About this Research Topic
Phosphorus is the fifth most abundant element in living cells. Microorganisms and plants take up phosphorus as dissolved (ortho)phosphate (Pi). Phosphorus does not usually participate in redox reactions, appearing in vivo as free Pi or forming esters or diesters in metabolites and macromolecules. Phosphorylation of key enzymes also controls major metabolic pathways and cell division cycle. A phosphate anion can react with another releasing a molecule of water and producing a dimer, pyrophosphate (PPi, P2O7-4). More Pi residues may be added to PPi by means of this linkage, known as “phosphoanhydride bond”, thus producing polyphosphates (polyP). Hydrolysis of phosphoanhydride bonds is thermodynamically favorable and kinetically stable, consequently, PPi and polyP are used for energy transfer and storage in many organisms.
PPi is produced from ATP in many biosynthetic reactions, its removal by hydrolysis allowing the shifting of anabolic reactions towards biosynthesis, thus regulating biosynthetic fluxes and allowing recycling of Pi by incorporating it to ADP to form ATP. This links PPi metabolism with the control of the cellular energy status. PPi hydrolysis can be coupled to H+ or Na+-translocation across biological membranes in all members of the eukaryotic green evolutionary lineage (from unicellular algae to higher plants), and some protists, eubacteria and archaea. This establishes an electrochemical gradient, a useful form of biological energy, that might be crucial to overcome stress situations.
Phosphate is stored in different forms depending on organisms and tissues: algae and yeast store polyPs, whereas plants store Pi and inositol phosphates in vegetative tissues and seeds, respectively, although phytic acid and other Pi-containing metabolites also seem to be involved. Living organisms must finely regulate Pi uptake, incorporation to biomolecules, storage and mobilization, and PPi and polyP are known to be implicated in this regulation, although many aspects remain to be established. Consequently, the metabolism of PPi and polyP in plants and microorganisms has major agricultural and environmental implications, due to the role that these organisms play in the biogeochemical cycle of phosphorus.
This Research Topic therefore aims to showcase current and novel findings in the metabolism of pyrophosphates and polyphosphates in plants and microorganisms. Submissions of different article types (Reviews, Methods, and Original Research) are welcome.
Keywords: Pyrophosphate and Polyphosphates, Phosphate Metabolism, PPi and polyP
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