PMID:17135235

Citation	Pontier, D, Albrieux, C, Joyard, J, Lagrange, T and Block, MA (2007) Knock-out of the magnesium protoporphyrin IX methyltransferase gene in Arabidopsis. Effects on chloroplast development and on chloroplast-to-nucleus signaling. J. Biol. Chem. 282:2297-304
Abstract	Protoporphyrin IX is the last common intermediate between the heme and chlorophyll biosynthesis pathways. The addition of magnesium directs this molecule toward chlorophyll biosynthesis. The first step downstream from the branchpoint is catalyzed by the magnesium chelatase and is a highly regulated process. The corresponding product, magnesium protoporphyrin IX, has been proposed to play an important role as a signaling molecule implicated in plastid-to-nucleus communication. To get more information on the chlorophyll biosynthesis pathway and on magnesium protoporphyrin IX derivative functions, we have identified an magnesium protoporphyrin IX methyltransferase (CHLM) knock-out mutant in Arabidopsis in which the mutation induces a blockage downstream from magnesium protoporphyrin IX and an accumulation of this chlorophyll biosynthesis intermediate. Our results demonstrate that the CHLM gene is essential for the formation of chlorophyll and subsequently for the formation of photosystems I and II and cytochrome b6f complexes. Analysis of gene expression in the chlm mutant provides an independent indication that magnesium protoporphyrin IX is a negative effector of nuclear photosynthetic gene expression, as previously reported. Moreover, it suggests the possible implication of magnesium protoporphyrin IX methyl ester, the product of CHLM, in chloroplast-to-nucleus signaling. Finally, post-transcriptional up-regulation of the level of the CHLH subunit of the magnesium chelatase has been detected in the chlm mutant and most likely corresponds to specific accumulation of this protein inside plastids. This result suggests that the CHLH subunit might play an important regulatory role when the chlorophyll biosynthetic pathway is disrupted at this particular step.
Links	PubMed PMC2408936 Online version:10.1074/jbc.M610286200
Keywords	Arabidopsis/genetics; Arabidopsis/metabolism; Cell Nucleus/metabolism; Chlorophyll/biosynthesis; Chloroplasts/genetics; Chloroplasts/metabolism; Cytochrome b6f Complex/metabolism; Gene Deletion; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Methyltransferases/antagonists & inhibitors; Methyltransferases/genetics; Photosystem I Protein Complex/metabolism; Photosystem II Protein Complex/metabolism; Protoporphyrins/metabolism; Signal Transduction/genetics
edit table

Annotations

Gene product	Qualifier	GO ID	GO term name	Evidence Code	with/from	Aspect	Notes	Status
edit table

References

See Help:References for how to manage references in GONUTS.