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Tetrapyrrole profiling in Arabidopsis seedlings reveals that retrograde plastid nuclear signaling is not due to Mg-protoporphyrin IX accumulation.

Tetrapyrrole profiling in Arabidopsis seedlings reveals that retrograde plastid nuclear signaling is not due to Mg-protoporphyrin IX accumulation.
Tetrapyrrole profiling in Arabidopsis seedlings reveals that retrograde plastid nuclear signaling is not due to Mg-protoporphyrin IX accumulation.
Chloroplast biogenesis involves careful coordination of both plastid and nuclear gene expression, which is achieved in part by retrograde signaling from the chloroplast to the nucleus. This can be demonstrated by the fact that the herbicide, Norflurazon (NF), which causes bleaching of chloroplasts, prevents the light induction of photosynthesis-related genes in the nucleus. It has been proposed that the tetrapyrrole pathway intermediate Mg-protoporphyrin IX acts as the signaling molecule in this pathway and accumulates in the chloroplasts and cytosol of the cell after NF treatment. Here we present data that demonstrate that this model is too simplistic. We have developed a sensitive liquid chromatography-mass spectrometry (LC/MS) method to measure tetrapyrrole intermediates and have shown that no Mg-protoporphyrin IX, nor indeed any other chlorophyll-biosynthesis intermediate, can be detected in NF-treated plants under conditions in which nuclear gene expression is repressed. Conversely when endogenous Mg-protoporphyrin IX levels are artificially increased by supplementation with the tetrapyrrole precursor, 5-aminolevulinic acid, the expression of nuclear-encoded photosynthetic genes is induced, not repressed. We also demonstrate that NF-treatment leads to a strong down-regulation of tetrapyrrole biosynthesis genes, consistent with the absence of an accumulation of tetrapyrrole intermediates. Finally, there is no correlation between nuclear-gene expression and any of the chlorophyll biosynthetic intermediates over a range of growth conditions and treatments. Instead, it is possible that a perturbation of tetrapyrrole synthesis may lead to localized ROS production or an altered redox state of the plastid, which could mediate retrograde signaling.
0027-8424
15178-83
Moulin, Michael
40ae50cb-d31f-42de-b516-1a146f93c0b2
McCormac, Alex C.
41fd08ca-de17-4563-a1f8-d35e1f6c0e20
Terry, Matthew J.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b
Smith, Alison G.
30d591f0-8608-47bf-89ee-9278c4bef53d
Moulin, Michael
40ae50cb-d31f-42de-b516-1a146f93c0b2
McCormac, Alex C.
41fd08ca-de17-4563-a1f8-d35e1f6c0e20
Terry, Matthew J.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b
Smith, Alison G.
30d591f0-8608-47bf-89ee-9278c4bef53d

Moulin, Michael, McCormac, Alex C., Terry, Matthew J. and Smith, Alison G. (2008) Tetrapyrrole profiling in Arabidopsis seedlings reveals that retrograde plastid nuclear signaling is not due to Mg-protoporphyrin IX accumulation. Proceedings of the National Academy of Sciences of the United States of America, 105 (39), 15178-83. (doi:10.1073/pnas.0803054105).

Record type: Article

Abstract

Chloroplast biogenesis involves careful coordination of both plastid and nuclear gene expression, which is achieved in part by retrograde signaling from the chloroplast to the nucleus. This can be demonstrated by the fact that the herbicide, Norflurazon (NF), which causes bleaching of chloroplasts, prevents the light induction of photosynthesis-related genes in the nucleus. It has been proposed that the tetrapyrrole pathway intermediate Mg-protoporphyrin IX acts as the signaling molecule in this pathway and accumulates in the chloroplasts and cytosol of the cell after NF treatment. Here we present data that demonstrate that this model is too simplistic. We have developed a sensitive liquid chromatography-mass spectrometry (LC/MS) method to measure tetrapyrrole intermediates and have shown that no Mg-protoporphyrin IX, nor indeed any other chlorophyll-biosynthesis intermediate, can be detected in NF-treated plants under conditions in which nuclear gene expression is repressed. Conversely when endogenous Mg-protoporphyrin IX levels are artificially increased by supplementation with the tetrapyrrole precursor, 5-aminolevulinic acid, the expression of nuclear-encoded photosynthetic genes is induced, not repressed. We also demonstrate that NF-treatment leads to a strong down-regulation of tetrapyrrole biosynthesis genes, consistent with the absence of an accumulation of tetrapyrrole intermediates. Finally, there is no correlation between nuclear-gene expression and any of the chlorophyll biosynthetic intermediates over a range of growth conditions and treatments. Instead, it is possible that a perturbation of tetrapyrrole synthesis may lead to localized ROS production or an altered redox state of the plastid, which could mediate retrograde signaling.

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Published date: 30 September 2008
Organisations: Biological Sciences

Identifiers

Local EPrints ID: 142265
URI: http://eprints.soton.ac.uk/id/eprint/142265
ISSN: 0027-8424
PURE UUID: 80940e2a-fff7-4372-bb2c-87e682ea8767
ORCID for Matthew J. Terry: ORCID iD orcid.org/0000-0001-5002-2708

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Date deposited: 01 Apr 2010 14:32
Last modified: 14 Mar 2024 02:39

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Contributors

Author: Michael Moulin
Author: Alex C. McCormac
Author: Alison G. Smith

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