title: Silicon-mediated changes in polyamine and 1-aminocyclopropane-1-carboxylic acid are involved in silicon-induced drought resistance in Sorghum bicolor L.
abstract: The fact that silicon application alleviates drought stress has been widely reported, but the mechanism it underlying remains unclear. Here, morphologic and physiological changes were investigated in sorghum (Sorghum bicolor L.) seedlings treated with silicon and exposed to PEG-simulated drought stress for seven days. Drought stress dramatically decreased growth parameters (biomass, root/shoot ratio, leaf area, chlorophyll concentration and photosynthetic rate), while silicon application reduced the drought-induced decreases in those parameters. Leaf relative water content and transpiration rate were maintained at high levels compared to those in seedlings without silicon. The soluble sugar contents were increased, but the proline contents and the osmotic potential were decreased, showing that osmotic adjustment did not contribute to the silicon induced-drought resistance. Furthermore, levels of both free and conjugated polyamines (PAs) levels, including putrescine, spermidine and spermine, were all found to be increased by silicon under drought stress both in leaf and root. Meanwhile, 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, was markedly decreased by supplemental silicon. Several key PA synthesis genes were upregulated by silicon under drought stress. These results suggest that silicon improves sorghum drought resistance by mediating the balance of PAs and ethylene levels. In leaf, the increased PAs and decreased ACC help to retard leaf senescence. In root, the balance between PAs and ACC participates in the modulation of root plasticity, increases the root/shoot ratio, and contributes to an increase in water uptake. These results suggest that silicon increases drought resistance through regulating several important physiological processes in plants.
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China; College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China.
authors.forename: Lina
authors.initials: L
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China; College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China. Electronic address: shiwenwang@nwsuaf.edu.cn.
authors.forename: Shiwen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China; College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Wang
authors.affiliation: Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China.
authors.forename: Xiping
authors.initials: X
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China.
authors.forename: Suiqi
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000598:Amino Acids, Cyclic / Q000378:metabolism*; D055864:Droughts; D011073:Polyamines / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D012825:Silicon / Q000494:pharmacology*; D045868:Sorghum / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*
chemical_list: D000598:Amino Acids, Cyclic; D011073:Polyamines; C023863:1-aminocyclopropane-1-carboxylic acid; D012825:Silicon
keywords: 1-Aminocyclopropane-1-carboxylic acid; Drought stress; Ethylene; Polyamines; Silicon; Sorghum