Baculovirus-Mediated Production and Antifungal Activity of a Diapause-Specific Peptide, Diapausin, of the Adult Leaf Beetle, Gastrophysa atrocyanea (Coleoptera: Chrysomelidae)

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A diapause-specific conotoxin-like peptide, diapausin, of the adult leaf beetle, Gastrophysa atrocyanea, was produced by the baculovirus/Bombyx mori system. Recombinant diapausin secreted in the blood plasma was purified by a combination of acidic-methanol extraction and reverse-phase high performance liquid chromatography. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analysis indicated that the molecular mass (4463.3±4.5Da) of the recombinant diapausin agreed practically with the theoretical molecular mass (4467.6Da) calculated from the amino acid sequence of natural diapausin. The recombinant diapausin inhibited the growth of five tested species of phytopathogenic fungus including Fusarium solani, but was not active on two tested species of entomopathogenic fungus. For any of the tested phytopathogenic fungi, recombinant diapausin did not inhibit spore germination but diminished mycelial growth. The antifungal activity against F. solani was reduced by cations such as K⁺ and Ca²⁺, indicating cation-sensitive antifungal activity of this peptide. Recombinant diapausin was not active on four tested species of bacterium (i. e., one Gram-positive and three Gram-negative bacteria).