A Combination of Genomics, Transcriptomics, and Genetics Provides Insights into the Mineral Weathering Phenotype of Pseudomonas azotoformans F77

2021 ◽  
Author(s):  
Yuan-Li Wang ◽  
Wen Dong ◽  
Kai-Xiang Xiang ◽  
Qi Wang ◽  
Lin-Yan He ◽  
...  
Keyword(s):  
Metabolic Pathways ◽  
Gluconic Acid ◽  
Acid Production ◽  
Molecular Mechanisms ◽  
Acid Metabolism ◽  
Reducing Power ◽  
Acid Tolerance ◽  
Mineral Weathering ◽  
Silicate Mineral ◽  
Flagellar Assembly

Silicate mineral weathering (dissolution) plays important roles in soil formation and global biogeochemical cycling. In this study, a combination of genomics, transcriptomics, and genetics was used to identify the molecular basis of mineral weathering activity and acid tolerance in Pseudomonas azotoformans F77. Biotite was chosen as a silicate mineral to investigate mineral weathering. The genome of strain F77 was sequenced, and the genes significantly upregulated when grown in the presence of biotite included mineral weathering-related genes associated with gluconic acid metabolism, flagellar assembly, and pilus biosynthesis and acid tolerance-related genes associated with neutralizing component production, reducing power, and proton efflux. Then, the biotite-weathering behaviors of strain F77 and its mutants that were created by deleting the tkt , tal , gntP , potF , nuoF , and gdtO genes, which are involved in gluconic acid metabolism and acid tolerance, respectively, were determined. The Fe and Al concentrations in the strain F77-inoculated medium increased 2.2- to 13.7-fold compared to the controls. The cell numbers of strain F77 increased over time, while the pH values in the medium ranged from 3.75 to 3.90 between 20 and 36 h of incubation. The release of Al and Fe was significantly reduced in the mutants F77Δ tal , F77Δ gntP , F77Δ potF , and F77Δ nuoF . Bacterial growth was significantly reduced in the presence of biotite in the mutants F77Δ potF and F77Δ nuoF . Our results demonstrated the acid tolerance of strain F77 and suggested that multiple genes and metabolic pathways in strain F77 are involved in biotite weathering and acid tolerance during the mineral weathering process. IMPORTANCE Acid production and tolerance play important roles in effective and persistent mineral weathering in bacteria, although the molecular mechanisms governing acid production and acid tolerance in bacteria have not been fully elucidated. In this study, the molecular mechanisms underlying biotite (as a silicate mineral) weathering (dissolution) and acid tolerance of P. azotoformans F77 were characterized using genomics, transcriptomics, and genetics analyses. Our results showed that the genes and metabolic pathways for gluconic acid metabolism, flagellar assembly, and pilus biosynthesis may play important roles in mineral weathering by strain F77. Notably, the genes associated with neutralizing component production, reducing power, and proton efflux may be related to acid tolerance in strain F77. The expression of these acid production- and acid tolerance-related genes was observed to be increased by biotite in strain F77. Our findings may help to elucidate the molecular mechanisms governing mineral weathering and, especially, acid tolerance in mineral-weathering bacteria.

scholarly journals Interactions between Biotite and the Mineral-Weathering Bacterium Pseudomonas azotoformans F77

2020 ◽  
Vol 86 (7) ◽  
Author(s):  
Yuan-Li Wang ◽  
Li-Jing Sun ◽  
Chun-Mei Xian ◽  
Feng-Lian Kou ◽  
Ying Zhu ◽  
...  
Keyword(s):  
Gluconic Acid ◽  
Direct Contact ◽  
Molecular Mechanisms ◽  
Acid Metabolism ◽  
Cell Attachment ◽  
Mineral Weathering ◽  
Flow Area ◽  
Content Type ◽  
Silicate Minerals ◽  
Expression Levels

