【作者】 苏国兴；

【导师】 刘友良；

【作者基本信息】 南京农业大学 ， 植物学， 2006， 博士

【摘要】 精胺（Spm）、亚精胺（Spd）和它们的二胺前体腐胺（Put）是小分子脂肪族多聚阳离子，广泛存在于植物细胞中，与植物生长发育、形态建成和对逆境响应密切相关。然而，大多数研究主要集中在游离态多胺水平和生物合成酶活性的调节上，对多胺分解代谢及其降解产物的生理作用研究较少。特别是多胺氧化降解是否直接参与植物根系的发育?光是否可通过促进多胺氧化酶活性调节细胞木质素的合成?因而控制植物细胞的发育方向?在遭受盐胁迫时，耐盐性不同的植物基因型多胺氧化降解是有否差异?多胺氧化降解是否参与γ-氨基丁酸积累和向脯氨酸的转化?而通过调节脯氨酸和γ-氨基丁酸的积累参与植物的耐盐性尚缺乏研究。为此，笔者选用耐盐性不同的两个大豆品种Lee 68（耐盐性强）和苏协-1号（SX-1，耐盐性弱），根据不同的研究目的，采用不同的外源物质处理和高压液相色谱分析技术，研究多胺氧化降解在大豆幼苗生长发育和耐盐生理中的作用。结果如下： 2-羟乙基酰肼（2-HEH，多胺氧化化酶（PAO）、二胺氧化酶（DAO）专性抑制剂）可强烈抑制大豆侧根的发育，降低PAO、DAO活性和H₂O₂水平，增加内源游离态和结合态多胺含量。在2-HEH处理的同时，外源添加10μmol／L H₂O₂，可减缓2-HEH对侧根生长的抑制效应。1.0mmol／L环已胺（CHA，Spd合成酶抑制剂）和Put处理对侧根生长有微弱的促进作用，但这种促进作用可被CHA+DMTU（N,N-二甲基硫脲，H₂O₂清除剂）和Put+DMTU所降低，处理效果与主根内源H₂O₂的变化相一致。表明，大豆根系的发育与多胺氧化降解有关；多胺氧化降解产物，尤其是H₂O₂在大豆根系发育中起重要作用。 光照明显抑制大豆下胚轴的生长，促进PAO、DAO和过氧化物酶（POD）活性，增加H₂O₂和木质素的积累。H₂O₂含量与木质素的积累成正相关关系（R²=0.9688）。形成鲜明对比的是，在黑暗中生长的大豆黄化苗下胚轴的PAO、DAO、POD活性和H₂O₂含量呈下降趋势，木质素含量变化不大。在光照处理的同时，用不同浓度的2-HEH和氨基胍（AG,PAO和DAO专性抑制剂）处理根系，在抑制PAO、DAO活性的同时，显著降低在光照生长条件下大豆下胚轴的H₂O₂和木质素含量。实验结果为光照通过更多还原

【Abstract】 Polyamines （PAs）, spermidine （Spd）, spermine （Spm） and their diamine obligate precursor putrescine （Put）, are small aliphatic amines that are ubiquitous in all plant cells. They have been proposed to be closely associated with development, morphogenesis and responses to diverse stresses. In comparison with large and detailed investigations focused on the regulation of free PA levels and biosynthetic enzyme activities, little attention was paid to the physiological roles of PA catabolism and its catabolic products. Particularly, there are only limited information on whether PA oxidation is involved in root development, and whether light promotes the synthesis of lignin through stimulating the activities of polyamine oxidase （PAO） and diamine oxidase （DAO）. In addition, differences in PA catabolism of distinct salt tolerant genotypes in response to salt stress remain unknown. Whether PA oxidation under salt stress is implicated in a conversion to proline or accumulation of γ-aminobutyric acid is far from clear. Therefore, whether PAs accomplish their important functions in salt tolerance through modulating the accumulation of proline or GABA remains to be clarified. Here, two soybean [Glycine max （L.） Merr.] cultivars with different salt tolerance （Lee 68 cv., salt tolerant; SuXie-1 cv., salt sensitive） were used as experimental materials, using high performance liquid chromatography after different exogenous treatments according to different research purposes, to study the roles of PA oxidative degradation in development and salt tolerance of soybean seedlings. The results are as follow:2-Hydroxyethylhydrazine （2-HEH, a specific inhibitor of PAO and DAO） treatment strongly inhibited the development of lateral roots of soybean seedlings, decreased the activities of PAO and DAO as well as H₂O₂ levels, and led to the accumulation of endogenous free and conjugated PAs in main roots. This kind of 2-HEH inhibitory effect on soybean root development, however, could be alleviated by exogenously-applied 10 μ mol/L H₂O₂. The alleviative effects of exogenous H₂O₂ suggest H₂O₂ from PA oxidative更多还原