Biochemical events involved in downy mildew disease resistance in pearl millet in relation to H⁺-ATPase

Abstract

Pearl millet (Pennisetum glaucum L. Br.) is the most important crop in India and Africa. Downy mildew disease of pearl millet caused by the oomycetous fungus Sclerospora graminicola (Sacc.) Schroet., is the major biological constraint in the production of pearl millet. Plasma membrane H⁺-ATPase is induced in resistant pearl millet against downy mildew pathogen. Sodium orthovanadate, an inhibitor of H⁺-ATPase, was used in this study to understand its effect on other known defence responses in pearl millet including H⁺-ATPase. Results suggest that vanadate down-regulates all defence responses tested, such as H⁺-ATPase (53±5.0%), peroxidase (36±5.6%), phenylalanine ammonia lyase (43±4.5%), β-1,3 glucanase (25±4.2%), lytic activity (32±3.0%), hypersensitive response (57±4.3%) and pathogen colonisation. These data indicate that the plasma membrane H⁺-ATPase may be a key step in the signaling pathway leading to defence activation in pearl millet against downy mildew disease.