ABSTRACT In this study, the mineral-weathering bacterium Pseudomonas azotoformans F77, which was isolated from the soil of a debris flow area, was evaluated for its weathering activity under direct contact with biotite or without contact. Then, biotite-weathering behaviors of strain F77, mutants that had been created by deleting the gcd and adh genes (which are involved in gluconic acid metabolism and pilus formation, respectively), and the double mutant F77ΔgcdΔadh were compared. The relative gene expression levels of F77 and its mutants F77Δgcd and F77Δadh were also analyzed in the presence of biotite. Direct contact with biotite increased Fe and Al release from the mineral in the presence of F77. All strains had similar abilities to release Fe and Al from the mineral except for F77Δgcd and F77Δadh. Mobilized Fe and Al concentrations were decreased by up to 72, 26, and 87% in the presence of F77Δgcd, F77Δadh, and F77ΔgcdΔadh, respectively, compared to levels observed in the presence of F77 during the mineral-weathering process. Gluconic acid production was decreased for F77Δgcd and F77ΔgcdΔadh, while decreased cell attachment on the mineral surface was observed for F77Δadh, compared to findings for F77. The F77 genes involved in pilus formation and gluconic acid metabolism showed increased expression levels in the presence of biotite. The results of this study showed important roles for the genes involved in gluconic acid metabolism and pilus formation in mineral weathering by F77 and demonstrated the distinctive effect of these genes on mineral weathering by F77. IMPORTANCE Bacteria play important roles in mineral weathering and soil formation, although the molecular mechanisms underlying the interactions between bacteria and silicate minerals are poorly understood. In this study, the interactions between biotite and the highly effective mineral-weathering bacterium P. azotoformans F77 were characterized. Our results showed that the genes involved in gluconic acid metabolism and pilus formation play important roles in mineral weathering by F77. The presence of biotite could promote the expression of these genes in F77, and a distinctive effect of these genes on mineral weathering by F77 was observed in this study. Our results provide new knowledge and promote better understanding regarding the interaction between silicate minerals and mineral-weathering bacteria, as well as the molecular mechanisms involved in these processes.

scholarly journals Identification of a novel type of glucose dehydrogenase involved in the mineral weathering ability of Collimonas pratensis strain PMB3(1)

2020 ◽  
Author(s):  
L Picard ◽  
M-P Turpault ◽  
P M Oger ◽  
S Uroz
Keyword(s):  
Gluconic Acid ◽  
Molecular Mechanisms ◽  
Glucose Dehydrogenase ◽  
Random Mutagenesis ◽  
Mineral Weathering ◽  
Single Type ◽  
Biotite Weathering ◽  
Genomic Regions ◽  
Oxidation Of Glucose

Abstract The exact molecular mechanisms as well as the genes involved in the mineral weathering (MW) process by bacteria remain poorly characterized. To date, a single type of glucose dehydrogenase (GDH) depending on a particular co-factor named pyrroloquinoline quinone (PQQ) is known. These enzymes allow the production of gluconic acid through the oxidation of glucose. However, it remains to be determined how bacteria missing PQQ-dependent GDH and/or the related pqq biogenesis genes weather minerals. In this study, we considered the very effective mineral weathering bacterial strain PMB3(1) of Collimonas pratensis. Genome analysis revealed that it does not possess the PQQ based system. The use of random mutagenesis, gene complementation and functional assays allowed us to identify mutants impacted in their ability to weather mineral. Among them, three mutants were strongly altered on their acidification and biotite weathering abilities (58 to 75% of reduction compared to WT) and did not produce gluconic acid. The characterization of the genomic regions allowed noticeably to the identification of a Glucose/Methanol/Choline oxidoreductase. This region appeared very conserved among collimonads and related genera. This study represents the first demonstration of the implication of a PQQ-independent GDH in the mineral weathering process and explains how Collimonas weather minerals.

scholarly journals Effect of Micromelalopha sieversi (Staudinger) Oviposition Behavior on the Transcriptome of Two Populus Section Aigeiros Clones

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 1021
Author(s):  
Li Guo ◽  
Sufang Zhang ◽  
Fu Liu ◽  
Xiangbo Kong ◽  
Zhen Zhang
Keyword(s):  
Gene Expression ◽  
Linoleic Acid ◽  
Plant Resistance ◽  
Metabolic Pathways ◽  
Molecular Mechanisms ◽  
Woody Plant ◽  
Acid Metabolism ◽  
Defense Genes ◽  
Populus Euramericana ◽  
Linoleic Acid Metabolism

