In vivo visualization of Mg-ProtoporphyrinIX, a coordinator of photosynthetic gene expression in the nucleus and the chloroplast
In vivo visualization of Mg-ProtoporphyrinIX, a coordinator of photosynthetic gene expression in the nucleus and the chloroplast
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DOI：
10.1105/tpc.106.048744
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发表时间：
2007-06-01
期刊：
影响因子：
11.6
通讯作者：
Strand, Asa
中科院分区：
文献类型：
--
作者：
Ankele, Elisabeth;Kindgren, Peter;Strand, Asa
光合作用装置由来自细胞核和叶绿体的基因编码的蛋白质组成。为了确保光合复合体的化学计量组装，并使其能够快速重组以响应不断变化的环境，质体发出调节核基因表达的信号，以匹配质体的状态。作为叶绿体信号之一，叶绿素中间体Mg-ProtoporphyrinIX （Mg-ProtoIX）在逆境条件下积累，并作为光合基因表达的负调控因子。利用四吡咯的光反应性质，利用共聚焦激光扫描光谱技术可以在细胞中观察到Mg-ProtoIX。结果表明，在胁迫条件下，Mg-ProtoIX在叶绿体和细胞质中均有积累。因此，信号代谢物从叶绿体输出，将质体信号传递到细胞质。我们对Mg-ProtoIX过富集和过富集突变体铜响应缺陷和基因组解偶联突变体的研究结果表明，核和质体编码的光合作用基因的表达都受到Mg-ProtoIX富集的调控。因此，胁迫诱导的信号代谢产物Mg-ProtoIX的积累协调了核和塑性光合基因的表达。
The photosynthetic apparatus is composed of proteins encoded by genes from both the nucleus and the chloroplast. To ensure that the photosynthetic complexes are assembled stoichiometrically and to enable their rapid reorganization in response to a changing environment, the plastids emit signals that regulate nuclear gene expression to match the status of the plastids. One of the plastid signals, the chlorophyll intermediate Mg-ProtoporphyrinIX ( Mg-ProtoIX) accumulates under stress conditions and acts as a negative regulator of photosynthetic gene expression. By taking advantage of the photoreactive property of tetrapyrroles, Mg-ProtoIX could be visualized in the cells using confocal laser scanning spectroscopy. Our results demonstrate that Mg-ProtoIX accumulated both in the chloroplast and in the cytosol during stress conditions. Thus, the signaling metabolite is exported from the chloroplast, transmitting the plastid signal to the cytosol. Our results from the Mg-ProtoIX over- and underaccumulating mutants copper response defect and genome uncoupled5, respectively, demonstrate that the expression of both nuclear- and plastid-encoded photosynthesis genes is regulated by the accumulation of Mg-ProtoIX. Thus, stress-induced accumulation of the signaling metabolite Mg-ProtoIX coordinates nuclear and plastidic photosynthetic gene expression.