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dc.contributor.advisorHirt, Heribert
dc.contributor.authorAlhoraibi, Hanna
dc.date.accessioned2019-05-06T05:52:45Z
dc.date.available2020-05-05T00:00:00Z
dc.date.issued2019-04
dc.identifier.citationAlhoraibi, H. (2019). Identification, validation and characterization of putative cytosolic and nuclear targets of immune MAPKs involved in biotic stress responses in Arabidopsis thaliana. KAUST Research Repository. https://doi.org/10.25781/KAUST-Q943K
dc.identifier.doi10.25781/KAUST-Q943K
dc.identifier.urihttp://hdl.handle.net/10754/644897
dc.description.abstractPlants are sessile organisms and constantly encounter a myriad of pathogens; therefore, they rely on highly effective defense system for their survival. Our understanding of how plant immunity is triggered and regulated has seen tremendous progress over the last two decades, with many important players identified in the model systems, Arabidopsis thaliana. Mitogen activated protein kinases play a central role in signal transduction in biotic and abiotic stresses. MAPK pathways are regulated by three-interlinked protein kinases (MAPKKK, MAPKK, MAPK), which are sequentially activated by phosphorylation. The activation of the three MAPKs MPK3, MPK4 and MPK6 is one of the earliest cellular responses following pathogen attack leading to the phosphorylation of appropriate cytosolic or nuclear targets to regulate cellular processes. However, only few targets of MPK3, MPK4 and MPK6 have been identified and validated so far and many MAPK substrates remain to be discovered. We performed largescale phosphoproteomics on mock treated and flg22 treated WT and the three loss-of-function mutants mpk3, mpk4 and mpk6 to identify novel MAPKs substrates and their cellular functions in response to pathogen attack. We identify and validated some of the differentially phosphorylated cytosolic and chromatin targets of MPK3, MPK4 and MPK6. DEK2, a nuclear protein involved in multiple chromatin-related processes, was identified in the phosphoproteomics screen as an in vivo target of MPK6 and it interacts in planta and is phosphorylated in vitro by the three immune MAPKs. dek2 loss-of-function mutants were susceptible to bacterial as well as fungal pathogens. Additionally, transcriptome data of the dek2-1 mutant show that DEK2 is a transcriptional repressor inclusive of defense related genes and hormone synthesis and signaling genes. We determined that DEK2 is a reader of the histone mark, H3K9me1, by Microscale thermophoresis. From ChIP-Seq analysis, DEK2 was found to be enriched at class I TCP binding motif regions. We further need to determine whether DEK2 binds to TCP transcription factors directly or indirectly. Finally, based on our data we postulate a hypothetical working model for the function of DEK2 as a transcriptional repressor and a reader of H3K9me1 mark.
dc.language.isoen
dc.subjectArabidopsis
dc.subjectImmunity
dc.subjectPhosphoproteomics
dc.subjectEpigenetics
dc.subjectMAPK Signaling
dc.subjectAtDEK2
dc.titleIdentification, validation and characterization of putative cytosolic and nuclear targets of immune MAPKs involved in biotic stress responses in Arabidopsis thaliana
dc.typeDissertation
dc.contributor.departmentBiological and Environmental Science and Engineering (BESE) Division
dc.rights.embargodate2020-05-05
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberRayapuram, Naganand
dc.contributor.committeememberColcombet, Jean
dc.contributor.committeememberBlilou, Ikram
dc.contributor.committeememberArold, Stefan T.
thesis.degree.disciplineBioscience
thesis.degree.nameDoctor of Philosophy
dc.rights.accessrightsAt the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2020-05-05.
refterms.dateFOA2020-05-05T00:00:00Z
kaust.request.doiyes


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