Cyanide-resistant Respiration Research Articles

Effects of Long-Term High Temperatures in the Root Zone on the Physiological Characteristics of Grapevine Leaves and Roots: Implications for Viticulture Practices

Ridging cultivation and root restriction cultivation are beneficial due to their improvement of the soil permeability in the root zone of grapevine, and they are widely used in southern China, Japan, and other countries. However, with the intensification of global warming, when using ridging or root restriction cultivation, the soil temperature in the root zone can often reach 30 °C or even more than 35 °C during the summer, which is not conducive to the growth of grapevines. The aim of this study was to explore the effects of high root zone temperatures on the photosynthetic fluorescence characteristics of grapevine leaves, root respiration, and degree of lignification of roots and shoots, as well as to provide a theoretical foundation for the management of grapevine production and cultivation. One-year-old potted ‘Kyoho’ was used as the study material. Three root temperature treatments were implemented for 15 days (9:00–16:00): 25 °C (CK), 30 °C (T1), and 35 °C (T2). The results showed that the malondialdehyde and H2O2 levels in leaves increased, while the chlorophyll content decreased. The oxygen-evolving complex was inactivated, and PSII donor and acceptor sides were blocked, thus reducing the photosynthetic gas exchange capacity at high root zone temperatures. The grapevine root activity and root/shoot ratio decreased. Simultaneously, the lignin content in the roots and shoots increased. In addition, there was a significant increase in the expression of key genes (PAL, C4H, 4CL, F5H, COMT, CCR, and CAD) in the root lignin synthesis pathway. Heightened root zone temperatures increased cyanide-resistant respiration in roots and heat release in the PPP pathway to alleviate stress damage. Therefore, it is recommended to use grass, mulching, and other cultivation management methods to maintain root zone temperatures below 30 °C in order to ensure the normal growth of grapevines and promote a high and stable yield.

Effect of the overexpression of external alternative NADH dehydrogenase gene in Arabidopsis on the resistance of transformed tobacco plants to negative temperatures

The study aims to confirm the functional activity and localization of the At_NDB2 transgenic protein of Arabidopsis in tobacco cells and to evaluate the effect produced by the permanent expression of external alternative NADH dehydrogenase on the resistance of a heat-loving plant to low temperatures. Proteins and mitochondria were isolated from the leaves of tobacco plants grown at 25 °С (day/night) at the 7-leaf stage. At_NDB2 protein localization in mitochondria was determined via electrophoresis and immunoblotting. The functional activity of At_NDB2 was confirmed through the polarography of isolated mitochondria and the specific mitochondrial complex I inhibitor (rotenone). It was also found that the cyanide-resistant respiration rate and the activity of an alternative oxidase enzyme were significantly higher in transgenic plants than in wild-type plants. In order to determine the resistance to low temperatures, the parent and transgenic tobacco plants were grown in soil until the 2–3 and 6–7 leaf stages, after which they were kept at 3 to -3 °С for a day in the dark and left to regrow at 25 °С for seven days. Although it was previously shown that oxidative stress is reduced in transgenic plants at low temperatures as compared to wild-type plants, it was established that the tolerance of transgenic and nontransformed plants does not differ. Thus, alternative NADH dehydrogenase activity was found to reduce oxidative stress and increase alternative oxidase activity, without enhancing the resistance of Nicotiana tabacum to negative temperatures.

Resistance to Plant Parasites in Tomato Is Induced by Soil Enrichment with Specific Bacterial and Fungal Rhizosphere Microbiome.

