Plant Cell Rep (2007) 26:237–245 DOI 10.1007/s00299-006-0238-y BIOTIC AND ABIOTIC STRESS Ectopic expression of ThCYP1, a stress-responsive cyclophilin gene from Thellungiella halophila, confers salt tolerance in ﬁssion yeast and tobacco cells An-Ping Chen · Gui-Ling Wang · Zhan-Liang Qu · Chun-Xia Lu · Ning Liu · Fang Wang · Gui-Xian Xia Received: 30 July 2006 / Revised: 19 August 2006 / Accepted: 24 August 2006 / Published online: 14 September 2006 C  Springer-Verlag 2006 Abstract The halophyte Thellungiella halophila (salt cress) is an ideal model system for studying the molecular mech- anisms of salinity tolerance in plants. Herein, we report the identiﬁcation of a stress-responsive cyclophilin gene (ThCYP1) from T. halophila, using ﬁssion yeast as a func- tional system. The expression of ThCYP1 is highly inducible by salt, abscisic acid (ABA), H 2 O 2 and heat shock. Ec- topic overexpression of the ThCYP1 gene enhance the salt tolerance capacity of ﬁssion yeast and tobacco (Nicotiana tabacum L.) cv. Bright Yellow 2 (BY-2) cells signiﬁcantly. ThCYP1 is expressed constitutively in roots, stems, leaves and ﬂowers, with higher expression occurring in the roots and ﬂowers. The ThCYP1 proteins are distributed widely within the cell, but are enriched signiﬁcantly in the nucleus. The present results suggest that ThCYP1 may participate in response to stresses in the salt cress, perhaps by regulating appropriate folding of certain stress-related proteins, or in the signal transduction processes. Keywords Cyclophilin . Fission yeast . Salt tolerance . Thellungiella halophila . Tobacco BY-2 cell Communicated by W.-H. Wu A.-P. Chen · G.-L. Wang · Z.-L. Qu · C.-X. Lu · N. Liu · F. Wang · G.-X. Xia () National Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China e-mail: guixianx@yahoo.com A.-P. Chen · C.-X. Lu · N. Liu · F. Wang Graduate School of Chinese Academy of Sciences, Beijing 100049, China Z.-L. Qu College of Life Science, Hebei University, Baoding 071002, China Abbreviations ABA: Abscisic acid . CsA: Cyclosporine A . CyP: Cyclophilin . FDA: Fluorescein diacetate . GFP: Green ﬂuorescent protein . ORF: Open reading frame . PPIase: Peptidyl-prolyl cis-trans isomerase . UTR: Untranslated region Introduction Cyclophilins constitute a family of ubiquitous proteins that are present in organisms ranging from bacteria to plants and animals (Galat 1999). These proteins belong to the cluster of immunophilin proteins that possess peptidyl-prolyl cis- trans isomerase (PPIase) activities, the rate-limiting step in protein folding (Brandts et al. 1975). In animal cells, the CyP/CsA complex was found to inhibit the Ca 2+ -dependent phosphatase activity of the calcineurin protein (Schreiber 1991). In yeast, genetic studies of CyP-deﬁcient mutants de- termined that cyclophilin is essential for the recovery of heat- shocked cells (Sykes et al. 1993). Additionally, cyclophilins reportedly play roles in a wide variety of processes, includ- ing cell division (Faure et al. 1998), transcription regulation (Rycyzyn and Clevenger 2002), signaling (Brazin et al. 2002) and pre-mRNA splicing (Horowitz et al. 2002). In plants, cyclophilin genes exist as a large gene family in all plants investigated, with 29 members in Arabidopsis thaliana (Ro- mano et al. 2004). A striking feature of plant cyclophilin genes is that their expression is induced in response to var- ious abiotic or pathogenic stresses (Chou and Gasser 1997; Godoy et al. 2000; Kong et al. 2001; Luan et al. 1994; Marivet et al. 1994; Scholze et al. 1999; Sharma and Singh 2003). Although diverse functions of plant cyclophilins were re- ported or suggested (Deng et al. 1998; Berardini et al. 2001; Oh et al. 2006; Gullerova et al. 2006), the physiological relevance and the molecular basis of the stress-responsive Springer