EPITRANSCRIPTOMIC REGULATION OF STRESS: ROLE OF N6-METHYLADENOSINE IN ABIOTIC STRESS RESPONSE

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Degree type
PhD
Graduate group
Biology
Discipline
Biology
Biology
Life Sciences
Subject
Abiotic stress
cold stress
ECT8
m6A reader
mRNA modification
N6-methyladenosine
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Copyright date
01/01/2022
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Author
Sharma, Bishwas
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Abstract

The ability of living organisms to respond to changes in their environment is key to their survival. Due to their sessile nature, plants have evolved complex cellular and molecular response pathways to various biotic and abiotic stresses. At the heart of plants’ response to stress is their ability to regulate appropriate gene expression, both transcriptionally and post-transcriptionally. Covalent modifications of ribonucleotides within the RNA molecules, also known as the epitranscriptome, have recently emerged as an important aspect of post-transcriptional gene regulation. More specifically, studies have shown that N6-methyladenosine(m6A), the most prevalent internal mRNA modification, can alter gene expression by affecting the stability, processing, and translation of mRNA among other functions. Very few studies have explored the involvement of m6A in the epitranscriptomic regulation in a physiological context, specifically during stress response. In this thesis, I investigate the role of m6A in abiotic stress response in Arabidopsis thaliana, focusing on cold and oxidative stress conditions. First, we determined the stress-dependent dynamics of m6A by performing transcriptome-wide profiling of m6A in Arabidopsis under cold stress treatment, and identified categories of transcripts whose methylation was either enriched, depleted or unchanged upon stress. Overall, we showed that transcripts containing cold enriched m6A, including important cold stress regulators, associated with increased mRNA abundance and polysome association, suggesting a positive role of m6A for this select category of transcripts. Furthermore, we show that this association holds true in context of copper induced oxidative stress pointing towards a general epitranscriptomic regulatory pathway. Lastly, we attempt to establish a molecular mechanism involving the m6A reader protein ECT8 via which m6A regulates cold stress response. We identified transcripts binding to ECT8 using RIP-seq including many cold response transcripts. Using mRNA-seq in loss of function mutants, we showed that transcripts targeted by ECT8 increased in abundance in the absence of ECT8, suggesting that this protein may be a negative regulator of gene expression. Overall, using a combination of genomic, molecular, and phenotypic analyses, this project establishes m6A as an important regulator of abiotic stress response in plants and proposes an m6A reader mediated molecular pathway involved in this process.

Advisor
Gregory, Brian, D
Date of degree
2022
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