Research Highlights: The molecular mechanisms underlying woody plant resistance upon oviposition by herbivores remain unclear, as studies have focused on herbaceous plants. The effect of oviposition on gene expression in neighboring plants has also not been reported. Elucidating these molecular responses can help cultivate insect-resistant trees. Background and Objectives: Oviposition by herbivorous insects acts as an early warning signal, inducing plant resistance responses. Here, we employed poplar as a model woody plant to elucidate gene expression and the molecular mechanisms underlying plant resistance after oviposition by Micromelalopha sieversi (Staudinger) (Lepidoptera: Notodontidae). Materials and Methods: The differences in gene expression of two Populus section Aigeiros clones (‘108’ (Populus × euramericana ‘Guariento’) and ‘111’ (Populus × euramericana ‘Bellotto’)) were analyzed via high-throughput sequencing of oviposited, neighboring, and control plants. Results: We obtained 304,526,107 reads, with an average length of 300 bp and a total size of 40.77 Gb. Differentially expressed genes (DEGs) in gene ontology terms of biological process, cellular component, and molecular function were mainly enriched in the “cell part”, “catalytic”, and “metabolic process” functions. Moreover, DEGs were mainly enriched in the following pathways: plant-pathogen interaction, linoleic acid metabolism, and cyanoamino acid metabolism (108-O vs. 108-C); metabolic pathways, photosynthesis, photosynthesis-antenna proteins, nitrogen metabolism, and linoleic acid metabolism (111-O vs. 111-C); metabolic pathways and biosynthesis of secondary metabolites (111-N vs. 111-C); no pathways were significantly enriched in 108-N vs. 108-C. Up-regulated defense genes were associated with pathogenesis-related protein function, innate immune regulation, and biological stress response, with differences in specific genes. All genes related to photosynthetic activity were significantly down-regulated in oviposited and neighboring leaves of the two clones. Conclusions: Oviposited and neighboring ‘108’ and ‘111’ plants exhibited varying degrees of resistance upon oviposition, involving the up-regulation of various defense genes, decreased photosynthesis and nutrient accumulation, and increased secondary metabolic synthesis.

scholarly journals Genome-Wide Mapping of Histone H3 Lysine 4 Trimethylation (H3K4me3) and Its Involvement in Fatty Acid Biosynthesis in Sunflower Developing Seeds

Plants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 706
Author(s):  
Antonio J. Moreno-Pérez ◽  
Raquel Martins-Noguerol ◽  
Cristina DeAndrés-Gil ◽  
Mónica Venegas-Calerón ◽  
Rosario Sánchez ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Chromatin Remodeling ◽  
Molecular Mechanisms ◽  
Acid Metabolism ◽  
Fatty Acid Biosynthesis ◽  
Acid Synthesis ◽  
Sunflower Seeds ◽  
Acid Biosynthesis ◽  
Functional Regions ◽  
Genome Wide

Histone modifications are of paramount importance during plant development. Investigating chromatin remodeling in developing oilseeds sheds light on the molecular mechanisms controlling fatty acid metabolism and facilitates the identification of new functional regions in oil crop genomes. The present study characterizes the epigenetic modifications H3K4me3 in relationship with the expression of fatty acid-related genes and transcription factors in developing sunflower seeds. Two master transcriptional regulators identified in this analysis, VIV1 (homologous to Arabidopsis ABI3) and FUS3, cooperate in the regulation of WRINKLED 1, a transcriptional factor regulating glycolysis, and fatty acid synthesis in developing oilseeds.

scholarly journals Comprehensive transcriptome and metabolome profiling reveal metabolic mechanisms of Nitraria sibirica Pall. to salt stress

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Huanyong Li ◽  
Xiaoqian Tang ◽  
Xiuyan Yang ◽  
Huaxin Zhang
Keyword(s):  
Salt Stress ◽  
Amino Acid ◽  
Salt Tolerance ◽  
Metabolic Pathways ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Sulfur Metabolism ◽  
Enrichment Analysis ◽  
Extracellular Region ◽  
Nitraria Sibirica

