Purification and Characterization of a Novel Antifungal Protein from Paenibacillus macerans PM1 Antagonistic to Rice Blast Fungus, Pyricularia oryzae

An antifungal protein antagonistic to the rice blast fungus, Pyricularia oryzae was purified from Paenibacillus macerans PM-1 by ammonium sulfate fractionation, Q Sepharose Fast Flow column chromatography, Phenyl Sepharose CL-4B column chromatography and Superose 12 gen filtration. An apparent molecular mass of the purified antifungal protein was determined as 8 kDa by SDS-PAGE and 9 kDa by analytical gel filtration, respectively, suggesting that the purified protein is a monomer. The antifungal protein was stable at pH range from 7-12 and up to $100^{\circ}C$. The protein was also stable at 0.1-1% Tween 20 and Triton X-100. The N-terminal amino acid sequence of the antifungal protein was Thr-Glu-Leu-Pro-Leu-Gly-Ile-Val-Met-Asp-Lys-Tyr-Thr-Asp-Ala-Phe-Lys-Phe-Asp-Met-Phe. Comparison of the determined sequence with other peptide and DNA sequences did not reveal homology at all. Therefore, the purified antifungal protein was speculated to be a novel protein. The condidial germination in vitro of P. oryzae KJ301:93-39 by the purified protein ($5.9{\mu} g/ml$) was limited to $9{\pm}3.2%$ only, compared with $69{\pm}2.4%$ of the control. Ungerminated conidia were swollen at basa and mid cell by the purified protein. In vivo bioassay for inhibition of conidial germination of P. oryzae KJ 301, one of the most predominating racesin Korea. the purified protein ($5.9{\mu} g/ml$)strongly inhibited the conidial germination. The conidia, even though germinated, could not develop any further to produce appressoria efficiently.