Peroxisomal Catalase Research Articles

The role of peroxisomes in xylose alcoholic fermentation in the engineered Saccharomyces cerevisiae.

Xylose is a second-most abounded sugar after glucose in lignocellulosic hydrolysates and should be efficiently fermented for economically viable second-generation ethanol production. Despite significant progress in metabolic and evolutionary engineering, xylose fermentation rate of recombinant Saccharomyces cerevisiae remains lower than that for glucose. Our recent study demonstrated that peroxisome-deficient cells of yeast Ogataea polymorpha showed a decrease in ethanol production from xylose. In this work, we have studied the role of peroxisomes in xylose alcoholic fermentation in the engineered xylose-utilizing strain of S. cerevisiae. It was shown that peroxisome-less pex3Δ mutant possessed 1.5-fold decrease of ethanol production from xylose. We hypothesized that peroxisomal catalase Cta1 may have importance for hydrogen peroxide, the important component of reactive oxygen species, detoxification during xylose alcoholic fermentation. It was clearly shown that CTA1 deletion impaired ethanol production from xylose. It was found that enhancing the peroxisome population by modulation the peroxisomal biogenesis by overexpression of PEX34 activates xylose alcoholic fermentation.

Reactive oxygen species dosage in Arabidopsis chloroplasts can improve resistance towards Colletotrichum higginsianum by the induction of WRKY33.

Arabidopsis plants overexpressing glycolate oxidase in chloroplasts (GO5) and loss-of-function mutants of the major peroxisomal catalase isoform, cat2-2, produce increased hydrogen peroxide (H2 O2 ) amounts from the respective organelles when subjected to photorespiratory conditions like increased light intensity. Here, we have investigated if and how the signaling processes triggered by H2 O2 production in response to shifts in environmental conditions and the concomitant induction of indole phytoalexin biosynthesis in GO5 affect susceptibility towards the hemibiotrophic fungus Colletotrichum higginsianum. Combining histological, biochemical, and molecular assays, we found that the accumulation of the phytoalexin camalexin was comparable between GO genotypes and cat2-2 in the absence of pathogen. Compared with wild-type, GO5 showed improved resistance after light-shift-mediated production of H2 O2 , whereas cat2-2 became more susceptible and allowed significantly more pathogen entry. Unlike GO5, cat2-2 suffered from severe oxidative stress after light shifts, as indicated by glutathione pool size and oxidation state. We discuss a connection between elevated oxidative stress and dampened induction of salicylic acid mediated defense in cat2-2. Genetic analyses demonstrated that induced resistance of GO5 is dependent on WRKY33, but not on camalexin production. We propose that indole carbonyl nitriles might play a role in defense against C.higginsianum.

The protein expression profile and transcriptome characterization of Pichia caribbica induced by ascorbic acid under the oxidative stress

Ascorbic acid (vitamin C, Vc) is a well-known antioxidant, which can eliminate reactive oxygen species (ROS) in order to protect yeasts subjected oxidative stress. In our previous research, Pichia caribbica, one of the antagonistic yeasts showed an activity against postharvest diseases of apples, and Vc enhanced the tolerance to oxidative stress of P. caribbica, and improved its biocontrol efficacy to postharvest blue mold decay of apples. However, the mechanisms, especially the molecular mechanisms of the tolerance of P. caribbica improved by Vc under oxidative stress are not sufficiently clear. The purpose of this research was to investigate the protein expression profile and transcriptome characterization of P. caribbica induced by Vc under oxidative stress. The proteomics results showed that there were 31 differentially expressed proteins (DEPs), among them 25 DEPs were up-regulated and 6 DEPs were down-regulated. These up-regulated DEPs were associated with the energy metabolism and glucose metabolism, including fructose – bisphosphate aldolase, malate dehydrogenase, peroxisomal catalase and so on. Transcriptomics analysis showed that 68 genes were differentially expressed, among them 38 genes were up-regulated and 30 genes were down-regulated. These up-regulated genes were found to be related to cell wall, energy synthesis, polysaccharides hydrolysis and antioxidant activity.