Commercial formulations of beneficial microbes have been used to enrich the rhizosphere microbiome of tomato plants grown in pots located in a glasshouse. These plants have been subjected to attacks by soil-borne parasites, such as root-knot nematodes (RKNs), and herbivores, such as the miner insect Tuta absoluta. The development of both parasites and the symptoms of their parasitism were restricted in these plants with respect to plants left untreated. A mixture, named in the text as Myco, containing plant growth-promoting rhizobacteria (PGPR), opportunistic biocontrol fungi (BCF), and arbuscular mycorrhizal fungi (AMF) was more effective in limiting pest damage than a formulation containing the sole AMF (Ozor). Therefore, Myco-treated plants inoculated with RKNs were taken as a model for further studies. The PGPR contained in Myco were not able to reduce nematode infection; rather, they worsened symptoms in plants compared with those observed in untreated plants. Therefore, it was argued that both BCF and AMF were the microorganisms that colonized roots and stimulated the plant immune system against RKNs. Beneficial fungi colonized the roots by lowering the activities of the defense supporting enzymes endochitinases and β-1,3-glucanase. However, as early as three days after nematode inoculation, these enzyme activities and the expression of the encoding pathogenesis-related genes (PR-2, PR-3) were found to be enhanced in roots with respect to non-inoculated plants, thus indicating that plants had been primed against RKNs. The addition of paclobutrazol, which reduces salicylic acid (SA) levels in cells, and diphenyliodonium chloride, which inhibits superoxide generation, completely abolished the repressive effect of Myco on nematode infection. Inhibitors of copper enzymes and the alternative cyanide-resistant respiration did not significantly alter resistance induction by Myco. When Myco-treated plants were subjected to moderate water stress and inoculated with nematodes, they retained numbers of developed individuals in the roots similar to those present in regularly watered plants, in contrast to what occurred in roots of untreated stressed plants that hosted very few individuals because of poor nutrient availability.

The 2′,4′-Dichloro-chalcone Inhibits the In Vitro Growth and Pathogenicity of Fusarium tricinctum and Trichothecium roseum by Activating Cyanide-Resistant Respiration

Chalcones are a class of flavonoids possessing antimicrobial properties and have potential for use as coatings of plant products for the control of postharvest diseases. The effects of 2′,4′-dichloro-chalcone on the in vitro growth and in vivo pathogenicity of Fusarium tricinctum and Trichothecium roseum were investigated. First, 1 µM of 2′,4′-dichloro-chalcone strongly inhibited the mycelial growth and conidial production of F. tricinctum (32.3%) and T. roseum (65.2%) in vitro. Meanwhile, the cell membrane permeability was increased by 25% and 22.5% and the accumulation of reactive oxygen species was increased by 41.7 and 65.4%, respectively, of F. tricinctum and T. roseum. This treatment also significantly inhibited the total respiration rate and activated the cyanide-resistant respiratory pathway in both pathogens. The expression level of AOX was enhanced in F. tricinctum and T. roseum by 52.76 and 39.13%, respectively. This treatment also significantly inhibited the expansion of potato dry rot from F. tricinctum (48.6%) and apple rot spot from T. roseum (36.2%). Therefore, 2′,4′-dichloro-chalcone has potential use as an alternative safety method in the control of postharvest diseases by F. tricinctum and T. roseum in agricultural practices.

Enhanced cyanide-resistant respiration as the predominant respiratory metabolic pathway in abnormal chilling injury behavior of postharvest papaya

An increasing number of studies have demonstrated that reactive oxygen species (ROS) play a crucial role in the chilling injury (CI) of postharvest fruit and vegetables. This is not only associated with the free radical scavenging system but is also intimately connected to the electron transport chain pathway. However, it remains unclear whether ROS is associated with the electron transport chain in the abnormal chilling behavior observed in postharvest papaya. As such, this study investigated the electron transport chain of papaya fruit stored at 1 ℃ and 6 ℃ and its connection to ROS. In comparison to storage at 6 ℃, storage at 1 ℃ suppressed the expression of CpCCO, and induced the upregulation of CpAOX expression in papaya fruit. Throughout the middle and late stages of storage, there was an increase in pyruvate content and ubiquinone reduction level. The increase had two effects: it inhibited cytochrome oxidase (CCO) activity and promoted alternative oxidase (AOX) activity, leading to a blocked cytochrome pathway and an increased proportion of cyanide-resistant respiratory pathways. Consequently, the cyanide-resistant respiratory pathway supplanted the cytochrome pathway as the primary electron transport pathway. This transition effectively curbed the accumulation of ROS, thereby diminishing the damage degree of fruit cell membrane, boosting chilling tolerance, and ultimately inhibiting the CI of papaya fruit, which led to the emergence of abnormal chilling injury.

