Article
Characterization of the Arabidopsis clb6 Mutant Illustrates the Importance of Posttranscriptional Regulation of the Methyl-D-Erythritol 4-Phosphate Pathway
Autor
Arroyo Becerra, Analilia
Institución
Resumen
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.