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IN BRIEF

Retrograde Signaling from Chloroplast to Nucleus

neckardt{at}aspb.org

Plant organelles emit signals that regulate the expression of nuclear genes, a process known as retrograde signaling. The chlorophyll intermediate Mg-protoporphyrin IX (Mg-ProtoIX) is one such signal that accumulates under stress conditions and acts as a negative regulator of photosynthetic gene expression. Using confocal laser microscopy, Ankele et al. (pages 1964–1979) show that Mg-ProtoIX is a signaling metabolite that is exported from the chloroplast to the cytosol under certain conditions. The accumulation of Mg-ProtoIX under stress conditions in both the chloroplast and the cytosol is also shown to inhibit the expression of both chloroplastic and nuclear photosynthesis genes.

Plastid-encoded photosynthesis-related genes are transcribed by plastid-encoded RNA polymerase (PEP), whereas other plastid genes tend to be transcribed by a nuclear-encoded plastid RNA polymerase. The authors show that, in addition to regulating the expression of nuclear-encoded photosynthesis genes, stress-induced accumulation of Mg-ProtoIX also affects the expression of plastid-encoded photosynthesis genes, specifically by regulating the expression of the nuclear-encoded sigma factors necessary for the function of the multisubunit PEP enzyme. Thus, retrograde signaling of Mg-ProtoIX from plastid to nucleus constitutes a mechanism of coordinating gene expression in the two compartments.

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www.plantcell.org/cgi/doi/10.1105/tpc.107.190611

Related articles in Plant Cell:

In Vivo Visualization of Mg-ProtoporphyrinIX, a Coordinator of Photosynthetic Gene Expression in the Nucleus and the Chloroplast

Elisabeth Ankele, Peter Kindgren, Edouard Pesquet, and Åsa Strand
Plant Cell 2007 19: 1964-1979. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Cell Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eckardt, N. A. Search for Related Content PubMed Articles by Eckardt, N. A. Agricola Articles by Eckardt, N. A.