Characterization of SUMO proteases and other proteins involved in water stress responses in Triticum aestivum L.
| dc.contributor.advisor | Botha-Oberholster, Anna-Maria | en_ZA |
| dc.contributor.advisor | Kunert, Karl | en_ZA |
| dc.contributor.advisor | Cullis, Christopher | en_ZA |
| dc.contributor.author | Le Roux, Marlon-Schylor | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Agrisciences. Dept. of Genetics. | en_ZA |
| dc.date.accessioned | 2021-02-12T06:32:55Z | |
| dc.date.accessioned | 2021-04-22T10:11:40Z | |
| dc.date.available | 2021-08-12T03:00:09Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (PhDAgric)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Currently, approximately 4.5 billion people in developing countries consider wheat (Triticum aestivum L.) as a staple crop as it is a key source of daily calories. Therefore, it is ranked the second most important grain crop in the developing world. Meanwhile, climate change associated with severe drought conditions and the rising global mean temperatures has resulted in sporadic soil water shortages. Water deficit due to drought creates concerns because, historically, drought is the leading cause of yield loss in wheat. Thus, a more comprehensive understanding of the mechanisms underlying wheat drought responses is imperative. One of the latest avenues in plant-drought response is SUMOylation, which is a post-translational modification. SUMOylation is responsible for affecting essential proteins during water deficit stress changing their functionality, thus contributing to the plant succumbing to drought. SUMO proteases can counter the process by acting directly within the SUMOylation pathway. Therefore, SUMO proteases are an ideal target for manipulating stress-responses. In this Ph.D. study, novel findings have confirmed the overarching hypothesis “that soil water deficit stress influences an array of physiological, metabolic, and proteomic mechanisms mitigated by reducing levels of SUMOylation, consequently delaying protein turn over, thereby increasing drought tolerance in the cereal crop wheat.” Proof for this hypothesis has been that overexpression of an A. thaliana cysteine protease (Overly Tolerant To Salt-1, OTS1) (At1g60220), in wheat leads to improved plant growth under drought conditions. These overexpressing plants had an improved stomatal conductance and photosynthesis rate (Fv/Fm), accompanied by a higher total chlorophyll content than the controls. More importantly, these overexpressing plants had a reduced level of SUMOylated proteins with delayed senescence under drought conditions, allowing these plants to survive up to 14 days without water (with a final soil water content ± 15%). This finding further suggests that SUMO proteases may influence an array of mechanisms in wheat to the advantage of the crop to be more tolerant to water deficit stress caused by drought. This is the first report to elucidate SUMOylation effects in the hexaploid crop wheat. Furthermore, this Ph.D. work is also in agreement with various other studies that showed water deficit stress constrains almost every part of developing plants, inducing morphological and physiological changes, and cellular biochemical alterations as an adaptative response. To substantiate the aforementioned, random mutagenesis was also applied to produce two new wheat mutants, RYNO3926, and BIG8-1, with both expressing water deficit stress tolerance. While the BIG8-1 mutant survived three weeks without water, the RYNO3936 mutant could only endure two weeks without any water but rapidly recovered fully, despite leaves being completely dry/dehydrated after exposure to water deficit stress. Qualitative proteomic analysis further revealed that both the mutant and control have an improve regulation of SUMOylation when compared to non-mutant plants and in addition to having more ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Quantitative proteomic analysis also revealed that RYNO3936 mutant plants expressed a large number of proteins to endure drought conditions such as the abscisic stress-ripening protein, cold-induced protein, cold-responsive protein, dehydrin, Group 3 late embryogenesis, and a lipoprotein (LAlv9) belonging to the family of lipocalins. Moreover, BIG8-8 mutant uniquely expressed ABC transporter permeases and Xylanase inhibitor protein during severe water deficit stress. Collectively the research supports the idea that there is a multifaceted nature of how plants react to drought, which is a non-linear response, as it involves multiple pathways related to genomics, transcriptomics, proteomics, and phenomics responses. Though this dissertation does not argue a comparative analysis of which of the lines is more superior, it does advocate that each developed line will thrive better with specific dryland conditions, adding to the knowledge for future breeding programs to improve drought tolerance. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. | af_ZA |
| dc.description.version | Doctorate | en_ZA |
| dc.embargo.terms | 2022-08-31 | |
| dc.format.extent | xx, 198 pages : illustrations (some color), maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110265 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Wheat (Triticum aestivum L.) -- Growth | en_ZA |
| dc.subject.lcsh | Small ubiquitin-related modifiers | en_ZA |
| dc.subject.lcsh | Wheat -- Effect of drought on | en_ZA |
| dc.subject.lcsh | Plants -- Effect of salts on | en_ZA |
| dc.subject.lcsh | Sumoylation | en_ZA |
| dc.subject.lcsh | Proteins -- Regulation | en_ZA |
| dc.subject.lcsh | Protease inhibitors -- Genetic aspects | en_ZA |
| dc.subject.lcsh | Wheat -- Effect of stress on | en_ZA |
| dc.subject.lcsh | Wheat -- Water requirements | en_ZA |
| dc.subject.lcsh | Post-translational modification | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | Characterization of SUMO proteases and other proteins involved in water stress responses in Triticum aestivum L. | en_ZA |
| dc.type | Thesis | en_ZA |