Identification of signatory secondary metabolites during mycoparasitism of Rhizoctonia solani by Stachybotrys elegans (original) (raw)
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Visualizing fungal metabolites during mycoparasitic interaction by MALDI mass spectrometry imaging
PROTEOMICS, 2016
Studying microbial interactions by MALDI mass spectrometry imaging (MSI) directly from growing media is a difficult task if high sensitivity is demanded. We present a quick and robust sample preparation strategy for growing fungi (Trichoderma atroviride, Rhizoctonia solani) on glass slides to establish a miniaturized confrontation assay. By this we were able to visualize metabolite distributions by MALDI MSI after matrix deposition with a home-built sublimation device and thorough recrystallization. We present for the first time MALDI MSI data for secondary metabolite release during active mycoparasitism.
BMC Genomics, 2009
Background Combating the action of plant pathogenic microorganisms by mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since two decades. The fungal genus Trichoderma includes a high number of taxa which are able to recognize, combat and finally besiege and kill their prey. Only fragments of the biochemical processes related to this ability have been uncovered so far, however. Results We analyzed genome-wide gene expression changes during the begin of physical contact between Trichoderma atroviride and two plant pathogens Botrytis cinerea and Rhizoctonia solani, and compared with gene expression patterns of mycelial and conidiating cultures, respectively. About 3000 ESTs, representing about 900 genes, were obtained from each of these three growth conditions. 66 genes, represented by 442 ESTs, were specifically and significantly overexpressed during onset of mycoparasitism, and the expression of a subset thereof was verified by expression analysis. The upregulated genes comprised 18 KOG groups, but were most abundant from the groups representing posttranslational processing, and amino acid metabolism, and included components of the stress response, reaction to nitrogen shortage, signal transduction and lipid catabolism. Metabolic network analysis confirmed the upregulation of the genes for amino acid biosynthesis and of those involved in the catabolism of lipids and aminosugars. Conclusion The analysis of the genes overexpressed during the onset of mycoparasitism in T. atroviride has revealed that the fungus reacts to this condition with several previously undetected physiological reactions. These data enable a new and more comprehensive interpretation of the physiology of mycoparasitism, and will aid in the selection of traits for improvement of biocontrol strains by recombinant techniques.
Frontiers in Microbiology
Fungi grow in competitive environments, and to cope, they have evolved strategies, such as the ability to produce a wide range of secondary metabolites. This begs two related questions. First, how do secondary metabolites influence fungal ecology and interspecific interactions? Second, can these interspecific interactions provide a way to "see" how fungi respond, chemically, within a competitive environment? To evaluate these, and to gain insight into the secondary metabolic arsenal fungi possess, we co-cultured Aspergillus fischeri, a genetically tractable fungus that produces a suite of mycotoxins, with Xylaria cubensis, a fungus that produces the fungistatic compound and FDA-approved drug, griseofulvin. To monitor and characterize fungal chemistry in situ, we used the droplet-liquid microjunction-surface sampling probe (droplet probe). The droplet probe makes a microextraction at defined locations on the surface of the co-culture, followed by analysis of the secondary metabolite profile via liquid chromatography-mass spectrometry. Using this, we mapped and compared the spatial profiles of secondary metabolites from both fungi in monoculture versus coculture. X. cubensis predominantly biosynthesized griseofulvin and dechlorogriseofulvin in monoculture. In contrast, under co-culture conditions a deadlock was formed between the two fungi, and X. cubensis biosynthesized the same two secondary metabolites, along with dechloro-5-hydroxygriseofulvin and 5-hydroxygriseofulvin, all of which have fungistatic properties, as well as mycotoxins like cytochalasin D and cytochalasin C. In contrast, in co-culture, A. fischeri increased the production of the mycotoxins fumitremorgin B and verruculogen, but otherwise remained unchanged relative to its monoculture. To evaluate that secondary metabolites play an important role in defense and territory establishment, we co-cultured A. fischeri lacking the master regulator of secondary metabolism laeA with X. cubensis. We found that the reduced secondary metabolite biosynthesis of the laeA strain of A. fischeri eliminated the
Current opinion in food science, 2016
Fungi are very undemanding C-heterotrophic organisms. Nevertheless, the better the nutrient supply, the better the growth of the fungus. This however is not directly correlated to the onset of secondary metabolism, for example, mycotoxin biosynthesis, which often is activated or increased under nutrient limiting conditions or under conditions which impose abiotic stresses. This suggests that the biosynthesis of these secondary metabolites may support the adaptation to a certain, non-optimal and more stressful environment. Growth conditions in food environments are usually not optimal and may even be stressful for the fungus. Because of these complex external influences on fungal growth and the regulation of mycotoxins, predictions about food safety issues with regard to mycotoxin biosynthesis can only be made if a profound knowledge about the regulatory issues of the mycotoxin biosynthesis genes directly in the food is available.
