The characteristics in phenotype and drought tolerance of the transgenic tobacco plants by induced overexpression of TaEXPB23 gene from wheat 
Feng Li, Yangyang Han, Yanan Feng, Shichao Xing, Meirong Zhao, Jin Zhang, Wei Wang*

State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai’an, Shandong, 271018.
*Corresponding author, Tel.:+86-538-8246166; Fax: +86-538-8242288. E-mail : wangw@sdau.edu.cn

Abstrasct
Expansins are the key regulators of cell wall extension during plant growth. In our previous study, the drought tolerance of transgenic tobacco plants was improved by overexpressing a wheat expansin gene TaEXPB23 driven by a constitutive 35S cauliflower mosaic virus (CaMV) promoter, but the development and phenotype of transgenic plants were severely retarded under normal conditions. In this paper, we found that the cellular characteristics and carbohydrate metabolism were changed in 35S::TaEXPB23 transgenic tobacco plants. Then, the suitability of expressing TaEXPB23 driven by a stress-inducible RD29A promoter in order to improve the phenotype of the transgenic tobacco plants was investigated. The determination of physiological and biochemical parameters indicated that RD29A::TaEXPB23 transgenic tobacco plants exhibited enhanced tolerance in comparison with wild-type plants. This study demonstrates that the use of stress-inducible promoter, such as RD29A, may minimize the unfavorable phenotype caused by constitutive expression of transgene and improve the drought tolerance.

Key words: Drought tolerance; Expansin; Stress-inducible promoter; Transgenic plant