Plant and Cell Physiology Advance Access originally published online on January 8, 2007
Plant and Cell Physiology 2007 48(2):322-331; doi:10.1093/pcp/pcm005
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LOVASTATIN INSENSITIVE 1, a Novel Pentatricopeptide Repeat Protein, is a Potential Regulatory Factor of Isoprenoid Biosynthesis in Arabidopsis
1RIKEN Plant Science Center, 1-7-22, Suehirocho, Tsurumi-ku, Yokohama, 230-0045 Japan
2Graduate School of Science and Engineering, Saitama University, 255, Shimo-okubo, Sakura-ku, Saitama, Saitama, 338-8570 Japan
3Faculty of Science, Japan Women's University, 2-8-1, Mejirodai, Bunkyo-ku, Tokyo, 112-8681 Japan
4RIKEN Genomic Science Center, 1-7-22, Suehirocho, Tsurumi-ku, Yokohama, 230-0045 Japan
5Molecular Entomology Laboratory, RIKEN, 2-1, Hirosawa, Wako, Saitama, 351-0198 Japan
*Corresponding author: E-mail, muranaka{at}riken.jp; Fax, +81-45-503-9492.
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Abstract |
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Higher plants have two metabolic pathways for isoprenoid biosynthesis: the cytosolic mevalonate (MVA) pathway and the plastidal non-mevalonate (MEP) pathway. Despite the compartmentalization of these two pathways, metabolic flow occurs between them. However, little is known about the mechanisms that regulate the two pathways and the metabolic cross-talk. To identify such regulatory mechanisms, we isolated and characterized the Arabidopsis T-DNA insertion mutant lovastatin insensitive 1 (loi1), which is resistant to lovastatin and clomazone, inhibitors of the MVA and MEP pathways, respectively. The accumulation of the major products of these pathways, i.e. sterols and chlorophyll, was less affected by lovastatin and clomazone, respectively, in loi1 than in the wild type. Furthermore, the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity analysis showed higher activity of HMGR in loi1-1 treated with lovastatin than that in the WT. We consider that the lovastatin-resistant phenotype of loi1-1 was derived from this post-transcriptional up-regulation of HMGR. The LOI1 gene encodes a novel pentatricopeptide repeat (PPR) protein. PPR proteins are thought to regulate the expression of genes encoded in organelle genomes by post-transcriptional regulation in mitochondria or plastids. Our results demonstrate that LOI1 is predicted to localize in mitochondria and has the ability to bind single-stranded nucleic acids. Our investigation revealed that the post-transcriptional regulation of mitochondrial RNA may be involved in isoprenoid biosynthesis in both the MVA and MEP pathways.
Keywords: Arabidopsis - 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) - Isoprenoid biosynthesis - Lovastatin - Mevalonate (MVA) pathway - Pentatricopeptide repeat (PPR)
Abbreviations: DIG, digoxigenin; DMAPP, dimethylallyl diphosphate; DTT, dithiothreitol; DXS, 1-deoxy-D-xylulose 5-phosphate synthase; GFP, green fluorescent protein; GST, glutathione S-transferase; HMGR, 3-hydroxy-3-methylglutaryl coenzyme A reductase; HMGS, HMG-CoA synthase; IPP, isopentenyl diphosphate; loi, lovastatin insensitive; MEP, 2-C-methyl-D-erythritol-4-phosphate; MVA, mevalonate; PBS, phosphate-buffered saline; PPR, pentatricopeptide repeat; RT–PCR, reverse transcription–PCR; ssRNA, single-stranded RNA; WT, wild type
(Received November 29, 2006; Accepted December 27, 2006)
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