Biotic stresses such as infection by bacteria negatively affect plant growth and
pose a severe threat to human food production. Improving our understanding of
the immune systems of plants should help ensure food supplies in the years
ahead.
Bacterial infections induce Pattern-Triggered Immunity (PTI), a process in which
plants perceive bacterial molecules and trigger an immune response. Mitogen-
Activated Protein Kinase (MAPK) cascades are key players in this immunity
process. Since the MAP Kinases (MPKs) 3/4/6 are mainly responsible for flg22-
dependent phosphorylation events, we sought to find out how oxidation of MPK4
affects its ability to respond to stresses. Previous studies have shown varying
kinase activity of MPK4 upon oxidation. Therefore, this project aims to provide an
insight into the oxidative defense signaling mechanism of A. thaliana by
investigating the role of MPK4 Cysteine181 in vitro and in vivo. Analysis of
oxidation-mimicking as well as oxidation-dead mutants gave first hints that
Cysteine181, which is located in the MPK4 substrate binding pocket, is a highly
important regulatory residue of oxidative stress signaling by affecting MPK4 kinase
activity and the activation of MPK3 and MPK6. Binding studies revealed that those
events are due to sterical hindrance within the binding pocket of MPK4 and the
blockage of upstream activator binding.
The second part of this study characterizes compositional and post-translational
changes of plant ribosomes during pathogen infection. Ribosomal proteins
selectively participate in the formation of polysomes under different environmental
and developmental conditions. However, the function of these changes still
remains elusive. The current research project attempts to understand the plant
ribosomal changes that occur upon exposure to bacterial pathogens. To observe
ribosomal changes, A. thaliana plants were treated with a pathogen associated
molecular pattern (PAMP), flg22. Mass spectrometric analysis identified
quantitative changes of PAMP-induced ribosomal proteins in polysomes as well as
changes in post-translational modifications. Spatial simulations of ribosomes
revealed specific regions within the ribosomes to be PTI specific. This study
demonstrates that MPK6 contributes to modification of P-stalk composition and
phosphorylation status. The MPK6 mediated modifications may affect translation
and in combination indicate a mechanism of PTI-related translational control.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/676103 |
| Date | 04 1900 |
| Creators | Siodmak, Anna E. |
| Contributors | Hirt, Heribert, Biological and Environmental Science and Engineering (BESE) Division, Arold, Stefan T., Blilou, Ikram, Kopka, Joachim |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2023-04-04, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2023-04-04. |
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