Concurrence of losing a chromosome and the ability to produce destruxins in a mutant of Metarhizium anisopliae.

In a previous study, a spontaneous subtilisin pr1A and pr1B gene-deficient mutant of the entomopathogenic fungus Metarhizium anisopliae strain V275 has been identified [Wang, C.-S. et al. (2002) FEMS Microbiol. Lett. 213, 251-255]. The insecticidal metabolites of this mutant were studied further. High-performance liquid chromatography (HPLC) analysis indicated that the mutant isolate lost the ability to produce cyclic peptide toxins, destruxins, both in vitro and in vivo. Pulsed-field gel electrophoresis revealed that the mutant concurrently lost a 1.05 Mb (approximately) chromosome, demonstrating for the first time that a conditionally dispensable (CD) chromosome exists in the insect pathogenic fungus, M. anisopliae. Concurrence of losing the ability to produce destruxins and a CD chromosome in the mutant suggests that the toxin synthetase genes of M. anisopliae are located on this CD chromosome, as similarly described for plant pathogenic fungi. Semi-quantitative api ZYM analysis showed more biochemical disparities between the mutant and the wild-type strain.