AbstractNitraria sibirica Pall., a typical halophyte that can survive under extreme drought conditions and in saline-alkali environments, exhibits strong salt tolerance and environmental adaptability. Understanding the mechanism of molecular and physiological metabolic response to salt stress of plant will better promote the cultivation and use of halophytes. To explore the mechanism of molecular and physiological metabolic of N. sibirica response to salt stress, two-month-old seedlings were treated with 0, 100, and 400 mM NaCl. The results showed that the differentially expressed genes between 100 and 400 mmol L−1 NaCl and unsalted treatment showed significant enrichment in GO terms such as binding, cell wall, extemal encapsulating structure, extracellular region and nucleotide binding. KEGG enrichment analysis found that NaCl treatment had a significant effect on the metabolic pathways in N. sibirica leaves, which mainly including plant-pathogen interaction, amino acid metabolism of the beta alanine, arginine, proline and glycine metabolism, carbon metabolism of glycolysis, gluconeogenesis, galactose, starch and sucrose metabolism, plant hormone signal transduction and spliceosome. Metabolomics analysis found that the differential metabolites between the unsalted treatment and the NaCl treatment are mainly amino acids (proline, aspartic acid, methionine, etc.), organic acids (oxaloacetic acid, fumaric acid, nicotinic acid, etc.) and polyhydric alcohols (inositol, ribitol, etc.), etc. KEGG annotation and enrichment analysis showed that 100 mmol L−1 NaCl treatment had a greater effect on the sulfur metabolism, cysteine and methionine metabolism in N. sibirica leaves, while various amino acid metabolism, TCA cycle, photosynthetic carbon fixation and sulfur metabolism and other metabolic pathways have been significantly affected by 400 mmol L−1 NaCl treatment. Correlation analysis of differential genes in transcriptome and differential metabolites in metabolome have found that the genes of AMY2, BAM1, GPAT3, ASP1, CML38 and RPL4 and the metabolites of L-cysteine, proline, 4-aminobutyric acid and oxaloacetate played an important role in N. sibirica salt tolerance control. This is a further improvement of the salt tolerance mechanism of N. sibirica, and it will provide a theoretical basis and technical support for treatment of saline-alkali soil and the cultivation of halophytes.

scholarly journals Identification of Biomolecules Involved in the Adaptation to the Environment of Cold-Loving Microorganisms and Metabolic Pathways for Their Production

Biomolecules ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1155
Author(s):  
Eva Garcia-Lopez ◽  
Paula Alcazar ◽  
Cristina Cid
Keyword(s):  
Metabolic Pathways ◽  
Extracellular Polymeric Substances ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Analytical Techniques ◽  
Light Protection ◽  
Domains Of Life ◽  
Mechanisms Of Adaptation ◽  
Resistance To Stress ◽  
Function Discovery

Cold-loving microorganisms of all three domains of life have unique and special abilities that allow them to live in harsh environments. They have acquired structural and molecular mechanisms of adaptation to the cold that include the production of anti-freeze proteins, carbohydrate-based extracellular polymeric substances and lipids which serve as cryo- and osmoprotectants by maintaining the fluidity of their membranes. They also produce a wide diversity of pigmented molecules to obtain energy, carry out photosynthesis, increase their resistance to stress and provide them with ultraviolet light protection. Recently developed analytical techniques have been applied as high-throughoutput technologies for function discovery and for reconstructing functional networks in psychrophiles. Among them, omics deserve special mention, such as genomics, transcriptomics, proteomics, glycomics, lipidomics and metabolomics. These techniques have allowed the identification of microorganisms and the study of their biogeochemical activities. They have also made it possible to infer their metabolic capacities and identify the biomolecules that are parts of their structures or that they secrete into the environment, which can be useful in various fields of biotechnology. This Review summarizes current knowledge on psychrophiles as sources of biomolecules and the metabolic pathways for their production. New strategies and next-generation approaches are needed to increase the chances of discovering new biomolecules.

scholarly journals Integrative iTRAQ-based proteomic and transcriptomic analysis reveals the accumulation patterns of key metabolites associated with oil quality during seed ripening of Camellia oleifera

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Zhouchen Ye ◽  
Jing Yu ◽  
Wuping Yan ◽  
Junfeng Zhang ◽  
Dongmei Yang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Molecular Mechanisms ◽  
Acid Metabolism ◽  
Oil Quality ◽  
Gas Chromatography Mass Spectrometry ◽  
Glutathione Metabolism ◽  
Poor Correlation ◽  
Camellia Oleifera ◽  
Specific Expression

