Use of Enzyme-Linked Immunosorbent Assay for Characterization of Water Soluble Glucan, the Suppressor of Hypersensitive Response of Potato Cells Caused by Phytophthora infestans

Abstract

Polyclonal antibodies from rabbit immunized with water soluble glucan (WSG), the hypersensitivity-suppressor of Phytophthora infestans, were used to develop the enzyme-linked immunosorbent assay technique (ELISA) to detect WSG in germination fluid (GF) of the fungus. As little as 4.3 picomoles of WSG per assay well could be detected by this method. The ELISA test with anti-WSG-rabbit-antibodies showed that GF derived from race 0 and race I and 1, 2, 3, 4 of P. infestans, avirulent or virulent to cultivar Yukijiro (R₁-gene), respectively, contained the same WSG, but their contents were different. Race 1, 2, 3, 4 contained much more WSG in GF than in those of race 1 and race 0. The WSG was increasingly released into the GF up to 5 hr after germination of the fungal cystospores. An apparent molecular weight of the purified WSG from race 1, 2, 3, 4 was shown to be 4700 dalton by using high performance liquid chromatography. The WSG peak of race 1, 2, 3, 4 and race 0 extracts showed almost the same degree of suppressor activity with regard to hypersensitive reaction of host cells.