There are two independent pathways, the cytosolic mevalonate (MVA) pathway and the plastid nonmevalonate (nonMVA) pathway, to synthesize isopentenyl diphosphate and dimethylallyl diphosphate in plants. Carotenoids and the phytyl side chain of chlorophylls are isoprenoids derived from the plastid nonMVA pathway. All enzymes involved in the nonMVA pathway have been identified in Escherichia coli. The E. coli IspF protein catalyzes a unique cyclization reaction to convert 4-diphosphocytidyl-2-C-methyl-D-erythritol 2-phosphate into 2-C-methyl-D-erythritol 2,4-cyclodiphosphate in the nonMVA pathway. We have characterized an Arabidopsis T-DNA insertion mutant, ispF-1, which has a null mutation in the IspF gene. Homozygous ispF-1 mutants are albino lethal and the IspF transcripts are undetectable in these plants. Moreover, the ispF-1 mutant chloroplasts are filled with vesicles instead of thylakoids. Amino acid sequence alignment reveals that the IspF proteins are highly conserved between plants and bacteria. Interestingly, expression of the Arabidopsis IspF protein can rescue the lethal phenotype of an E. coliispF mutant. These results indicate that the Arabidopsis IspF may share similar enzymatic mechanisms with the E. coli protein.
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Queen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, EnglandQueen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, England
Brown, Amanda C.
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Eberl, Matthias
Crick, Dean C.
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Colorado State Univ, Dept Microbiol Immunol & Pathol, Ft Collins, CO 80523 USAQueen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, England
Crick, Dean C.
Jomaa, Hassan
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Univ Klinikum Giessen & Marburg, Inst Klin Immunol & Tranfus Med, D-35392 Giessen, GermanyQueen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, England
Jomaa, Hassan
Parish, Tanya
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Queen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, England
Infect Dis Res Inst, Seattle, WA 98104 USAQueen Mary Univ London, Barts & London Sch Med & Dent, London E1 2AD, England