GERMIN GENE-EXPRESSION IS INDUCED IN WHEAT LEAVES BY POWDERY-MILDEW INFECTION

Germin gene expression is induced in wheat (Triticum aestivum L.) leav es by powdery mildew (Erysiphe graminis f. sp. tritici) infection. Ger min is a protein marker for early cereal development and is an oxalate oxidase, an enzyme that catalyzes the conversion of oxalate to CO2 an d H2O2. The induction of germin gene expression by powdery mildew infe ction is consistent with the importance of H2O2 to plant defense and i dentifies a mechanism for the elevation of H2O2 levels in wheat leaves . Germin mRNA levels increased 2 d after inoculation of seedlings with powdery mildew and continued to increase throughout an 8-d time cours e. The increase in accumulation of germin mRNA was accompanied by an i ncrease in the germin oligomer, which reached maximal levels by d 6. A n increase in oxalate oxidase activity paralleled germin oligomer accu mulation. Germin gene expression was induced in a relatively resistant cultivar (Bobwhite) as well as in a susceptible cultivar (Cheyenne), suggesting that the induction of germin gene expression is an indicato r of powdery mildew infection rather than cultivar resistance.