Environmental Technology, 2020
An alternative to controlling weeds resistant to conventional herbicides is the isolation of new active principles. Fungi can produce phytotoxic metabolites that may be used in the development of new herbicides. The objectives of this study were: (1) isolate, select, and identify a fungus producer of phytotoxic metabolites and (2) optimize the culture conditions of this fungus in a low-cost culture medium, with the aim of increasing the phytotoxic effects of their metabolites in weeds and commercial plants. Fungi were isolated from the leaves of Conyza spp. with disease symptoms and selected according to the production of phytotoxic metabolites in solid and submerged fermentation in a low-cost culture medium. A Plackett-Burman Design and Central Composite Rotational Design were used to optimize the conditions of temperature, agitation, pH, and concentrations of glucose and yeast extract in submerged fermentation. The phytotoxic metabolites produced under optimal conditions were tested on 10 commercial plants and weeds that are difficult to control. Of the nine fungi isolated, Mycoleptodiscus indicus UFSM54 produced higher leaf lesions. The production of phytotoxic metabolites was optimized when the fungus was cultivated at 35 ºC, 50 rpm, and 1.5 g L-1 of glucose in submerged fermentation. The metabolites of M. indicus caused severe phytotoxic effects on germination and seedling growth, and enhanced lesion development on detached plant leaves. The present study is the first to report on the production of phytotoxic metabolites by M. indicus, a potential producer of bioherbicides.
Toxicology Letters, 2006
The development of fungal biocontrol agents (BCAs) as alternatives to chemical pesticides is of increasing public interest. Tools to assess the toxicity of the secondary metabolites that these BCAs produce are often not available or existing methods have not yet been evaluated for these compounds. This study compares five different test systems, which include a representative bacterium, protozoan, arthropod and insect and human cell lines, as regards their sensitivity. It also compares the cost in time and resources for conducting the tests. Pure metabolites and crude extracts from two fungal BCAs as well as two chemical pesticides (hoestar and chlorpyrifos) and the mycotoxin patulin were employed as test compounds. All tests systems proved to be suitable for toxicity studies of metabolites from fungal BCAs and showed different grades of sensitivity to the different substances. The possibility of employing an array of test systems to determine ecotoxicological properties is discussed.
Secondary metabolites in fungus-plant interactions
Fungiandplantsarerichsourcesofthousandsofsecondarymetabolites.Thegeneticallycodedpossibilitiesforsecondarymetaboliteproduction,thestimulioftheproduction,andthespecialphytotoxinsbasicallydeterminethemicroscopicfungi-hostplantinteractionsandthepathogeniclifestyleoffungi.Thereviewintroducesplantsecondarymetabolitesusuallywithantifungaleffectaswellastheimportanceofsignalingmoleculesininducedsystemicresistanceandsystemicacquiredresistanceprocesses.Thereviewalsoconcernsthemimickingofplanteffectormoleculeslikeauxins,gibberellinsandabscisicacidbyfungalsecondarymetabolitesthatmodulateplantgrowthorevencansubverttheplantdefenseresponsessuchasprogrammedcelldeathtogainnutrientsforfungalgrowthandcolonization.Italsolooksthroughthespecialsecondarymetaboliteproductionandhostselectivetoxinsofsomesignificantfungalpathogensandtheplantresponseinformofphytoalexinproduction.Newresultscomingfromgenomeandtranscriptionalanalysesincontextofselectedfungalpathogensandtheirhostsarealsodiscussed.
Manipulation of fungal development as source of novel secondary metabolites for biotechnology
Applied microbiology and biotechnology, 2014
Fungal genomics revealed a large potential of yet-unexplored secondary metabolites, which are not produced during vegetative growth. The discovery of novel bioactive compounds is increasingly gaining importance. The high number of resistances against established antibiotics requires novel drugs to counteract increasing human and animal mortality rates. In addition, growth of plant pathogens has to be controlled to minimize harvest losses. An additional critical issue is the post-harvest production of deleterious mycotoxins. Fungal development and secondary metabolite production are linked processes. Therefore, molecular regulators of development might be suitable to discover new bioactive fungal molecules or to serve as targets to control fungal growth, development, or secondary metabolite production. The fungal impact is relevant as well for our healthcare systems as for agriculture. We propose here to use the knowledge about mutant strains discovered in fungal model systems for a ...