The role of cyanoalanine synthase and alternative oxidase in promoting salt stress tolerance in Arabidopsis thaliana

BackgroundCyanide is a toxic chemical that inhibits cellular respiration. In plants, cyanide can be produced by themselves, especially under stressful conditions. Cyanoalanine synthase (CAS) is a key enzyme involved in plant cyanide detoxification. There are three genes encoding CAS in Arabidopsis thaliana, but the roles of these genes in the plant’s response to stress are less studied. In addition, it is known that alternative oxidase (AOX) mediates cyanide-resistant respiration, but the relationship between CAS and AOX in regulating the plant stress response remains largely unknown.ResultsHere, the effects of the overexpression or mutation of these three CAS genes on salt stress tolerance were investigated. The results showed that under normal conditions, the overexpression or mutation of the CAS genes had no significant effect on the seed germination and growth of Arabidopsis thaliana compared with wild type (WT). However, under 50, 100, and 200 mM NaCl conditions, the seeds overexpressing CAS genes showed stronger salt stress resistance, i.e., higher germination speed than WT seeds, especially those that overexpressed the CYS-C1 and CYS-D1 genes. In contrast, the seeds with CAS gene mutations exhibited salt sensitivity, and their germination ability and growth were significantly damaged by 100 and 200 mM NaCl. Importantly, this difference in salt stress resistance became more pronounced in CAS-OE, WT, and mutant seeds with increasing salt concentration. The CAS-OE seeds maintained higher respiration rates than the WT and CAS mutant seeds under salt stress conditions. The cyanide contents in CAS mutant seeds were approximately 3 times higher than those in WT seeds and more than 5 times higher than those in CAS-OE seeds. In comparison, plants overexpressing CYS-C1 had the fastest detoxification of cyanide and the best salt tolerance, followed by those overexpressing CYS-D1 and CYS-D2. Furthermore, less hydrogen sulfide (H2S) was observed in CAS-OE seedlings than in WT seedlings under long-term salt stress conditions. Nonetheless, the lack of AOX impaired CAS-OE-mediated plant salt stress resistance, suggesting that CAS and AOX interact to improve salt tolerance is essential. The results also showed that CAS and AOX contributed to the reduction in oxidative damage by helping maintain relatively high levels of antioxidant enzyme activity.ConclusionIn summary, the findings of the present study suggest that overexpression of Arabidopsis CAS family genes plays a positive role in salt stress tolerance and highlights the contribution of AOX to CAS-mediated plant salt resistance, mainly by reducing cyanide and H2S toxicity.

Gasotransmitter H2S accelerates seed germination via activating AOX mediated cyanide-resistant respiration pathway

Hydrogen sulfide (H2S) has been witnessed as a crucial gasotransmitter involving in various physiological processes in plants. H2S signaling has been reported to involve in regulating seed germination, but the underlying mechanism remains poorly understood. Here, we found that endogenous H2S production was activated in germinating Arabidopsis seeds, correlating with upregulated both the transcription and the activity of L-cysteine desulfhydrase (EC 4.4.1.28, LCD and DES1) responsible for H2S production. Moreover, seed germination could be significantly accelerated by exogenous NaHS (the H2S donor) fumigation and over-expressing DES1, while H2S-generation defective (lcd/des1) seeds exhibited decreased germination speed. We also confirmed that the alternative oxidase (AOX), a cyanide-insensitive terminal oxidase, can be stimulated by imbibition. Furthermore, exogenous H2S fumigation and over-expressing DES1 could significantly reinforced imbibition induced increase of both the AOX1A expression and AOX protein abundance, while this increase could be obviously weakened in lcd/des1. Additionally, exogenous H2S fumigation mediated post-translational modification to keep AOX in its reduced and active state, which might involve H2S induced improvement of the reduced GSH content and the cell reducing power. The promotive effect of H2S on germination was clearly impaired by inducing aox1a mutation, indicating that AOX acts downstream of H2S signaling to accelerate seed germination. Consequently, H2S signaling was activated during germination then acted as a trigger to induce AOX mediated cyanide-resistant respiration to accelerate seed germination. Our study correlates H2S signaling to cyanide-resistant respiration, providing evidence for more extensive studies of H2S signaling.

Reprint of: Intracellular Production of Superoxide Radical and of Hydrogen Peroxide by Redox Active Compounds

