title: A sphingolipid elicitor-inducible mitogen-activated protein kinase is regulated by the small GTPase OsRac1 and heterotrimeric G-protein in rice 1[w].
abstract: Mitogen-activated protein kinase (MAPK) cascades are activated in plants during responses to pathogens or to pathogen-derived elicitors and mediate intracellular stress responses. Here, we show that a rice (Oryza sativa) MAPK, OsMAPK6, was posttranslationally activated in a cell culture by a sphingolipid elicitor. Suppression of OsMAPK6 expression by RNA interference resulted in a strong reduction of pathogen-induced Phe ammonia-lyase mRNA, whereas the mRNA level of another rice MAPK, OsMAPK5a, was highly increased. Silencing of a small GTPase, OsRac1, by RNA interference or loss-of-function mutation (d1) of the heterotrimeric G-protein alpha-subunit gene resulted in a strong reduction of the OsMAPK6 protein levels and of kinase activation by a sphingolipid elicitor. Furthermore, coimmunoprecipitation experiments with OsRac1 and OsMAPK6 proteins showed that OsMAPK6 is closely associated with the active form of OsRac1, but not with inactive forms of OsRac1. These results indicate that these two G-proteins regulate an elicitor-inducible MAPK in rice at the protein level.
authors.affiliation: Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan.
authors.forename: Damien
authors.initials: D
authors.lastname: Lieberherr
authors.forename: Nguyen Phuong
authors.initials: NP
authors.lastname: Thao
authors.forename: Ayako
authors.initials: A
authors.lastname: Nakashima
authors.forename: Kenji
authors.initials: K
authors.lastname: Umemura
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Ko
authors.initials: K
authors.lastname: Shimamoto
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D004789:Enzyme Activation; D048053:Mitogen-Activated Protein Kinase 6 / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000502:physiology*; D010940:Plant Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013107:Sphingolipids / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011994:Recombinant Proteins; D013107:Sphingolipids; D048053:Mitogen-Activated Protein Kinase 6; D020928:Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein