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PubMed2006

Fit-for-purpose shellfish reference materials for internal and external quality control in the analysis of phycotoxins.

The need for reference materials for quality control of analysis of foodstuffs has been stressed frequently. This has been particularly true in the phycotoxins field, where there is a great shortage of both pure calibration standards and reference materials. Worldwide there are very few independent bodies that produce certified reference materials for phycotoxins, the main producers currently being the National Research Council Canada and the Japanese Food Research Laboratory. Limited availability of contaminated shellfish and algae, as well as the time and knowledge necessary for the production of adequate reference materials, continuously lead to limited editions of certified reference materials and even more limited production of in-house reference materials. The restricted availability of in-house quality control materials promotes the rapid use of the limited certified reference materials, which in turn hampers the production of the suite of materials required globally for complete protection of public health. This paper outlines the various options that analysts can pursue in the use of reference materials for internal and external quality control, with a view to optimising the efforts of both reference materials users and reference materials producers. For this purpose, the logical sequence is reviewed from the discovery of a new bioactive compound in shellfish, through initial method development up to regulation for food safety purposes including accepted reference methods. Subsequently, the requirements for and efforts typically spent in the production and characterisation of laboratory reference materials, certified reference materials and other test materials used in inter-laboratory studies or proficiency testing, in the area of marine biotoxins are evaluated. Particular emphasis is put on practical advice for the preparation of in-house reference materials. The intricate link between reference material characterisation and method performance is outlined to give guidance on the appropriate in-house method validation in the rapidly developing field of phycotoxins.

Animals↗

PubMed1998

Biomarker responses in whitefish (Coregonus lavaretus L. s.l.) experimentally exposed in a large lake receiving effluents from pulp and paper industry.

Physiological and biochemical biomarker responses were studied in juvenile whitefish (Coregonus lavaretus L. s.l.) exposed experimentally to effluent from the forest industry. The large study area (609 km2), Southern Lake Saimaa, in Southeast Finland, receives 330,000 m3 d-1 of biologically and 55,000 m3 d-1 of chemically treated effluents, discharged from two integrated elementary chlorine free (ECF) bleached kraft pulp and paper mills, from one ECF pulp mill, and from one mill producing unbleached pulp and cardboard. The assessment of exposure to effluent discharged from the mills was based on lake water chlorophenolics (CPs) and resin acids (RAs) measured in samples collected from the 22 experimental sites along the area. Despite the low levels of effluent constituents in the lake, they were still accumulated in detectable levels in fish bile, indicating an exposure to the bioactive compounds of effluents. In comparison to the reference area, a two- to four-fold increase in ethoxyresorufin O-deethylase (EROD) activity was observed in whitefish exposed in the vicinity (1-6 km) of all the mills. However, cytochrome P450 1A1 (CYP1A1) gene expression was increased in only one of the receiving areas, indicating higher sensitivity of the EROD activity in the present study. There were no statistically significant correlations between EROD activity and the ambient water concentrations of the CPs, the RAs, or effluent dilution expressed by water sodium concentration. Neither bile chlorophenolics nor bile resin acids showed a significant correlation with EROD. No significant changes in circulating reproductive steroids, 17beta-estradiol and testosterone, in juvenile whitefish were observed. The vitellogenin gene was expressed in the vicinity of the pulp mill discharging the most wood-derived compounds, i.e. resin acids and wood-sterols, including beta-sitosterol. No differences were observed in plasma immunoglobulin M, glucose, or lactate concentrations between the effluent sources.

Animals↗

PubMed2000

Sensitivity of Two Disjunct Bacterioplankton Communities to Exudates from the Cyanobacterium Microcystis aeruginosa Kützing.