Impaired Peroxisomal Import Triggers a Peroxisomal Retrograde Signaling

Distinct retrograde signaling pathways have been identified for several cellular organelles. These pathways are important to maintain the function of these organelles in response to organelle-specific stress. Using Caenorhabditis elegans, we show for the first time that such a retrograde signaling also exists for peroxisomes. Specifically, peroxisomal import stress caused by the knock-down of the peroxisomal matrix protein import receptor prx-5/PEX5 triggers the NHR-49/PPARα dependent transcriptional up-regulation of the peroxisomal Lon protease lonp-2/LONP2 and the peroxisomal catalase ctl-2/CAT. We also show that impairment of peroxisomal beta-oxidation activates this response. We propose that a reduced import of peroxisomal beta-oxidation enzymes and the resulting change in fatty acid composition is the signal that activates this response. Proteomic analysis revealed that peroxisomal import stress induces the compensatory up-regulation of peroxisomal beta-oxidation enzymes. We, therefore, propose that the peroxisomal retrograde signaling participates in the maintenance of peroxisomal beta-oxidation in response to peroxisomal import stress.

Functional insight into the glycosomal peroxiredoxin of Leishmania

Glycosomes of trypanosomatids are peroxisome-like organelles comprising unique metabolic features, among which the lack of the hallmark peroxisomal enzyme catalase. The absence of this highly efficient peroxidase from glycosomes is presumably compensated by other antioxidants, peroxidases of the peroxiredoxin (PRX) family being the most promising candidates for this function. Here, we follow on this premise and investigate the product of a Leishmania infantum gene coding for a putative glycosomal PRX (LigPRX). First, we demonstrate that LigPRX localizes to glycosomes, resorting to indirect immunofluorescence analysis. Second, we prove that purified recombinant LigPRX is an active peroxidase in vitro. Third, we generate viable LigPRX-depleted L. infantum promastigotes by classical homologous recombination. Surprisingly, phenotypic analysis of these knockout parasites revealed that promastigote survival, replication, and protection from oxidative and nitrosative insults can proceed normally in the absence of LigPRX. Noticeably, we also witness that LigPRX-depleted parasites can infect and thrive in mice to the same extent as wild type parasites. Overall, by disclosing the dispensable character of the glycosomal peroxiredoxin in L. infantum, this work excludes this enzyme from being a key component of the glycosomal hydroperoxide metabolism and contemplates alternative players for this function.

Sweet Pepper (Capsicum annuum L.) Fruits Contain an Atypical Peroxisomal Catalase That is Modulated by Reactive Oxygen and Nitrogen Species.

During the ripening of sweet pepper (Capsicum annuum L.) fruits, in a genetically controlled scenario, enormous metabolic changes occur that affect the physiology of most cell compartments. Peroxisomal catalase gene expression decreases after pepper fruit ripening, while the enzyme is also susceptible to undergo post-translational modifications (nitration, S-nitrosation, and oxidation) promoted by reactive oxygen and nitrogen species (ROS/RNS). Unlike most plant catalases, the pepper fruit enzyme acts as a homodimer, with an atypical native molecular mass of 125 to 135 kDa and an isoelectric point of 7.4, which is higher than that of most plant catalases. These data suggest that ROS/RNS could be essential to modulate the role of catalase in maintaining basic cellular peroxisomal functions during pepper fruit ripening when nitro-oxidative stress occurs. Using catalase from bovine liver as a model and biotin-switch labeling, in-gel trypsin digestion, and nanoliquid chromatography coupled with mass spectrometry, it was found that Cys377 from the bovine enzyme could potentially undergo S-nitrosation. To our knowledge, this is the first report of a cysteine residue from catalase that can be post-translationally modified by S-nitrosation, which makes it especially important to find the target points where the enzyme can be modulated under either physiological or adverse conditions.

