Plant Molecular Biology Unit, Department of Botany, Sri Krishnadevaraya University, Anantapur, 515 003, India,
Plant Cell Rep. 2015 Jan;34(1):141-56. doi: 10.1007/s00299-014-1695-3. Epub 2014 Oct 29.
Polyamines can regulate the expression of antioxidant enzymes and impart plants tolerance to abiotic stresses. A comparative analysis of polyamines, their biosynthetic enzymes at kinetic and at transcriptional level, and their role in regulating the induction of antioxidant defense enzymes under salt stress condition in two foxtail millet (Setaria italica L.) cultivars, namely Prasad, a salt-tolerant, and Lepakshi, a salt-sensitive cultivar was conducted. Salt stress resulted in elevation of free polyamines due to increase in the activity of spermidine synthase and S-adenosyl methionine decarboxylase enzymes in cultivar Prasad compared to cultivar Lepakshi under different levels of NaCl stress. These enzyme activities were further confirmed at the transcript level via qRT-PCR analysis. The cultivar Prasad showed a greater decrease in diamine oxidase and polyamine oxidase activity, which results in the accumulation of polyamine pools over cultivar Lepakshi. Generation of free radicals, such as O 2 (·-) and H2O2, was also analyzed quantitatively. A significant increase in O 2 (·-) and H2O2 in the cultivar Lepakshi compared with cultivar Prasad was recorded in overall pool sizes. Further, histochemical staining showed lesser accumulation of O 2 (·-) and of H2O2 in the leaves of cultivar Prasad than cultivar Lepakshi. Our results also suggest the ability of polyamine oxidation in regulating the induction of antioxidative defense enzymes, which involve in the elimination of toxic levels of O 2 (·-) and H2O2, such as Mn-superoxide dismutase, catalase and ascorbate peroxidase. The contribution of polyamines in modulating antioxidative defense mechanism in NaCl stress tolerance is discussed.
多胺可以调节抗氧化酶的表达，使植物能够耐受非生物胁迫。本研究以谷子（Setaria italica L.）两个品种，即耐盐品种 Prasad 和盐敏感品种 Lepakshi 为材料，比较分析了多胺及其生物合成酶在动力学和转录水平上的差异，以及它们在盐胁迫条件下调节抗氧化防御酶诱导中的作用。与 Lepakshi 品种相比，盐胁迫导致 Prasad 品种游离多胺含量升高，这是由于盐胁迫下，其 spermidine synthase 和 S-adenosyl methionine decarboxylase 酶活性增加。通过 qRT-PCR 分析进一步证实了这些酶活性在转录水平上的变化。与 Lepakshi 品种相比，Prasad 品种二胺氧化酶和多胺氧化酶活性下降更大，导致多胺库积累增加。还定量分析了自由基（如 O 2 (·-)和 H2O2）的产生。与 Prasad 品种相比，Lepakshi 品种的 O 2 (·-)和 H2O2 总量显著增加。进一步的组织化学染色显示，Prasad 品种叶片中 O 2 (·-)和 H2O2 的积累比 Lepakshi 品种少。我们的研究结果还表明，多胺氧化在调节抗氧化防御酶的诱导中起作用，这涉及到消除 O 2 (·-)和 H2O2 等有毒水平，如 Mn-超氧化物歧化酶、过氧化氢酶和抗坏血酸过氧化物酶。本文讨论了多胺在调节 NaCl 胁迫耐受中的抗氧化防御机制中的作用。
