In vivo visualization of Mg-protoporphyrin IX, a coordinator of photosynthetic gene expression in the nucleus and the chloroplast.
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.
Ankele
Elisabeth
E
Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
Kindgren
Peter
P
Pesquet
Edouard
E
Strand
Asa
A
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000648:ultrastructure; D002138:Calibration; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics*; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008274:Magnesium / Q000378:metabolism*; D018613:Microscopy, Confocal; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010788:Photosynthesis / Q000187:drug effects / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011524:Protoporphyrins / Q000737:chemistry / Q000378:metabolism*; D011724:Pyridazines / Q000494:pharmacology; D012808:Sigma Factor / Q000378:metabolism; D045725:Tetrapyrroles / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry
D010940:Plant Proteins; D011524:Protoporphyrins; D011724:Pyridazines; D012808:Sigma Factor; D045725:Tetrapyrroles; C028025:protoporphyrin IX; D012321:DNA-Directed RNA Polymerases; D008274:Magnesium; C008677:norflurazone