An EST catalogue from the resurrection plant Selaginella lepidophylla reveals abiotic stress-adaptive genes

The resurrection plant Selaginella lepidophylla (Division Lycophyta) belongs to an ancient lineage of vascular plants that can withstand complete desiccation for years and be revived after only a few hours of rehydration. To better understand the molecular basis of dehydration tolerance, a complementary DNA library was constructed from S. lepidophylla microphyll fronds dehydrated for 2.5 It and used to generate an expressed sequence tag (EST) database. ESTs were obtained for 1046 clones representing 874 unique transcripts. Putative functions were assigned to 653 (62.4%) of these clones after comparison with protein databases, whereas 212 (20.2%) sequences having significant similarity to known sequences whose functions are unclear and 181 (17.3%) sequences having no similarity to known sequences. The S. lepidophylla ESTs were compared to the Selaginella moellendorffii EST database using the tBLASTX algorithm. Approximately 36-38% of the S. lepidophylla ESTs exhibited similarity to the S. moellendorffii ESTs, whereas 62-63% were unique to S. lepidophylla and S. moellendorffi, respectively. For those S. lepidophylla ESTs for which functional assignments could be made, the largest functional categories included photosynthesis (17%), followed by primary metabolism (14%) and disease/defense-related functions (11%). S. lepidophylla had a higher relative percentage of ESTs within the transporter, cell structure, secondary metabolism, molecular chaperones (i.e., heat shock proteins), and abiotic stress-related (i.e., late embryogenesis abundance proteins) functional categories than did S. moellendorffii. Thus, S. lepidophylla may serve as a rich genetic resource for the identification of novel genes associated with environmental stress and dehydration tolerance. (c) 2006 Elsevier Ireland Ltd. All rights reserved.