Biology subjects

Liepins, J.

Publications and source records attributed to Liepins, J..

3 recordsLinked to original sources

bioRxiv2026

Position of de novo purine biosynthesis gene disruptions shapes purine-starvation phenotypes in Saccharomyces cerevisiae

Purine starvation induces a quiescence-like and stress-resistant physiological state in Saccharomyces cerevisiae, but it remains unclear whether this response is uniform across all disruptions of the de novo adenine biosynthetic pathway. Here, we used a pathway-position series of adenine-biosynthesis deletion mutants to test how the location of the metabolic blockage shapes cellular adaptation to purine starvation, using nitrogen starvation as a reference condition. Across mutants, purine starvation induced a shared core response marked by reduced growth, repression of ribosome-biogenesis and rRNA-processing modules, and accumulation of cells in G1/G0 phase. However, the magnitude and composition of the response varied systematically with pathway position. Early-pathway mutants showed the strongest desiccation tolerance and stress-associated transcriptional remodelling, whereas late-pathway mutants showed weaker protection. The ade16{Delta}ade17{Delta} double mutant was a distinct outlier, with altered carbon-flux distribution and limited stress resilience, suggesting that late-pathway disruption produces a physiologically different starvation state. Transcriptome analysis showed partial overlap with nitrogen starvation, but also pathway-position-dependent regulation of metabolic, ribosome-related, mitochondrial, and stress-response modules. Together, these results indicate that purine starvation is not a single physiological condition, but a set of related starvation states shaped by the position of the metabolic block within the purine biosynthetic pathway.

microbiology↗

bioRxiv2023

Pichia pastoris growth - coupled heme biosynthesis analysis using metabolic modelling

Soy legHemoglobin is one of the most important and key ingredients in plant-based meat substitutes that can imitate the colour and flavour of the meat. In order to improve the high-yield production of legHemoglobin protein and its main component - heme in the yeast Pichia pastoris, glycerol and methanol cultivation conditions were studied. Additionally, in-silico metabolic modelling analysis of growth-coupled enzyme quantity, suggests metabolic gene up/down-regulation strategies for heme production. First, cultivations and metabolic modelling analysis of P. pastoris were performed on glycerol and methanol in different growth media. Glycerol cultivation uptake and production rates can be increased by 50 % according to metabolic modelling results, but methanol cultivation - is near the theoretical maximum. Growth-coupled metabolic optimisation results revealed the best feasible upregulation (33 reactions) (1.47 % of total reactions) and 67 downregulation/deletion (2.98 % of total) reaction suggestions. Finally, we describe reaction regulation suggestions with the highest potential to increase heme production yields.

systems biology↗

bioRxiv2021

Purine auxotrophic starvation evokes quiescence like phenotype in the budding yeast

Purine auxotrophy is a typical marker for many laboratory yeast strains. Supplementation of additional purine source (like adenine) is necessary to cultivate these strains. If not supplied in adequate amounts, purine starvation sets in. We tested purine starvation effects in budding yeast Saccharomyces cerevisiae ade8 knockout. We explored effects brought by purine starvation in cellular, central carbon metabolism and in the global transcriptome level. We observed that cells cultivated in purine depleted media became significantly more tolerant to severe thermal, oxidative and desiccation stresses when compared to the cells cultivated in media with all necessary supplements. When starved for purine, cells stop their cell cycle in G1 or G0 state; intracellular concentration of ATP, ADP and AMP decreases, but adenylate charge remains stable. Intracellular RNA concentration decreases and massive downregulation of ribosomal RNA occurs. We think that purine auxotrophic starvation in a way mimics "natural" nitrogen or carbon starvations and therefore initiates elements of a transcriptional program typical for stationary phase cells (cell cycle arrest, increased stress resistance). Therefore our results demonstrate that organised metabolic response is initiated not only via "natural starvations", but also when starving for metabolic intermediates, like purines.

cell biology↗