This thesis evaluated the role of Serine/Arginine-rich proteins, also known as SR proteins, in addition to LAMMER kinases in the cold acclimation response using Brassica napus and Arabidopsis thaliana. Transcription profile analyses of SR and LAMMER kinase genes in Brassica napus and BnCBF overexpressor lines showed that exposure to low temperatures led to increased transcript levels for nine SR genes and two kinases. BnCBF overexpression was found to exacerbate this response. This was associated with increases in SR protein abundance and phosphorylation status, suggesting that SR proteins play an essential role in cold acclimation. These findings prompted further studies to assess the role of SR proteins and kinases in the cold acclimation induced adjustment of photosynthesis, the acquisition of freezing tolerance and the transcriptional profile of CBF, SPS and COR genes, which play an important role in the transcriptional cascade allowing plants to undergo cold acclimation. Using Arabidopsis loss-of-function mutants of SR proteins and AME3 LAMMER kinase, it was shown that At-RSZ22 and At-SR45 are indispensable in the regulation of photosynthesis under non-acclimated and cold acclimation conditions. At-RSZ22a, At-SCL30 and At-RS41 were then proposed to play a crucial role in the cold acclimation induced adjustment of photosynthetic performance. Moreover, the deletion of At-AME3 kinase not only jeopardized the cold acclimation induced adjustment of photosynthetic performance, but also the acquisition of freezing tolerance. This was associated with attenuation of the transcription profile of key cold responsive genes and protein abundance of COR15 A/B and dehydrins. These findings prompted further physiological characterization of ame3 mutants, and the elucidation of Serine/Arginine-rich proteins capable of interacting with this LAMMER kinase of interest. Under cold stress and acclimation conditions, the deletion of At-AME3 LAMMER kinase impeded Photosystem I physiology and state-1 state-2 transitions. These findings were associated with decreases in Photosystem II and Photosystem I protein abundance. Yeast 2-hybrid assays showed that six SR proteins are capable of physically interacting with AME3. Taken together, the results of this study demonstrate that At-RSZ22 and At-SR45 are essential in the photosynthetic performance of Arabidopsis, that At-RSZ22a, At-SCL30 and At-RS41 play an essential role in the cold acclimation induced recovery of photosynthetic performance, and that At-AME3 plays an essential role in the cold acclimation response.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/35927 |
| Date | January 2017 |
| Creators | Rosembert, Marc |
| Contributors | Johnson, Douglas |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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