An Efficient Method to Screen for Salt Tolerance Genes in Salt Cress

Abstract

Arabidopsis thaliana is the most widely used model organism in plant molecular biology (Bressan et al., 2001) and it is an ideal model system for many reasons. Arabidopsis can be cultured in solid and liquid media and in soil. Greenhouses and growth chambers are suitable for Arabidopsis growth, meaning that different environmental conditions can be selected. Compared with crop plants, such as rice, wheat and tomato, Arabidopsis is more attractive due to its small size, high fecundity and short life cycle. Arabidopsis can be stably transformed using Agrobacterium tumefaciens-mediated transfer of T-DNA. Using the vacuum-infiltration procedure, transformants can be obtained at high efficiency. The small genome size of Arabidopsis meant that it was the first model plant to have its whole genome sequenced. Mutant lines, especially T-DNA insertion lines, of most Arabidopsis genes are obtained easily from several large seed stock libraries around the world. In conclusion, as a plant genetic model, Arabidopsis has played a significant role in characterizing the biological functions of plant genes, including salt stress-related genes. Nevertheless, Arabidopsis is a typical glycophyte in that does not display tolerance to intense salt stress. Thus, to solve this problem, a halophytic model system needs be developed. Any new model plant must provide experimental expediency similar to that of Arabidopsis. Salt cress (Thellungiella salsuginea), which is closely related to Arabidopsis, has emerged as a candidate (Amtmann, 2009). Like Arabidopsis, salt cress meets certain criteria that are important for any model plant, such as small size, short life cycle, self-pollination, high seed number, small genome and efficient transformation. Salt cress can withstand dramatic salinity shocks up to 500 mM NaCl and it can grow in high salt environments that are lethal to Arabidopsis (Bressan et al., 2001). Salt cress does not produce salt glands or other complex morphological alterations either before or after salt adaptation. Expressedsequence tag (EST) analyses of several hundred salt cress clones have shown that there is approximately 90 to 95% identity between salt cress and Arabidopsis cDNA sequences