title: Aquaporin-mediated increase in root hydraulic conductance is involved in silicon-induced improved root water uptake under osmotic stress in Sorghum bicolor L.
abstract: The fact that silicon application alleviates water deficit stress has been widely reported, but the underlying mechanism remains unclear. Here the effects of silicon on water uptake and transport of sorghum seedlings (Sorghum bicolor L.) growing under polyethylene glycol-simulated osmotic stress in hydroponic culture and water deficit stress in sand culture were investigated. Osmotic stress dramatically decreased dry weight, photosynthetic rate, transpiration rate, stomatal conductance, and leaf water content, but silicon application reduced these stress-induced decreases. Although silicon application had no effect on stem water transport capacity, whole-plant hydraulic conductance (Kplant) and root hydraulic conductance (Lp) were higher in silicon-treated seedlings than in those without silicon treatment under osmotic stress. Furthermore, the extent of changes in transpiration rate was similar to the changes in Kplant and Lp. The contribution of aquaporin to Lp was characterized using the aquaporin inhibitor mercury. Under osmotic stress, the exogenous application of HgCl2 decreased the transpiration rates of seedlings with and without silicon to the same level; after recovery induced by dithiothreitol (DTT), however, the transpiration rate was higher in silicon-treated seedlings than in untreated seedlings. In addition, transcription levels of several root aquaporin genes were increased by silicon application under osmotic stress. These results indicate that the silicon-induced up-regulation of aquaporin, which was thought to increase Lp, was involved in improving root water uptake under osmotic stress. This study also suggests that silicon plays a modulating role in improving plant resistance to osmotic stress in addition to its role as a mere physical barrier.
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, 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, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi, 712100, China Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, 712100, China Faculty of Agriculture, Tottori University, Koyama Minami 4-101, Tottori 680-8533, Japan.
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, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi, 712100, China Institute of Soil and Water Conservation, Northwest A&F University, 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, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi, 712100, China Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, 712100, China shiwenwang@nwsuaf.edu.cn.
authors.forename: Shiwen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Faculty of Agriculture, Tottori University, Koyama Minami 4-101, Tottori 680-8533, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi, 712100, China Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Suiqi
authors.initials: S
authors.lastname: Zhang
mesh_terms: D020346:Aquaporins / Q000235:genetics* / Q000378:metabolism; D009997:Osmotic Pressure; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000502:physiology; D016133:Polymerase Chain Reaction; D036226:Seedlings / Q000502:physiology; D012825:Silicon / Q000502:physiology*; D045868:Sorghum / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D014867:Water; D012825:Silicon
keywords: Aquaporin; osmotic stress; root hydraulic conductance; silicon; transpiration rate; whole-plant hydraulic conductance.