Arabidopsis thaliana D group MPKs interactions with RLPH2 and PP1
Date
2021-01-08
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Abstract
Mitogen activated protein kinases (MPK) are key members of the MPK cascade, a pathway that results in an immediate response from (external) stimuli such as infection, cold, or drought. The activation of an MPK relies its activation loop being phosphorylated on a threonine and tyrosine residue. A unique bacteria-like phosphatase Rhizobiales-like phosphatase 2 (RLPH2), which we bioinformatically characterized as a serine/threonine phosphatase, has been discovered to act as a tyrosine phosphatase. In this thesis, data monitoring RLPH2s dephosphorylation of different peptides derived from MPK activation loops would reveal a preference for the dephosphorylation of D group MPKs over non-D group MPKs, and indicate that the central residue in the TXY motif plays a key role in RLPH2 substrate determination. Additionally, RLPH2 would show a preference for the in vitro dephosphorylation of MPK9 (a D group MPK) over MPK3 (a non-D group MPK). An engaging observation is that right next to the TxY motif in D group MPKs is a putative Protein Phosphatase 1 (PP1) regulatory protein binding RVxF motif. This motif is not present in any other characterized MPK, suggesting an interaction between PP1 and D group MPKs. In this thesis, PP1 protein binding assays with MPK9 WT and an MPK9 RASA mutant would show binding occurs between MPK9 and PP1 through the RVXF motif in vitro. Peptide and protein substrate dephosphorylation assays with PP1 would show threonine dephosphorylation on MPK9 and the effect the RVXF motif plays on this interaction. In summary, the specificity of RLPH2 as a D group MPK regulator was examined along with the interaction between PP1 and the D group MPKs via the RVXF motif, with mention of a potential relationship between these three interactions.
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Keywords
Phosphorylation, Phosphatase, Tyrosine, Arabidopsis
Citation
Toth, R. B. (2021). Arabidopsis thaliana D group MPKs interactions with RLPH2 and PP1 (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.