一氧化氮作为过氧化氢下游信号分子参与调节白菜幼苗对镉胁迫的耐受性

Nitric Oxide Acting as A Downstream Signaling Molecule of H_2O_2 Regulates Cd Tolerance in Brassica var. pekinensis

信号分子过氧化氢(H2O2)和一氧化氮(NO)在缓解重金属镉(Cd)对植物的胁迫过程中分别发挥着重要的作用。该实验通过生理生化技术研究了白菜幼苗Cd胁迫时H2O2和NO之间的关系。结果表明,H2O2预处理可以增强白菜幼苗对Cd的耐受,包括减少丙二醛(malondialdehyde,MDA)的浓度、降低电解质的渗漏、增强一氧化氮合酶(nitric oxide synthase,NOS)的活力,进而提高体内NO的水平;用外源NO的供体硝普钠预处理白菜幼苗,同样减少MDA的浓度以及电解质的渗漏。此外,白菜幼苗对Cd的耐受性在被H2O2增强的基础上,还能进一步被NO增强,且这种增强作用也会受到NO的清除剂和合成抑制剂的抑制。在Cd的胁迫下,H2O2预处理可以减少白菜幼苗地上部分对Cd的富集,但根中Cd的含量不受H2O2的影响,而且NO会加剧由H2O2引起的白菜幼苗地上部分Cd的富集的减少。以上结果表明,Cd胁迫时H2O2可通过增强NOS的活性,促进生成NO,进而提高白菜幼苗对Cd的耐受性。

Hydrogen peroxide （H2O2） and nitric oxide （NO） acting as a endogenous signal regulate and respond to a variety of biotic and abiotic stresses including cadmium （Cd） stress in plants. In this study, the interaction between H2O2 and NO in Chinese cabbage （Brassica var. pekinensis） under Cd stress was investigated with physiological and biochemical method. The results indicated that the seedlings pretreated with H2O2 exhibited enhanced tolerance to Cd stress, including the decreasing of malondialdehyde （MDA） concentration, the reduction of electrolyte leakage, the increasing of the nitric oxide synthase （NOS） activity and the raising of endogenous NO content. In parallel, the very similar results were shown when the seedlings were pretreated with sodium nitro prusside, a donor of exogenous NO. It was further verified with pharmacological experiments that the enhanced tolerence to Cd stress in seedlings pretreated by H2O2 was dramatically repressed by NO scavenger and inhibitor. Accordingly, it is concluded that the enhanced tolerance to Cd by H2O2 in seedlings highly depended on the endogenous NO signaling, which is fulfilled by enhancement of NOS activity with the application of H2O2.