A mobile C2-domain protein confers salt tolerance in plant
Gang Li, Ran Xia, Yiyue Zhang, Huawei Zhang, Qi Xie^*

Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China

^*Corresponding Author：Tel: (+8610) 6480 6619; Fax: (+8610)6666 8888; E-mail: qxie@genetics.ac.cn

Abstract
A mobile C2-domain protein TsST03 has been isolated from Thellungiella salsuginea through functional expression of random cDNA libraries of T. salsuginea in Arabidopsis due to its ability to increase the salt tolerance. The expression levels of TsST03 was found to be induced quickly by NaCl, drought, cold and heat stress as well as stress-related hormones including ABA, JA, ACC and SA, which suggests TsTh03 perhaps participates in the early response to these stresses. Studies of subcellular localization of TsTh03 in TsTh03-GFP transgenic Arabidopsis droved by the native promoter of TsTh03 revealed that TsTh03-GFP green fluorescence was uniformly dispersed throughout the cytosol, nucleus and plasma membrane. However, subject to salt stress, signals emitted from TsTh03-GFP disappeared from the nucleus and cytosol, and could only be detected on the plasma membrane. These results indicated the subcellular localization of TsTh03 was regulated by salt stress. Heterograft experiments in Arabidopsis revealed the protein of TsTh03 could participate in long distance translocation, by which the wild type part in chimera plant could be endowed with salt tolerant abilities. Peptide analysis of the TsTh03 sequence revealed that TsTh03 had the highest sequence similarity with C2 domain-containing proteins. Details will be presented and discussed.

Key Words: Thellungiella salsuginea; salt tolerance; C2-domain; movement protein