Microcystis aeruginosa Kützing releases a variety of bioactive compounds during growth. This study determined whether bacteria from communities co-occurring (M+) or not (M-) with this cosmopolitan cyanobacterium respond similarly to its products. Fifty M+ bacteria from a M. aeruginosa bloom site (Western Basin of Lake Erie) and 50 M- bacteria from a Microcystis-free site (East Twin Lake, Portage Co., OH) were isolated and grown on Standard Methods Agar. Three levels of testing were performed: chemotaxis, antibiotic response, and 48-h cell abundance. Chemotaxis was compared using capillary tubes placed in contact with bacterial, Standard Methods Broth (SMB) suspensions. The capillary choices were conditioned SMB, M. aeruginosa exudate, and BG-11. M+ bacteria showed significantly greater (Tukey's test, p < 0.005) positive chemotaxis to M. aeruginosa exudate compared to control conditions and to M-strains. The latter showed a negative chemotactic response to M. aeruginosa exudate compared to control conditions. Antibiotic response was tested by sensitivity disk assays, first using M. aeruginosa exudates, whole cells, and homogenized cells, and then placing the disks on bacterial lawns of each strain. M+ bacteria were significantly more resistant to inhibition than M- bacteria (chi-square test, p < 0.01). M. aeruginosa exudate, BG-11 algal medium, SMB, and distilled water effects on 48-h abundance of the strains were compared. The M- community bacteria exhibited significantly lower growth yields (Tukey's comparison of means test, p < 0.005) in M. aeruginosa exudate than did the M+ strains. It is evident that those bacteria co-occurring with M. aeruginosa are more likely to be attracted to it, able to withstand exposure to it, and able to utilize its products without inhibition than are bacteria from communities without previous exposure to this cyanobacterium.

Journal Article↗

PubMed2006

Effect of culture conditions on mycelial growth, antibacterial activity, and metabolite profiles of the marine-derived fungus Arthrinium c.f. saccharicola.

The effects of culture conditions and competitive cultivation with bacteria on mycelial growth, metabolite profile, and antibacterial activity of the marine-derived fungus Arthrinium c.f. saccharicola were investigated. The fungus grew faster at 30 degrees C, at pH 6.5 and in freshwater medium, while exhibited higher antibacterial activity at 25 degrees C, at pH 4.5, 5.5, and 7.5, and in 34 ppt seawater medium. The fungus grew faster in a high-nitrogen medium that contained 0.5% peptone and/or 0.5% yeast extract, while exhibiting higher bioactivity in a high-carbon medium that contained 2% glucose. The fungal growth was inhibited when it was co-cultured with six bacterial species, particularly the bacterium Pseudoalteromonas piscida. The addition of a cell free culture broth of this bacterium significantly increased the bioactivity of the fungus. Metabolite profiles of the fungus revealed by gas chromatography (GC)-mass spectrometry showed clear difference among different treatments, and the change of relative area of three peaks in GC profile followed a similar trend with the bioactivity variation of fungal extracts. Our results showed clear differences in the optimal conditions for achieving maximal mycelial growth and bioactivity of the fungus, which is important for the further study on the mass cultivation and bioactive compounds isolation from this fungus.

Ascomycota↗

PubMed1999

Biosynthesis of gibberellins in Gibberella fujikuroi: biomolecular aspects.

Gibberellins (GAs) are a large family of isoprenoid plant hormones hormones, some of which are bioactive growth regulators, controlling seed germination, stem elongation, and flowering. The rice pathogen Gibberella fujikuroi (mating population C) is able to produce large amounts of GAs, especially the bioactive compounds gibberellic acid (GA3) and its precursors, GA4 and GA7. The main steps of the biosynthetic pathway have long been established from the identification of intermediates in wild-type G. fujikuroi and mutant strains. However, the genetics of the fungus have been rather under-developed, and molecular genetic studies of the GA pathway started just recently. The progress in researching GA biosynthesis in the last 2 years resulted primarily from development of the molecular tools, e.g. transformation systems for the fungus, and cloning the genes encoding GA biosynthesis enzymes, such as the bifunctional ent-copalyl diphosphate/kaurene synthase and several cytochrome P450 monooxygenases. The availability of these genes opened new horizons both for detailed study of the pathway and the regulation mechanisms at the molecular level, and for modern strain improvement programs. This review gives a short overview of the well-known physiological and biochemical studies and concentrates mainly on the new molecular genetic data from GA research, including new information on the regulation of GA biosynthesis.

