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Rice Chlorina-1 and Chlorina-9 encode ChlD and ChlI subunits of Mg-chelatase, a key enzyme for chlorophyll synthesis and chloroplast development

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Photosynthetic organisms exhibit a green color due to the accumulation of chlorophyll pigments in chloroplasts. Mg-protoporphyrin IX chelatase (Mg-chelatase) comprises three subunits (ChlH, ChlD and ChlI) and catalyzes the insertion of Mg2+ into protoporphyrin IX, the last common intermediate precursor in both chlorophyll and heme biosyntheses, to produce Mg-protoporphyrin IX (MgProto). Chlorophyll deficiency in higher plants results in chlorina (yellowish-green) phenotype. To date, 10 chlorina (chl) mutants have been isolated in rice, but the corresponding genes have not yet been identified. Rice Chl1 and Chl9 genes were mapped to chromosome 3 and isolated by map-based cloning. A missense mutation occurred in a highly conserved amino acid of ChlD in the chl1 mutant and ChlI in the chl9 mutant. Ultrastructural analyses have revealed that the grana are poorly stacked, resulting in the underdevelopment of chloroplasts. In the seedlings fed with aminolevulinate-dipyridyl in darkness, MgProto levels in the chl1 and chl9 mutants decreased up to 25% and 31% of that in wild-type, respectively, indicating that the Mg-chelatase activity is significantly reduced, causing the eventual decrease in chlorophyll synthesis. Furthermore, Northern blot analysis indicated that the nuclear genes encoding the three subunits of Mg-chelatase and LhcpII in chl1 mutant are expressed about 2-fold higher than those in WT, but are not altered in the chl9 mutant. This result indicates that the ChlD subunit participates in negative feedback regulation of plastid-to-nucleus in the expression of nuclear genes encoding chloroplast proteins, but not the ChlI subunit.

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chl1 :


chl9 :



amino acid

ChlH :

Mg-chelatase H subunit

ChlI :

Mg-chelatase I subunit

ChlD :

Mg-chelatase D subunit




protoporphyrin IX


Mg-Protoporphyrin IX


Mg-Protoporphyrin IX monomethyl ester


MgProto + MgProtoME




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We thank the Rice Genome Research Program (Japan) for providing cDNA stocks and the AIMS (USA) for T-DNA insertional mutant stocks. This research was supported by a grant (CG3131) from Crop Functional Genomics Center of the 21st century Frontier Research Program funded by the Ministry of Science and Technology (MOST) and Rural Development Administration (RDA) of Republic of Korea. Mr. H. Zhang was supported by a fellowship from the Korea Research Foundation Grant Funded by the Korea Government (MOEHRD) (KRF-2004-211-410039). Mr. J.-H. Yoo and S.-H.␣Cho were supported by Brain Korea 21 Project of Korean Research Foundation.

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Correspondence to Nam-Chon Paek.

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Haitao Zhang and Jinjie Li contributed equally to this work

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Zhang, H., Li, J., Yoo, JH. et al. Rice Chlorina-1 and Chlorina-9 encode ChlD and ChlI subunits of Mg-chelatase, a key enzyme for chlorophyll synthesis and chloroplast development. Plant Mol Biol 62, 325–337 (2006).

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