Investigations on the role of mitogen-activated protein kinases 11 and 17 in defense response of Arabidopsis thaliana

  • Untersuchungen zur Beteiligung der Mitogen-aktivierten Proteinkinasen 11 und 17 an den Abwehrreaktionen von Arabidopsis thaliana

Neumann, Martin; Conrath, Uwe (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2011, 2012)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2011

Abstract

Priming of defense for a stronger and faster response to abiotic and biotic stress is an important part of acquired immunity in plants and animals. Recent findings revealed the involvement of the two mitogen-activated protein kinases MPK3 and MPK6 in the regulation of priming in Arabidopsis thaliana. Since the A. thaliana genome encodes 20 MPKs, I wondered, whether one or more of the other MPKs would be involved in priming. Bioinformatic analysis revealed a strong transcriptional upregulation of MPK11 upon treatment with the priming-inducing chemicals BTH, BABA, and salicylic acid, and upon several biotic and abiotic stress stimuli. In addition, I performed a phenotypic screen of mpk mutants that revealed strong morphological defects in mpk17 T-DNA knockout plants. To elucidate the potential role of MPK11 and MPK17 in plant defense, I treated mpk11 and mpk17 mutants with various plant pathogens and analyzed basal plant defense responses. Furthermore, I performed drought stress experiments to investigate one abiotic stress response in mpk11 and mpk17 mutants. I found that both mutants are not affected in their response against Pseudomonas syringae and the necrotrophic fungus Botrytis cinerea, whereas I could reveal a slight reduction in basal defense against the biotrophic oomycete Hyaloperonospora arabidopsidis. In addition, I showed that both mutants are not affected in the production of reactive oxygen species or in deposition of callose, two typical basal defense responses. Furthermore, by analysis of protein phosphorylation, I excluded a compensational effect of MPK3, MPK4, and MPK6, the major players in plant defense signaling, for the loss of mpk11 and mpk17. In all experiments, I did not see significant alterations in primed defense responses, suggesting that both kinases do, if at all, only play a minor role in plant defense. According to bioinformatic analysis, I propose a role for MPK17 in the regulation of developmental processes. Furthermore, I discuss a possible role of MPK11 as a backup system for other kinases.

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