Pyrimidine and Purine Biosynthesis and Degradation in Plants

Abstract

Nucleotide metabolism operates in all living organisms, embodies an evolutionarily ancient and indispensable complex of metabolic pathways and is of utmost importance for plant metabolism and development. In plants, nucleotides can be synthesized de novo from 5-phosphoribosyl-1-pyrophosphate and simple molecules (e.g., CO(2), amino acids, and tetrahydrofolate), or be derived from preformed nucleosides and nucleobases via salvage reactions. Nucleotides are degraded to simple metabolites, and this process permits the recycling of phosphate, nitrogen, and carbon into central metabolic pools. Despite extensive biochemical knowledge about purine and pyrimidine metabolism, comprehensive studies of the regulation of this metabolism in plants are only starting to emerge. Here we review progress in molecular aspects and recent studies on the regulation and manipulation of nucleotide metabolism in plants.

Expression of Sucrose Transporter cDNAs Specifically in Companion Cells Enhances Phloem Loading and Long-Distance Transport of Sucrose but Leads to an Inhibition of Growth and the Perception of a Phosphate Limitation

“…In a classic study of barley growing on limiting P supply, about 26% was in free P, 17% was in phospholipids, 26% was in P-containing metabolites, including sugar Ps and nucleotide Ps, and 30% was in nucleic acids (Chapin and Bieleski, 1982). The vast majority of nucleic acids are in ribosomes, which are especially abundant in growing tissues (Detchon and Possingham, 1972;Dean and Leech, 1982;Baerenfaller et al, 2012), where they may represent an even greater proportion of the total P. Suc is known to increase gene expression for nucleotide synthesis and coordinately induce genes for ribosomal proteins and ribosome assembly, especially those for cytosolic ribosomes (Contento et al, 2004;Price et al, 2004;Bläsing et al, 2005;Zrenner et al, 2006;Kojima et al, 2007;Osuna et al, 2007;Usadel et al, 2008;Pal et al, 2013). It is thus plausible that an increased supply of Suc may induce pathways for nucleotide synthesis and ribosome biogenesis, which, in turn, creates an increased demand for P in growing sink tissues.…”

The Folylpolyglutamate Synthetase Plastidial Isoform Is Required for Postembryonic Root Development in Arabidopsis

“…In this regard, it is worth noting that the main form of folate found in chloroplasts is polyglutamylated 5,10-CH=THF, which comprises both 5,10-CH=THF and 10-CHO-THF (Klaus et al, 2005;Orsomando et al, 2005, Mehrshahi et al, 2010. In Arabidopsis, de novo purine biosynthesis occurs in plastids and requires 10-CHO-THF in two transformylation steps (Zrenner et al, 2006). A reduction of polyglutamylated 10-CHO-THF could prevent its retention within plastids and thus hinder its efficiency to be used as a cofactor in reactions leading to the biosynthesis of purines (Zrenner et al, 2006; Fig.…”

“…In Arabidopsis, de novo purine biosynthesis occurs in plastids and requires 10-CHO-THF in two transformylation steps (Zrenner et al, 2006). A reduction of polyglutamylated 10-CHO-THF could prevent its retention within plastids and thus hinder its efficiency to be used as a cofactor in reactions leading to the biosynthesis of purines (Zrenner et al, 2006; Fig. 1).…”

“…The reduced levels of adenine and guanosine that may result from inadequate 10-CHO-THF polyglutamates could also contribute to defective atdfb root growth, given their important role as building blocks of DNA and as major energy donors in numerous metabolic reactions of the cell (Zrenner et al, 2006). However, only guanosine caused a promotion in root length of atdfb.…”

Structural and Functional Insights into the Chloroplast ATP-Dependent Clp Protease in Arabidopsis

“…RNA helicases are equally important enzymes required for many homeostatic processes, such as transcription and mRNA processing, ribosome biogenesis, initiation of translation, and RNA catabolism (Rocak and Linder, 2004). UPRT performs a similar housekeeping function in the salvaging of the pyrimidine base uracil, an important component in the recycling processes that provide sufficient nucleobases for the continued synthesis of nucleic acids (Zrenner et al, 2006). Finally, NDP kinases also perform a critical housekeeping role involving the generation of nucleoside triphosphates, thereby regulating the available nucleotide pool (Hasunuma et al, 2003).…”