Several compounds have been found capable of diverting the electron flow in Escherichia coli and thus causing increased intracellular production of O2− and H2O2. One indication of this electron-shunting action was increased cyanide-resistant respiration and one cellular response was increased biosynthesis of the manganese-containing superoxide dismutase and of catalase. Blocking cytochrome oxidase with cyanide or azide increased the electron flow available for reduction of paraquat and presumably of the other exogenous compounds tested and thus increased their biological effects. Paraquat, pyocyanine, phenazine methosulfate, streptonigrin, juglone, menadione, plumbagin, methylene blue, and azure C were all effective in elevating intracellular production of O2− and H2O2. The effect of alloxan appeared paradoxical in that it increased cyanide-resistant respiration without significantly increasing the cell content of the manganese-superoxide dismutase and with only a small effect on the level of catalase. The alloxan effect on cyanide-resistant respiration was artifactual and was due to an oxygen-consuming reaction between alloxan and cyanide, rather than to a diversion of the intracellular electron flow. With paraquat as a representative electron-shunting compound, the increase in biosynthesis of the manganese-superoxide dismutase was prevented by inhibitors of transcription or of translation, but not by an inhibitor of replication. The increase in this enzyme activity, caused by paraquat and presumably by the other compounds, was thus due to de novo enzyme synthesis activated or derepressed at the level of transcription.

Cyanide resistant respiration and the alternative oxidase pathway: A journey from plants to mammals

In a large number of organisms covering all phyla, the mitochondrial respiratory chain harbors, in addition to the conventional elements, auxiliary proteins that confer adaptive metabolic plasticity. The alternative oxidase (AOX) represents one of the most studied auxiliary proteins, initially identified in plants. In contrast to the standard respiratory chain, the AOX mediates a thermogenic cyanide-resistant respiration; a phenomenon that has been of great interest for over 2 centuries in that energy is not conserved when electrons flow through it. Here we summarize centuries of studies starting from the early observations of thermogenicity in plants and the identification of cyanide resistant respiration, to the fascinating discovery of the AOX and its current applications in animals under normal and pathological conditions.

Xylose and yeasts: A story beyond xylitol production

Six different yeasts were used to study their metabolism of glucose and xylose, and mainly their capacity to produce ethanol and xylitol. The strains used were Candida guilliermondii, Debaryomyces hansenii, Saccharomyces cerevisiae, Kluyveromyces marxianus, Meyerozyma guilliermondii and Clavispora lusitaniae, four isolated from a rural mezcal fermentation facility. All of them produced ethanol when the substrate was glucose. When incubated in a medium containing xylose instead of glucose, only K. marxianus and M. guilliermondii were able to produce ethanol from xylose. On the other hand, all of them could produce some xylitol from xylose, but the most active in this regard were K. marxianus, M. guilliermondii, C. lusitaniae, and C. guilliermondii with the highest amount of xylitol produced. The capacity of all strains to take up glucose and xylose was also studied. Xylose, in different degrees, produced a redox imbalance in all yeasts. Respiration capacity was also studied with glucose or xylose, where C. guilliermondii, D. hansenii, K. marxianus and M. guilliermondii showed higher cyanide resistant respiration when grown in xylose. Neither xylose transport nor xylitol production were enhanced by an acidic environment (pH 4), which can be interpreted as the absence of a proton/sugar symporter mechanism for xylose transport, except for C. lusitaniae. The effects produced by xylose and their magnitude depend on the background of the studied yeast and the conditions in which these are studied.

Postharvest nitric oxide treatment induced the alternative oxidase pathway to enhance antioxidant capacity and chilling tolerance in peach fruit

Nitric oxide (NO) is an important regulator of plant response to cold stress. In this study, NO treatment delayed the development of chilling injury (CI), inhibited the increase in H2O2 content, O2− production rate and decrease in firmness of postharvest peach fruit. Meanwhile, through RNA-seq analysis, NO treatment up-regulated gene expression of PpG-6-PDH, Pp6-PGDH and PpAOX while it down-regulated the expression of PpGPI and PpHK, suggesting that the pentose phosphate respiratory pathway and cyanide-resistant respiratory pathway were promoted and the glycolysis pathway was inhibited. Furthermore, the PpAOX expression was consistent with the trend of PpPOD1/2 expression and H2O2 content, indicating that AOX may play a role in reducing oxidative damage of peach fruit by scavenging H2O2. Thus, it was concluded that NO treatment could induce the cyanide-resistant respiration pathway to enhance antioxidant ability and chilling tolerance in post-harvest peach fruit.

Effect of Anticancer Quinones on Reactive Oxygen Production by Adult Rat Heart Myocytes.

