First and fifth authors: Centre de Physiologie Végétale, Université Paul Sabatier, Laboratoire de Mycologie, 118, route de Narbonne, 31062 Toulouse, France; and second, third, fourth, and sixth authors: Centre de Physiologie Végétale, Université Paul Sabatier, UMR 5546 CNRS-UPS, 118, route de Narbonne, 31062 Toulouse, France
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Accepted for publication 12 June 1997.
A glycoprotein of 34 kDa (GP 34) was solubilized at acidic pH from the mycelium of Phytophthora parasitica var. nicotianae and was purified by ion exchange and gel permeation chromatography. Whole tobacco plants treated with GP 34 through their roots showed an enhanced lipoxygenase activity as well as hydroxyproline-rich glycoprotein accumulation, indicating that this molecule had elicitor properties. An antiserum raised against the pure glycoprotein allowed localization of GP 34 by immunogold-labeling on the cell surface of the mycelium when the fungus was grown in vitro. In the wall-less zoospores, GP 34 was limited to the flagellum surface. It was then abundantly synthesized at the onset of encystment. During infection of tobacco plants, labeling was very faint at early stages of colonization, particularly in the susceptible host cultivar. It appeared earlier in the resistant host cultivar and was restricted to the living fungus, declining with mycelium cell death.
© 1997 The American Phytopathological Society