Pomegranate (Punica granatum L.) Fruits: Characterization of the Main Enzymatic Antioxidants (Peroxisomal Catalase and SOD Isozymes) and the NADPH-Regenerating System

Pomegranate (Punica granatum L.) is a common edible fruit. Its juice can be used as a source of antioxidative compounds, primarily polyphenols and vitamin C, in addition to other vitamins and minerals. Nevertheless, little is still known about how the enzymatic machinery, mainly that related to oxidative metabolism, is influenced by the genotype and the environmental and climate conditions where pomegranate plants grow. In this work, seeds and juices from two pomegranate varieties (Valenciana and Mollar) grown in two different Spanish locations were assayed. Both varieties showed clear differences in their respective polypeptide profiles. The analysis of the isoenzymatic superoxide dismutase (SOD) activity pattern displayed one Mn-SOD and five CuZn-SODs (I–V) whose abundances depended on the variety. Furthermore, by immunoblot assays, at least one additional Fe-SOD with a subunit size of about 23 kDa was also detected in both varieties. Besides this, the presence of the H2O2-scavenging peroxisomal catalase in seeds and juice indicates that an active metabolism of reactive oxygen species (ROS) takes place in this fruit, but the two pomegranate varieties showed opposite activity profiles. The activities of the main NADPH-regenerating enzymes, including glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphlogluconate dehydrogenase (6PGDH), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), and NADP-dependent malic enzyme (NADP-ME), were studied in the same plant materials, and they behaved differently depending on the genotype. Finally, our data demonstrate the presence of two specific enzymes of the peroxisomal glyoxylate cycle, malate synthase (MS) and isocitrate lyase (ICL). These enzymes participate in oilseeds by channeling the lipid catabolism to the carbohydrate synthesis for further use in seed germination and early seedling growth. The results obtained in this work indicate that a similar mechanism to that reported in oilseeds may also operate in pomegranate.

Peroxisomal catalases from the yeasts Pichia pastoris and Kluyveromyces lactis as models for oxidative damage in higher eukaryotes

Catalases are among the main scavengers of reactive oxygen species (ROS) present in the peroxisome, thereby preventing oxidative cellular and tissular damage. In human, multiple diseases are associated with malfunction of these organelles, which causes accumulation of ROS species and consequently the inefficient detoxification of cells. Despite intense research, much remains to be clarified about the precise molecular role of catalase in cellular homeostasis. Yeast peroxisomes and their peroxisomal catalases have been used as eukaryotic models for oxidative metabolism, ROS generation and detoxification, and associated pathologies. In order to provide reliable models for oxidative metabolism research, we have determined the high-resolution crystal structures of peroxisomal catalase from two important biotechnology and basic biology yeast models, Pichia pastoris and Kluyveromyces lactis. We have performed an extensive functional, biochemical and stability characterization of both enzymes in order to establish their differential activity profiles. Furthermore, we have analyzed the role of the peroxisomal catalase under study in the survival of yeast to oxidative burst challenges combining methanol, water peroxide, and sodium chloride. Interestingly, whereas catalase activity was induced 200-fold upon challenging the methylotrophic P. pastoris cells with methanol, the increase in catalase activity in the non-methylotrophic K. lactis was only moderate. The inhibitory effect of sodium azide and β-mercaptoethanol over both catalases was analyzed, establishing IC50 values for both compounds that are consistent with an elevated resistance of both enzymes toward these inhibitors. Structural comparison of these two novel catalase structures allows us to rationalize the differential susceptibility to inhibitors and oxidative bursts. The inherent worth and validity of the P. pastoris and K. lactis yeast models for oxidative damage will be strengthened by the availability of reliable structural-functional information on these enzymes, which are central to our understanding of peroxisomal response toward oxidative stress.

Localization and expression analysis of a novel catalase from Triticum monococcum TmCAT1 involved in response to different environmental stresses

