Thellungiella halophila (salt cress; synonymous to Thellungiella salsuginea, Al-Shebaz et al., 1999) is a close relative of Arabidopsis thaliana. Analysis of ESTs revealed 90-95% nucleotide identity in transcripts for well-known housekeeping genes, although sequences with lower identity were also found suggesting the presence of paralogous genes (Inan et al., 2004). Despite this close genetic relationship and a similar morphological appearance, the two species differ considerably in their physiology. In particular, and in sharp contrast to Arabidopsis, Thellungiella tolerates extreme cold, drought and salinity. Introduced into the laboratory by Ziyi Cao, Hui Zhang and their colleagues (Shandong Normal University, China), its use for salinity research has been promoted by Jian-Kang Zhu and colleagues in the US (Zhu, 2001; Bressan et al. 2001; Amtmann et al., 2005). Since then several groups worldwide have started to study its physiology, metabolism and molecular genetics.

As of 2006, several ecotypes have been collected from Central Asia and North America. Global insertion mutagenesis is underway. BAC libraries, ESTs, and full-length cDNA libraries are available. Several multi-disciplinary, multi-institutional groups have begun to focus on the distinctive mechanisms that cause the extreme stress tolerance of this species. The evolutionary position of the species between Brassica and Arabidopsis has attracted attention and phylogenetic studies. Recently, JGI announced that the genome of Thellungiella halophila, approximately twice the size of the Arabidopsis genome, will be sequenced (JGI Website).