Aerobiosis↗

PubMed2003

Structural development of synthetic retinoids and thalidomide-related molecules.

The full-scale commercial appearance of antibiotics in the 1950s caused a shift in the nature of lethal diseases from infectious and acute to noninfectious and chronic. In this situation, biological response modifiers (BRMs), which are not based on selective toxicity, could be expected to be useful. Several types of BRM exist, including retinoids, which act directly on cells at the level of gene expression, and thalidomide and related molecules, which modulate the production of various cytokines. We have been engaged in medicinal, chemical, and structural development studies based on these bioactive compounds. Retinoids include all- trans-retinoic acid (ATRA), a major active form of vitamin A (retinol), and its bioisosters, which elicit their biological effects by binding to their nuclear receptors, retinoic acid receptors (RARs). ATRA has been used in differentiation therapy, typically for the treatment of acute promyelocytic leukemia, and the treatment of dermatological diseases. Our structural development studies of retinoids, including computer-assisted molecular design, have yielded class/subtype-selective agonists, synergists, and antagonists of RARs and their partner nuclear receptors, retinoid X receptors. Among them, the benzanilide-type compounds, Am80 and TAC101, are under phase II and I/II clinical studies in Japan and the USA, respectively. Thalidomide is a hypnotic/sedative drug that was withdrawn from the market because of teratogenicity. However, thalidomide has been established to be useful in the treatment of various diseases including cancer. Thalidomide elicits a wide range of pharmacological effects, including anticachexia, anti-tumor-promoting, antiangiogenic, immunosuppressing, antiviral, hypoglycemic, and antimetastatic activities. We have found that thalidomide is a multitarget drug. Hypothetical target events/molecules of thalidomide include tumor necrosis factor-alpha production, nuclear androgen receptor, cyclooxygenases, aminopeptidases, and alpha-glucosidase. Specific and potent compounds for each of these target phenomena/molecules have been prepared by appropriate modification of the thalidomide structure, and are expected to be superior lead compounds for novel immunomodulators, antiangiogenic agents, and anti-tumor-promoting agents.

Computer Simulation↗

PubMed2006

Amplification of DNA encoding entire type I polyketide synthase domains and linkers from streptomyces species.

Polyketides are a group of bioactive compounds from bacteria, plants, and fungi. To increase the availability of analogs for testing, the active sites of polyketide synthases are often substituted with homologous domains having altered substrate specificities. This study reports the design of polymerase chain reaction primers that enables isolation of entire active site domains from type I polyketide synthases with native interdomain linkers. This bypasses the need for further genetic screening to obtain functional units for use in genetic engineering. This is especially important in bioprospecting projects exploring new environments for bioresources.

Antifungal Agents↗

PubMed2004

Integrated assessment by multiple gene expression analysis of quercetin bioactivity on anticancer-related mechanisms in colon cancer cells in vitro.

