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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Emerging Pests and Pathogens Research

2013 Annual Report

1a. Objectives (from AD-416):
1. Culture, conserve, characterize, and exchange insect pathogenic fungi, fungal genetic resources and associated information from the ARS Collection of Entomopathogenic Fungal Cultures (ARSEF). 2. Develop molecular tools of functional genomics for use in systematics and in defining secondary metabolites and products of insect pathogenic fungi that affect biological control potential. 3. Discover natural fungal metabolites and products to evaluate their roles in the survival, development, virulence, and pathogenicity of fungal biological control agents. 4. Identify and characterize novel lead chemistries for the development of new fungal metabolite-based pesticides for agricultural applications.

1b. Approach (from AD-416):
Use various preservation methods (lyophil, cryogenic, offsite backup) to maintain culture collection and to accession new germplasm for customer base. Develop new methods to isolate, culture, and preserve isolates. Conduct studies on the systematics, taxonomy, and organismal biology of these fungi. Use molecular and bioinformatic tools to evaluate insect pathogenic genomes and gene families. Use molecular tools to target secondary metabolite pathways. Characterize biological activity and chemistries of compounds produced by fungi at various developmental stages.

3. Progress Report:
Holdings of ARS Collection of Entomopathogenic Fungal Cultures (ARSEF). In the last 12 months (15 July 2012 – 14 July 2013), the ARSEF culture collection has accessioned 499 isolates, received 537 cultures awaiting completion of formal accessioning and long-term preservation, and distributed 531 cultures in response to 93 requests. ARSEF currently comprises 12068 accessions of 681 fungal taxa from 2371 locations worldwide, and 1285 different hosts and substrates. Accession information for ARSEF holdings continues to be revised as molecular reidentifications are received from collaborating laboratories. Material Transfer Agreements (MTA) IN PLACE with EMBRAPA Genetic Resources (Brasilia, Brazil). MTAs covering planned exchanges of germplasm between the ARSEF collection and its Brazilian counterpart at EMBRAPA's insect pathogenic fungal collection, have been made unnecessary by relaxed Brazilian regulatory policies; shipments of key reference isolates of fungi to Brazil to facilitate the development of a novel new (mass spectroscopic) approach for the taxonomy of Beauveria and Metarhizium are now in progress. Siderophores, iron-binding metabolites, in Metarhizium identified. Iron is an essential nutrient for virtually all organisms, including fungi. Since bioavailable forms of iron are scarce, microorganisms secrete small peptide compounds called siderophores to acquire iron and the presence of these compounds has also been linked to virulence traits in pathogen-host interactions. The insect pathogenic fungus Metarhizium was found to be an unusually rich source of these compounds, found both inside and outside of the cells. Unlike other pathogens, there was no effect on virulence in mutants disrupted for extracellular siderophore production, possibly due to their mode of infection into the insect body where iron is not a limiting resource. International Rules to Alter Names of Key Insect Pathogenic Species. New international rules adopted last year on the naming of organisms will change the coding for fungi to use a single name rather than separate names for the sexual and non-sexual (conidial) life stages of a fungus. These rules will affect fungal culture collections, and especially the ARS Collection of Entomopathogenic Fungal Cultures (ARSEF), since the names will need to be approved through a series of committees. The practical effects of these naming rules are still being determined; it is unclear as to how extensive the changes may affect those fungi in which only one life stage of the fungus is known and what impact it may have on the long-term use of these fungi.

4. Accomplishments
1. Identifying the target of the mutagenic toxin, NGx from Metarhizium. Biological control fungi can infect many different insect pests, but it is especially important to identify all possible bioactive chemistries that are present, both from regulatory and safety concerns as well as to further understand how to make biological control more effective. ARS researchers at Ithaca, New York, further explored the biological activity of NG391, a compound we previously isolated and identified as a mutagenic toxin present only in early growth stages of the fungus. At relatively low micromolar concentrations, NG391 greatly inhibits biosynthesis of RNA and to a lesser extent, DNA, in human cancer cell cultures, consistent with its antiproliferative effect. This finding does increase the need to develop a more complete understanding of the factors that regulate expression of these products and especially as they relate to biocontrol activity and safety.

Review Publications
Humber, R.A. 2012. Entomophthoromycota: a new phylum and reclassification for entomophthoroid fungi. Mycotaxon. 120:477-492.

Gryganskyi, A., Humber, R.A., Smith, M., Miadlikovska, J., Wu, S., Voigt, K., Walter, G., Anishchenko, I., Vilgalys, R. 2012. Molecular phylogeny of Entomophthoromycota. Molecular Phylogenetics and Evolution. 65:682-694.

Gryganskyi, A.P., Humber, R.A., Smith,, M.E., Hodge, K., Huang, B., Voigt, K., Vilgalys, R. 2013. Phylogenetic lineages in Entomophthoromycota. Persoonia: Molecular Phylogeny and Evolution of Fungi. 30:94-105.

Humber, R.A., Rocha, L., Inglis, P.W., Kipnis, A., Luz, C. 2012. Morphology and molecular taxonomy of Evlachovaea-like fungi, and the status of this unusualconidial genus. Fungal Biology. 117:1-12.

Barry, S.M., Kers, J.A., Johnson, E.G., Song, L., Aston, P., Patel, B., Krasnoff, S., Crane, B.R., Gibson, D.M., Loria, R., Challis, G.L. 2012. Regiospecific cytochrome P450-catalyzed nitration of L-tryptophan in thaxtomin phytotoxin biosynthesis. Nature Chemical Biology. 8:814-816.

Crane, J.M., Gibson, D.M., Vaughan, R.H., Bergstrom, G.C. 2013. Iturin levels on wheat spikes linked to biological control of fusarium head blight by Bacillus amyloliquefaciens. Phytopathology. 103:146-155.

Bohnert, M., Hans-Martin, D., Gibson, D.M., Krasnoff, S., Hoffmeister, D. 2013. The fusarin analogue NG-391 impairs nucleic acid formation in K-562 leukemia cells. Phytochemistry Letters. 6:189-192.

Worley, J.N., Russell, A.B., Wexler, A.G., Bronstein, P., Kvitko, B.H., Krasnoff, S., Munkvold, K.R., Swingle, B.M., Gibson, D.M., Collmer, A. 2013. Pseudomonas syringae pv. tomato DC3000 CmaL (PSPTO4723), a DUF1330 family member, is needed to produce L-allo-isoleucine, a precursor for the phytotoxin coronatine. Journal of Bacteriology. 195(2):287-296.

Last Modified: 05/25/2017
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