Induced Deactivation of Genes Encoding Chlorophyll Biosynthesis Enzymes Disentangles Tetrapyrrole-Mediated Retrograde Signaling
Induced Deactivation of Genes Encoding Chlorophyll Biosynthesis Enzymes Disentangles Tetrapyrrole-Mediated Retrograde Signaling
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DOI：
10.1093/mp/ssu034
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发表时间：
2014-07-01
期刊：
影响因子：
27.5
通讯作者：
Grimm, Bernhard
中科院分区：
文献类型：
--
作者：
Schlicke, Hagen;Hartwig, Annabel Salinas;Grimm, Bernhard
在光合生物中，四吡咯介导的逆行信号被认为有助于平衡核基因表达（NGE），以响应叶绿体的代谢活性。我们采用了一种实验性的短期方法，在四吡咯生物合成的Mg分支的特异性修饰酶步骤的最初几个小时内，当其他信号的多效性效应可以避免时，可以评估修饰的NGE。对编码Mg螯合酶、Mg原卟啉甲基转移酶和Mg原卟啉单甲基环化酶CHLH亚基的CHLH、CHLM和CHL27分别进行24小时的沉默处理后，基因表达失活迅速导致相应酶的活性降低和Mg卟啉水平改变。但是NGE并没有实质性的改变。当这三个基因连续失活达4 d时，测定了核基因转录物水平的变化。CHL27沉默超过24小时会导致叶片坏死，并调节氧化应激反应和光合作用相关核基因（PhANGs）的转录水平。CHLH和CHLM的长期失活导致PhANGs和四吡咯相关基因的转录水平略有升高。这些时间分辨的研究表明，四吡咯生物合成对由O-1(2)诱导的信号传导和反馈调节的ALA合成介导的NGE的贡献是复杂的。
In photosynthetic organisms, tetrapyrrole-mediated retrograde signals are proposed to contribute to a balanced nuclear gene expression (NGE) in response to metabolic activity in chloroplasts. We followed an experimental short-term approach that allowed the assessment of modified NGE during the first hours of specifically modified enzymatic steps of the Mg branch of tetrapyrrole biosynthesis, when pleiotropic effects of other signals can be avoided. In response to 24-h-induced silencing of CHLH, CHLM, and CHL27 encoding the CHLH subunit of Mg chelatase, the Mg protoporphyrin methyltransferase and Mg protoporphyrin monomethylester cyclase, respectively, deactivated gene expression rapidly led to reduced activity of the corresponding enzymes and altered Mg porphyrin levels. But NGE was not substantially altered. When these three genes were continuously inactivated for up to 4 d, changes of transcript levels of nuclear genes were determined. CHL27 silencing for more than 24 h results in necrotic leaf lesions and modulated transcript levels of oxidative stress-responsive and photosynthesis-associated nuclear genes (PhANGs). The prolonged deactivation of CHLH and CHLM results in slightly elevated transcript levels of PhANGs and tetrapyrrole-associated genes. These time-resolved studies indicate a complex scenario for the contribution of tetrapyrrole biosynthesis on NGE mediated by O-1(2)-induced signaling and feedback-regulated ALA synthesis.