pyrG is required for maintaining stable cellular uracil level and normal sporulation pattern under excess uracil stress in Aspergillus nidulans

Abstract

Tight control of the intracellular uracil level is believed to be important to reduce the occurrence of uracil incorporation into DNA. The pyrG gene of Aspergillus nidulans encodes orotidine 5′-phosphate decarboxylase, which catalyzes the conversion of orotidine monophosphate (OMP) to uridine monophosphate (UMP). In this study, we found that pyrG is critical for maintaining uracil at a low concentration in A. nidulans cells in the presence of exogenous uracil. Excess uracil and its derivatives had a stronger inhibitory effect on the growth of the pyrG89 mutant with defective OMP decarboxylase activity than on the growth of wild type, and induced sexual development in the pyrG89 mutant but not in wild type. Analysis of transcriptomic responses to excess uracil by digital gene expression profiling (DGE) revealed that genes related to sexual development were transcriptionally activated in the pyrG89 mutant but not in wild type. Quantitative analysis by HPLC showed that the cellular uracil level was 6.5 times higher in the pyrG89 mutant than in wild type in the presence of exogenous uracil. This study not only provides new information on uracil recycling and adaptation to excess uracil but also reveals the potential effects of OMP decarboxylase on fungal growth and development. orotidine 5′-phosphate decarboxylase, stress, uracil, sexual development Citation:Sun X Y, Zhu J F, Bao L, et al. pyrG is required for maintaining stable cellular uracil level and normal sporulation pattern under excess uracil stress in

Physiological characterization of a pyrimidine auxotroph exposes link between uracil phosphoribosyltransferase regulation and riboflavin production in Ashbya gossypii

“…addition of uridine to the medium [4], being inhibited by high uracil concentrations [11]. A similar phenotype has been reported for uracil auxotrophs of A. nidulans [8]. Although not experimentally demonstrated, the growth-inhibitory effect of high uracil concentrations observed in A. nidulans pyrimidine auxotrophs was proposed to be linked with misincorporation of uracil into the DNA.…”

“…Candida famata) [5], Candida guilliermondii (syn. Pichia guilliermondii) [6], Aspergillus fumigatus [7] and Aspergillus nidulans [8]. Despite the importance of this apparently uncommon phenotype, it is poorly understood at the molecular level.…”

Disruption or reduced expression of the orotidine-5′-decarboxylase gene pyrG increases citric acid production: a new discovery during recyclable genome editing in Aspergillus niger

“…Considering the EMP intermediates decreased while the citric acid precursors acetyl-CoA and oxaloacetate were significantly increased, it suggested that this metabolic change may be caused by the accelerated glycolysis pathway and the insufficient activity of the citrate synthetase. In Aspergillus nidulans, it is reported that the genes involved in carbon metabolism, such as α-glucosidase B (agdB) and sugar transporter, were significantly up-regulated in a pyrG deleted mutant [36], which is consistent with the EMP metabolism changes in this study. Therefore, we speculated that higher citrate synthetase expression could further improve citric acid production when pyrG expression was disrupted or reduced.…”

Blockage of the pyrimidine biosynthetic pathway affects riboflavin production in Ashbya gossypii

“…Excess of exogenous uracil (but not uridine) was recently reported to have a strong inhibitory effect on the Aspergillus nidulans growth, being an auxotrophic strain deleted in pyrG (encoding orotidine-5 -phosphate decarboxylase) also more sensitive to uracil than the wild type strain (Sun et al, 2013). This uracil toxicity is believed to be related with the misincorporation of uracil into DNA when uracil is accumulated in excess (Sun et al, 2013).…”

“…This uracil toxicity is believed to be related with the misincorporation of uracil into DNA when uracil is accumulated in excess (Sun et al, 2013). Uridine cannot be directly incorporated into DNA, which may explain why excess uridine did not cause growth inhibition in A. nidulans (Sun et al, 2013) and A. gossypii.…”