The biosynthesis of flavonoids is enhanced similarly by UV radiation and root zone salinity in L. vulgare leaves
The biosynthesis of flavonoids is enhanced similarly by UV radiation and root zone salinity in L. vulgare leaves
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DOI：
10.1016/j.jplph.2010.07.016
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发表时间：
2011-02-15
影响因子：
4.3
通讯作者：
Tattini, Massimiliano
中科院分区：
文献类型：
--
作者：
Agati, Giovanni;Biricolti, Stefano;Tattini, Massimiliano
最近有人提出，黄酮类化合物在光保护中除了有效的紫外线衰减剂外，还具有作为抗氧化剂的潜力。在这里，我们测试的假设，即黄酮类化合物的积累在响应“过量的光”在存在或不存在的紫外线辐射。在紫外线阻隔实验中，我们在30%或100%的太阳光辐照度下，通过切断整个紫外线波段，种植女贞植物。这些植物还暴露于UV辐照或在根区供应125 mM NaCl。在100%光照下，植物叶片光过剩，根区盐胁迫加剧了这种现象。盐胁迫抑制了抗氧化酶的活性，特别是在充足的阳光下，并导致严重的叶片氧化损伤。二羟基B-环取代的黄酮类化合物，即槲皮素3-O-和木犀草素7-O-糖苷，积累急剧响应于在没有紫外线辐射的情况下的阳光照射。紫外线辐射和根区NaCl增加，以类似的程度，这些黄酮类化合物的浓度，有很大的潜力，以消除各种形式的活性氧。处理引起的叶苯丙素浓度的变化影响的抗氧化活性在更大程度上比叶提取物的紫外线屏蔽能力。在阳光辐照度的突然增加的早期反应包括槲皮素衍生物和矢车菊素3-O-葡萄糖苷的浓度急剧增加，后者在紫外光谱区的吸收可以忽略不计。与此相反，有效的紫外线衰减剂，如羟基肉桂酸酯和单羟基B-环类黄酮，对光处理无反应。总的来说，这些发现导致的假设，黄酮类化合物可能有一个重要的抗氧化功能的光保护。这一假设进一步证实了大量分布的槲皮素和木犀草素衍生物的液泡中的叶肉，不仅在相应的车厢的表皮细胞，而且在充分的阳光处理的叶子在没有紫外线辐射。未来的实验，旨在评估复杂的抗氧化防御系统中的叶类黄酮的相对贡献，以帮助最终解决其抗氧化功能在光保护的相关性。(C)2010年Elsevier GmbH。All rights reserved.
Flavonoids have recently been suggested to have the potential to serve as antioxidants other than effective UV attenuators in photoprotection. Here, we tested the hypothesis that flavonoids accumulate in response to "excess light" in the presence or in the absence of UV radiation. In a UV exclusion experiment, we grew Ligustrum vulgare plants outdoors under 30% or 100% sunlight irradiance, by cutting-off the whole UV waveband. These plants were also exposed to UV irradiance or supplied with 125 mM NaCl at the root zone. Leaves of plants under 100% sunlight irradiance suffered from excess light, which was exacerbated greatly by root zone salinity stress. Salinity stress repressed the activities of antioxidant enzymes, particularly in full sunlight, and led to severe leaf oxidative damage. Dihydroxy B-ring-substituted flavonoids, namely quercetin 3-O- and luteolin 7-O-glycosides, accumulated steeply in response to sunlight irradiance in the absence of UV radiation. UV radiation and root zone NaCl increased, to a similar degree, the concentration of these flavonoids, which have a great potential to scavenge various forms of reactive oxygen. Treatment-induced changes in leaf phenylpropanoid concentration affected antioxidant activities to a greater extent than the UV-screening capacities of leaf extracts. Early responses to an abrupt increase in sunlight irradiance included a steep increase in the concentrations of quercetin derivatives and cyanidin 3-O-glucoside, with the latter negligibly absorbing in the UV-spectral region. In contrast, effective UV attenuators, such as hydroxycinnamates and monohydroxy B-ring flavonoids, were unresponsive to the light treatments. Overall, these findings lead to the hypothesis that flavonoids may have an important antioxidant function in photoprotection. This hypothesis is further corroborated by the large distribution of quercetin and luteolin derivatives in the vacuoles of mesophyll, not only in the corresponding compartments of epidermal cells, but also in full sunlight-treated leaves in the absence of UV radiation. Future experiments aimed at evaluating the relative contribution of flavonoids within the complex antioxidant defense systems operating in the leaf are needed to help conclusively address the relevance of their antioxidant functions in photoprotection. (C) 2010 Elsevier GmbH. All rights reserved.