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The Germinlike Protein GLP4 Exhibits Superoxide Dismutase Activity and Is an Important Component of Quantitative Resistance in Wheat and Barley

January 2004 , Volume 17 , Number  1
Pages  109 - 117

Anders B. Christensen , 1 Hans Thordal-Christensen , 1 Grit Zimmermann , 2 Torben Gjetting , 1 Michael F. Lyngkjær , 1 Robert Dudler , 3 and Patrick Schweizer 2

1Risø National Laboratory, Frederiksborgvej 399, P.O. 49, DK-4000 Roskilde, Denmark; 2Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466 Gatersleben, Germany; 3University of Zürich, Institute of Plant Biology, Zollikerstrasse 107, CH-8000 Zürich, Switzerland

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Accepted 15 September 2003.

Germinlike proteins (GLP) are encoded in plants by a gene family with proposed functions in plant development and defense. Genes of GLP subfamily 4 of barley (HvGLP4, formerly referred to as HvOxOLP) and the wheat orthologue TaGLP4 (formerly referred to as TaGLP2a) were previously found to be expressed in pathogen-attacked epidermal tissue of barley and wheat leaves, and the corresponding proteins are proposed to accumulate in the apoplast. Here, the role of HvGLP4 and TaGLP4 in the defense of barley and wheat against Blumeria graminis (DC.) E. O. Speer, the cereal powdery mildew fungus, was examined in an epidermal transient expression system and in transgenic Arabidopsis thaliana plants overexpressing His-tagged HvGLP4. Leaf extracts of transgenic Arabidopsis overexpressing HvGLP4 contained a novel His-tagged protein with superoxide dismutase activity and HvGLP4 epitopes. Transient overexpression of TaGLP4 and HvGLP4 enhanced resistance against B. graminis in wheat and barley, whereas transient silencing by RNA interference reduced basal resistance in both cereals. The effect of GLP4 overexpression or silencing was strongly influenced by the genotype of the plant. The data suggest that members of GLP subfamily 4 are components of quantitative resistance in both barley and wheat, acting together with other, as yet unknown, plant components.

Additional keywords: RNAi, transgene.

© 2004 The American Phytopathological Society