title: Biochemical identification of the OsMKK6-OsMPK3 signalling pathway for chilling stress tolerance in rice.
abstract: MAPK (mitogen-activated protein kinase) pathways have been implicated in stress signalling in plants. In the present study, we performed yeast two-hybrid screening to identify partner MAPKs for OsMKK (Oryza sativa MAPK kinase) 6, a rice MAPK kinase, and revealed specific interactions of OsMKK6 with OsMPK3 and OsMPK6. OsMPK3 and OsMPK6 each co-immunoprecipitated OsMKK6, and both were directly phosphorylated by OsMKK6 in vitro. An MBP (myelin basic protein) kinase assay of the immunoprecipitation complex indicated that OsMPK3 and OsMPK6 were activated in response to a moderately low temperature (12°C), but not a severely low temperature (4°C) in rice seedlings. A constitutively active form of OsMKK6, OsMKK6DD, showed elevated phosphorylation activity against OsMPK3 and OsMPK6 in vitro. OsMPK3, but not OsMPK6, was constitutively activated in transgenic plants overexpressing OsMKK6DD, indicating that OsMPK3 is an in vivo target of OsMKK6. Enhanced chilling tolerance was observed in the transgenic plants overexpressing OsMKK6DD. Taken together, our data suggest that OsMKK6 and OsMPK3 constitute a moderately low-temperature signalling pathway and regulate cold stress tolerance in rice.
authors.affiliation: Crop Breeding Research Division, Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization, Hitsujigaoka 1, Toyohira-ku, Sapporo 062-8555, Japan.
authors.forename: Guosheng
authors.initials: G
authors.lastname: Xie
authors.forename: Hideki
authors.initials: H
authors.lastname: Kato
authors.forename: Ryozo
authors.initials: R
authors.lastname: Imai
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D003081:Cold Climate; D003080:Cold Temperature; D048371:MAP Kinase Kinase 3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048669:MAP Kinase Kinase 6 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D016297:Mutagenesis, Site-Directed; D012275:Oryza / Q000201:enzymology / Q000502:physiology*; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D013312:Stress, Physiological
chemical_list: D010940:Plant Proteins; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6