title: Effects of exogenous spermidine on photosynthetic capacity and expression of Calvin cycle genes in salt-stressed cucumber seedlings.
abstract: We investigated the effects of exogenous spermidine (Spd) on growth, photosynthesis and expression of the Calvin cycle-related genes in cucumber seedlings (Cucumis sativus L.) exposed to NaCl stress. Salt stress reduced net photosynthetic rates (PN), actual photochemical efficiency of PSII (ΦPSII) and inhibited plant growth. Application of exogenous Spd to salinized nutrient solution alleviated salinity-induced the inhibition of plant growth, together with an increase in PN and ΦPSII. Salinity markedly reduced the maximum carboxylase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Vcmax), the maximal velocity of RuBP regeneration (Jmax), triose-phosphate utilization capacity (TPU) and carboxylation efficiency (CE). Spd alleviated the negative effects on CO2 assimilation induced by salt stress. Moreover, Spd significantly increased the activities and contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and fructose-1,6-biphosphate aldolase (ALD; aldolase) in the salt-stressed cucumber leaves. On the other hand, salinity up-regulated the transcriptional levels of ribulose-1,5-bisphosphate (RCA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribrokinase (PRK) and down-regulated the transcriptional levels of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (RbcL), ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RbcS), ALD, triose-3-phosphate isomerase (TPI), fructose-1,6-bisphosphate phosphatase (FBPase) and 3-phosphoglyceric acid kinase (PGK). However, Spd application to salt-stressed plant roots counteracted salinity-induced mRNA expression changes in most of the above-mentioned genes. These results suggest that Spd could improve photosynthetic capacity through regulating gene expression and activity of key enzymes for CO2 fixation, thus confers tolerance to salinity on cucumber plants.
authors: College of Horticulture, Nanjing Agricultural University, Key Laboratory of Southern Vegetable Crop Genetic Improvement, Ministry of Agriculture, Weigang No.1, Nanjing, 210095, Jiangsu, People's Republic of China, shusheng@njau.edu.cn.
authors: Sheng
authors: S
authors: Shu
authors: Lifang
authors: L
authors: Chen
authors: Wei
authors: W
authors: Lu
authors: Jin
authors: J
authors: Sun
authors: Shirong
authors: S
authors: Guo
authors: Yinhui
authors: Y
authors: Yuan
authors: Jun
authors: J
authors: Li
mesh_terms: D018553:Cucumis sativus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D013095:Spermidine / Q000494:pharmacology*
chemical_list: D010940:Plant Proteins; D012965:Sodium Chloride; D013095:Spermidine