title: Cloning and characterization of a maize SnRK2 protein kinase gene confers enhanced salt tolerance in transgenic Arabidopsis.
abstract: SnRK2 (sucrose non-fermenting 1-related protein kinases 2) represents a unique family of protein kinase in regulating signaling transduction in plants. Although the regulatory mechanisms of SnRK2 have been well demonstrated in Arabidopsis thaliana, their functions in maize are still unknown. In our study, we cloned an SnRK2 gene from maize, ZmSAPK8, which encoded a putative homolog of the rice SAPK8 protein. ZmSAPK8 had two copies in the maize genome and harbored eight introns in its coding region. We demonstrated that ZmSAPK8 expressed differentially in various organs of maize plants and was up-regulated by high-salinity and drought treatment. A green fluorescent protein (GFP)-tagged ZmSAPK8 showed subcellular localization in the cell membrane, cytoplasm and nucleus. In vitro kinase assays indicated that ZmSAPK8 preferred Mn(2+) to Mg(2+) as cofactor for phosphorylation, and Ser-182 and Thr-183 in activation loop was important for its activity. Heterologous overexpression of ZmSAPK8 in Arabidopsis could significantly strengthen tolerance to salt stress. Under salt treatment, ZmSAPK8-overexpressed transgenic plants exhibited higher germination rate and proline content, low electrolyte leakage and higher survival rate than wild type. Further analysis indicated that transgenic plants showed increased transcription of the stress-related genes, RD29A, RD29B, RAB18, ABI1, DREB2A and P5CS1, under high-salinity conditions. The results demonstrated that ZmSAPK8 was involved in diverse stress signal transduction. Moreover, no obvious adverse effects on growth and development in the ZmSAPK8-overexpressed transgenic plants implied that ZmSAPK8 was potentially useful in transgenic breeding to improve salt tolerance in crops.
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Ying
authors.forename: Deng-Feng
authors.initials: DF
authors.lastname: Zhang
authors.forename: Hui-Yong
authors.initials: HY
authors.lastname: Li
authors.forename: Ying-Hui
authors.initials: YH
authors.lastname: Liu
authors.forename: Yun-Su
authors.initials: YS
authors.lastname: Shi
authors.forename: Yan-Chun
authors.initials: YC
authors.lastname: Song
authors.forename: Tian-Yu
authors.initials: TY
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004573:Electrolytes / Q000378:metabolism; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018525:Germination; D008345:Manganese / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D055049:Salt Tolerance; D015398:Signal Transduction; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological; D014158:Transcription, Genetic; D015854:Up-Regulation; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D004573:Electrolytes; D011993:Recombinant Fusion Proteins; D008345:Manganese; D012965:Sodium Chloride; D017346:Protein Serine-Threonine Kinases