Enzymatic, covalent attachment of the Small Ubiquitin-like Modifier (SUMO) protein to a substrate protein, SUMOylation, is a stress inducible post-translational modification conserved throughout eukaryotes. SUMO conjugation to proteins alters protein interactions, regulating signalling pathways in the cell, and modulating response. SUMO proteases process SUMO into its mature form as a prerequisite to conjugation, in addition to providing reversibility to the SUMOylation pathway by cleaving SUMO from substrate proteins. Salicylic acid (SA) is a key hormone in propagating defense activation and signalling against biotrophic pathogens in plants. An investigation into the role of SUMO proteases OVERLY TOLERANT to SALT1 and -2 (OTS1 and -2) in SA regulation was performed using Arabidopsis thaliana mutants and transgenic over expressing lines. OTS1 and -2 were required for the restriction of SA biosynthesis and signalling in unchallenged plants. Further, SA treatment promoted OTS1 degradation and accumulation of SUMO conjugates, suggesting a positive relationship between SUMO conjugation and SA synthesis. Mutants of the SUMO E3 ligase SAP and MIZ1 (SIZ1) possess reduced levels of SUMO conjugates whilst displaying elevated SA content and activated defenses. This apparent contradiction was investigated using single siz1 and triple ots1 ots2 siz1 mutants, which were found to possess comparable SA related phenotypes to the ots1 ots2 double mutant. Finally it was concluded that there is more to the regulation between SA biosynthesis and SUMOylation than the presence or absence of SUMOylated proteins, and further, that promotion of SUMO conjugates by SA may facilitate modulation of other signalling pathways.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641011 |
| Date | January 2014 |
| Creators | Bailey, Mark |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/67030/ |
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