Molecular cloning and expression analysis of spermidine synthase gene during sex reversal induced by Ethrel in cucumber (Cucumis sativus L.)

A full-length cDNA encoding spermidine synthase CsSPDS of 317 amino acids was isolated from cucumber. CsSPDS showed high similarity to SPDSs of other species, with the greatest similarity to SPDS of Coffea arabica (identity, 87%). Northern blot analysis revealed that CsSPDS was expressed predominantly in rapid growing tissues, such as roots, young leaves and flower buds. The response of CsSPDS to the sex reversal of three-leaf stage androecious cucumber seedlings by Ethrel treatment was also examined. Our results showed that the CsSPDS was up-regulated in shoot apex during sex reversal process, which correlated with increases of spermidine synthase activity and free spermidine (Spd) content, and a decrease of putrescine (Put) content in shoot apices.