Iron deficiency leads to repression of a non-canonical methionine salvage pathway in Schizosaccharomyces pombe

Impact of maternal anemia during pregnancy on neonatal metabolic profiles: evidence from the Beijing Birth Cohort Study

BACKGROUND

Anemia during pregnancy is associated with various adverse neonatal outcomes. However, the association between maternal anemia during pregnancy and newborn metabolic profiles remains unclear. This study aimed to investigate whether anemia during pregnancy is associated with alterations in neonatal metabolic profiles.

METHODS

This prospective observational cohort study included 12,116 pregnant women, with or without gestational anemia, recruited through the Beijing Birth Cohort Study (ChiCTR2200058395), along with their neonates born between July 2021 and October 2022 in Beijing, China.

RESULTS

Among the 12,116 participants, 576 pregnant women were diagnosed with anemia (Anemia group), while 11,540 did not have anemia (Control group). The rates of metabolic profile abnormalities were significantly higher in the Anemia group compared to the Control group (P < 0.05): 20.83% vs. 16.1% for the overall metabolic profile, 11.9% vs. 9.25% for amino acid profiles, and 11.11% vs. 8.04% for acylcarnitine profiles. Individual metabolic indicators showed significant differences: alanine and arginine levels significantly decreased, while tyrosine levels significantly increased in the Anemia group. Notably, most acylcarnitines indicators (C0, C2, C4DC + C5-OH, C5DC + C6-OH, C6, C6DC, C10, C10:1, C12, C12:1, C14, C14:1, C14:2, C16, C16:1, C16:1-OH, C18, and C18:1) were significantly reduced in the Anemia group, except for C5, which was elevated. Pathway analysis revealed that these alterations were associated with beta-oxidation of very long-chain fatty acids, oxidation of branched-chain fatty acids, mitochondrial beta-oxidation of long-chain saturated fatty acids, and fatty acid metabolism. All of these pathways were related to fatty acid oxidation. Sensitive analyses in normal birth weight (NBW) and term infants (TI) confirmed these findings and demonstrated their robustness. In addition, in NBW infants and TIs, citrulline and arginine were significantly decreased, which were associated with aspartate metabolism and the urea cycle.

CONCLUSIONS

Maternal anemia during pregnancy is significantly associated with alterations in neonatal metabolic profiles, particularly in fatty acid beta-oxidation and related pathways. These findings highlight the potential metabolic consequences of gestational anemia and provide insights into its role in adverse neonatal outcomes and abnormal newborn screening results.

The Schizosaccharomyces pombe ornithine-N5-oxygenase Sib2 interacts with the N5-transacetylase Sib3 in the ferrichrome biosynthetic pathway

The fission yeast Schizosaccharomyces pombe produces the hydroxamate-type siderophore ferrichrome (Fc). The biosynthesis of Fc requires the Fc synthase Sib1, the ornithine-N5-oxygenase Sib2, and the N5-hydroxyornithine-N5-transacetylase Sib3. In this study, we demonstrate the critical importance of the His248 residue of Sib3 in Fc production. Cells expressing a sib3H248A mutant allele fail to grow in iron-poor media without Fc supplementation. These sib3H248A mutant cells are consistently unable to promote Fc-dependent growth of Saccharomyces cerevisiae cells in cross-feeding experiments. Green fluorescent protein (GFP)-tagged wild-type Sib3 and mutant Sib3H248A exhibit a pancellular distribution. Coimmunoprecipitation assays revealed that both wild-type and Sib3H248A physically interact with Sib2. Further analysis identified a minimal C-terminal region from amino acids 290-334 of Sib3 that is required for interaction with Sib2. Deletion mapping analysis identified two regions of Sib2 as being required for its association with Sib3. The first region encompasses amino acids 1-135, and the second region corresponds to amino acids 281-358 of Sib2. Taken together, these results describe the first example of a physical interaction between an ornithine-N5-oxygenase and an N5-hydroxyornithine-N5-transacetylase controlling the biosynthesis of a hydroxamate-type siderophore.

Methionine biosynthetic genes and methionine sulfoxide reductase A are required for Rhizoctonia solani AG1-IA to cause sheath blight disease in rice

Rhizoctonia solani is a polyphagous necrotrophic fungal pathogen that causes sheath blight disease in rice. It deploys effector molecules as well as carbohydrate-active enzymes and enhances the production of reactive oxygen species for killing host tissues. Understanding R. solani ability to sustain growth under an oxidative-stress-enriched environment is important for developing disease control strategies. Here, we demonstrate that R. solani upregulates methionine biosynthetic genes, including Rs_MET13 during infection in rice, and double-stranded RNA-mediated silencing of these genes impairs the pathogen's ability to cause disease. Exogenous treatment with methionine restores the disease-causing ability of Rs_MET13-silenced R. solani and facilitates its growth on 10 mM H2O2-containing minimal-media. Notably, the Rs_MsrA gene that encodes methionine sulfoxide reductase A, an antioxidant enzyme involved in the repair of oxidative damage of methionine, is upregulated upon H2O2 treatment and also during infection in rice. Rs_MsrA-silenced R. solani is unable to cause disease, suggesting that it is important for the repair of oxidative damage in methionine during host colonization. We propose that spray-induced gene silencing of Rs_MsrA and designing of antagonistic molecules that block MsrA activity can be exploited as a drug target for effective control of sheath blight disease in rice.

