Submitted to: Society for Invertebrate Pathology Annual Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 15, 2003
Publication Date: August 15, 2003
Citation: CHURCHILL, A.C., KRASNOFF, S.B., MOON, Y., MCLANE, H., WILLIAMS, J.E., VANDENBERG, J.D., GIBSON, D.M. CHARACTERIZATION OF IN VITRO DESTRUXIN PRODUCTION, PATHOGENICITY, AND RFLP PATTERNS OF PEPTIDE SYNTHETASE GENES IN METARHIZIUM ANISOPLIAE. PROCEEDINGS OF THE ANNUAL MEETING OF THE SOCIETY FOR INVERTEBRATE PATHOLOGY. 2003. v. 36. p. 51.
Metarhizium species have been at the forefront of efforts to develop entomopathogenic fungi as insect biocontrol agents. Yet we have an incomplete understanding of the biological and genetic factors that make them effective, such as the role of toxins as virulence factors. We cloned DNA fragments encoding putative PS genes from Metarhizium spp. and identified restriction fragment length polymorphisms (RFLP) that differentiate M. anisopliae strains and closely-related species. We measured destruxin production in vitro by 16 strains of M. anisopliae and characterized the virulence of 8 strains against beet armyworm. All isolates produced detectable amounts of destruxins A, B, and E in vitro, but quantities varied greatly among isolates. Approximately one-third of the isolates produced low (<1 mg/liter), intermediate (5-30 mg/liter) or high amounts (70-170 mg/liter) of destruxins. Greater destruxin production in vitro generally correlated with a decrease in insect survival time. However, one isolate that produced low amounts of destruxins in vitro killed larvae in the same amount of time as high destruxin producers. This result and similar examples reported in the literature might suggest that destruxins are not required for virulence. An alternative explanation is that in vitro production of destruxins does not predict virulence or metabolite production in vivo. Our results form the basis for further genetic studies to explore the pathway for destruxin biosynthesis and its relationship to fungal virulence.