Identification and Characterization of a Novel Plastidic Adenine Nucleotide Uniporter from Solanum tuberosum

Leroch, Michaela; Kirchberger, Simon; Haferkamp, Ilka; Wahl, Markus; Neuhaus, H. Ekkehard; Tjaden, Joachim

doi:10.1074/jbc.m412462200

Cited by 84 publications

(126 citation statements)

References 81 publications

Supporting

Mentioning

121

Contrasting

Order By: Relevance

“…Interestingly, members of the MCF do not seem to be restricted to the mitochondrial inner membrane. Recently, another MCF member was demonstrated to function as a plastidic folate transporter (Bedhomme et al, 2005), and other MCF members have been shown to be involved in adenine nucleotide uniport into plastids (Leroch et al, 2005) and in the uptake of ADP-glucose into maize (Zea mays) endosperm plastids (Sullivan and Kaneko, 1995). Moreover, a yeast peroxisomal ATP transporter also belongs to the MCF (Palmieri et al, 2001), (E) RT-PCR analysis of the transcript level of Nb SAMT1.…”

Section: Discussionmentioning

confidence: 99%

ArabidopsisSAMT1 Defines a Plastid Transporter Regulating Plastid Biogenesis and Plant Development

et al. 2006

View full text Add to dashboard Cite

S-Adenosylmethionine (SAM) is formed exclusively in the cytosol but plays a major role in plastids; SAM can either act as a methyl donor for the biogenesis of small molecules such as prenyllipids and macromolecules or as a regulator of the synthesis of aspartate-derived amino acids. Because the biosynthesis of SAM is restricted to the cytosol, plastids require a SAM importer. However, this transporter has not yet been identified. Here, we report the molecular and functional characterization of an Arabidopsis thaliana gene designated SAM TRANSPORTER1 (SAMT1), which encodes a plastid metabolite transporter required for the import of SAM from the cytosol. Recombinant SAMT1 produced in yeast cells, when reconstituted into liposomes, mediated the counter-exchange of SAM with SAM and with S-adenosylhomocysteine, the by-product and inhibitor of transmethylation reactions using SAM. Insertional mutation in SAMT1 and virus-induced gene silencing of SAMT1 in Nicotiana benthamiana caused severe growth retardation in mutant plants. Impaired function of SAMT1 led to decreased accumulation of prenyllipids and mainly affected the chlorophyll pathway. Biochemical analysis suggests that the latter effect represents one prominent example of the multiple events triggered by undermethylation, when there is decreased SAM flux into plastids.

show abstract

Section: Discussionmentioning

confidence: 99%

ArabidopsisSAMT1 Defines a Plastid Transporter Regulating Plastid Biogenesis and Plant Development

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Quantitative RT-PCR was performed as described (Leroch et al, 2005). Total RNA was prepared from Arabidopsis plants using the RNeasy plant mini kit (Qiagen).…”

Section: Quantitative Rt-pcrmentioning

confidence: 99%

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

et al. 2012

View full text Add to dashboard Cite

Nucleotide de novo synthesis is highly conserved among organisms and represents an essential biochemical pathway. In plants, the two initial enzymatic reactions of de novo pyrimidine synthesis occur in the plastids. By use of green fluorescent protein fusions, clear support is provided for a localization of the remaining reactions in the cytosol and mitochondria. This implies that carbamoyl aspartate, an intermediate of this pathway, must be exported and precursors of pyrimidine salvage (i.e., nucleobases or nucleosides) are imported into plastids. A corresponding uracil transport activity could be measured in intact plastids isolated from cauliflower (Brassica oleracea) buds. PLUTO (for plastidic nucleobase transporter) was identified as a member of the Nucleobase:Cation-Symporter1 protein family from Arabidopsis thaliana, capable of transporting purine and pyrimidine nucleobases. A PLUTO green fluorescent protein fusion was shown to reside in the plastid envelope after expression in Arabidopsis protoplasts. Heterologous expression of PLUTO in an Escherichia coli mutant lacking the bacterial uracil permease uraA allowed a detailed biochemical characterization. PLUTO transports uracil, adenine, and guanine with apparent affinities of 16.4, 0.4, and 6.3 mM, respectively. Transport was markedly inhibited by low concentrations of a proton uncoupler, indicating that PLUTO functions as a proton-substrate symporter. Thus, a protein for the absolutely required import of pyrimidine nucleobases into plastids was identified.

show abstract

“…This carrier is a member of the functionally diverse mitochondrial carrier family (MCF) (8). It is located in the inner plastid envelope and catalyzes the export of AMP, ADP, or ATP (9). Until now it was unclear how pyrimidine nucleotides leave the plastid (7).…”

mentioning

confidence: 99%

Diatom plastids depend on nucleotide import from the cytosol

Ast¹,

Gruber

Schmitz‐Esser

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

112

View full text Add to dashboard Cite

Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms with primary plastids. Diatom plastids are surrounded by 4 membranes; the outermost membrane is continuous with the endoplasmic reticulum. Genome analyses suggest that nucleotide biosynthesis is, in contrast to higher plants, not located in the plastid, but in the cytosol. As a consequence, nucleotides have to be imported into the organelle. However, the mechanism of nucleotide entry into the complex plastid is unknown. We identified a high number of putative nucleotide transporters (NTTs) in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum and characterized the first 2 isoforms (NTT1 and NTT2). GFP-based localization studies revealed that both investigated NTTs are targeted to the plastid membranes, and that NTT1 most likely enters the innermost plastid envelope via the stroma. Heterologously expressed NTT1 acts as a proton-dependent adenine nucleotide importer, whereas NTT2 facilitates the counter exchange of (deoxy-)nucleoside triphosphates. Therefore, these transporters functionally resemble NTTs from obligate intracellular bacteria with an impaired nucleotide metabolism rather than ATP/ADP exchanging NTTs from primary plastids. We suggest that diatoms harbor a specifically-adapted nucleotide transport system and that NTTs are the key players in nucleotide supply to the complex plastid.chloroplast ͉ complex plastids ͉ nucleotide synthesis ͉ nucleotide transport

show abstract

Identification and Characterization of a Novel Plastidic Adenine Nucleotide Uniporter from Solanum tuberosum

Cited by 84 publications

References 81 publications

ArabidopsisSAMT1 Defines a Plastid Transporter Regulating Plastid Biogenesis and Plant Development

ArabidopsisSAMT1 Defines a Plastid Transporter Regulating Plastid Biogenesis and Plant Development

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

Diatom plastids depend on nucleotide import from the cytosol

Contact Info

Product

Resources

About