A novel role of the fission yeast sulfiredoxin Srx1 in heme acquisition

The transporter Str3 promotes heme import in Schizosaccharomyces pombe cells that lack the heme receptor Shu1 and are deficient in heme biosynthesis. Under microaerobic conditions, the peroxiredoxin Tpx1 acts as a heme scavenger within the Str3-dependent pathway. Here, we show that Srx1, a sulfiredoxin known to interact with Tpx1, is essential for optimal growth in the presence of hemin. The expression of Srx1 is induced in response to low iron and repressed under iron repletion. Coimmunoprecipitation and bimolecular fluorescence complementation experiments show that Srx1 interacts with Str3. Although the interaction between Srx1 and Str3 is weakened, it is still observed in tpx1Δ mutant cells or when Str3 is coexpressed with a mutant form of Srx1 (mutD) that cannot bind Tpx1. Further analysis by absorbance spectroscopy and hemin-agarose pull-down assays confirms the binding of Srx1 to hemin, with an equilibrium constant value of 2.56 μM. To validate the Srx1-hemin association, we utilize a Srx1 mutant (mutH) that fails to interact with hemin. Notably, when Srx1 binds to hemin, it partially shields hemin from degradation caused by hydrogen peroxide. Collectively, these findings elucidate an additional function of the sulfiredoxin Srx1, beyond its conventional role in oxidative stress defense.

Schizosaccharomyces pombe Grx4, Fep1, and Php4: In silico analysis and expression response to different iron concentrations

Due to iron's essential role in cellular metabolism, most organisms must maintain their homeostasis. In this regard, the fission yeast Schizosaccharomyces pombe (sp) uses two transcription factors to regulate intracellular iron levels: spFep1 under iron-rich conditions and spPhp4 under iron-deficient conditions, which are controlled by spGrx4. However, bioinformatics analysis to understand the role of the spGrx4/spFep1/spPhp4 axis in maintaining iron homeostasis in S. pombe is still lacking. Our study aimed to perform bioinformatics analysis on S. pombe proteins and their sequence homologs in Aspergillus flavus (af), Saccharomyces cerevisiae (sc), and Homo sapiens (hs) to understand the role of spGrx4, spFep1, and spPhp4 in maintaining iron homeostasis. The three genes' expression patterns were also examined at various iron concentrations. A multiple sequence alignment analysis of spGrx4 and its sequence homologs revealed a conserved cysteine residue in each PF00085 domain. Blast results showed that hsGLRX3 is most similar to spGrx4. In addition, spFep1 is most closely related in sequence to scDal80, whereas scHap4 is most similar to spFep1. We also found two highly conserved motifs in spFep1 and its sequence homologs that are significant for iron transport systems because they contain residues involved in iron homeostasis. The scHap4 is most similar to spPhp4. Using STRING to analyze protein-protein interactions, we found that spGrx4 interacts strongly with spPhp4 and spFep1. Furthermore, spGrx4, spPhp4, and spFep1 interact with spPhp2, spPhp3, and spPhp5, indicating that the three proteins play cooperative roles in iron homeostasis. At the highest level of Fe, spgrx4 had the highest expression, followed by spfep1, while spphp4 had the lowest expression; a contrast occurred at the lowest level of Fe, where spgrx4 expression remained constant. Our findings support the notion that organisms develop diverse strategies to maintain iron homeostasis.

Sporulation: A response to starvation in the fission yeast Schizosaccharomyces pombe

The fission yeast Schizosaccharomyces pombe employs two main strategies to adapt to the environment and survive when starved for nutrients. The strategies employ sporulation via sexual differentiation and extension of the chronological lifespan. When a cell is exposed to nutrient starvation in the presence of a cell of the opposite sex, the cells undergo fusion through conjugation and sporulation through meiosis. S. pombe spores are highly resistant to diverse stresses and may survive for a very long time. In this minireview, among the various sexual differentiation processes induced by starvation, we focused on and summarized the findings of the molecular mechanisms of spore formation in fission yeast. Furthermore, comparative measurements of the chronological lifespan of stationary phase cells and G0 cells and the survival period of spore cells revealed that the spore cells survived for a long period, indicating the presence of an effective mechanism for survival. Currently, many molecules involved in sporulation and their functions are being discovered; however, our understanding of these is not complete. Further understanding of spores may not only deepen our comprehension of sexual differentiation but may also provide hints for sustaining life.

Expression of Mug14 is regulated by the transcription factor Rst2 through the cAMP-dependent protein kinase pathway in Schizosaccharomyces pombe

The cAMP-dependent protein kinase (Pka1) regulates many cellular events, including sexual development and glycogenesis, and response to the limitation of glucose, in Schizosaccharomyces pombe. Despite its importance in many cellular events, the targets of the cAMP/PKA pathway have not been fully investigated. Here, we demonstrate that the expression of mug14 is induced by downregulation of the cAMP/PKA pathway and limitation of glucose. This regulation is dependent on the function of Rst2, a transcription factor that regulates transition from mitosis to meiosis. The loss of the C2H2-type zinc finger domain in Rst2, termed Rst2 (C2H2∆), abolished the induction of Mug14 expression. Upon deletion of the stress starvation response element of the S. pombe (STREP: CCCCTC) sequence, which is a potential binding site of Rst2 on mug14, in the pka1∆ strain, its induction was abolished. The expression of Mug14 was significantly reduced and delayed by the limitation of glucose and also by nitrogen starvation in the rst2∆ strain. Mug14 is known to share a common function with Mde1 and Mta3 in the methionine salvage pathway, but the expression of mde1 and mta3 mRNAs was not enhanced by pka1 deletion and limitation of glucose. We conclude that the expression of Mug14 is upregulated by Rst2 under the control of the cAMP/PKA signaling pathway, which senses the limitation of glucose.