Catalase proteins play a crucial role in detoxifying hydrogen peroxide, generated during plant growth, and in response to various environmental stresses. Despite their importance, little is known about their localization and expression in wheat. In this study, we identified and characterized a novel peroxisomal catalase gene from Triticum monococcum, designated as TmCAT1. Phylogenetic analysis revealed that TmCAT1 shared high identity with TdCAT1 and other plant catalases belonging to subfamily 1. We predicted the 3D structure model and the oligomerization arrangement of TmCAT1. Besides, we displayed an arrangement in asymmetric unit, which involved interactions including, mainly, residues from N-terminal domain. Interestingly, sequence analysis indicated that TmCAT1, like TdCAT1, had the peroxisomal targeting signal (PTS1) around its C-terminus. Transient expression of TmCAT1-GFP and TdCAT1-GFP in tobacco leaves revealed that the two fused proteins are targeted into peroxisomes. However, the truncated forms lacking the tripeptide QKL remained in the cytosol. Concerning the expression profile analysis, TmCAT1 is expressed especially in leaves in normal condition. On the other hand, it is up-regulated by different stress incorporating salt, osmotic, oxidative, heavy metal and hormones stresses. Functional analysis by heterologous expression in yeast cells showed that TmCAT1 improved tolerance to multiple abiotic stresses. The presence of important cis-regulatory elements in the promoter region of TmCAT1 strongly reinforces the interest of this gene in plant adaptation to various stresses.

Polyphenol-enriched azuki bean (Vina angularis) extract reduces the oxidative stress and prevents DNA oxidation in the hearts of streptozotocin-induced early diabetic rats

We examined the changes in the heart of rats at the early stages of streptozotocin (STZ)-induced diabetes, and whether azuki bean extract (ABE) could influence these changes. The experimental diabetic rats received 0 or 40 mg/kg of ABE orally for 4 weeks, whereas the control group rats received distilled water. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) and expression of proteins associated with peroxisomal FA β-oxidation as well as oxidative stress markers were examined. The levels of peroxisomal ACOX1 and catalase of the diabetic groups were significantly higher than those in the control group. The levels of p62, phosphorylated-p62 (p-p62) and HO-1 in the STZ group were significantly higher than those in the control group, and the levels of p-p62, HO-1, and 8-OHdG were significantly lower by ABE administration. The STZ-induced early diabetes increases the levels of proteins related to peroxisomal FA β-oxidation and oxidative stress markers in hearts. ABE protects diabetic hearts from oxidative damage.

Trehalose increases the oxidative stress tolerance and biocontrol efficacy of Candida oleophila in the microenvironment of pear wounds

Harvested fruit tissues produce reactive oxygen species (ROS) in response to wounding. ROS production is further elevated when biocontrol yeasts are introduced into the wounds, where they act as a bio-elicitor and this results in an environment in which the biocontrol yeast is subject to oxidative stress. In the present study, the effect of trehalose, a non-reducing disaccharide and a major reserve carbohydrate, on the level of oxidative stress tolerance of the biocontrol yeast Candida oleophila was examined in wounded pear fruits. Results indicated that the level of trehalose in C. oleophila yeast cells increased when they were cultured in a trehalose-containing medium. Exposure to a trehalose-medium and the increase in internal trehalose improved the adaptation of C. oleophila to the oxidative environment present in pear fruit wounds. Trehalose-treated cells exhibited a lower accumulation of ROS and mitochondrial impairment compared to untreated, control cells when they were introduced into wounded pear fruit. The trehalose treatment up-regulated the expression of antioxidant genes, including peroxisomal catalase and thioredoxin reductase, in yeast cells. Trehalose-treated yeast also exhibited a faster growth rate in pear wounds and greater biocontrol efficacy against blue mold (Penicillium expansum) and Alternaria rot (Alternaria alternata) than untreated, control yeast. These results support the premise that trehalose improves the biocontrol efficacy of C. oleophila via the activation of antioxidant defense systems which support a faster rate of growth of the yeast in wounds of pear fruit.

Role of peroxisome proliferator-activated receptor alpha (PPARα) and PPARα-mediated species differences in triclosan-induced liver toxicity.

