Phosphate Translocators in Plastids

Abstract

During photosynthesis, energy from solar radiation is used to convert atmospheric carbon dioxide into intermediates that are used within and outside the chloroplast for a multitude of metabolic pathways. The daily fixed carbon is exported from the chloroplasts as triose phosphates and 3-phosphoglycerate. In contrast, nongreen plastids rely on the import of carbon, mainly hexose phosphates. Most organelles require the import of phosphoenolpyruvate as an immediate substrate for carbon to enter the shikimate pathway, leading to a variety of important secondary compounds. The envelope membrane of plastids contains specific translocators that are involved in these transport processes. Elucidation of the molecular structure of some of these translocators during the past few years has provided new insights in the functioning of particular translocators. This review focuses on the characterization of different classes of phosphate translocators in plastids that mediate the transport of the phosphorylated compounds in exchange with inorganic phosphate.

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

“…In most plant cells, exogenous acetate is not usually incorporated into C18 and shorter fatty acids because acetate does not readily cross the plastidic membranes, and plastids have their own endogenous pool of acetate used for fatty acid synthesis (32)(33)(34). Even when endogenous acetate has been reported to be incorporated in short fatty acids, glucose has been demonstrated to be a far better substrate, because it can either be imported in nongreen plastids directly as glucose 6-phosphate and used as the source for the plastidic pool of acetate (35,36) or be broken down to triose phosphates in the cytosol and taken up in plastids via triose phosphate translocators (37).…”

Fast Retrograde Signaling in Response to High Light Involves Metabolite Export, MITOGEN-ACTIVATED PROTEIN KINASE6, and AP2/ERF Transcription Factors in Arabidopsis

“…DHAP increases after illumination of darkened leaves within seconds as shown in nonaqueously fractionated chloroplasts that reflect the metabolic situation of the chloroplasts in vivo (Dietz and Heber, 1984). Exported triose phosphate is converted to 3-phosphoglycerate with simultaneous generation of ATP and NADPH and subsequent Suc biosynthesis (Flügge, 1999). Thus, concentration changes of DHAP, ATP, and NAD(P)H are connected and may activate protein phosphorylation cascades.…”

“…The assumption was that metabolite changes are among the very fast and first changes that occur in light shifts. Triose phosphate translocator (TPT) is of prime importance for the export of triose phosphate from the chloroplast in exchange for cytosolic phosphate (Flügge, 1999) and appeared to be an ideal candidate for transmission of metabolite signals from the chloroplast to the nucleus since metabolites of the Calvin cycle are known to be autocatalytically built up immediately with activation of photosynthesis (Dietz and Heber, (A) The AP2/ERF-TFs from the coexpression network (Supplemental Figure 1) were classified in four groups according to their time-dependent transcript regulation during L→H shift. Expression patterns in ecotype Col-0 were analyzed using nonquantitative RT-PCR.…”

EST-analysis of the thermo-acidophilic red microalga Galdieriasulphuraria reveals potential for lipid A biosynthesis and unveils the pathway of carbon export from rhodoplasts

“…During the day, the path for carbon export from chloroplasts in green plants is via the plastidic triose phosphate/phosphate translocator (Flu¨gge, 1999). Up to 50% of the carbon dioxide assimilated during the day is stored as transitory starch within chloroplasts and exported to the cytosol during the night in the form of glucose and maltose (Niittyla et al, 2004;Weise et al, 2004).…”