AbstractCamellia oleifera (C. oleifera) is one of the four major woody oil-bearing crops in the world and has relatively high ecological, economic, and medicinal value. Its seeds undergo a series of complex physiological and biochemical changes during ripening, which is mainly manifested as the accumulation and transformation of certain metabolites closely related to oil quality, especially flavonoids and fatty acids. To obtain new insights into the underlying molecular mechanisms, a parallel analysis of the transcriptome and proteome profiles of C. oleifera seeds at different maturity levels was conducted using RNA sequencing (RNA-seq) and isobaric tags for relative and absolute quantification (iTRAQ) complemented with gas chromatography-mass spectrometry (GC-MS) data. A total of 16,530 transcripts and 1228 proteins were recognized with significant differential abundances in pairwise comparisons of samples at various developmental stages. Among these, 317 were coexpressed with a poor correlation, and most were involved in metabolic processes, including fatty acid metabolism, α-linolenic acid metabolism, and glutathione metabolism. In addition, the content of total flavonoids decreased gradually with seed maturity, and the levels of fatty acids generally peaked at the fat accumulation stage; these results basically agreed with the regulation patterns of genes or proteins in the corresponding pathways. The expression levels of proteins annotated as upstream candidates of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) as well as their cognate transcripts were positively correlated with the variation in the flavonoid content, while shikimate O-hydroxycinnamoyltransferase (HCT)-encoding genes had the opposite pattern. The increase in the abundance of proteins and mRNAs corresponding to alcohol dehydrogenase (ADH) was associated with a reduction in linoleic acid synthesis. Using weighted gene coexpression network analysis (WGCNA), we further identified six unique modules related to flavonoid, oil, and fatty acid anabolism that contained hub genes or proteins similar to transcription factors (TFs), such as MADS intervening keratin-like and C-terminal (MIKC_MADS), type-B authentic response regulator (ARR-B), and basic helix-loop-helix (bHLH). Finally, based on the known metabolic pathways and WGCNA combined with the correlation analysis, five coexpressed transcripts and proteins composed of cinnamyl-alcohol dehydrogenases (CADs), caffeic acid 3-O-methyltransferase (COMT), flavonol synthase (FLS), and 4-coumarate: CoA ligase (4CL) were screened out. With this exploratory multiomics dataset, our results presented a dynamic picture regarding the maturation process of C. oleifera seeds on Hainan Island, not only revealing the temporal specific expression of key candidate genes and proteins but also providing a scientific basis for the genetic improvement of this tree species.

FC 102PD INDUCED ARTERIOLAR AND PERITONEAL PATHOMECHANISMS ARE PARTIALLY REVERSED AFTER KIDNEY TRANSPLANTATION

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Conghui Zhang ◽  
Maria Bartosova ◽  
Betti Schaefer ◽  
Rebecca Herzog ◽  
Rimante Cerkauskiene ◽  
...  
Keyword(s):  
Kidney Transplantation ◽  
Fatty Acid ◽  
Fatty Acid Metabolism ◽  
Fatty Acid Synthase ◽  
Molecular Mechanisms ◽  
Acid Metabolism ◽  
Parietal Peritoneum ◽  
Gene Set Enrichment Analysis ◽  
Biological Processes ◽  
Cell Counts

