Root-specific expression of wheat expansin gene TaEXPB23 enhances root growth and water stress tolerance in tobacco

Expansins are key regulators of cell wall extension during plant growth. In our previous study, transgenic tobacco plants constitutively overexpressing beta-expansin gene TaEXPB23 under the control of the 35S promoter exhibited enhanced drought tolerance, but the development process of 35S::TaEXPB23 transgenic tobacco plants was altered. In the present study, we instead used the root-specific promoter PYK10. P10::TaEXPB23 plants exhibited an increase in lateral roots and a higher root biomass than 35S::TaEXPB23 and WT plants without observing obvious changes in other areas of development. Furthermore, P10::TaEXPB23 plants showed increased water stress tolerance than WT plants, as indicated by the higher levels of photosynthetic rate (Pn) and actual quantum efficiency of PSII photochemistry (Phi PSII) than WT plants under water stress conditions. Additionally, the P10::TaEXPB23 plants exhibited improved water status, accumulated fewer reactive oxygen species (ROS), and contained higher levels of antioxidant enzyme activity. These results suggest that root-specific expression of TaEXPB23 can improve water stress tolerance while minimizing the unfavorable effects found in constitutive 35S::TaEXPB23 plants. (C) 2014 Elsevier B.V. All rights reserved.