Generation and analysis of expressed sequence tags from a cDNA library of Tamarix androssowii

Tamarix androssowii is one of the most remarkable salt-tolerance woody plant species in China. To investigate its expression profile in response to NaHCO3 stress, expressed sequence tags (ESTs) was analyzed. We have constructed a 0.4 mol/l NaHCO3 treated cDNA library of T. androssowii and sequenced more than 3000 randomly selected clones. A total of 2455 high-quality ESTs were generated, 1268 (51.65%) of these ESTs showed significant similarity to the sequences in NCBI Nr database. Nearly 400 ESTs were found to be involved in salt-tolerance; among them, metallothionein-like protein and germin-like protein are the most abundant transcripts, and account for 2.44 and 1.91% of total ESTs, respectively. The database-matched ESTs were further grouped into 12 function categories including: metabolism (19.72%), cell rescue, defense (20.19%), protein synthesis (7.33%), energy (5.12%), transport facilitation (6.78%), protein destination (6.94%), signal transduction (4.89%), cell growth, division (4.42%), transcription (6.62%), photosynthesis (9.94%), cell structure (1.66%) and function unknown (6.39%). Ninety-six unique genes were selected for small cDNA microarray analysis. Six were down-regulated and three up-regulated significantly. The experimental results obtained from this research will represent a key step in understanding the molecular mechanism of NaHCO3 tolerance of Tamarix species.