BACKGROUND: Many different mechanisms are involved in nutrient-related prevention of colon cancer. In this study, a comprehensive assessment of the spectrum of possible biological actions of the bioactive compound quercetin is made using multiple gene expression analysis. Quercetin is a flavonoid that can inhibit proliferation of tumor cells and reduce the number of aberrant crypt foci, although increase of number of colon tumors was also reported. AIM OF THE STUDY: In order to elucidate possible mechanisms involved in its mode of action the effect of quercetin on expression of 4000 human genes in Caco-2 cells was studied and related to functional effects. METHODS: Caco-2 cells were exposed to 5 or 50 microM quercetin for 48 hours, differential expression of 4000 human genes was studied using microarrays and related to functional effects. Differentially expressed genes were categorized in seven functional groups: cell cycle and differentiation, apoptosis, tumor suppressor genes and oncogenes, cell adhesion and cell-cell interaction, transcription, signal transduction and energy metabolism. Also, cell proliferation and cell cycle distribution were measured. RESULTS: Quercetin (5 microM) downregulated expression of cell cycle genes (for example CDC6, CDK4 and cyclin D1), downregulated cell proliferation and induced cell cycle arrest in Caco-2 cells. After exposure to 50 microM quercetin cell proliferation decreased to 51.3% of control, and further decrease of the percentage of cells in the G1 phase coincided with an increase of the percentage of cells in the sub-G1 phase. Quercetin upregulated expression of several tumor suppressor genes. In addition, genes involved in signal transduction pathways like beta catenin/TCF signalling and MAPK signal transduction were influenced by quercetin. CONCLUSIONS: This study shows that large-scale gene expression analysis in combination with functional assays yields a considerable amount of information on (anti-)carcinogenic potential of food components like quercetin.

Antineoplastic Agents↗

PubMed2004

Atherosclerosis--epidemiological studies on the health effects of a Mediterranean diet.

Mediterranean diets are characterized by olive oil, as the dominant fat source and a high to moderate consumption of fruit and vegetables, cereal products, fish, legumes, in combination with little meat and wine with meals. The "reference" Mediterranean diet seems to differ according to country, but is associated with good health and a long life expectancy. From the Seven Countries Studies, it has been shown that especially the traditional Cretan diet was associated with very low 25-year mortality rates for coronary heart disease, cancer and all-causes. In terms of nutrients and bioactive compounds the "reference" Mediterranean diet is low in saturated fat and high in monounsaturated fatty acids, high in antioxidants especially vitamin C and E, and high in fiber and folic acid. Several epidemiological studies have investigated these dietary components either separately or in combination in other than Mediterranean populations. In general, also in other populations beneficial effects on the coronary risk profile have been observed, which gives further support to the positive health effects of the Mediterranean diet. Intervention studies in East Finland and Southern Italy have convincingly shown that the coronary risk profile (lower LDL cholesterol and blood pressure levels) is improved by a Mediterranean diet. Moreover, the Cretan diet was tested in cardiac patients and showed a 70 % lower cardiac and all-causes mortality compared to the control diet. In conclusion, epidemiological studies and intervention trials suggest that the Cretan Mediterranean diet lowers the risk of coronary heart disease.

Antioxidants↗

PubMed2000

Bcl-2 transfected HaCaT keratinocytes resist apoptotic signals of ceramides, tumor necrosis factor alpha and 1 alpha, 25-dihydroxyvitamin D(3).

During the last few years increasing evidence has shown that sphingolipid metabolites are highly bioactive compounds that play important roles in cellular regulation. The induction of ceramide signalling in primary human keratinocytes and HaCaT keratinocytes has recently been demonstrated using 1 alpha,25-dihydroxyvitamin D(3). The data obtained indicate that approximately one-third of the proapoptotic effect of 1 alpha,25-dihydroxyvitamin D(3) is mediated by an intracellular ceramide increase induced via tumor necrosis factor. expression and autocrine stimulation of sphingomyelin hydrolysis. In the present study the role of bcl-2 in this process was investigated. HaCaT keratinocytes were transfected with bcl-2 and the effects of C(2)-ceramide, tumor necrosis factor alpha and 1 alpha,25-dihydroxyvitamin D(3) on HaCaT keratinocytes stably overexpressing bcl-2 were determined. Apoptosis was measured by detection of soluble DNA-histone complexes using the ELISA technique. In situ analysis of apoptotic cells was also carried out by detecting phosphatidylserine flip using the annexin V method and by detecting DNA fragmentation using the TUNEL assay. The results obtained showed that apoptosis induced by C(2)-ceramide, tumor necrosis factor alpha or 1 alpha,25-dihydroxyvitamin D(3) occurred in a vector-transfected clone but not in a bcl-2-transfected HaCaT clone. This indicates the important role of bcl-2 in the regulation of ceramide-mediated signalling pathways in human keratinocytes and supports the involvement of ceramide as a signalling molecule in 1 alpha,25-dihydroxyvitamin D(3)-induced biological responses.

