Construction of a SSH library of Aegiceras corniculatum under salt stress and expression analysis of four transcripts

Suppressive subtractive hybridization was used to clone transcripts that showed enhanced expression during salt stress in the leaves of a salt-tolerant mangrove species, Aegiceras corniculatum. cDNAs of freshwater germinated and irrigated seedling were used as driver and cDNAs of 6 h salt-stress seedling were used as tester. By sequencing the whole SSH library, we got 577 ESTs. Among which, 30 had no significant homology to any previously identified genes. Five hundred and twenty-seven of the remaining 547 ESTs represent singletons. Real-time quantitative RT-PCR analysis of four transcripts' expression pattern showed that all of their transcripts were up-regulated during 24 h after salt shock. Their sequences showed high homology to the delta 1-pyrroline-5-carboxylate synthetase, Na+/H+ antiporter and plasma membrane intrinsic proteins, respectively. Rapid amplification of cDNA ends (RACE) was used for obtaining full-length cDNAs of AcPIP1 and AcPIP2. Characterization and phylogenetic analyses were then carried out according to their sequences.