Abstract Background and Aims Due to the unphysiological composition of PD fluids, chronic peritoneal dialysis (PD) induces progressive peritoneal fibrosis, hypervascularization, and vasculopathy. The evolution of the PD membrane and vasculopathy following kidney transplantation (KTx) is largely unknown. Method Arteriolar and peritoneal tissues were obtained from 107 children with chronic kidney disease (CKD5), 72 children on PD (treated with neutral pH PD fluids, with low glucose degradation product content, GDP) and 21 children, who underwent KTx 4-5 weeks after a median 21 months of PD. Specimen underwent standardized digital quantitative histomorphometry. Molecular mechanisms were studied in omental arterioles microdissected from surrounding fat by multi-omics followed by Gene Set Enrichment Analysis (GSEA); key findings were validated in parietal tissues of independent, matched cohorts by quantitative immunohistochemistry (n=15/group). Results Arteriolar transcriptome and proteome GSEA revealed suppression of leucocyte migration and T-cell activation / secretory pathways regulation, of sprouting angiogenesis biological processes and of epithelial proliferation and cell cycle after KTx as compared to PD. Lipid / fatty acid metabolism, autophagy and ATP synthesis pathways were activated. Transcriptome analysis including KTx, PD and CKD5 specifically attributed regulation of arteriolar lipid and fatty acid metabolism to transplantation and comprised 140 transcripts; their regulation was confirmed on the proteome level. Hub gene fatty acid synthase was identified by protein interaction analysis (string-db.org). 15 arteriolar genes activated by PD were inactivated after KTx and included glucose metabolisms and cytoskeleton related transcripts. 24 transcripts and 10 corresponding proteins induced by PD were still active after KTx and associated with biological processes related to TGF-ß signaling, fibrosis and mineral absorption. In line with arteriolar multi-omics findings, peritoneal hypervascularization induced by chronic PD was reversed after Tx to CKD5 level. CD45 positive tissue infiltrating leucocytes count was reduced by 40% and was independently associated with microvessel density in multivariable analysis including PD vintage, daily GDP exposure and recent KTx. Peritoneal lymphatic vessel density, submesothelial thickness, activated fibroblast, fibrin deposit, macrophage and EMT cell counts remained unchanged after KTx compared to PD. Arteriolar lumen to vessel ratios (a marker of vasculopathy) were similar in both groups. Vessel-homeostasis-related proteins in independent, matched cohorts demonstrated increased caspase-3 abundance in peritoneal arterioles after KTx. Arteriolar VEGF-A, thrombospondin, angiopoietin1/2, and hypoxia-inducible factor-1 (HIF-1a) were unchanged, while submesothelial HIF-1a and angiopoietin1/2 were decreased after Tx, favoring vessel maturation. The abundance of the key driver of fibrosis, TGF-ß-effector pSMAD2/3, was unchanged in the peritoneum and arterioles after Tx. Conclusion Our multi-omics analyses of fat covered omental arterioles, not directly exposed to PD fluids, demonstrate inhibition of PD induced immune response and angiogenesis pathways, of glucose metabolism and cytoskeleton regulation to levels similar as seen in children with CKD5. Arteriolar lipid and fatty acid metabolism is selectively altered after KTx. Reversal of low GDP PD induced hypervascularization and inflammation of the parietal peritoneum after KTx, mirror molecular changes in omental arterioles, while profibrotic activity persists after KTx in omental arterioles and in the parietal peritoneum.

scholarly journals Sphingolipid biosynthesis upregulation by TOR complex 2–Ypk1 signaling during yeast adaptive response to acetic acid stress

2016 ◽  
Vol 473 (23) ◽  
pp. 4311-4325 ◽  
Author(s):  
Joana F. Guerreiro ◽  
Alexander Muir ◽  
Subramaniam Ramachandran ◽  
Jeremy Thorner ◽  
Isabel Sá-Correia
Keyword(s):  
Acetic Acid ◽  
Protein Kinase ◽  
Cellular Response ◽  
Molecular Mechanisms ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Industrial Biotechnology ◽  
Acetic Acid Tolerance ◽  
Spoilage Yeasts ◽  
Sphingolipid Biosynthesis

Acetic acid-induced inhibition of yeast growth and metabolism limits the productivity of industrial fermentation processes, especially when lignocellulosic hydrolysates are used as feedstock in industrial biotechnology. Tolerance to acetic acid of food spoilage yeasts is also a problem in the preservation of acidic foods and beverages. Thus understanding the molecular mechanisms underlying adaptation and tolerance to acetic acid stress is increasingly important in industrial biotechnology and the food industry. Prior genetic screens for Saccharomyces cerevisiae mutants with increased sensitivity to acetic acid identified loss-of-function mutations in the YPK1 gene, which encodes a protein kinase activated by the target of rapamycin (TOR) complex 2 (TORC2). We show in the present study by several independent criteria that TORC2–Ypk1 signaling is stimulated in response to acetic acid stress. Moreover, we demonstrate that TORC2-mediated Ypk1 phosphorylation and activation is necessary for acetic acid tolerance, and occurs independently of Hrk1, a protein kinase previously implicated in the cellular response to acetic acid. In addition, we show that TORC2–Ypk1-mediated activation of l-serine:palmitoyl-CoA acyltransferase, the enzyme complex that catalyzes the first committed step of sphingolipid biosynthesis, is required for acetic acid tolerance. Furthermore, analysis of the sphingolipid pathway using inhibitors and mutants indicates that it is production of certain complex sphingolipids that contributes to conferring acetic acid tolerance. Consistent with that conclusion, promoting sphingolipid synthesis by adding exogenous long-chain base precursor phytosphingosine to the growth medium enhanced acetic acid tolerance. Thus appropriate modulation of the TORC2–Ypk1–sphingolipid axis in industrial yeast strains may have utility in improving fermentations of acetic acid-containing feedstocks.

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