title: NaCl stress induces CsSAMs gene expression in Cucumis sativus by mediating the binding of CsGT-3b to the GT-1 element within the CsSAMs promoter.
abstract: The CsSAMs promoter is a salt-stress-inducible promoter containing three GT-1 elements that are sufficient for the salt-stress response. The transcription factor CsGT-3b was found to bind to the GT-1 element. The S-adenosyl-L-methionine synthase (SAMs) gene is among the functional genes induced during environmental stress. However, little is known about the regulatory mechanism and upstream regulators of this salt-inducible gene in cucumber plants. Thus, it is necessary to understand the characteristics of the SAMs gene by analyzing its promoter and transcription factors. In this study, we isolated and functionally analyzed a 1743-bp flanking fragment of the CsSAMs gene from Cucumis sativus. To examine promoter activity, the full-length promoter, as well as different promoter fragments, were fused to the β-glucuronidase (GUS) reporter gene and introduced into the tobacco genome. The full-length promoter displayed maximal promoter activity, whereas the P4 promoter, containing 321 bp of upstream sequence, showed no basal promoter activity. In addition, the CsSAMs promoter exhibited stress-inducible regulation rather than tissue-specific activity in transgenic tobacco. Histochemical analysis revealed strong GUS staining in leaves, stems, and roots, especially in the veins of leaves, the vascular bundle of stems, and root tip zones following NaCl stress. A transient expression assay confirmed that the 242-bp region (-1743 to -1500) was sufficient for the NaCl-stress response. Yeast one-hybrid assays further revealed interaction between the NaCl-response protein CsGT-3b and the GT-1 (GAAAAA) element within the 242-bp region. Taken together, we revealed the presence of four salt-stress-responsive elements (GT-1 cis-elements) in the CsSAMs promoter and identified a transcription factor, CsGT-3b, that specifically binds to this sequence. These results might help us better understand the intricate regulatory network of the cucumber SAMs gene.
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Wang
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China.
authors.forename: Mei-Wen
authors.initials: MW
authors.lastname: He
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China.
authors.forename: Shi-Rong
authors.initials: SR
authors.lastname: Guo
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhong
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Shu
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, 210095, Nanjing, China. jinsun@njau.edu.cn.
authors.forename: Jin
authors.initials: J
authors.lastname: Sun
mesh_terms: D001483:Base Sequence; D018553:Cucumis sativus / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D053263:Gene Regulatory Networks; D017930:Genes, Reporter; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018547:Plant Stems / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D012965:Sodium Chloride
keywords: Cis-acting element; Cucumber; NaCl stress; Promoter cloning; Subcellular localization; Yeast one hybrid