Mitochondrial osmoregulation in evolution, cation transport and metabolism

Recent Advances and Multiple Strategies of Monoterpenoid Overproduction in Saccharomyces cerevisiae and Yarrowia lipolytica

Monoterpenoids are an important subclass of terpenoids that play important roles in the energy, cosmetics, pharmaceuticals, and fragrances fields. With the development of biotechnology, microbial synthesis of monoterpenoids has received great attention. Yeasts such Saccharomyces cerevisiae and Yarrowia lipolytica are emerging as potential hosts for monoterpenoids production because of unique advantages including rapid growth cycles, mature gene editing tools, and clear genetic background. Recently, advancements in metabolic engineering and fermentation engineering have significantly enhanced the accumulation of monoterpenoids in cell factories. First, this review introduces the biosynthetic pathway of monoterpenoids and comprehensively summarizes the latest production strategies, which encompass enhancing precursor flux, modulating the expression of rate-limited enzymes, suppressing competitive pathway flux, mitigating cytotoxicity, optimizing substrate utilization, and refining the fermentation process. Subsequently, this review introduces four representative monoterpenoids. Finally, we outline the future prospects for efficient construction cell factories tailored for the production of monoterpenoids and other terpenoids.

Halophilic lactic acid bacteria - Play a vital role in the fermented food industry

Halophilic lactic acid bacteria have been widely found in various high-salt fermented foods. The distribution of these species in salt-fermented foods contributes significantly to the development of the product's flavor. Besides, these bacteria also have the ability to biosynthesize bioactive components which potentially apply to different areas. In this review, insights into the metabolic properties, salt stress responses, and potential applications of these bacteria have been have been elucidated. The purpose of this review highlights the important role of halophilic lactic acid bacteria in improving the quality and safety of salt-fermented products and explores the potential application of these bacteria.

Spatiotemporal Regulation and Transport Engineering for Sustainable Production of Geraniol in Candida glycerinogenes

Geraniol is an attractive natural monoterpene with significant industrial and commercial value in the fields of pharmaceuticals, condiments, cosmetics, and bioenergy. The biosynthesis of monoterpenes suffers from the availability of key intermediates and enzyme-to-substrate accessibility. Here, we addressed these challenges in Candida glycerinogenes by a plasma membrane-anchoring strategy and achieved sustainable biosynthesis of geraniol using bagasse hydrolysate as substrate. On this basis, a remarkable 2.4-fold improvement in geraniol titer was achieved by combining spatial and temporal modulation strategies. In addition, enhanced geraniol transport and modulation of membrane lipid-associated metabolism effectively promoted the exocytosis of toxic monoterpenes, significantly improved the resistance of the engineered strain to monoterpenes and improved the growth of the strains, resulting in geraniol yield up to 1207.4 mg L-1 at shake flask level. Finally, 1835.2 mg L-1 geraniol was obtained in a 5 L bioreactor using undetoxified bagasse hydrolysate. Overall, our study has provided valuable insights into the plasma membrane engineering of C. glycerinogenes for the sustainable and green production of valuable compounds.

Risks of using mitoquinone during in vitro maturation and its potential protective effects against lipotoxicity-induced oocyte mitochondrial stress

PURPOSE

Oxidative stress and mitochondrial dysfunction play central roles in reduced oocyte quality and infertility in obese patients. Mitochondria-targeted treatments containing co-enzyme Q10 such as mitoquinone (MitoQ) can increase mitochondrial antioxidative capacity; however, their safety and efficiency when supplemented to oocytes under lipotoxic conditions have not been described.

METHODS

We tested the effect of different concentrations of MitoQ or its cationic carrier (TPP) (0, 0.1, 0.5, 1.0 μM each) during bovine oocyte IVM. Then, we tested the protective capacity of MitoQ (0.1 μM) against palmitic acid (PA)-induced lipotoxicity and mitochondrial dysfunction in oocytes.

RESULTS

Exposure to MitoQ, or TPP only, at 1 μM significantly (P<0.05) reduced oocyte mitochondrial inner membrane potential (JC-1 staining) and resulted in reduced cleavage and blastocyst rates compared with solvent control. Lower concentrations of MitoQ or TPP had no effects on embryo development under control (PA-free) conditions. As expected, PA increased the levels of MMP and ROS in oocytes (CellROX staining) and reduced cleavage and blastocyst rates compared with the controls (P<0.05). These negative effects were ameliorated by 0.1 μM MitoQ. In contrast, 0.1 μM TPP alone had no protective effects. MitoQ also normalized the expression of HSP10 and TFAM, and partially normalized HSP60 in the produced blastocysts, indicating at least a partial alleviation of PA-induced mitochondrial stress.

CONCLUSION

Oocyte exposure to MitoQ may disturb mitochondrial bioenergetic functions and developmental capacity due to a TPP-induced cationic overload. A fine-tuned concentration of MitoQ can protect against lipotoxicity-induced mitochondrial stress during IVM and restore developmental competence and embryo quality.

