多胺氧化降解在莴苣种子萌发过程中的作用

The Role of Polyamine Oxidative Degradation in the Process of Lettuce Seed Germination

[目的]了解多胺氧化降解在莴苣种子萌发过程中的作用。[方法]用多胺氧化酶专性抑制剂氨基胍(AG)对莴苣(Lactuca sativa)种子进行浸种处理,测定种子的萌发率、多胺氧化酶(PAO)和二胺氧化酶(DAO)活性、内源多胺和H2O2含量变化。[结果]AG可强烈抑制种子的萌发,12 h后种子萌发率与对照相比差异就达极显著水平。随着莴苣种子的萌发,PAO和DAO活性发生显著的变化,2种酶活性都是先上升后下降,在24和48 h分别测得DAO和PAO活性高峰。AG对DAO和PAO活性有强烈的抑制作用,培养24和36 h后就检测不到DAO和PAO活性。在种子萌发过程中,内源Put在前24 h快速降低,24～60 h降低趋缓;Spd在萌发前期降低缓慢,48 h后急剧下降;Spm含量低但略呈增加趋势;多胺总量逐渐降低。AG处理可显著增加内源多胺尤其是Put和Spd含量。在种子萌发过程中,种子H2O2含量逐渐增高,36～48 h时出现高峰后一直维持较高水平。AG处理可明显降低种子H2O2含量。[结论]在种子萌发期间,内源多胺和H2O2含量的变化与PAO和DAO活性变化相对应,暗示在莴苣种子萌发期间进行着活跃的多胺氧化降解代谢。

[Objective]The aim was to understand the role of polyamine oxidative degradation in the process of lettuce seed germination.[Method]After imbibition treatments of lettuce seeds with aminoguanidine（AG,a specific inhibitor of polyamine oxidases）,seed germination rate,activities of polyamine oxidase（PAO）and diamine oxidase（DAO）,endogenous free polyamine and H2O2 contents were determined.[Result]Compared with the control,AG treatment strongly inhibited the seed germination,and had extremely significant differences with the control after 12 h incubation.During the seed germination,the activities of DAO and PAO had significant changes,their activities firstly increased and then decreased,and reached peaks at 24 h and 48 h,respectively.AG treatment was strongly inhibitory for the activities of DAO and PAO,whose activities even disappeared after incubation with AG for 24 h and 36 h.During the seed germination,endogenous Put reduced sharply in the first 24 h,then reduced slowly in 24-60 h;Spd decreased slowly in the early stage of germination,and then sharply declined after 48 h;Spm content was low but slightly increased.The total polyamine gradually decreased.AG treatment could significantly increase endogenous polyamines,especially Put and Spd contents.During the germination process,H2O2 content was gradually increased,had a peak at 36-48 h,and kept a high level at last.AG treatment could significantly reduce the H2O2 content.[Conclusion]During the seed germination,the changes of H2O2 and endogenous polyamine content correspond with the changes of PAO and DAO activities,implying that there is active oxidative degradation of the polyamine metabolism during the lettuce seed germination.