GERMINATION INDUCES ACCUMULATION OF SPECIFIC PROTEINS AND ANTIFUNGAL ACTIVITIES IN CORN KERNELS

This study examined protein induction and accumulation during imbibiti on and germination of corn kernels, as well as antifungal activities o f extracts from germinating kernels against Aspergillus flavus and Fus arium moniliforme. Genotypes studied included GT-MAS:gk and Mp420, whi ch are resistant to A. flavus infection and aflatoxin accumulation, an d Pioneer 3154 and Deltapine G-4666, which are susceptible to A. flavu s infection and aflatoxin accumulation. Sodium dodecyl sulfate-polyacr ylamide gel electrophoresis resolved five protein bands that were pres ent at higher concentrations in germinated kernels than in nongerminat ed kernels. Western blot analyses revealed that one of these proteins reacted with the 22-kDa zeamatin antiserum, and a zeamatin-like protei n accumulated to a higher concentration in germinated kernels. Two pro tein bands from dry kernels that reacted with ribosome-inactivating pr otein (RIP) antiserum were identified as the 32-kDa proRIP-like form a nd an 18-kDa peptide of the two peptides that form active RIP. However , in germinated kernels, two protein bands that reacted with RIP antis erum were identified as two RIP-like peptides with a molecular mass of approximate to 18 and 9 kDa. Purified RIP and zeamatin from corn inhi bited growth of A. flavus. Bioassays of germinated kernel extracts fro m all four genotypes exhibited antifungal activity against A. flavus a nd F. moniliforme, with extracts from the susceptible genotypes showin g greater inhibition zones. This study provides evidence of protein in duction in corn kernels during imbibition or the early stages of germi nation, and the induced proteins may be related to our previous findin gs of germination-associated resistance in the corn kernel, especially in the susceptible kernels.