Migration of the Fungal Protein Cryptogein within Tobacco Plants

Abstract

Cryptogein (CRY), a protein secreted by Phytophthora cryptogea, causes necrosis on tobacco (Nicotiana tabacum) plants at the site of application (the stem or the roots) and also on distant leaves. Autoradiography of plantlets after root absorption of radioiodinated CRY demonstrated a rapid migration of the label to the leaf lamina via the veins. Using an anti-CRY antiserum, a CRY-related antigen was detected in the stem and leaves of CRY-treated plants at a distance from the site of application. This antigen had the same molecular weight as CRY and was detected in the leaves as early as 1 hour after stem treatment, i.e. long before necrosis was detectable. The antigen was also detected in plants inoculated with P. cryptogea. The distant location of the necrosis induced by the fungus or by CRY can be ascribed to the migration of this protein, which is toxic to tobacco cells. It is proposed that CRY, which also elicits defense reactions in tobacco, might contribute to the hypersensitive response of tobacco to P. cryptogea.The interaction between the phytopathogenic fungus Phytophthora cryptogea and the nonhost plant tobacco (Nicotiana tabacum) leads to an HR2 characterized by plant tissue necrosis and a restricted growth of the fungus (5). An unusual feature of this HR is that necrosis occurs not only at the inoculation court but also on the leaves at a distance from the fungus. In culture, P. cryptogea secretes a protein, CRY (mol wt 10,323), which causes the rapid death of tobacco cells and is an elicitor of phytoalexin accumulation (4,6,11,12). When applied to the wounded stem or roots of a tobacco plant, CRY induces necrosis within 24 h at the point of application and also on distant leaves (14). This raises two questions: (a) does this elicitor actually move within the plant; and (b) interaction, then it should be possible to detect this proteinaceous elicitor in noninfected tissues from inoculated plants.We have investigated the possibility that CRY migrates in tobacco by two approaches: (a) autoradiography of plantlets after absorption of radioiodinated CRY by the roots; and (b) immunodetection of the protein in the stem and the leaves after application of exogenous CRY to the stem or to the roots, or after stem-inoculation with P. cryptogea. In addition, the behavior of CRY was compared with that of CAP, a related protein produced by Phytophthora capsici, which has slightly different biological effects on tobacco (14). MATERIALS AND METHODSTobacco plants (Nicotiana tabacum cv Xanthi nc) grown in a greenhouse for 30 d were transferred into a growth chamber (240C, 16 h daylength), and CRY was applied 10 d later to the stem or to the roots. Stem treatments were as previously described (14): the plant was decapitated above the third highest fully expanded leaf, and the wounded stem received 2.5 ,ug of elicitor as a 20-,uL drop of aqueous solution or a plug taken from a malt-agar culture of Phytophthora cryptogea; only the two upper remaining leaves (Li and L2) were left attached. In root treatments, t...

Physiological and Molecular Characteristics of Elicitin-Induced Systemic Acquired Resistance in Tobacco

“…The hypersensitive-like response provoked in tobacco leaves by application of cryptogein is accompanied by ethylene production, capsidiol synthesis (Milat et al, 1991a), and accumulation of PR l a protein. These responses appear to be preceded by the translocation of the fungal protein within the plant (Devergne et al, 1992).…”

Evidence for specific, high‐affinity binding sites for a proteinaceous elicitor in tobacco plasma membrane

“…Elicitins constitute a family of 10 kDa holoproteins that cause leaf necrosis and induce systemic acquired resistance of tobacco plants against fungal and bacterial pathogens [9]. Our attention is particularly focussed on cryptogein, a basic elicitin produced by P. cryptogea that causes hypersensitive reaction-like necrosis in tobacco (Nicotiana tabacum) plants [10]. Cryptogein induces a series of metabolic events in tobacco cells such as accumulation of phytoalexins, ethylene production, fast changes in ion fluxes through the plasma membrane, and a rapid but transient production of active oxygen species [11,12,13].…”

Involvement of lipid-protein complexes in plant-microorganism interactions

“…The development of this hypersensitive cell death involves the lipoxygenase-dependent production of fatty acid hydroperoxides [12]. Using cryptogein antibodies, it was shown that this elicitin can migrate through the plant and can be responsible for the systemic acquired resistance induced in tobacco [13][14][15]. A possible extension towards other plants could be offered with another family of the oomycete class, the Pythium which can induce protection of tomato against Fusarium oxysporum f. sp.…”