Boldt R, Scandalios J G
Institut für Biochemie und Molekulare Physiologie, Universität Potsdam, Germany.
Free Radic Biol Med. 1997;23(3):505-14. doi: 10.1016/s0891-5849(97)00111-1.
The effects of UV (ultraviolet) -irradiation on the expression of the antioxidant genes Cat2 and Cat3, encoding the CAT-2 and CAT-3 catalases in maize were examined. Cat2 and Cat3 transcript accumulation was analyzed in leaves of maize seedlings grown under different light conditions, and subsequently exposed to UV-light. Under DD-(constant darkness) and LL- (continuous light) conditions, as well as under a 12h D/L- (dark/light) photoperiod, the Cat2 mRNA was expressed at low and constant levels. In contrast, Cat3 transcript accumulation was constant and about 10 times higher than that of Cat2 under DD or LL, while the expression of Cat3 exhibits a typical circadian rhythm under a 12h D/L photoperiod. UV- light pulses in the range of 290 to 400 nm strongly induce the expression of Cat2. Upon removing the UV-B portion (290-310 nm) of the UV-spectrum the maximal Cat2 transcript level was reduced by about 60%. On applying UV-light of the same quality in addition to visible light, the expression of Cat2 was induced. DNA damage caused by UV-light and induction mediated by a UV-light photosensory system are suggested. Further, it is suggested that the Cat3 circadian rhythm may be regulated by a blue light/UV-A and a UV-B photoreceptor. If DD and LL grown plants that exhibit no circadian oscillation, were exposed to constant UV-light in the range of 290 to 400 nm a circadian rhythm was induced; indicating that UV-light may function as an additional environmental cue to entrain the Cat3 circadian rhythm. Since, Cat2 and Cat3 showed distinct responses to UV light, it is suggested that both genes may act to scavenge reactive oxygen species (ROS) generated by UV-light to protect the plant from oxidative damage.
研究了紫外线（UV）照射对玉米中编码CAT-2和CAT-3过氧化氢酶的抗氧化基因Cat2和Cat3表达的影响。分析了在不同光照条件下生长并随后暴露于紫外光的玉米幼苗叶片中Cat2和Cat3转录本的积累情况。在持续黑暗（DD）和持续光照（LL）条件下，以及在12小时暗/光（D/L）光周期下，Cat2 mRNA以低水平且恒定的方式表达。相比之下，在DD或LL条件下，Cat3转录本的积累是恒定的，且比Cat2高约10倍，而在12小时D/L光周期下，Cat3的表达呈现出典型的昼夜节律。290至400纳米范围内的紫外线脉冲强烈诱导Cat2的表达。去除紫外光谱中的UV-B部分（290 - 310纳米）后，Cat2转录本的最大水平降低了约60%。除可见光外施加相同质量的紫外光时，Cat2的表达被诱导。这表明存在由紫外线引起的DNA损伤以及由紫外线光感系统介导的诱导作用。此外，有人提出Cat3的昼夜节律可能受蓝光/UV-A和UV-B光感受器调节。如果将在DD和LL条件下生长且无昼夜振荡的植物暴露于290至400纳米范围内的恒定紫外光下，会诱导出昼夜节律；这表明紫外光可能作为一种额外的环境信号来调节Cat3的昼夜节律。由于Cat2和Cat3对紫外光表现出不同的反应，因此有人认为这两个基因可能都起到清除由紫外光产生的活性氧（ROS）的作用，以保护植物免受氧化损伤。
