过量Zn^(2+)对水花生(Alternanthera philoxeroides)愈伤组织氧化胁迫及多胺代谢的影响

Oxidative stress and changes in polyamines metabolism caused by excessive zinc in Alternanthera philoxeroides callus

以植物组织培养技术培养的水花生愈伤组织为实验材料,研究了过量Zn2+(0、0.2、0.4、0.8、1.6 mmol/L)对水花生愈伤组织的氧化损伤及多胺代谢的影响.结果表明,随着Zn2+浓度增加:(1)水花生愈伤组织的超氧阴离子产生速率和硫代巴比妥酸反应物水平显著提升,超氧化物歧化酶活性明显抑制,叶绿素a含量显著降低;(2)精氨酸脱羧酶和鸟氨酸脱羧酶活性均升高,多胺氧化酶和二胺氧化酶活性在低Zn2+浓度处升高、高Zn2+浓度处降低;(3)总腐胺和总精胺含量在低Zn2+浓度处降低、高Zn2+浓度处增加,总亚精胺含量仅在Zn2+浓度为1.6 mmol/L时有显著增加;(4)游离态腐胺含量变化与总腐胺含量相似,游离态亚精胺含量在高Zn2+浓度时下降,游离态精胺含量仅在Zn2+浓度为0.2 mmol/L时略有下降;(5)结合态腐胺和精胺在Zn2+浓度为0.2 mmol/L时下降而在其余处理组中上升,结合态亚精胺含量各处理组中均增加;(6)束缚态腐胺和亚精胺含量均下降.可见,过量Zn2+胁迫导致水花生愈伤组织氧化性损伤,并扰乱其多胺代谢平衡;束缚态多胺向结合态多胺的转化是过量Zn2+胁迫下水花生愈伤组织多胺代谢变化的一个显著特征;以结合态为代表的内源性多胺积累对水花生愈伤组织抵抗过量Zn2+胁迫具有重要意义.

Alternanthera philoxeroides callus, cultured by tissue culture technique, was exposed to gradient concentration of Zn^＋ （0, 0.2, 0.4, 0.8, 1.6 mmol/L）for 7 d. Oxidative stress and changes in polyamines metabolism caused by excessive zinc were investigated. Results showed that, with the increasing of Zn^＋ concentration ： （ 1 ） the rate of O2-. generation and thiobarbituric acid reacting substances content was enhanced remarkably, and the superoxide dismutase activity and the chlorophyll-a content were decreased singnificantly; （2） the activities of arginine decarboxylase and ornithine decarboxylase were increased gradually, while the activities of polyamine oxidases and diamine oxidases were increased at first and then decreased at higher concentrations ; （3） the contents of total-putrescine and total-spermine was decreased at first and then increased, and the contents of total-spermidine only showed an remarkable increase at 1.6 mmol/L Zn^＋ treatment ; （4） the free-putrescine content changed in a similar pattern as its total counterpart, the free-spermidine content showed a decline at 0.8 mmol/L and 1.6 mmol/L Zn^＋ treatment, the free-spermine content had little fluctuation except a decrease at 0.2 mmol/L Zn^＋ ; （ 5 ） the contents of perchloric acid soluble conjugated （PS-conjugated） putrescine and spermine declined at 0.2 mmoL/L Zn^＋ treatment and then increased, the PS-conjuga- ted spermine content continued to rise ; and （ 6 ） the contents of perchlofic acid insoluble bound （ PIS-bound ） putrescine and spermine were descended gradually. The data presented here showed that excessive Zn^＋ treatment can cause evident oxidative stress and alter the polyamines metabolism balance. The conversion from PIS-bound polyamines to PS-conjugated polyamines was one of the key characters of polyamines metabolism alternation in A. philoxeroides callus under excessive Zn^＋ treatment. The ac cumulation in the total polyamines characterized by the PS-conjugated polyamines played an important role in A. philoxeroides callus in response to excessive Zn2 ＋ treatment.