Construction Of EST Database From A Salt-Treated Tamarix Androssowii CDNA Library And Analysis Of Gene Sequences

Tamarix spp. is a good material to study the salt-resistance molecular mechanism because it has high ability to resist drought and salt stress. A cDNA library was constructed from the tissue of Tamarix androssowii treated with NaHCOs Expressed sequence tags (EST) analysis was carried out to study the molecular mechanism of salt-resistance in Tamarix androssowii.The library primary titer was 1.14×10 pfu/mL, and the rate of recombination was 96%, the titer of amplified library was 4.0×109 pfu/mL. The average length of inserted fragments in the library was 1.2kb, which was testified by both PCR and sequencing analysis. From this library, 2 328 high quality ESTs were obtained.Homology analysis by local BLAST and multiple alignment showed that these clones represented 1 001 unique transcripts. Results of comparing with the genes in unigene database of GenBank based on BLASTX algorithm indicated that 428 ESTs were homologous to the genes identified previously by BLAST from the Internet, while other 234 ESTs matched unknown protein coding regions and 339 ESTs were completely novel sequences. Eleven functional categories were carried out from all the tentative unique genes that were identified. Three group transcripts were significantly expressed: Defence, Metabolism and Protein synthesis and destination that respesented 25.26%, 20.65% and 15.37% respectively. The result of genes related to salt stress-tolerance indicated that Signaling components, Transcriptional regulators, Stress protein and Reactive oxygen scavengers contained more genes than the others, 4.1%, 1.9%, 3.3%and 0.9% respectively. So we can say these four processes played important action in the process of salt-resistance for Tamarix androssowii. Transmembrane transport and ion homeostasis, Protein syntheise and Metabolism were less.From above, we can conclude that salt-resistance of Tamarix androssowii was an complex process involved in signaling conduction, Transcription regulation, Transmembrane transport and ion homeostasis, reactive oxygen scavenging, osmolyte biosynthesis. The cDNA library construction and the acquiring of many ESTs relation to stess-resistance will make a foundation for thoroughly studying the mechanism of stress resistance of Tamarix androssowii.