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Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection
Thesis (MSc)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613949781868544 |
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| access_status_str | Open Access |
| author | Walker, Leanne Nicole |
| author2 | Peters, Shaun Wayne |
| author_browse | Peters, Shaun Wayne Walker, Leanne Nicole |
| author_facet | Peters, Shaun Wayne Walker, Leanne Nicole |
| author_sort | Walker, Leanne Nicole |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/135580 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:16.501Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/135580 Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection Walker, Leanne Nicole Peters, Shaun Wayne Loedolff, Bianke Stellenbosch University. Faculty of Sciences. Dept. of Genetics and Institute of Plant Biotechnology. Thesis (MSc)--Stellenbosch University, 2026. Walker, L. N. 2026. Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/89941e9e-5d9f-4bc2-a573-9fc57450e477 In an era of rapid climate change, increasing population pressure and declining arable land necessitate urgent agricultural adaptation. The global population is expected to reach approximately 9.3 billion people by 2050, creating pressure to increase food production by up to 60 % within the same time frame. Traditional crop breeding is approaching a plateau in yield improvement and consequently, new breeding technologies (NBTs) are considered the next frontier towards rapid yield improvement in modern agriculture. Over 15 years (1997-2013), genetically modified (GM) crops (mainly introducing insect and herbicide resistance traits) have facilitated an average global yield increase of 22 % while improving farmers profit margins by up to 68 % and, reducing the amount of land farmed owing to higher productivity. Future agriculture must integrate such NBTs within the current elite crop varieties, towards improving climate-resilience while addressing future food security concerns. Central to this is a nuanced understanding of how GM NBT strategies can be deployed where stress-protection-genes and transcription factors (TFs) are expressed in GM plants in an orchestrated manner using customised stress-inducible promoters, which govern gene expression. Many studies have argued against constitutive promoters in GM-crop strategies, because while they allow for a continuous and stable expression pattern, this also often leads to unintended pleiotropic effects resulting in crop penalties. Inducible promoters, such as the Arabidopsis RD29APr, have provided an archetype demonstrating stress-induced expression of transgenes and crop protection under stressful conditions. Genetic engineering currently relies on a limited set of large, constitutive plant promoters, yet high-precision research requires targeted and controlled gene expression. Minimal stress-inducible promoters present a promising strategy to address this challenge, as their compact size simplifies molecular experimentation and reduces background activity, while their inducibility enables fine-tuned gene expression, ultimately minimizing the metabolic cost to the plant. This study characterized the putative Arabidopsis Abscisic Acid Repressor 1 (ABR1/ERF111; At5g64750) promoter (ABR1PR) and successfully incorporated it into a binary vector system which drives strong reporter transgene expression (enhanced yellow fluorescent protein, eYFP) under multiple abiotic stress conditions in transgenic tobacco (Nicotiana tabacum). The ABR1/ERF111 gene is a member of the group X AP2/ERF transcription factor (TF) family, which is transcriptionally responsive to abscisic acid (ABA) and multiple abiotic stresses, including low temperature, osmotic imbalance, and water deficit. The relatively small promoter region (804 bp) upstream of ABR1/ERF111 contains multiple conserved binding motifs for two TFs associated with abiotic stress across diverse plant species: the dehydration-responsive element (DRE) and the MYC binding site. A binary vector was engineered placing the enhanced yellow fluorescent protein (eYFP) reporter gene under the control of this promoter and introduced into tobacco via Agrobacterium-mediated transformation. The bar gene conferring glufosinate resistance was used as a selectable marker, but its harsh regeneration limits transformation efficiency. This study optimized a nitrogen-starvation regeneration protocol to enable efficient callus regeneration from tobacco leaf discs, consequently establishing a versatile platform for high-throughput promoter screening. The responsiveness of the ABR1Pr to multiple abiotic stresses was evaluated in three independently transformed tobacco lines carrying the ABR1Pr:eYFP reporter construct. Under low temperature acclimation, the transgenic lines showed inducible eYFP fluorescence concurrent to an increase in the abundance of eYFP transcripts. Similarly, under water deficit conditions, the transgenic lines showed inducible eYFP fluorescence, but unexpectedly, the eYFP transcript levels decreased. As the roots first perceive water deficit stress and given ABAs role in root-to-shoot signalling, the roots were exposed to an osmotic stress. This resulted in an increase in transcript levels in the roots and a decrease in the leaves. These findings suggest that ABR1Pr may function within the ABA-mediated systemic signalling network, facilitating rapid communication coordinating whole-plant stress responses. Overall, this study is the first functional validation of ABR1Pr as a compact multi-abiotic stress-inducible promoter. Owing to its compact size and inducible nature, ABR1Pr represents a promising minimal promoter candidate for next-generation climate-resilient crop engineering. Masters 2026-04-02T06:18:32Z 2026-04-02T06:18:32Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/135580 en Stellenbosch University 119 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Walker, Leanne Nicole Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title | Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title_full | Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title_fullStr | Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title_full_unstemmed | Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title_short | Characterization of a minimal abiotic stress-inducible promoter in the development of a binary vector for crop protection |
| title_sort | characterization of a minimal abiotic stress inducible promoter in the development of a binary vector for crop protection |
| url | https://scholar.sun.ac.za/handle/10019.1/135580 |
| work_keys_str_mv | AT walkerleannenicole characterizationofaminimalabioticstressinduciblepromoterinthedevelopmentofabinaryvectorforcropprotection |