Triclosan, a widely used broad spectrum anti-bacterial agent, is hepatotoxic in rodents and exhibits differential effects on mouse and human peroxisome proliferator-activated receptor alpha (PPARα) in vitro; however, the mechanism underlying triclosan-induced liver toxicity has not been elucidated. This study examined the role of mouse and human PPARα in triclosan-induced liver toxicity by comparing the effects between wild-type and PPARα-humanized mice. Female mice of each genotype received dermal applications of 0, 58, or 125mg triclosan/kg body weight daily for 13 weeks. Following the treatment, triclosan caused an increase in liver weight and relative liver weight only in wild-type mice. The expression levels of PPARα target genes cytochrome P450 4A and acyl-coenzyme A oxidase 1 were increased in livers of both wild-type and PPARα-humanized mice, indicating that triclosanactivated PPARα. Triclosan also elevated the expression levels of peroxisomal membrane protein PMP70 and catalase in the livers of both genotypes, suggesting that triclosan promoted the production of hepatocyte peroxisomes. There was an enhanced expression of cyclin D1, c-myc, proliferating cell nuclear antigen, and Ki67, and a higher percentage of BrdU-labeled hepatocytes in wild-type mice, but not in PPARα-humanized mice, demonstrating triclosan-activated PPARα had differential effects on the hepatocyte proliferation. These findings imply that the differential effects of triclosan-activated PPARα on cell proliferation may play a role in the species differences in triclosan-induced liver toxicity.

Intracellular organelles in health and kidney disease

Subcellular organelles consist of smaller substructures called supramolecular assemblies and these in turn consist of macromolecules. Various subcellular organelles have critical functions that consist of genetic disorders of organelle biogenesis and several metabolic disturbances that occur during non-genetic diseases e.g. infection, intoxication and drug treatments. Mitochondrial damage can cause renal dysfunction as ischemic acute renal injury, chronic kidney disease progression. Moreover, mitochondrial dysfunction is an early event in aldosterone-induced podocyte injury and cardiovascular disease due to oxidative stress in chronic kidney disease. Elevated production of reactive oxygen species could be able to activate NLRP3 inflammasome representing new deregulated biological machinery and a novel therapeutic target in hemodialysis patients. Peroxisomes are actively involved in apoptosis and inflammation, innate immunity, aging and in the pathogenesis of age related diseases, such as diabetes mellitus and cancer. Peroxisomal catalase causes alterations of mitochondrial membrane proteins and stimulates generation of mitochondrial reactive oxygen species. High concentrations of hydrogen peroxide exacerbate organelles and cellular aging. The importance of proper peroxisomal function for the biosynthesis of bile acids has been firmly established. Endoplasmic reticulum stress-induced pathological diseases in kidney cause glomerular injury and tubulointerstitial injury. Furthermore, there is a link between oxidative stress and inflammations in pathological states are associated with endoplasmic reticulum stress. Proteinuria and hyperglycemia in diabetic nephropathy may induce endoplasmic reticulum stress in tubular cells of the kidney. Due to the accumulation in the proximal tubule lysosomes, impaired function of these organelles may be an important mechanism leading to proximal tubular toxicity.

Mechanisms of glacial-to-future atmospheric CO2 effects on plant immunity.

Summary The impacts of rising atmospheric CO2 concentrations on plant disease have received increasing attention, but with little consensus emerging on the direct mechanisms by which CO2 shapes plant immunity. Furthermore, the impact of sub‐ambient CO 2 concentrations, which plants have experienced repeatedly over the past 800 000 yr, has been largely overlooked.A combination of gene expression analysis, phenotypic characterisation of mutants and mass spectrometry‐based metabolic profiling was used to determine development‐independent effects of sub‐ambient CO 2 (sa CO 2) and elevated CO 2 (eCO 2) on Arabidopsis immunity.Resistance to the necrotrophic Plectosphaerella cucumerina (Pc) was repressed at sa CO 2 and enhanced at eCO 2. This CO 2‐dependent resistance was associated with priming of jasmonic acid (JA)‐dependent gene expression and required intact JA biosynthesis and signalling. Resistance to the biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa) increased at both eCO 2 and sa CO 2. Although eCO 2 primed salicylic acid (SA)‐dependent gene expression, mutations affecting SA signalling only partially suppressed Hpa resistance at eCO 2, suggesting additional mechanisms are involved. Induced production of intracellular reactive oxygen species (ROS) at sa CO 2 corresponded to a loss of resistance in glycolate oxidase mutants and increased transcription of the peroxisomal catalase gene CAT2, unveiling a mechanism by which photorespiration‐derived ROS determined Hpa resistance at saCO2.By separating indirect developmental impacts from direct immunological effects, we uncover distinct mechanisms by which CO 2 shapes plant immunity and discuss their evolutionary significance.