Apoptosis↗

PubMed2002

Antiproliferative and leishmanicidal effect of ajoene on various Leishmania species: ultrastructural study.

Ajoene [(E,Z)-4,5,9 trithiadodeca 1,6,11 triene 9-oxide], the major bioactive compound derived from garlic, shows a potent trypanolytic and antimicotic activity. In this paper we evaluate its effect on Leishmania mexicana(Lm:MHOM/VE/80/NR), L eishmania mexicana venezuelensis (Lmv: MHOM/VE/80/H16), L eishmania mexicana amazonensis (Lma: M112, IFLA/BR/67/PH8) and L eishmania donovani chagasi (Ldch: MHOM/BR/74/PP75). Ajoene showed a potent leishmanicidal activity in vitro against all species studied. Concentrations higher than 0.3 microM led to total inhibition of growth, and 10 microM induced 100% lysis of Leishmaniaafter 96 h of incubation in a chemically defined culture medium. The 50% inhibitory concentration (IC(50)) for lysis, for all species, was about to 2 microM. The effect was dose-dependent and a threefold increase in concentration (30 microM) produced 100% lysis of cultured forms after 72 h. Ultrastructural studies showed a time- and dose-dependent morphological alteration of the mitochondrial membrane and nuclear envelope, as well as the formation of large autophagic vacuoles.

Animals↗

PubMed2004

Genetic analysis of the biosynthesis of non-ribosomal peptide- and polyketide-like antibiotics, iron uptake and biofilm formation by Bacillus subtilis A1/3.

The Bacillus subtilis strain A1/3 shows exceptionally diverse antibiotic capacities compared to other B. subtilis strains. To analyze this phenomenon, mutants for the putative pantotheinyltransferase gene (pptS), and for several genes involved in non-ribosomal peptide synthesis and polyketide synthesis were constructed and characterized, using bioassays with blood cells, bacterial and fungal cells, and mass spectrometry. Among at least nine distinct bioactive compounds, five antibiotics and one siderophore activity were identified. The anti-fungal and hemolytic activities of strain A1/3 could be eliminated by mutation of the fen and srf genes essential for the synthesis of fengycins and surfactins. Both pptS- and dhb -type mutants were defective in iron uptake, indicating an inability to produce a 2,3-dihydroxybenzoate-type iron siderophore. Transposon mutants in the malonyl CoA transacylase gene resulted in the loss of hemolytic and anti-fungal activities due to the inhibition of bacillomycin L synthesis, and this led to the discovery of bmyLD-LA-LB* genes. In mutants bearing disruption mutations in polyketide (pksM- and/or pksR -like) genes, the biosynthesis of bacillaene and difficidins, respectively, was inactivated and was accompanied by the loss of discrete antibacterial activities. The formation of biofilms (pellicles) was shown to require the production of surfactins, but no other lipopeptides, indicating that surfactins serve specific developmental functions.

Acyl-Carrier Protein S-Malonyltransferase↗

PubMed2004

The proprotein convertase furin colocalizes with caveolin-1 in the Golgi apparatus and endosomes of hepatocytes.

The significance of furin in the maturation and activation of a wide array of proproteins in the secretory pathway has been well demonstrated. However, despite efforts made to characterize the subcellular locations where furin activates its substrates, doubts on the proprotein-processing compartments still persist. Using in vivo gene delivery, together with high-resolution immunogold electron microscopy, we were able to assign precise subcellular locations to furin. In rat hepatocyte, the enzyme was found concentrated in the Golgi apparatus, along the basolateral (sinusoidal) plasma membrane and in underlying endosomes. An asymmetry was detected in respect to amounts of furin between the basolateral domain and the apical (canalicular) one, favoring the former. The asymmetric recycling of furin through the basolateral domain may be of high importance for the polarized secretion of processed bioactive compounds. Double immunogold labelings indicate that furin colocalizes with the caveolae/raft-marker caveolin-1 in the Golgi apparatus and in the basolateral endosomes. Furthermore, co-immunoprecipitation experiments show the possible interaction of caveolin-1 and furin. Our results suggest that, in addition to the Golgi, furin-/caveolin-1-containing endosomes could represent a compartment where furin processes its substrates at the basolateral domain of the hepatocyte.

