title: Arabidopsis mitogen-activated protein kinase MPK18 mediates cortical microtubule functions in plant cells.
abstract: Mitogen-activated protein kinase (MAPK) signalling networks are important regulators of environmental responses and developmental processes in plants. To understand the role of MAPK signalling modules in the regulation of plant microtubule functions, we searched for MAPKs that interact with the dual-specificity MAPK phosphatase, PROPYZAMIDE HYPERSENSITIVE 1 (PHS1), whose mutation has previously been reported to confer hypersensitivity to microtubule-disrupting drugs in Arabidopsis. Yeast two-hybrid assays demonstrated that PHS1 specifically interacts with two MAPKs, MPK12 and MPK18. Bimolecular fluorescence complementation (BiFC) studies confirmed that the PHS1 and MPK18 proteins are physically coupled, and that this interaction occurs in the cytoplasm. At the biochemical level, in vitro dephosphorylation assays indicated that phospho-MPK18 can be dephosphorylated by recombinant PHS1. Mutant mpk18 seedlings show defects in microtubule-related functions, and have moderately stabilized microtubules. Absence of MPK18 in the phs1-1 background partially complements the phs1-1 root growth phenotypes, providing genetic evidence for involvement of MPK18 signalling in microtubule-related functions. We propose a model whereby the PHS1-MPK18 signalling module is involved in a phosphorylation/dephosphorylation switch that regulates cortical microtubule functions.
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, V6T 1Z4 BC, Canada.
authors.forename: Ankit
authors.initials: A
authors.lastname: Walia
authors.forename: Jin S
authors.initials: JS
authors.lastname: Lee
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Wasteneys
authors.forename: Brian
authors.initials: B
authors.lastname: Ellis
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008870:Microtubules / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D020928:Mitogen-Activated Protein Kinases; C514675:PHS1 protein, Arabidopsis; D017027:Protein Tyrosine Phosphatases