This study investigated the effect of anthracycline antibiotics, mitomycin C, and menadione on oxygen consumption and hydrogen peroxide production by intact, beating, rat heart myocytes. Doxorubicin produced a dose-dependent increase in the rate of cyanide-resistant respiration by beating myocytes. The anthracycline analogs 4-demethoxydaunorubicin, 4′-epidoxorubicin, 4′-deoxydoxorubicin, and menogaril, as well as the anticancer quinones mitomycin C and menadione, also significantly increased oxygen consumption by cardiac myocytes. However, 5-iminodaunorubicin (which has a substituted quinone group) and mitoxantrone (which is not easily reduced by flavin dehydrogenases) had no effect on cardiac respiration. Both catalase (43%) and acetylated cytochrome c (19%) significantly decreased oxygen consumption that had been stimulated by doxorubicin; furthermore, extracellular hydrogen peroxide production was increased from undetectable control levels to 1.30 ± 0.02 nmol/min/107 myocytes (n = 4, P < 0.01) in the presence of 400 μM doxorubicin. These experiments suggest that the anthracycline antibiotics and other anticancer quinones stimulate cardiac oxygen radical production in intact heart myocytes; such a free radical cascade could contribute to the cardiac toxicity of these drugs.

The role of cyanide-resistant respiration in Solanum tuberosum L. against high light stress.

Cyanide-resistant respiration in potato mitochondria is an important pathway for energy dissipation. It can be activated by high light; however, it is unclear what roles cyanide-resistant respiration plays in the response to high light stress in potato. We designed a CRISPR vector for the functional gene StAOX of the potato cyanide-resistant respiratory pathway. Agrobacterium tumefaciens GV3101 was transformed into potato. Hydrogen peroxide level, MDA content, antioxidant activity and cyanide-resistant respiratory capacity of potato leaves under high light stress were determined. Photosynthetic efficiency and chlorophyll content were determined. In addition, the operation of the malate-oxaloacetate shuttle route and transcription level of photorespiration-related enzymes were also examined. The results showed that two base substitutions occurred at the sequencing target site on leaves of the transformed potato. Accumulation of ROS and increased membrane lipid peroxidation were detected in the transformed potato leaves and lower photosynthetic efficiency was observed. The transcription level of the malate-oxaloacetate shuttle route and photorespiration-related enzymes also significantly increased. These results indicate that the cyanide-resistant respiration is an important physiological pathway in potato in response to high light stress. It also suggests that plant cyanide-resistant respiration is closely related to photosynthesis. This implies the unexplored importance of plant cyanide-resistant respiration in plant photosynthesis, energy conversion and carbon skeleton formation.

Reactive oxygen species induce cyanide-resistant respiration in potato infected by Erwinia carotovora subsp. Carotovora

Studies have shown that pathogenic bacteria infections induce the overproduction of reactive oxygen species (ROS) in plants. Cyanide-resistant respiration, an energy-dissipating pathway in plants, has also been induced by a pathogenic bacteria infection. However, it is unknown whether the induction of cyanide-resistant respiration under the pathogenic bacteria infection was caused by ROS. In this study, two pathogenic Erwinia strains were used to infect potato tuber, and membrane lipid peroxidation levels and the cyanide-resistant respiration capacity were determined. In addition, StAOX expression and regulation by ROS in potato tuber were analyzed. Moreover, the role of the Ca2+ pathway in regulating cyanide-resistant respiration was determined. The results showed that ROS induced cyanide-resistant respiration in potato tuber infected by Erwinia. Cyanide-resistant respiration inhibited the production of H2O2. Intracellular Ca2+ regulated the expression of calcium-dependent protein kinase (StCDPK1, StCDPK4, and StCDPK5) in potato, which indirectly controlled intracellular ROS levels. These results indicate that Ca2+ metabolism is involved in ROS-induced cyanide-resistant respiration.

Mechanisms of Anthracycline-Enhanced Reactive Oxygen Metabolism in Tumor Cells.

