Purification and characterization of an antifungal thaumatin-like protein from sorghum (Sorghum bicolor) leaves

A protein with an apparent molecular mass of 17 kDa that cross-reacts with an antibody to corn zeamatin was induced in sorghum (Sorghum bicolor (L.) Moench) plants when infected with Fusarium moniliforme, the causal agent of stalk rot. The 17-kDa protein was purified from F. moniliforme-inoculated sorghum tissues by ammonium sulfate fractionation, anion exchange chromatography on DEAE-Sephacel followed by gel filtration on a Sephadex G-75 column. The N-terminal amino acid sequence analysis of the purified 17-kDa protein revealed sequence homology to thaumatin-like proteins (TLPs) of maize, barley, wheat, oats, rice and zeamatin. Western blot analysis showed that the purified 17-kDa TLP cross-reacted well with zeamatin antiserum and to a lesser extent with a bean TLP antiserum. The purified 17-kDa TLP inhibited the mycelial growth of F. moniliforme and Trichoderma viride in vitro.