title: Glycine betaine-mediated potentiation of HSP gene expression involves calcium signaling pathways in tobacco exposed to NaCl stress.
abstract: Glycine betaine (GB) can enhance heat tolerance and the accumulation of heat-shock protein (HSP) in plants, but the effects of GB on HSP accumulation during salt stress were not previously known. To investigate the mechanism of how GB influences the expression of HSP, wild-type tobacco (Nicotiana tabacum) seedlings pretreated with exogenous GB and BADH-transgenic tobacco plants that accumulated GB in vivo were studied during NaCl stress. A transient Ca(2+) efflux was observed in the epidermal cells of the elongation zone of tobacco roots after NaCl treatment for 1-2 min. After 24 h of NaCl treatment, an influx of Ca(2+) was observed; a low concentration of GB significantly increased NaCl-induced Ca(2+) influx. GB increased the intracellular free calcium ion concentration and enhanced the expression of the calmodulin (CaM) and heat-shock transcription factor (HSF) genes resulting in potentiated levels of HSPs. Pharmacological experiments confirmed that Ca(2+) and CaM increased HSFs and HSPs gene expression, which coincided with increased the levels of HSP70 accumulation. These results suggest a mechanism by which GB acted as a cofactor in the NaCl induction of a Ca(2+) -permeable current. A possible regulatory model of Ca(2+) -CaM in the signal transduction pathway for induction of transcription and translation of the active HSPs is described.
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, Shandong Agricultural University, Taian, 271018, China; College of Life Science, Liaocheng University, Liaocheng, 252000, China.
authors.forename: Meifang
authors.initials: M
authors.lastname: Li
authors.forename: Shangjing
authors.initials: S
authors.lastname: Guo
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.forename: Qingwei
authors.initials: Q
authors.lastname: Meng
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Xinghong
authors.initials: X
authors.lastname: Yang
mesh_terms: D001622:Betaine / Q000737:chemistry*; D050728:Betaine-Aldehyde Dehydrogenase / Q000378:metabolism; D020013:Calcium Signaling / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics; D019441:Plant Epidermis / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000737:chemistry; D054712:Salinity; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000009:adverse effects / Q000737:chemistry*; D013312:Stress, Physiological; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D001622:Betaine; D012965:Sodium Chloride; D050728:Betaine-Aldehyde Dehydrogenase