White leaf sectors in yellow variegated2 are formed by viable cells with undifferentiated plastids
White leaf sectors in yellow variegated2 are formed by viable cells with undifferentiated plastids
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DOI：
10.1104/pp.107.099002
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发表时间：
2007-06-01
期刊：
影响因子：
7.4
通讯作者：
Sakamoto, Wataru
中科院分区：
文献类型：
--
作者：
Kato, Yusuke;Miura, Eiko;Sakamoto, Wataru
黄色杂色2（var2）是表现出叶杂色的最佳表征的拟南芥（Arabidopsis thaliana）突变体之一。var2的叶斑是由于ATP依赖的金属蛋白酶FtsH2的丢失，FtsH2是类囊体膜中FtsH杂合物的主要成分。虽然FtsH2在蛋白质质量控制中的功能作用已被广泛研究，但var 2的白色组织中质体的生理状态尚未得到很好的表征。在这里，我们表明var2中的白色组织既不是光漂白的结果，也不是衰老增强的结果。质体的可视化质体靶向的绿色荧光蛋白显示，质体在白色部门是不同的，具有未分化的特点。质体也是不同的，因为它们含有大的类核，质体DNA和蛋白质的复杂结构，通常在未分化的质体中发现。对绿色和白色组织蛋白质谱的比较分析表明，这种差异主要存在于光合作用相关蛋白质中，而与其它细胞器蛋白质无关。因此，白色组织中的细胞是活的，它们的缺陷仅限于质体功能。质体积累正常水平的叶绿体转录本，而核编码的光合基因的实质性抑制是显而易见的，在白色部门。基于这些结果，我们推断var2中的白色区段是由具有在类囊体形成中被阻止的质体的活细胞制成的。提出了一种在var2中形成杂色扇区的模型。
The yellow variegated2 (var2) is one of the best- characterized Arabidopsis (Arabidopsis thaliana) mutants showing leaf variegation. Leaf variegation of var2 results from the loss of an ATP-dependent metalloprotease, FtsH2, which is a major component of the FtsH heterocomplex in thylakoid membranes. While the functional role of FtsH2 in protein quality control has been extensively studied, the physiological state of plastids in white tissues of the var2 is not well characterized. Here we show that the white tissue in var2 is neither the result of photobleaching nor enhanced senescence. Visualization of plastids by plastid-targeted green fluorescent protein revealed that plastids in the white sector are distinct and have undifferentiated characteristics. The plastids are also distinct in that they contain large nucleoids, a complex structure of plastid DNA and proteins, that are typically found in undifferentiated plastids. Comparative analyses of protein profiles from green and white tissues suggested that the difference was observed in the proteins related to photosynthesis but not due to proteins of other organelles. Thus, cells in the white tissue are viable and their defect is limited to plastid function. The plastid accumulates normal levels of chloroplast transcripts, whereas a substantial repression of nuclear-encoded photosynthetic genes was evident in the white sector. Based upon these results, we inferred that the white sectors in var2 are made by viable cells that have plastids arrested in thylakoid formation. A proposed model to form the variegated sector in var2 is provided.