title: Cloning and molecular characterization of a mitogen-activated protein kinase gene from Poncirus trifoliata whose ectopic expression confers dehydration/drought tolerance in transgenic tobacco.
abstract: The mitogen-activated protein kinase (MAPK) cascade plays pivotal roles in diverse signalling pathways related to plant development and stress responses. In this study, the cloning and functional characterization of a group-I MAPK gene, PtrMAPK, in Poncirus trifoliata (L.) Raf are reported. PtrMAPK contains 11 highly conserved kinase domains and a phosphorylation motif (TEY), and is localized in the nucleus of transformed onion epidermal cells. The PtrMAPK transcript level was increased by dehydration and cold, but was unaffected by salt. Transgenic overexpression of PtrMAPK in tobacco confers dehydration and drought tolerance. The transgenic plants exhibited better water status, less reactive oxygen species (ROS) generation, and higher levels of antioxidant enzyme activity and metabolites than the wild type. Interestingly, the stress tolerance capacity of the transgenic plants was compromised by inhibitors of antioxidant enzymes. In addition, overexpression of PtrMAPK enhanced the expression of ROS-related and stress-responsive genes under normal or drought conditions. Taken together, these data demonstrate that PtrMAPK acts as a positive regulator in dehydration/drought stress responses by either regulating ROS homeostasis through activation of the cellular antioxidant systems or modulating transcriptional levels of a variety of stress-associated genes.
authors.affiliation: Key Laboratory of Horticultural Plant Biology of the Ministry of Education, National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xiao-San
authors.initials: XS
authors.lastname: Huang
authors.forename: Tao
authors.initials: T
authors.lastname: Luo
authors.forename: Xing-Zheng
authors.initials: XZ
authors.lastname: Fu
authors.forename: Qi-Jun
authors.initials: QJ
authors.lastname: Fan
authors.forename: Ji-Hong
authors.initials: JH
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D055864:Droughts; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010944:Plants / Q000737:chemistry / Q000145:classification / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology*; D032104:Poncirus / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D020928:Mitogen-Activated Protein Kinases