Polyamines and salt stress response and tolerance in Arabidopsis thaliana flowers

In the present study we analysed polyamine metabolism in Arabidopsis thaliana (ecotype Columbia) flowers and stalks collected from plants germinated and grown under increasing salt-stress conditions (0–75 mM NaCl). The expression level of the different isoforms of polyamine biosynthetic enzymes was analysed by reverse transcriptase–polymerase chain reaction (RT–PCR). Spermidine synthase enzyme activity determined both in supernatant and pellet fractions, together with RT–PCR results, led us to hypothesize a different intracellular compartmentation of the isoforms of these enzymes. Free and conjugated polyamines (perchloric acid-soluble and -insoluble) were measured. Free spermidine was the most abundant polyamine and its levels, such as those of free spermine, increased with salt concentration, supporting the hypothesis for a specific role of those polyamines in the response and tolerance to salt stress of Arabidopsis thaliana flowers.