Effect of Salinity Stress on Degradation of Polyamines and Amine Oxidase Activity in Maize Seedlings

Abstract

The objective of this study was to obtain information on the interrelation between polyamine (PA) degradation and diamine oxidase (DAO) activity under salt stress. To identify a quantitative correlation between PA degradation and DAO activity in maize under salt stress, the changes in
endogenous free PA levels and DAO activity were analyzed in maize seedling roots, using treatments with different concentrations of NaCl and aminoguanidine (AG, a specific inhibitor of DAO). The results showed that the levels of putrescine (Put), cadaverine (Cad), spermidine (Spd) and spermine (Spm) decreased significantly with increasing salt concentrations. This occurred because salt stress strongly promoted DAO activity to stimulate PA degradation. AG treatment increased the accumulation of endogenous free PAs because of a strong retardation of DAO activity. A close correlation was observed between the changes in DAO activity and the PA contents among various treatments. The results indicated that salt stress could enhance PA degradation, suggesting that DAOs might increase their functions under salt stress.