In this investigation, we examined the effect of anthracycline antibiotics on oxygen radical metabolism in Ehrlich tumor cells. In tumor microsomes and nuclei, doxorubicin increased superoxide anion production in a dose-dependent fashion that appeared to follow saturation kinetics; the apparent Km and Vmax for superoxide formation by these organelles was 124.9 μM and 22.6 nmol/min/mg, and 103.4 μM and 4.8 nmol/min/mg, respectively. In both tumor microsomes and nuclei, superoxide formation required NADPH as a cofactor, was accompanied by the formation of hydrogen peroxide, and resulted from the transfer of electrons from NADPH to the doxorubicin quinone by NADPH:cytochrome P-450 reductase (NADPH:ferricytochrome oxidoreductase, EC 1.6.2.4). Anthracycline antibiotics also significantly enhanced superoxide anion production by tumor mitochondria with an apparent Km and Vmax for doxorubicin of 123.2 μM and 14.7 nmol/min/mg. However, drug-stimulated superoxide production by mitochondria required NADH and was increased by rotenone, suggesting that the proximal portion of the electron transport chain in tumor cells was responsible for reduction of the doxorubicin quinone at this site. The net rate of drug-related oxygen radical production was also determined for intact Ehrlich tumor cells; in this system, treatment with doxorubicin produced a dose-related increase in cyanide-resistant respiration that was enhanced by changes in intracellular reducing equivalents. Finally, we found that in the presence of iron, treatment with doxorubicin significantly increased the production of formaldehyde from dimethyl sulfoxide, an indication that the hydroxyl radical could be produced by intact tumor cells following anthracycline exposure. These experiments suggest that the anthracycline antibiotics are capable of significantly enhancing oxygen radical metabolism in Ehrlich tumor cells at multiple intracellular sites by reactions that could contribute to the cytotoxicity of this class of drugs.

Salicylic acid and cold priming induce late-spring freezing tolerance by maintaining cellular redox homeostasis and protecting photosynthetic apparatus in wheat

An increasing number of studies provide evidence that priming (pre-exposure of plants to moderate stress or chemical stimulus) can confer plant tolerance to a later occurring severe stress. The main objective of this study was to explore and compare the physiological mechanisms of salicylic acid (SA) and cold priming to enhance freezing tolerance. Wheat plants were firstly primed with SA (100 μM) or cold temperature (day/night temperature of 6 °C/2 °C), and then grown without any treatment for 8 days, and subsequently subjected to a freezing stress (day/night temperature of 2 °C/0 °C on the first day and − 2 °C/− 4 °C on the second day) at the jointing stage. The results showed that primed plants up-regulated the expression level of WRKY gene (WRKY19), heat shock transcription factor (HSF3), mitochondrial alternative oxidase (AOX1a), and heat shock protein (HSP70) under freezing stress, which contribute to increase of antioxidant capacity and protection of photosystem in parallel with lower malonaldehyde content, superoxide radical production and higher photochemistry efficiency of photosystem II under freezing stress as compared with non-primed plants. Furthermore, primed plants had a better photosynthesis performance and higher biomass production during the recovery period, and higher grain yield at maturity as compared with non-primed plants. Collectively, these results indicated that SA and cold priming effectively upregulated the expression of cold-responsive genes under freezing stress, resulting in increased antioxidant activity and cyanide-resistant respiration capacity and molecular chaperones level, maintaining cellular redox homeostasis and protecting photosynthetic apparatus, thereby conferring tolerance to freezing stress in wheat plants.

Overexpression of BnaAOX1b Confers Tolerance to Osmotic and Salt Stress in Rapeseed.

Alternative oxidases (AOXs) are the terminal oxidase in the cyanide-resistant respiration pathway in plant mitochondria, which play an important role in abiotic stress and are proposed as a functional marker for high tolerant breeding. In this study, ten AOX genes (BnaAOXs) were identified, and CysI and CysII of AOX isoforms were highly conserved in rapeseed. Among them, Bna.AOX1b was mainly expressed in the ovule and displayed varying expression between rapeseed cultivars which showed different salt resistance in seed germination. We identified its mitochondrial localization of this gene. To investigate the function of BnaAOX1b in rapeseed, transgenic rapeseed lines with overexpressed BnaAOX1b were created and seed germination and seedling establishment assays were performed under osmotic, salt, and ABA treatment. The results indicated that overexpression of BnaAOX1b significantly improved seed germination under osmotic and salt stress and weakened ABA sensitivity. In addition, post-germination seedling growth was improved under high salt condition, but showed hypersensitivity to ABA. RNA-sequencing analysis indicated that the genes involved in electron transport or energy pathway were induced and a number of gene responses to salt stress and ABA were regulated in Bna.AOX1b overexpressing seeds. Taken together, our results imply that Bna.AOX1b confers tolerance to osmotic and salt stress in terms of seed germination and seedling establishment by regulating stress responsive genes and the response to ABA, and could be utilized as a candidate gene in transgenic breeding.

