Increased RNA production in Saccharomyces cerevisiae by simultaneously overexpressing FHL1, IFH1, and SSF2 and deleting HRP1

Genetic Strategies and Mechanisms for Improving Ribonucleic Acid Levels of Saccharomyces pastorianus

Developing microorganisms with a high ribonucleic acid (RNA) content is crucial for the RNA industry. Numerous studies have been conducted to enhance RNA production in yeast cells through genetic engineering, yet precise mechanisms remain elusive. Previously, upregulation of TAL1 or PGM2 and deleting PRS5 or DBP8 individually could increase the RNA content in Saccharomyces pastorianus. In this study, within these genetically modified strains, the intracellular nucleotide levels notably increased following cell fragmentation. Deletion of PRS5 and DBP8 within the strain prompted the upregulation of genes sharing similar functions, consequently augmenting the flow of the gene pathway. Furthermore, the upregulation of genes encoding cell-cycle-dependent protein kinases (CDK) was observed in the G03-△PRS5 strain. The influence of TAL1 and PGM2 on RNA content was attributed to the pentose phosphate pathway (PPP). The RNA content of polygenic recombinant strains, G03-△PRS5+△DBP8 and G03-△PRS5+△DBP8+PGM2, displayed the most significant improvement, increasing by 71.8 and 80.1% when compared to the parental strain. Additionally, the maximum specific growth rate of cells increased in these strains. This study contributes valuable insights into the genetic mechanisms underlying high nucleic acid synthesis in S. pastorianus.

Improvement of ribonucleic acid production in Cyberlindnera jadinii and optimization of fermentation medium

To enhance the ribonucleic acid (RNA) productivity for industrial applications, this study employed strain screening and medium optimization to improve the content of RNA in Cyberlindnera jadinii. A rapid screening method, combining atmospheric and room temperature plasma mutagenesis, 48-deep-well plates fermentation, and microplate reader detection, was developed. A mutant strain named WB15 with high RNA content was successfully obtained, exhibiting the RNA content of 156 ± 4.5 mg/g DCW, 1.4 times of the starting strain CCTCC AY 92020. Furthermore, Plackett-Burman design and response surface methodology were employed to identify three significant factors (yeast extract, soybean peptone, and KH2PO4) affecting the RNA content. By utilizing the optimal medium composed of 13.43 g/L yeast extract, 12.12 g/L soybean peptone and 2.78 g/L KH2PO4, the RNA content of WB15 further increased to 184 ± 4.9 mg/g DCW. Additionally, the mutant strain WB15 exhibited a greater cellular width compared to AY 92020, along with increased growth rate and single-cell RNA content by 22% and 48.9%, respectively. Perturbations in ribosome assembly, specifically a reduction in the ratio of ribosomal proteins to ribosomal RNA of the large subunit, might indirectly contribute to the higher RNA content in the WB15 strain. Overall, the combination of rapid screening with fermentation medium optimization proved to be an effective approach for improving the RNA content of C. jadinii, thus facilitating the industrial production of RNA.

Promoting Nucleic Acid Synthesis in Saccharomyces cerevisiae through Enhanced Expression of Rrn7p, Rrn11p, IMPDH, and Pho84p

Saccharomyces cerevisiae has emerged as a preferred source for industrial production of ribonucleic acids (RNAs) and their derivatives, which find wide applications in the food and pharmaceutical sectors. In this study, we employed a modified RNA polymerase I-mediated green fluorescent protein expression system, previously developed by our team, to screen and identify an industrial S. cerevisiae strain with an impressive 18.2% increase in the RNA content. Transcriptome analysis revealed heightened activity of genes and pathways associated with rRNA transcription, purine metabolism, and phosphate transport in the high nucleic acid content mutant strains. Our findings highlighted the crucial role of the transcription factor Sfp1p in enhancing the expression of two key components of the transcription initiation factor complex, Rrn7p and Rrn11p, thereby promoting rRNA synthesis. Moreover, elevated expression of 5'-inosine monophosphate dehydrogenases, regardless of the specific isoform (IMD2, 3, or 4), resulted in increased rRNA synthesis through heightened GTP levels. Additionally, exogenous phosphate application, coupled with overexpression of the phosphate transporter PHO84, led to a 61.4% boost in the RNA yield, reaching 2050.4 mg/L. This comprehensive study provides valuable insights into the mechanism of RNA synthesis and serves as a reference for augmenting RNA production in the food industry.

Ppan is essential for preimplantation development in mice†

PETER PAN (PPAN), located to nucleoli and mitochondria, is a member of the Brix domain protein family, involved in rRNA processing through its rRNA binding motif and mitochondrial apoptosis by protecting mitochondria structure and suppressing basal autophagic flux. Ppan is important for cell proliferation and viability, and mutation of Ppan in Drosophila caused larval lethality and oogenesis failure. Yet, its role in mammalian reproduction remains unclear. In this study, we explored the function of Ppan in oocyte maturation and early embryogenesis using conditional knockout mouse model. Deficiency of maternal Ppan significantly downregulated the expression level of 5.8S rRNA, 18S rRNA, and 28S rRNA, though it had no effect on oocyte maturation or preimplantation embryo development. However, depletion of both maternal and zygotic Ppan blocked embryonic development at morula stage. Similar phenotype was obtained when only zygotic Ppan was depleted. We further identified no DNA binding activity of PPAN in mouse embryonic stem cells, and depletion of Ppan had minimum impact on transcriptome but decreased expression of 5.8S rRNA, 18S rRNA, and 28S rRNA nevertheless. Our findings demonstrate that Ppan is indispensable for early embryogenesis in mice.