Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.
Physiol Plant. 2010 Jan;138(1):60-73. doi: 10.1111/j.1399-3054.2009.01297.x.
The growth of the wild-type and three salt tolerant mutants of barnyard grass (Echinochloa crusgalli L.) under salt stress was investigated in relation to oxidative stress and activities of the antioxidant enzymes superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), phenol peroxidase (POD: EC 1.11.1.7), glutathione reductase (GR: EC 1.8.1.7) and ascorbate peroxidase (APX: EC 1.11.1.1). The three mutants (fows B17, B19 and B21) grew significantly better than the wild-type under salt stress (200 mM NaCl) but some salt sensitive individuals were still detectable in the populations of the mutants though in smaller numbers compared with the wild-type. The salt sensitive plants had slower growth rates, higher rates of lipid peroxidation and higher levels of reactive oxygen species (ROS) in their leaves compared with the more tolerant plants from the same genotype. These sensitivity responses were maximized when the plants were grown under high light intensity suggesting that the chloroplast could be a main source of ROS under salt stress. However, the salt sensitivity did not correlate with reduced K(+)/Na(+) ratios or enhanced Na(+) uptake indicating that the sensitivity responses may be mainly because of accumulation of ROS rather than ion toxicity. SOD activities did not correlate to salt tolerance. Salt stress resulted in up to 10-fold increase in CAT activity in the sensitive plants but lower activities were found in the tolerant ones. In contrast, the activities of POD, APX and GR were down regulated in the sensitive plants compared with the tolerant ones. A correlation between plant growth, accumulation of ROS and differential modulation of antioxidant enzymes is discussed. We conclude that loss of activities of POD, APX and GR causes loss of fine regulation of ROS levels and hence the plants experience oxidative stress although they have high CAT activities.
在盐胁迫下，研究了稗草（Echinochloa crusgalli L.）野生型和三种耐盐突变体的生长情况与氧化应激和抗氧化酶超氧化物歧化酶（SOD：EC 1.15.1.1）、过氧化氢酶（CAT：EC 1.11.1.6）、过氧化物酶（POD：EC 1.11.1.7）、谷胱甘肽还原酶（GR：EC 1.8.1.7）和抗坏血酸过氧化物酶（APX：EC 1.11.1.1）的活性关系。三种突变体（B17、B19 和 B21）在盐胁迫（200 mM NaCl）下的生长明显优于野生型，但在突变体种群中仍能检测到一些对盐敏感的个体，只是数量比野生型少。与来自同一基因型的更耐盐的植物相比，对盐敏感的植物叶片生长速度较慢，脂质过氧化速率较高，活性氧（ROS）水平较高。当植物在高光强下生长时，这些敏感性反应达到最大值，这表明叶绿体可能是盐胁迫下 ROS 的主要来源。然而，盐敏感性与降低的 K+/Na+比值或增强的 Na+吸收无关，这表明敏感性反应可能主要是由于 ROS 的积累而不是离子毒性。SOD 活性与盐耐受性无关。盐胁迫导致敏感植物 CAT 活性增加了 10 倍，但在耐盐植物中发现的 CAT 活性较低。相比之下，敏感植物中 POD、APX 和 GR 的活性较耐盐植物下调。讨论了植物生长、ROS 积累和抗氧化酶差异调节之间的相关性。我们得出结论，POD、APX 和 GR 活性的丧失导致 ROS 水平的精细调节丧失，因此尽管植物 CAT 活性较高，但它们仍会经历氧化应激。
