Modified pea apyrase has altered nuclear functions and enhances the growth of yeast and Arabidopsis.

Apyrases (NTPDases) regulate growth and development in multiple eukaryotic organisms and function in multiple sub-cellular locales. An earlier report showed that the ectopic expression of psNTP9 (PS), a chromatin-associated pea () apyrase, enhanced the uptake of inorganic phosphate (Pi) and increased the growth of yeast and Arabidopsis. In this follow-up study, we generated a modified form of PS, abbreviated DM ("double mutant"), in which two-point mutations, S208L and P216R, were introduced into its DNA-binding domain.

Transcriptional reprogramming of nucleotide metabolism in response to altered pyrimidine availability in Arabidopsis seedlings.

In Arabidopsis seedlings, inhibition of aspartate transcarbamoylase (ATC) and pyrimidine synthesis resulted in pyrimidine starvation and developmental arrest a few days after germination. Synthesis of pyrimidine nucleotides by salvaging of exogenous uridine (Urd) restored normal seedling growth and development. We used this experimental system and transcriptional profiling to investigate genome-wide responses to changes in pyrimidine availability.

Constitutive expression of a pea apyrase, psNTP9, increases seed yield in field-grown soybean.

To address the demand for food by a rapidly growing human population, agricultural scientists have carried out both plant breeding and genetic engineering research. Previously, we reported that the constitutive expression of a pea apyrase (Nucleoside triphosphate, diphosphohydrolase) gene, psNTP9, under the control of the CaMV35S promoter, resulted in soybean plants with an expanded root system architecture, enhanced drought resistance and increased seed yield when they are grown in greenhouses under controlled conditions. Here, we report that psNTP9-expressing soybean lines also show significantly enhanced seed yields when grown in multiple different field conditions at multiple field sites, including when the gene is introgressed into elite germplasm.

Ectopic expression of a pea apyrase enhances root system architecture and drought survival in Arabidopsis and soybean.

Ectoapyrases (ecto-NTPDases) function to decrease levels of extracellular ATP and ADP in animals and plants. Prior studies showed that ectopic expression of a pea ectoapyrase, psNTP9, enhanced growth in Arabidopsis seedlings and that the overexpression of the two Arabidopsis apyrases most closely related to psNTP9 enhanced auxin transport and growth in Arabidopsis. These results predicted that ectopic expression of psNTP9 could promote a more extensive root system architecture (RSA) in Arabidopsis.

A functional analysis of the pyrimidine catabolic pathway in Arabidopsis.

* Reductive catabolism of pyrimidine nucleotides occurs via a three-step pathway in which uracil is degraded to beta-alanine, CO(2) and NH(3) through sequential activities of dihydropyrimidine dehydrogenase (EC 1.3.1.

Expression and functional analysis of aspartate transcarbamoylase and role of de novo pyrimidine synthesis in regulation of growth and development in Arabidopsis.

Aspartate transcarbamoylase (ATCase, EC 2.1.3.

Genes, enzymes and regulation of arginine biosynthesis in plants.

Arabidopsis genes encoding enzymes for each of the eight steps in L-arginine (Arg) synthesis were identified, based upon sequence homologies with orthologs from other organisms. Except for N-acetylglutamate synthase (NAGS; EC 2.3.

Effects of phosphate limitation on expression of genes involved in pyrimidine synthesis and salvaging in Arabidopsis.

Arabidopsis seedlings grown for 14 d without phosphate (P) exhibited stunted growth and other visible symptoms associated with P deficiency. RNA contents in shoots decreased nearly 90%, relative to controls. In shoots, expression of Pht1;2, encoding an inducible high-affinity phosphate transporter, increased threefold, compared with controls, and served as a molecular marker for P limitation.

UPS1 and UPS2 from Arabidopsis mediate high affinity transport of uracil and 5-fluorouracil.

Salvage pathways play an important role in providing nucleobases to cells, which are unable to synthesize sufficient amounts for their needs. Cellular uptake systems for pyrimidines have been described, but in higher eukaryotes, transporters for thymine and uracil have not been identified. Two plant transporters, AtUPS1 and PvUPS1, were recently identified as transporters for allantoin in Arabidopsis and French bean, respectively.