Histology and Ultrastructure of the Nephron and Kidney Interstitial Cells in the Atlantic Salmon (Salmo salar Linnaeus 1758) at Different Stages of Life Cycle

This article presents data on the mesonephros histology and ultrastructure in the Atlantic salmon from the Baltic Sea and Barents Sea populations, with an emphasis on comparisons between the following ontogenetic stages: parr, smolting, adult life at sea, the adults' return to their natal river to spawn, and spawning. The ultrastructural changes in the renal corpuscle and cells of the proximal tubules of the nephron occurred as early as the smolting stage. Such changes reflect fundamental alterations during the pre-adaptation to life in saltwater. In the Barents Sea population, the adult salmon sampled in the sea had the smallest diameters of the renal corpuscle and proximal and distal tubules, the most narrow urinary space, and the thickest basement membrane. In the group of salmon that entered the mouth of the river and spent less than 24 h in freshwater, the structural rearrangements occurred only in the distal tubules. Better development of the smooth endoplasmic reticulum and a greater abundance of mitochondria in the tubule cells were observed in the adult salmon from the Barents Sea compared to those from the Baltic Sea. Cell-immunity activation was initiated during the parr-smolt transformation. Another pronounced innate-immunity response was registered in the adults returning to the river to spawn.

TMBIM5 is the Ca2+ /H+ antiporter of mammalian mitochondria

Mitochondrial Ca2+ ions are crucial regulators of bioenergetics and cell death pathways. Mitochondrial Ca2+ content and cytosolic Ca2+ homeostasis strictly depend on Ca2+ transporters. In recent decades, the major players responsible for mitochondrial Ca2+ uptake and release have been identified, except the mitochondrial Ca2+ /H+ exchanger (CHE). Originally identified as the mitochondrial K+ /H+ exchanger, LETM1 was also considered as a candidate for the mitochondrial CHE. Defining the mitochondrial interactome of LETM1, we identify TMBIM5/MICS1, the only mitochondrial member of the TMBIM family, and validate the physical interaction of TMBIM5 and LETM1. Cell-based and cell-free biochemical assays demonstrate the absence or greatly reduced Na+ -independent mitochondrial Ca2+ release in TMBIM5 knockout or pH-sensing site mutants, respectively, and pH-dependent Ca2+ transport by recombinant TMBIM5. Taken together, we demonstrate that TMBIM5, but not LETM1, is the long-sought mitochondrial CHE, involved in setting and regulating the mitochondrial proton gradient. This finding provides the final piece of the puzzle of mitochondrial Ca2+ transporters and opens the door to exploring its importance in health and disease, and to developing drugs modulating Ca2+ exchange.

Salinity-induced transcriptome profiles in marine and freshwater threespine stickleback after an abrupt 6-hour exposure

Saltwater and freshwater environments have opposing physiological challenges, yet, there are fish species that are able to enter both habitats during short time spans, and as individuals they must therefore adjust quickly to osmoregulatory contrasts. In this study, we conducted an experiment to test for plastic responses to abrupt salinity changes in two populations of threespine stickleback, Gasterosteus aculeatus, representing two ecotypes (freshwater and ancestral saltwater). We exposed both ecotypes to abrupt native (control treatment) and non‐native salinities (0‰ and 30‰) and sampled gill tissue for transcriptomic analyses after 6 h of exposure. To investigate genomic responses to salinity, we analyzed four different comparisons; one for each ecotype (in their control and exposure salinity; (1) and (2), one between ecotypes in their control salinity (3), and the fourth comparison included all transcripts identified in (3) that did not show any expressional changes within ecotype in either the control or the exposed salinity (4)). Abrupt salinity transfer affected the expression of 10 and 1530 transcripts for the saltwater and freshwater ecotype, respectively, and 1314 were differentially expressed between the controls, including 502 that were not affected by salinity within ecotype (fixed expression). In total, these results indicate that factors other than genomic expressional plasticity are important for osmoregulation in stickleback, due to the need for opposite physiological pathways to survive the abrupt change in salinity.

Enhancement of linalool production in Saccharomyces cerevisiae by utilizing isopentenol utilization pathway

BACKGROUND

Linalool is a monoterpenoid, also a vital silvichemical with commercial applications in cosmetics, flavoring ingredients, and medicines. Regulation of mevalonate (MVA) pathway metabolic flux is a common strategy to engineer Saccharomyces cerevisiae for efficient linalool production. However, metabolic regulation of the MVA pathway is complex and involves competition for central carbon metabolism, resulting in limited contents of target metabolites.

RESULTS

In this study, first, a truncated linalool synthase (t26AaLS1) from Actinidia arguta was selected for the production of linalool in S. cerevisiae. To simplify the complexity of the metabolic regulation of the MVA pathway and increase the flux of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), we introduced the two-step isopentenyl utilization pathway (IUP) into S. cerevisiae, which could produce large amounts of IPP/DMAPP. Further, the S. cerevisiae IDI1 (ecoding isopentenyl diphosphate delta-isomerase) and ERG20^F96W-N127W (encoding farnesyl diphosphate synthase) genes were integrated into the yeast genome, combined with the strategies of copy number variation of the t26AaLS1 and ERG20^F96W-N127W genes to increase the metabolic flux of the downstream IPP, as well as optimization of isoprenol and prenol concentrations, resulting in a 4.8-fold increase in the linalool titer. Eventually, under the optimization of carbon sources and Mg²⁺ addition, a maximum linalool titer of 142.88 mg/L was obtained in the two-phase extractive shake flask fermentation.

CONCLUSIONS

The results show that the efficient synthesis of linalool in S. cerevisiae could be achieved through a two-step pathway, gene expression adjustment, and optimization of culture conditions. The study may provide a valuable reference for the other monoterpenoid production in S. cerevisiae.