PLANT PHYSIOLOGY , Vol 111, Issue 3 735-739, Copyright © 1996 by American Society of Plant Biologists
|
PLANT-MICROBE AND PLANT-INSECT INTERACTIONS |
Germin Gene Expression Is Induced in Wheat Leaves by Powdery Mildew Infection
W. J. Hurkman and C. K. Tanaka
United States Department of Agriculture, Agricultural Research Service, Western Regional Research Center, Crop Improvement and Utilization Research Unit, Albany, California 94710
Germin gene expression is induced in wheat (Triticum aestivum L.) leaves by
powdery mildew (Erysiphe graminis f. sp. tritici) infection. Germin is a
protein marker for early cereal development and is an oxalate oxidase, an
enzyme that catalyzes the conversion of oxalate to CO2 and H2O2. The
induction of germin gene expression by powdery mildew infection is
consistent with the importance of H2O2 to plant defense and identifies 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 course. The increase in
accumulation of germin mRNA was accompanied by an increase in the germin
oligomer, which reached maximal levels by d 6. An increase in oxalate
oxidase activity paralleled germin oligomer accumulation. 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 indicator of powdery mildew infection
rather than cultivar resistance.
