Characterization of the Arabidopsis clb6 mutant illustrates the importance of posttranscriptional regulation of the methyl-D-erythritol 4-phosphate pathway.
The biosynthesis of isopentenyl diphosphate and dimethylallyl diphosphate, the two building blocks for isoprenoid biosynthesis, occurs by two independent pathways in plants. The mevalonic pathway operates in the cytoplasm, and the methyl-d-erythritol 4-phosphate (MEP) pathway operates in plastids. Plastidic isoprenoids play essential roles in plant growth and development. Plants must regulate the biosynthesis of isoprenoids to fulfill metabolic requirements in specific tissues and developmental conditions. The regulatory events that modulate the plant MEP pathway are not well understood. In this article, we demonstrate that the CHLOROPLAST BIOGENESIS6 (CLB6) gene, previously shown to be required for chloroplast development, encodes 1-hydroxy-2-methyl-butenyl 4-diphosphate reductase, the last-acting enzyme of the MEP pathway. Comparative analysis of the expression levels of all MEP pathway gene transcripts and proteins in the clb6-1 mutant background revealed that posttranscriptional control modulates the levels of different proteins in this central pathway. Posttranscriptional regulation was also found during seedling development and during fosmidomycin inhibition of the pathway. Our results show that the first enzyme of the pathway, 1-deoxy-d-xylulose 5-phosphate synthase, is feedback regulated in response to the interruption of the flow of metabolites through the MEP pathway.
Guevara-García
Arturo
A
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Morelos 62271, Mexico. aguevara@ibt.unam.mx
San Román
Carolina
C
Arroyo
Analilia
A
Cortés
María Elena
ME
de la Luz Gutiérrez-Nava
María
M
León
Patricia
P
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D060365:Chloroplast Proteins; D004896:Erythritol / Q000031:analogs & derivatives* / Q000378:metabolism; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D030821:Plants, Genetically Modified; D013403:Sugar Phosphates / Q000378:metabolism*
D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; C504528:IspH protein, Arabidopsis; D013403:Sugar Phosphates; C081898:erythritol 4-phosphate; D004896:Erythritol