Cell Death or Survival Against Oxidative Stress.

Peroxisomes contain anabolic and catabolic enzymes including oxidases that produce hydrogen peroxide as a by-product. Peroxisomes also contain catalase to metabolize hydrogen peroxide. It has been recognized that catalase is localized to cytosol in addition to peroxisomes. A recent study has revealed that loss of VDAC2 shifts localization of BAK, a pro-apoptotic member of Bcl-2 family, from mitochondria to peroxisomes and cytosol, thereby leading to release of peroxisomal matrix proteins including catalase to the cytosol. A subset of BAK is localized to peroxisomes even in wild-type cells, regulating peroxisomal membrane permeability and catalase localization. The cytosolic catalase potentially acts as an antioxidant to eliminate extra-peroxisomal hydrogen peroxide.

Proteomic changes in response to low-light stress during cotton fiber elongation

Numerous studies have illustrated that low light is one of the major abiotic stresses limiting cotton (Gossypium hirsutum L.) fiber length, but studies addressing molecular mechanisms contributing to reduced fiber growth under low light are lacking. To investigate the molecular mechanisms of cotton fiber elongation in response to low light, an experiment of low light caused by shading was conducted with cotton cultivar NuCOTN 33B. The results showed that low light resulted in shorter fiber length. Proteomic analysis of four developmental stages (5, 10, 15 and 20 days post-anthesis) showed that 49 proteins were significantly responsive to low light. 39 differentially expressed proteins that included some known as well as some novel low-light stress-responsive proteins were identified. These differentially expressed proteins were involved in signal transduction, carbohydrate/energy metabolism, cell wall component synthesis, protein metabolism, cytoskeleton, nitrogen metabolism and stress responses. The results also showed that the decrease in fiber length might be because the levels of signal-related protein (phospholipase D), cytoskeletal proteins (two annexins isoforms), cell wall component-related proteins (sucrose synthase, UDP-d-glucuronic acid 4-epimerase and rhamnose synthase), carbohydrate metabolism-proteins (phosphofructokinase, dihydrolipoamide dehydrogenase, vacuolar H+-ATPase catalytic subunit, malate dehydrogenase and isocitrate dehydrogenase), and stress-related proteins (peroxisomal catalase, short chain alcohol dehydrogenase) were decreased under low light.

The levels of peroxisomal catalase protein and activity modulate the onset of cell death in tobacco BY-2 cells via reactive oxygen species levels and autophagy.

In plant cells, peroxisomes participate in the metabolism of reactive oxygen species (ROS). One of the major regulators of cellular ROS levels - catalase (CAT) - occurs exclusively in peroxisomes. CAT activity is required for immunity-triggered autophagic programmed cell death (PCD). Autophagy has been recently demonstrated to represent a route for degradation of peroxisomes in plant cells. In the present study, the dynamics of the cellular peroxisome pool in tobacco BY-2 cell suspension cultures were used to analyse the effects of inhibition of basal autophagy with special attention to CAT activity. Numbers of peroxisomes per cell, levels of CAT protein and activity, cell viability, ROS levels and expression levels of genes encoding components of antioxidant system were analysed upon application of 3-methyladenine (3-MA), an inhibitor of autophagy, and/or aminotriazole (AT), an inhibitor of CAT. When applied separately, 3-MA and AT led to an increase in cell death, but this effect was attenuated by their simultaneous application. The obtained data suggest that both the levels of CAT protein in peroxisomes as well as CAT activity modulate the onset of cell death in tobacco BY-2 cells via ROS levels and autophagy.

