The Arabidopsis FtsH metalloprotease gene family: interchangeability of subunits in chloroplast oligomeric complexes.
The Arabidopsis FtsH metalloprotease gene family: interchangeability of subunits in chloroplast oligomeric complexes.
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DOI：
10.1111/j.1365-313x.2003.02014.x
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发表时间：
2004-03
期刊：
影响因子：
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通讯作者：
Fei Yu;Sungsoon Park;S. Rodermel
中科院分区：
文献类型：
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作者：
Fei Yu;Sungsoon Park;S. Rodermel
拟南芥AtFtsH金属蛋白酶基因家族包括12个成员（AtFtsH 1-AtFtsH 12），其中包括三对紧密相关的靶向叶绿体的基因（AtFtsH 2和AtFtsH 8; AtFtsH 1和AtFtsH 5;以及AtFtsH 7和AtFtsH 9）。AtFtsH 5（var 1）和AtFtsH 2（var 2）中的突变产生具有绿色和白色扇形叶的杂色植物。绿色扇区中的细胞含有形态正常的叶绿体，而白色扇区中的细胞在叶绿体生物发生中被阻断。一个主要的问题是叶绿体是如何在具有突变基因型的细胞中产生的。我们已经发现，通过二维（2-D）的绿色凝胶和凝胶过滤分析，AtFtsH 2/VAR 2形成寡聚复合物。在二维绿色凝胶中鉴定出两条对应于AtFtsH 5/VAR 1 + AtFtsH 1和AtFtsH 2/VAR 2 + AtFtsH 8的条带，并且这些条带在缺乏AtFtsH 5/VAR 1和AtFtsH 2/VAR 2的var 1和var 2类囊体中的量分别协调地减少。这些减少不是因为转录本丰度的改变。过表达AtFtsH 8在var 2 -4（一个假定的无效等位基因）正常化的突变体的杂色表型，并恢复到野生型水平的两个波段。这些结果表明，AtFtsH 8是可互换的AtFtsH 2/VAR 2在AtFtsH的寡聚体，这两种蛋白质有冗余的功能。与这一假设相一致，AtFtsH 2和AtFtsH 8具有相似的表达模式，通过启动子-β-葡萄糖醛酸酶（GUS）融合和RT-PCR实验监测。基于我们的研究结果，我们提出，AtFtsH 1，AtFtsH 2/VAR 2，AtFtsH 5/VAR 1，和AtFtsH 8相互作用，形成寡聚体结构，和亚基化学计量控制转录后的var 1和var 2，也许营业额。提出了一个阈值模型来解释的模式杂色在var 2中，AtFtsH 8提供了一个补偿活动的突变体的绿色部门。
The Arabidopsis At filamentation temperature sensitive (FtsH) metalloprotease gene family comprises 12 members (AtFtsH1-AtFtsH12), including three pairs of closely related genes that are targeted to chloroplasts (AtFtsH2 and AtFtsH8; AtFtsH1 and AtFtsH5; and AtFtsH7 and AtFtsH9). Mutations in AtFtsH5 (var1) and AtFtsH2 (var2) give rise to variegated plants with green- and white-sectored leaves. Cells in the green sectors contain morphologically normal chloroplasts, whereas cells in the white sectors are blocked in chloroplast biogenesis. A major question is how chloroplasts arise in cells that have a mutant genotype. We have found by two-dimensional (2-D) green gel and gel filtration analyses that AtFtsH2/VAR2 forms oligomeric complexes. Two bands in the 2-D green gels that correspond to AtFtsH5/VAR1 + AtFtsH1 and AtFtsH2/VAR2 + AtFtsH8 have been identified, and these bands are coordinately reduced in amount in var1 and var2 thylakoids that lack AtFtsH5/VAR1 and AtFtsH2/VAR2, respectively. These reductions are not because of alterations in transcript abundance. Overexpression of AtFtsH8 in var2-4 (a putative null allele) normalizes the variegation phenotype of the mutant and restores the two bands to their wild-type levels. These results suggest that AtFtsH8 is interchangeable with AtFtsH2/VAR2 in AtFtsH-containing oligomers, and that the two proteins have redundant functions. Consistent with this hypothesis, AtFtsH2 and AtFtsH8 have similar expression patterns, as monitored by promoter-beta-glucuronidase (GUS) fusion and RT-PCR experiments. Based on our findings, we propose that AtFtsH1, AtFtsH2/VAR2, AtFtsH5/VAR1, and AtFtsH8 interact to form oligomeric structures, and that subunit stoichiometry is controlled post-transcriptionally in var1 and var2, perhaps by turnover. A threshold model is presented to explain the pattern of variegation in var2 in which AtFtsH8 provides a compensating activity in the green sectors of the mutant.