| Expressed sequence tag (EST) analysis was carried out to study the molecular mechanism of salt tolerance for Polygonum sibiricum Laxm..A cDNA library was constructed from Polygonum sibiricum Laxm. treated by salt using Stratagene cDNA synthesis & Gigapack III Gold Cloning Kit. The library size is 1.2x 106 recombinants. The average length of inserted fragments in the library was longer than 450bp, which was testified by both PCR and sequencing analysis.2 688 clones selected randomly were sequenced, where partial sequences were obtained from 2 575 clones. Homology analysis by local blast and multiple alignment showed that these clones represented 1 651 unique transcripts. It suggested that 1118 contigs were homologous to the genes identified previously by blast from the Internet while other 533 contigs matched unknown protein coding regions (in which 101 had been found before in other organisms and 432 were completely novel).Transcripts of plant stress response genes were abundant in the library, especially those involved in osmotic stress, for instance, the genes encoding H+-transporting ATP synthase protein, BADH (betaine aldehyde dehydrogenase), permease, CaM (calmodulin), catalase, sorbitol dehydrogenase, prolyl isomerase, heat-shock protein and so on. Open reading frames (ORF) were found in some novel sequences from the library, after that, putative amino acid sequences were obtained, and hydrophobicity profile were analysed.The dbEST and the associated DNA materials in this study will be a useful resource to stress-tolerance research in the future.
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