High-affinity transport, cyanide-resistant respiration, and ethanol production under aerobiosis underlying efficient high glycerol consumption by Wickerhamomyces anomalus

Wickerhamomyces anomalus strain LBCM1105 was originally isolated from the wort of cachaça (the Brazilian fermented sugarcane juice-derived Brazilian spirit) and has been shown to grow exceptionally well at high amounts of glycerol. This paramount residue from the biodiesel industry is a promising cheap carbon source for yeast biotechnology. The assessment of the physiological traits underlying the W. anomalus glycerol consumption ability in opposition to Saccharomyces cerevisiae is presented. A new WaStl1 concentrative glycerol-H+ symporter with twice the affinity of S. cerevisiae was identified. As in this yeast, WaSTL1 is repressed by glucose and derepressed/induced by glycerol but much more highly expressed. Moreover, LBCM1105 aerobically growing on glycerol was found to produce ethanol, providing a redox escape to compensate the redox imbalance at the level of cyanide-resistant respiration (CRR) and glycerol 3P shuttle. This work is critical for understanding the utilization of glycerol by non-Saccharomyces yeasts being indispensable to consider their industrial application feeding on biodiesel residue.

Alternative oxidase functions in the excess excitation energy-induced resistance to pathogen infection

Although excess excitation energy (EEE) can damage the photosynthetic apparatus and deregulate many cellular processes, some studies have reported that EEE can be used by plants to optimize the resistance to pathogen infection. Here, we investigated whether the EEE-induced resistance to pathogen infection might be mediated by mitochondrial alternative oxidase (AOX). The present work showed that exposure of Arabidopsis (Arabidopsis thaliana) leaves to short-term excess light or treatment of Arabidopsis leaves with the electron transport inhibitor, DBMIB (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone), restricted the growth of virulent biotrophic bacteria, Pseudomonas syringae pv tomato (Pst) DC3000. Exposure to short-term excess light or DBMIB treatment also enhanced the level of the capacity of the cyanide-resistant respiration of the infected leaves. The lack of AOX1a gene in the AtAOX1a anti-sense line attenuated the excess light- or DBMIB-induced resistance toward Pst DC3000. These results indicate that AOX may play a role in regulating the EEE-induced resistance to virulent pathogen infection.

Effect of inhibitors of two isoprenoid biosynthetic pathways on physiological and biosynthetic characteristics of Dioscorea deltoidea cell suspension culture

The effect of phosmidomycin and mevinolin, which inhibit MEP and MVA isoprenoid biosynthetic pathways, respectively, on the growth (biomass accumulation, growth index, specific growth rate), physiological (respiration intensity and ratio between the cytochrome and cyanide-resistant respiration types), and biosynthetic (steroid glycoside biosynthesis) characteristics of the cell suspension culture of Dioscorea deltoidea Wall. has been studied. Both inhibitors decreased the growth index of a cell culture by 20–25%, but their influence on the cell growth dynamics was different. Mevinolin treatment reduced the maximum biomass accumulation by 20% as against the control but did not change the character of a growth curve. Phosmidomycin treatment caused a significant growth delay (a 6-day lag phase) followed by a short active growth period (μ = 0.29 days-1). Treatment of cells with inhibitors did not significantly influence on their total oxygen uptake rate, whose average value at different growth phases was equal to 100–200 mg О2/g of dry cell weight per hour, but cardinally changed characteristics of respiratory metabolism. The inhibitors increased the activity of a cyanide-resistant respiration and decreased the intensity of a cytochrome respiration; each inhibitor worked in its specific manner. In the case of mevinolin, the maximum level of cyanide-resistant respiration (70% of the total respiration intensity) was observed at initial growth phases; during the further cell culture growth, this value gradually reduced to 6–8%. Phosmidomycin treatment caused a reverse dynamics: at the initial growth phases, the contribution of cyanide-resistant respiration was 30%, whereas at the stationary and degradation phases it increased to 50–60%. The treatment of cells with phosmidomycin resulted in a double increase in the content of furostanol glycosides at the stationary growth phase, whereas the use of mevinolin-containing medium reduced the content of these compounds as against the control. Inhibitors also influenced on the ratio of individual glycosides, such as protodioscin, deltoside, and their 26-S-isomers. The obtained results confirm the hypothesis of a possible intermediate exchange between the plastid (MEP) and cytosolic (MVA) isoprenoid biosynthetic pathways; this exchange is directed mainly from the plastids to the cytosol.