Animals↗

PubMed1998

A sponge/dinoflagellate association in the haplosclerid sponge Haliclona sp.: cellular origin of cytotoxic alkaloids by percoll density gradient fractionation.

Light-microscopic and electron-microscopic studies of the tropical marine sponge Haliclona sp. (Order: Haplosclerida; Family: Haliclonidae) from Heron Island, Great Barrier Reef, have revealed that this sponge is characterized by the presence of dinoflagellates and by nematocysts. The dinoflagellates are 7-10 micrometer in size, intracellular, and contain a pyrenoid with a single stalk, whereas the single chloroplast is branched, curved, and lacks grana. Mitochondria are present, and the nucleus is oval and has distinct chromosomal structure. The dinoflagellates are morphologically similar to Symbiodinium microadriaticum, the common intracellular symbiont of corals, although more detailed biochemical and molecular studies are required to provide a precise taxonomic assignment. The major sponge cell types found in Haliclona sp. are spongocytes, choanocytes, and archaeocytes; groups of dinoflagellates are enclosed within large vacuoles in the archaeocytes. The occurrence of dinoflagellates in marine sponges has previously been thought to be restricted to a small group of sponges including the excavating hadromerid sponges; the dinoflagellates in these sponges are usually referred to as symbionts. The role of the dinoflagellates present in Haliclona sp. as a genuine symbiotic partner requires experimental investigation. The sponge grows on coral substrates, from which it may acquire the nematocysts, and shows features, such as mucus production, which are typical of some excavating sponges. The cytotoxic alkaloids, haliclonacyclamines A and B, associated with Haliclona sp. are shown by Percoll density gradient fractionation to be localized within the sponge cells rather than the dinoflagellates. The ability to synthesize bioactive compounds such as the haliclonacyclamines may help Haliclona sp. to preserve its remarkable ecological niche.

Alkaloids↗

PubMed2003

Synthesis and use of N, N-di-Boc-glutamate gamma-semialdehydes and related aldehydes.

This review article focuses on the synthesis and reactions of N, N-di-Boc glutamate and aspartate semialdehydes as well as related aldehydes. These building blocks are prepared according to various strategies from glutamic and aspartic acids and find interesting synthetic applications. In the first part, the methods for the synthesis of N, N-di-Boc-amino aldehydes are summarized. The applications of these chiral synthons for the synthesis of unnatural amino acids and other bioactive compounds are discussed in the second section.

Aldehydes↗

PubMed2000

COX-2-Specific inhibitors--the emergence of a new class of analgesic and anti-inflammatory drugs.

