Chloroplast localization of methylerythritol 4-phosphate pathway enzymes and regulation of mitochondrial genes in ispD and ispE albino mutants in Arabidopsis.
Plant isoprenoids are derived from two independent pathways, the cytosolic mevalonate pathway and the plastid methylerythritol 4-phosphate (MEP) pathway. We used green fluorescent fusion protein assays to demonstrate that the Arabidopsis MEP pathway enzymes are localized to the chloroplast. We have also characterized three Arabidopsis albino mutants, ispD-1, ispD-2 and ispE-1, which have T-DNA insertions in the IspD and IspE genes of the MEP pathway. Levels of photosynthetic pigments are almost undetectable in these albino mutants. Instead of thylakoids, the ispD and ispE mutant chloroplasts are filled with large vesicles. Impairments in chloroplast development and functions may signal changes in the expression of nuclear, chloroplast and mitochondrial genes. We used northern blot analysis to examine the expression of photosynthetic and respiratory genes in the ispD and ispE albino mutants. Steady-state mRNA levels of nucleus- and chloroplast-encoded photosynthetic genes are significantly decreased in the albino mutants. In contrast, transcript levels of nuclear and mitochondrial genes encoding subunits of the mitochondrial electron transport chain are increased or not affected in these mutants. Genomic Southern blot analysis revealed that the DNA amounts of mitochondrial genes are not enhanced in the ispD and ispE albino mutants. These results support the notion that the functional state of chloroplasts may affect the expression of nuclear and mitochondrial genes. The up-regulation of mitochondrial genes in the albino mutants is not caused by changes of mitochondrial DNA copy number in Arabidopsis.
Hsieh
Ming-Hsiun
MH
Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan. ming@gate.sinica.edu.tw
Chang
Chiung-Yun
CY
Hsu
Shih-Jui
SJ
Chen
Ju-Jiun
JJ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015139:Blotting, Southern; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D004272:DNA, Mitochondrial / Q000235:genetics; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D004896:Erythritol / Q000031:analogs & derivatives / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D050259:Genes, Mitochondrial / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013403:Sugar Phosphates / Q000378:metabolism
D029681:Arabidopsis Proteins; D004272:DNA, Mitochondrial; D004798:Enzymes; D011993:Recombinant Fusion Proteins; D013403:Sugar Phosphates; D049452:Green Fluorescent Proteins; D004896:Erythritol