Induced Deactivation of Genes Encoding Chlorophyll Biosynthesis Enzymes Disentangles Tetrapyrrole- Mediated Retrograde Signaling  

作　　者：Hagen Schlicke Annabel Salinas Hartwig Vivien Firtzlaff Andreas S. Richter , Christine Glasser Klaus Maier Iris Finkemeier Bernhard Grimm 

机构地区：[1]Institute of Biology/Plant Physiology, Humboldt University Berlin, Philippstr. 13, Building 12, D 10115 Berlin, Germany [2]Helmholtz Zentrum Monchen, Deutsches Forschungszentrum for Gesundheit und Umwelt (GmbH), Ingolstadter Landstr. 1, 85764 Neuherberg, Germany [3]Max-Planck-lnstitute for Plant Breeding Research. Plant Proteomics and Mass Spectrometry Group, Carl-von-Linne Weg 10, 50829 Cologne, Germany

出　　处：《Molecular Plant》2014年第7期1211-1227,共17页分子植物（英文版）

摘　　要：In photosynthetic organisms, tetrapyrrole-mediated retrograde signals are proposed to contribute to a bal- anced 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 24h 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 IO2-induced signaling and feedback-regulated ALA synthesis.In photosynthetic organisms, tetrapyrrole-mediated retrograde signals are proposed to contribute to a bal- anced 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 24h 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 IO2-induced signaling and feedback-regulated ALA synthesis.

关 键 词：plastid signal transcription analysis retrograde signal tetrapyrrole metabolism Mg protoporphyrin. 

分 类 号：Q785[生物学—分子生物学] Q55