A mutant impaired in the production of plastome-encoded proteins uncovers a mechanism for the homeostasis of isoprenoid biosynthetic enzymes in Arabidopsis plastids. Plant Cell

Departament de Genètica Molecular de Plantes, Centre for Research on Agricultural Genomics, 08034 Barcelona, Spain.
The Plant Cell (Impact Factor: 9.58). 06/2008; 20(5):1303-15. DOI: 10.1105/tpc.108.058768
Source: PubMed

ABSTRACT The plastid-localized methylerythritol phosphate (MEP) pathway synthesizes the isoprenoid precursors for the production of essential photosynthesis-related compounds and hormones. We have identified an Arabidopsis thaliana mutant, rif1, in which posttranscriptional upregulation of MEP pathway enzyme levels is caused by the loss of function of At3g47450, a gene originally reported to encode a mitochondrial protein related to nitric oxide synthesis. However, we show that nitric oxide is not involved in the regulation of the MEP pathway and that the encoded protein is a plastid-targeted homolog of the Bacillus subtilis YqeH protein, a GTPase required for proper ribosome assembly. Consistently, in rif1 seedlings, decreased levels of plastome-encoded proteins were observed, with the exception of ClpP1, a catalytic subunit of the plastidial Clp protease complex. The unexpected accumulation of ClpP1 in plastids with reduced protein synthesis suggested a compensatory mechanism in response to decreased Clp activity levels. In agreement, a negative correlation was found between Clp protease activity and MEP pathway enzyme levels in different experiments, suggesting that Clp-mediated degradation of MEP pathway enzymes might be a mechanism used by individual plastids to finely adjust plastidial isoprenoid biosynthesis to their functional and physiological states.

Download full-text


Available from: Manuel Rodríguez-Concepción, Jan 13, 2015
1 Follower
  • Source
    • "Thus, the assembly of photosynthetic complexes and the build-up of thylakoid membranes and plastoglobules in chloroplasts increase the capacity to sequester the newly synthesized carotenoid molecules. Defects in chloroplast development hence result in a decreased accumulation of carotenoids, even under conditions in which an enhanced supply of their isoprenoid precursors is available (Sauret-Güeto et al., 2006; Flores-Perez et al., 2008b). Differentiation of chloroplasts into chromoplasts involves the development of larger plastoglobules and/or carotenoid-sequestering structures of different shapes, allowing the deposition of massive amounts of carotenoids in a matrix of lipoproteins (Deruere et al., 1994; Vishnevetsky et al., 1999; Simkin et al., 2007; Walter and Strack, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Plant carotenoids are a family of pigments that participate in light harvesting and are essential for photoprotection against excess light. Furthermore, they act as precursors for the production of apocarotenoid hormones such as abscisic acid and strigolactones. In this review, we summarize the current knowledge on the genes and enzymes of the carotenoid biosynthetic pathway (which is now almost completely elucidated) and on the regulation of carotenoid biosynthesis at both transcriptional and post-transcriptional levels. We also discuss the relevance of Arabidopsis as a model system for the study of carotenogenesis and how metabolic engineering approaches in this plant have taught important lessons for carotenoid biotechnology.
    The Arabidopsis Book 01/2012; 10:e0158. DOI:10.1199/tab.0158
  • Source
    • "noa1 phenotypes of delayed maturation and pale green leaves are rescued by growth on sucrose-containing media noa1 displays a number of visible phenotypes. Mutant plants accumulate less biomass and have pale green leaves when compared with the wild type grown under comparable conditions (Figure 4) (Guo et al., 2003; Flores-Pé rez et al., 2008). To address whether the availability of fixed carbon affects the overt phenotypes of noa1, we compared wildtype and noa1 phenotypes grown with and without sucrose supplementation in the growth media. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric oxide signals diverse responses in animals and plants. Whereas nitric oxide synthesis mechanisms in animals are well understood, how nitric oxide is synthesized and regulated in plants remains controversial. NOA1 is a circularly permuted GTPase that is important for chloroplast function and is implicated in nitric oxide synthesis. However, the reported consequences of a null mutation in NOA1 are inconsistent. Whereas some studies indicate that the noa1 mutant has severe reductions in nitric oxide accumulation, others report that nitric oxide levels are indistinguishable between noa1 and the wild type. Here, we identify a correlation between the reported ability of noa1 to accumulate nitric oxide with growth on sucrose-supplemented media. We report that noa1 accumulates both basal and salicylic acid-induced nitric oxide only when grown on media containing sucrose. In contrast, nitric oxide accumulation in wild type is largely insensitive to sucrose supplementation. When grown in the absence of sucrose, noa1 has low fumarate, pale green leaves, slow growth and reduced chlorophyll content. These phenotypes are consistent with a defect in chloroplast-derived photosynthate production and are largely rescued by sucrose supplementation. We conclude that NOA1 has a primary role in chloroplast function and that its effects on the accumulation of nitric oxide are likely to be indirect.
    The Plant Journal 06/2011; 68(2):225-33. DOI:10.1111/j.1365-313X.2011.04680.x · 6.82 Impact Factor
  • Source
    • "Columbus, OH, USA) and was named rif1-2 (Flores-Pérez et al., 2008). To observe the root morphology, Arabidopsis seeds were surface-sterilized in 70% ethanol for 5 min and then in 5% bleach solution for 15 min. "
    [Show abstract] [Hide abstract]
    ABSTRACT: *The bacterial protein YqeH is a circularly permuted GTPase with homologs encoded by plant nuclear genomes. The rice homolog OsNOA1/RIF1 is encoded by the single-copy gene Os02g01440. OsNOA1/RIF1 is expressed in different tissues and is light-inducible. The OsNOA1/RIF1-EYFP fusion protein was targeted to chloroplasts in transgenic Arabidopsis plants. In addition, the rice homolog was able to rescue most of the growth phenotypes in an Arabidopsis rif1 mutant. *Rice (Oryza sativa) OsNOA1/RIF1 RNAi mutant seedlings were chlorotic with reduced pigment contents and lower photosystem II (PSII) efficiency. However, the expressions of the chloroplast-encoded genes rbcL, atpB, psaA and psbA were not affected. By contrast, reduced abundance of the chloroplast 16S rRNA was observed in the mutant. *Quantitative iTRAQ-LC-MS/MS proteomics investigations revealed proteome changes in the rice mutant consistent with the expected functional role of OsNOA1/RIF1 in chloroplast translation. The RNAi mutant showed significantly decreased expression levels of chloroplast-encoded proteins as well as nuclear-encoded components of chloroplast enzyme complexes. Conversely, upregulation of some classes of nonchloroplastic proteins, such as glycolytic and phenylpropanoid pathway enzymes, was detected. *Our work provides independent indications that a highly conserved nuclear-encoded cGTPase of likely prokaryotic origin is essential for proper chloroplast ribosome assembly and/or translation in plants.
    New Phytologist 04/2010; 187(1):83-105. DOI:10.1111/j.1469-8137.2010.03264.x · 7.67 Impact Factor
Show more