The Roles Of Polyamine Oxidative Degradation In The Adventitious Budding And Adventitious Rooting Of Soybean Cotyledon Node

Spermine （Spm）, spermidine （Spd） and their diamine obligate precursor putrescine（Put） are micro molecular aliphatic polycations that are ubiquitous in plant organisms.They are involved in the regulation of plant growth and differentiation, such as theregulation of cell proliferation, somatic embryogenesis, differentiation andmorphogenesis, and so on. Hydrogen peroxide （H₂O₂） is a reactive oxygen species, andfunctions as a singalling molecule that mediates cell proliferation, somaticembryogenesis, differentiation and morphogenesis. Many reports indicate that bothpolyamines and H₂O₂are proved promoting the differentiation of plant adventitiousbuds and adventitious roots. It has been confirmed that H₂O₂is one of the polyamineoxidation products. However, wheather the polyamine oxidative degradation is relatedto the differentiation of plant adventitious buds and adventitious roots? What kind ofrole can H₂O₂play in the process of differentiation? These questions are far from clear.In this study, we selected soybean [Glycine max （L.） Merr.] cv.‘Jilin pellets7’seeds as the material. Using plant tissue culture techniques, we screened the best cultureconditions for the growth of steriled soybean seedlings and the differentiation ofadventitious buds and roots, focused on studing the role of polyamine oxidativedegradation in the budding and rooting of soybean cotyledon node. The results are asfollows:（1） The best medium for inducing adventitious buds contains MS salts, B5vitamins,30g/L sucrose,6g/L agar,4mg/L6-BA and0.025mg/L IBA; The bestmedium for inducing adventitious roots contains MS salts, B5vitamins,30g/L sucrose,6g/L agar,0.5mg/L6-BA and0.025mg/L IBA.（2） During the process of budding and rooting of soybean cotyledon node, with theextension of culture time, DAO activity and H₂O₂contents were gradually decreased.Treatment with three of the exogenous polyamines significantly enhanced budding androoting of soybean cotyledon node, DAO activity and H₂O₂contents were also increased.0.5mM Put was more effective than Spm, but less than Spd. Meanwhilecyclohexylamine which is an inhibitor of Spd synthase inhibited budding and rooting ofsoybean cotyledon node, DAO activity and H₂O₂contents were decreased.（3） Aminoguanidine which is a specific inhibitor of polyamine oxidases stronglyblocked budding and rooting of soybean cotyledon node, and the explants becameseriously browned, DAO activity was almost not detected. Endogenous polyaminecontent analysis showed that treatment with AG induced endogenous polyamineaccumulation, demonstrated a different role with exogenous polyamines.（4） Treatment with N,N-dimethylthiourea （DMTU）, a scavenger of H₂O₂, H₂O₂contents in explant significantly reduced, and the differentiation of adventitious budsand roots were inhibited. Treatment with1.0mM DMTU and0.5mM PAs at the sametime showed that DMTU could induce the positive effects of polyamine ondifferentiation.The above results suggest that the differentiation of soybean cotyledon node toform adventitious buds and roots are associated with the oxidative degradation ofpolyamines, and that their products, especially H₂O₂, may be involved in this process.