Hirsutellin A, a toxic protein produced in vitro by Hirsutella thompsonii

Abstract

A toxic protein, hirsutellin A, has been purified from the mite fungal pathogen, Hirsutella thompsonii, using ammonium sulphate precipitation, ion exchange chromatography and gel filtration on BiolGel P-10. The protein has been characterized as a monomer with a molecular mass of 15 kDa and an isoelectric point of 10.5. The amino acid composition and the N-terminal sequence of hirsutellin A (34 amino acids) have been determined. From these results, the toxin appears to be distinct from other known proteins. It is not glycosylated, and does not show proteolytic activity. The toxin is also antigenic, thermostable and not inactivated by treatments with proteolytic enzymes. Toxicity bioassays showed that injection of larvae of the waxmoth, Galleria mellonella, with hirsutellin A at low dosages [I pg toxin (g body wt)-l] caused a high mortality rate. Hirsutellin A was also toxic per 0s to neonatal larvae of the mosquito Aedes aegypti.

Specific adaptation of Ustilaginoidea virens in occupying host florets revealed by comparative and functional genomics

“…5b). Interestingly, UV_2286 encodes a peptide highly similar to Hirsutellin A, an insecticidal ribotoxin produced by Hirsutella thompsonii 44 . UV_6647 encodes a homologue to phosphohistidine phosphatase SixA from Escherichia coli that modulates the ArcB phosphorelay signal transduction 45 .…”

Entomopathogenic fungal endophytes

“…: Fr. produces isariin (Briggs et al, 1966); Hirsutella thompsonii Fisher produces phomalactone (Krasnoff and Gupta, 1994) and hirsutellin A (Mazet et al, 1995), which are known to have ribonuclease activity (Liu et al, 1996) and to be toxic to the citrus rust mite (Omoto and McCoy, 1998); Oospora destructor (Metschn.) Delacr.…”

Fungal extracellular ribotoxins as insecticidal agents

“…Along the 1990s, crude filtrates of H. thompsonii, a particular species of this genus, were found to be toxic to a wide variety of arthropods including moth, fly, and mosquito larvae, aphids and mites (Liu et al, 1995;Omoto and McCoy, 1998;Vey et al, 1993). A toxic protein, Hirsutellin A (HtA), was then isolated from these cultures and proved to show broad pathogenic activity against insects (Krasnoff and Gupta, 1994;Mazet and Vey, 1995). HtA was lethal to Galleria mellonella larvae upon injection (Mazet and Vey, 1995) and caused detectable cytopathic effects on Spodoptera frugiperda cells (Sf9), inhibiting cell growth (Liu et al, 1995), for example.…”

“…A toxic protein, Hirsutellin A (HtA), was then isolated from these cultures and proved to show broad pathogenic activity against insects (Krasnoff and Gupta, 1994;Mazet and Vey, 1995). HtA was lethal to Galleria mellonella larvae upon injection (Mazet and Vey, 1995) and caused detectable cytopathic effects on Spodoptera frugiperda cells (Sf9), inhibiting cell growth (Liu et al, 1995), for example. The ribosomal RNA (rRNA) extracted from these cells contained a small fragment of about 500-600 nt (Liu et al, 1996) resembling the -fragment produced by fungal ribotoxins upon inactivation of eukaryotic ribosomes (Chan et al, 1983;Endo and Wool, 1982;Endo et al, 1983;Schindler and Davies, 1977).…”