The prostaglandin series of bioactive compounds is formed by the interaction of two distinct but related enzymes, cyclo-oxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). COX-1 is a constitutive form which is present mainly in the gastric mucosa, kidney and platelets. COX-2 is mainly an inducible form, although also to some extent present constitutively in the CNS, the juxtaglomerular apparatus of the kidney and in the placenta during late gestation. Both isoforms contribute to the inflammatory process, but COX-2 is of considerable therapeutic interest as it is induced, resulting in an enhanced formation of prostaglandins, during acute as well as chronic inflammation. Conventional NSAIDs inhibit both isoforms to a similar extent and in an approximately equal dose and concentration range. The two recently developed and clinically available selective COX-2 inhibitors, celecoxib and rofecoxib, are about 100-1000 times more selective on the COX-2 than on the COX-1 isoform. In Europe rofecoxib is today indicated for the symptoms and signs of osteoarthritis, whereas celecoxib is indicated for both osteoarthritis and rheumatoid arthritis. The major clinical interest of these drugs has been related to the lower incidence of gastrointestinal bleeding which, with the conventional COX-1/COX-2 agents has been a source of hospitalisation, disablement and death, especially in the elderly. Clinical trials have convincingly demonstrated that celecoxib and rofecoxib in clinical use induce very few gastrointestinal complications compared to conventional and non-selective NSAIDs. However, the well known contraindications for NSAIDs, such as late pregnancy, aspirin-induced asthma, congestive heart failure and renal dysfunction, will so far apply also to the COX-2 inhibitors. Compared to the traditional and non-selective NSAIDs, COX-2 inhibitors may provide an insight into additional therapeutic areas, such as gastrointestinal cancer and dementia, where the potential relevance to COX-2 mechanisms are currently being explored and clinical trials being performed. With the rapid clinical acceptance of celecoxib and rofecoxib, knowledge about their clinical usefulness in various inflammatory disease states and pain disorders is increasing. For the many patients suffering from such conditions, the selective COX-2 inhibitors are likely to become a significant addition to the therapeutic arsenal of analgesic and anti-inflammatory drugs.

Analgesics↗

PubMed2026

Heterologous expression of DobHLH25 from Dendrobium officinale enhances drought tolerance in Arabidopsis.

Drought stress severely constrains the growth, yield, and accumulation of bioactive compounds in Dendrobium officinale (D. officinale), a valuable medicinal orchid, and this challenge is exacerbated under simulated wild cultivation where plants are inevitably exposed to recurring water deficits. Basic helix-loop-helix (bHLH) transcription factors are well-established regulators of plant abiotic stress responses. However, the molecular mechanisms by which bHLH transcription factors respond to drought stress in this species remain largely unknown. In this study, a bHLH transcription factor gene, DobHLH25, was cloned from D. officinale. Phylogenetic analysis revealed that DobHLH25 shares the highest sequence identity with its ortholog in Dendrobium nobile. Additionally, subcellular localization analysis indicated that DobHLH25 is targeted to the nucleus and possesses a functional transcriptional activation domain. Expression pattern analysis showed that DobHLH25 is most abundantly expressed in old leaves, and its expression in roots, stems, and leaves is induced by polyethylene glycol treatments. Heterologous expression of DobHLH25 in Arabidopsis thaliana resulted in higher seed germination rates and longer root lengths under mannitol-induced osmotic stress compared to wild-type plants. Under drought stress, DobHLH25 heterologous expression lines exhibited higher survival rates, reduced leaf water loss, lower malondialdehyde accumulation, and increased proline content. Moreover, the activities of antioxidant enzymes such as superoxide dismutase and peroxidase were significantly enhanced, and the expression levels of multiple drought-responsive genes were markedly upregulated. Collectively, these findings suggest a correlation between DobHLH25 expression and plant drought tolerance, as evidenced by reduced oxidative damage, increased osmolyte accumulation, enhanced antioxidant enzyme activities, and upregulation of drought-responsive genes. Together, these results suggest that DobHLH25 plays a positive role in drought tolerance, and provides a basis for future dissection of its regulatory network in D. officinale.

Drought Resistance↗

PubMed2006

Are antibiotics naturally antibiotics?

Antibiotics have been used for more than 50 years and are the cornerstone of infectious disease treatment; in addition, these low-molecular-weight bioactive compounds have been applied to many other therapeutic purposes. However, there is almost no information on the evolutionary biology or ecology of naturally occurring low-molecular-weight compounds. The large number of different structural types and the extremely broad range of biological activities of organic molecules produced by microbes raise many questions concerning their roles in nature. Recent evidence for the enormous complexity of microbial populations in the environment favors the notion that the principal roles of small molecules in microbial ecology are cell-cell communication and not antibiosis.

Anti-Bacterial Agents↗