Flavodoxins are electron carrier flavoproteins present in bacteria and photosynthetic microorganisms which duplicate the functional properties of iron-sulphur containing ferredoxins and replace them under adverse environmental situations that lead to ferredoxin decline. When expressed in plant chloroplasts, flavodoxin complemented ferredoxin deficiency and improved tolerance to multiple sources of biotic, abiotic and xenobiotic stress. Analysis of flavodoxin-expressing plants grown under normal conditions, in which the two carriers are present, revealed phenotypic effects unrelated to ferredoxin replacement. Flavodoxin thus provided a tool to alter the chloroplast redox poise in a customized way and to investigate its consequences on plant physiology and development. We describe herein the effects exerted by the flavoprotein on the function of the photosynthetic machinery. Pigment analysis revealed significant increases in chlorophyll a, carotenoids and chlorophyll a/b ratio in flavodoxin-expressing tobacco lines. Results suggest smaller antenna size in these plants, supported by lower relative contents of light-harvesting complex proteins. Chlorophyll a fluorescence and P700 spectroscopy measurements indicated that transgenic plants displayed higher quantum yields for both photosystems, a more oxidized plastoquinone pool under steady-state conditions and faster plastoquinone dark oxidation after a pulse of saturating light. Many of these effects resemble the phenotypes exhibited by leaves adapted to high irradiation, a most common environmental hardship faced by plants growing in the field. The results suggest that flavodoxin-expressing plants would be better prepared to cope with this adverse situation, and concur with earlier observations reporting that hundreds of stress-responsive genes were induced in the absence of stress in these lines.

中文翻译：

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表达黄素氧还蛋白的烟草植物的光合特征揭示了类似高光适应的表型。


黄素氧还蛋白是存在于细菌和光合微生物中的电子载体黄素蛋白，其复制含有铁氧还蛋白的铁硫的功能特性，并在导致铁氧还蛋白下降的不利环境条件下取代它们。当在植物叶绿体中表达时，黄素氧还蛋白补充了铁氧还蛋白的缺乏，并提高了对多种生物、非生物和外源胁迫来源的耐受性。对正常条件下生长的表达黄素氧还蛋白的植物（其中存在两种载体）的分析揭示了与铁氧还蛋白替代无关的表型效应。因此，黄素氧还蛋白提供了一种以定制方式改变叶绿体氧化还原平衡并研究其对植物生理和发育的影响的工具。我们在此描述了黄素蛋白对光合机器功能的影响。色素分析显示，在表达黄素氧还蛋白的烟草品系中，叶绿素 a、类胡萝卜素和叶绿素 a/b 比率显着增加。结果表明，这些植物的天线尺寸较小，这得益于光捕获复合蛋白相对含量较低。叶绿素 a 荧光和 P700 光谱测量表明，转基因植物的两个光系统均表现出更高的量子产率，在稳态条件下氧化程度更高的质体醌池，在饱和光脉冲后质体醌暗氧化速度更快。其中许多效应类似于适应高辐射的叶子所表现出的表型，这是田间生长的植物面临的最常见的环境困难。 结果表明，表达黄素氧还蛋白的植物能够更好地应对这种不利情况，并且与早期的观察结果一致，即在这些品系中没有胁迫的情况下诱导了数百个胁迫反应基因。