Mechanisms of glycine betaine enhancing oxidative stress tolerance and biocontrol efficacy of Pichia caribbica against blue mold on apples

The effects of glycine betaine (GB) treatment on biocontrol efficacy of Pichia caribbica against blue mold decay of apples and oxidative stress tolerance were investigated. To reveal the mechanism of GB enhancing oxidative stress tolerance and biological control efficacy of P. caribbica, the accumulation of intracellular reactive oxygen species (ROS), protein carbonylation, lipid oxidation and differentially expressed proteins were analyzed. Compared with P. caribbica treated without GB, P. caribbica treated with GB exhibited enhanced biocontrol activity (disease incidence decreased from 48.81% to 32.14%) and oxidative stress tolerance when exposed to oxidative stress (survival ability increased from 60.1% to 77.7%), as well as improved growth in wounds of apples. GB treatment reduced accumulation of ROS, levels of oxidative damage to cellular proteins and lipids in P. caribbica. The proteomic analysis showed that 51 proteins were differentially expressed in P. caribbica after GB treatment, 33 proteins of which were successfully identified by MALDI-TOF-MS and database Queries. The up-regulation of some identified proteins related to carbohydrate transport and metabolism (enolase, pyruvate kinase and isocitrate lyase), stress response and regulation (peroxisomal catalase and Serine/threonine protein kinase) were involved in the enhancement of oxidative stress tolerance and biocontrol efficacy of P. caribbica.

Casein phosphopeptides and CaCl2 increase penicillin production and cause an increment in microbody/peroxisome proteins in Penicillium chrysogenum

Transport of penicillin intermediates and penicillin secretion are still poorly characterized in Penicillium chrysogenum (re-identified as Penicillium rubens). Calcium (Ca2+) plays an important role in the metabolism of filamentous fungi, and casein phosphopeptides (CPP) are involved in Ca2+ internalization. In this study we observe that the effect of CaCl2 and CPP is additive and promotes an increase in penicillin production of up to 10–12 fold. Combination of CaCl2 and CPP greatly promotes expression of the three penicillin biosynthetic genes. Comparative proteomic analysis by 2D-DIGE, identified 39 proteins differentially represented in P. chrysogenum Wisconsin 54-1255 after CPP/CaCl2 addition. The most interesting group of overrepresented proteins were a peroxisomal catalase, three proteins of the methylcitrate cycle, two aminotransferases and cystationine β-synthase, which are directly or indirectly related to the formation of penicillin amino acid precursors. Importantly, two of the enzymes of the penicillin pathway (isopenicillin N synthase and isopenicillin N acyltransferase) are clearly induced after CPP/CaCl2 addition. Most of these overrepresented proteins are either authentic peroxisomal proteins or microbody-associated proteins. This evidence suggests that addition of CPP/CaCl2 promotes the formation of penicillin precursors and the penicillin biosynthetic enzymes in peroxisomes and vesicles, which may be involved in transport and secretion of penicillin. SignificancePenicillin biosynthesis in Penicillium chrysogenum is one of the best characterized secondary metabolism processes. However, the mechanism by which penicillin is secreted still remains to be elucidated. Taking into account the role played by Ca2+ and CPP in the secretory pathway and considering the positive effect that Ca2+ exerts on penicillin production, the analysis of global protein changes produced after CPP/CaCl2 addition is very helpful to decipher the processes related to the biosynthesis and secretion of penicillin.

Isolation and Abiotic Stress Resistance Analyses of a Catalase Gene from Ipomoea batatas (L.) Lam.

As an indicator of the antioxidant capability of plants, catalase can detoxify reactive oxygen species (ROS) generated by environmental stresses. Sweet potato is one of the top six most important crops in the world. However, its catalases remain largely unknown. In this study, a catalase encoding gene, IbCAT2 (accession number: KY615708), was identified and cloned from sweet potato cv. Xushu 18. It contained a 1479 nucleotides' open reading frame (ORF). S-R-L, Q-K-L, and a putative calmodulin binding domain were located at the C-terminus of IbCAT2, which suggests that IbCAT2 could be a peroxisomal catalase. Next-generation sequencing (NGS) based quantitative analyses showed that IbCAT2 was mainly expressed in young leaves and expanding tuberous roots under normal conditions. When exposed to 10% PEG6000 or 200 mmol/L NaCl solutions, IbCAT2 was upregulated rapidly in the first 11 days and then downregulated, although different tissues showed different degree of change. Overexpression of IbCAT2 conferred salt and drought tolerance in Escherichia coli and Saccharomyces cerevisiae. The positive response of IbCAT2 to abiotic stresses suggested that IbCAT2 might play an important role in stress responses.