An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis
An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis
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DOI：
10.1104/pp.110.164111
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发表时间：
2010-12-01
期刊：
影响因子：
7.4
通讯作者：
Rodermel, Steve
中科院分区：
文献类型：
--
作者：
Liu, Xiayan;Yu, Fei;Rodermel, Steve
拟南芥（Arabidopsis thaliana）黄色杂色2（var 2）突变体由于缺失VAR 2（叶绿体FtsH蛋白酶/伴侣复合物的亚基）而具有绿色和白色扇形叶。抑制剂筛选是深入了解var 2功能和var 2杂色机制的有价值的工具。在这里，我们报告了004-003的分子特征，这是一个抑制var 2杂色的品系。我们发现该品系的抑制表型是由于缺乏叶绿体五肽重复序列（PPR）蛋白引起的，我们将其命名为变异提供者7（SVR 7）。PPR蛋白含有串联重复的PPR基序，它们结合特定的RNA，被认为是植物叶绿体和线粒体核酸代谢的中心调节因子。svr 7突变体的叶绿体核糖体RNA（rRNA）加工的缺陷是不同于其他svr突变体，这些缺陷与一些叶绿体蛋白质的积累，直接或间接的减少。我们还发现，var 2在22摄氏度下表现出叶片杂色表型，而在8摄氏度下具有明显的失绿表型，这与叶绿体rRNA加工缺陷和叶绿体蛋白质积累急剧减少有关。令人惊讶的是，var 2的冷诱导表型不能被svr 7抑制。我们的研究结果加强了先前建立的VAR 2杂色和叶绿体rRNA加工/叶绿体翻译之间的联系，他们也指向VAR 2介导不同的活动在正常和低温下的叶绿体生物发生的可能性。
The Arabidopsis (Arabidopsis thaliana) yellow variegated2 (var2) mutant has green- and white-sectored leaves due to loss of VAR2, a subunit of the chloroplast FtsH protease/chaperone complex. Suppressor screens are a valuable tool to gain insight into VAR2 function and the mechanism of var2 variegation. Here, we report the molecular characterization of 004-003, a line in which var2 variegation is suppressed. We found that the suppression phenotype in this line is caused by lack of a chloroplast pentatricopeptide repeat (PPR) protein that we named SUPPRESSOR OF VARIEGATION7 (SVR7). PPR proteins contain tandemly repeated PPR motifs that bind specific RNAs, and they are thought to be central regulators of chloroplast and mitochondrial nucleic acid metabolism in plants. The svr7 mutant has defects in chloroplast ribosomal RNA (rRNA) processing that are different from those in other svr mutants, and these defects are correlated with reductions in the accumulation of some chloroplast proteins, directly or indirectly. We also found that whereas var2 displays a leaf variegation phenotype at 22 degrees C, it has a pronounced chlorosis phenotype at 8 degrees C that is correlated with defects in chloroplast rRNA processing and a drastic reduction in chloroplast protein accumulation. Surprisingly, the cold-induced phenotype of var2 cannot be suppressed by svr7. Our results strengthen the previously established linkage between var2 variegation and chloroplast rRNA processing/chloroplast translation, and they also point toward the possibility that VAR2 mediates different activities in chloroplast biogenesis at normal and chilling temperatures.