title: The phosphomimetic mutation of an evolutionarily conserved serine residue affects the signaling properties of Rho of plants (ROPs).
abstract: Plant ROP (Rho of plants) proteins form a unique subgroup within the family of Rho-type small G-proteins of eukaryotes. In this paper we demonstrate that the phosphomimetic mutation of a serine residue conserved in all Rho proteins affects the signaling properties of plant ROPs. We found that the S74E mutation in Medicago ROP6 and Arabidopsis ROP4 prevented the binding of these proteins to their plant-specific upstream activator the plant-specific ROP nucleotide exchanger (PRONE)-domain-containing RopGEF (guanine nucleotide exchange factor) protein and abolished the PRONE-mediated nucleotide exchange reaction in vitro. Structural modeling supported the hypothesis that potential phosphorylation of the S74 residue interferes with the binding of the PRONE-domain to the adjacent plant-specific R76 residue which plays an important role in functional ROP-PRONE interaction. Moreover, we show that while the binding of constitutively active MsROP6 to the effector protein RIC (ROP-interactive CRIB-motif-containing protein) was not affected by the S74E mutation, the capability of this mutated protein to bind and activate the RRK1 kinase in vitro was reduced. These observations are in agreement with the morphology of tobacco pollen tubes expressing mutant forms of yellow fluorescent protein (YFP):MsROP6. The S74E mutation in MsROP6 had no influence on pollen tube morphology and attenuated the phenotype of a constitutively active form of MsROP6. The presented Medicago and Arabidopsis data support the notion that the phosphorylation of the serine residue in ROPs corresponding to S74 in Medicago ROP6 could be a general principle for regulating ROP activation and signaling in plants.
authors.affiliation: Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, Temesvári krt. 62, 6726 Szeged, Hungary.
authors.forename: Csilla
authors.initials: C
authors.lastname: Fodor-Dunai
authors.forename: Inka
authors.initials: I
authors.lastname: Fricke
authors.forename: Martin
authors.initials: M
authors.lastname: Potocký
authors.forename: Dulguun
authors.initials: D
authors.lastname: Dorjgotov
authors.forename: Mónika
authors.initials: M
authors.lastname: Domoki
authors.forename: Manuela E
authors.initials: ME
authors.lastname: Jurca
authors.forename: Krisztina
authors.initials: K
authors.lastname: Otvös
authors.forename: Viktor
authors.initials: V
authors.lastname: Zárský
authors.forename: Antje
authors.initials: A
authors.lastname: Berken
authors.forename: Attila
authors.initials: A
authors.lastname: Fehér
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D046913:Medicago truncatula / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011058:Pollen / Q000033:anatomy & histology / Q000235:genetics; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D012694:Serine; D019204:GTP-Binding Proteins; C511948:Rop4 protein, Arabidopsis