Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco

Abstract

The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non‐host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianae, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 μg/plant, whereas 50‐fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10323 and 10155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C‐terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.

Modification of Plasma Membrane Organization in Tobacco Cells Elicited by Cryptogein

“…Cryptogein was purified according to a previously published method (Ricci et al, 1989), prepared in distilled water, and used at a final concentration of 50 nM. For sterol depletion, BY2 cells were incubated 15 min with 5 mM MbCD (cell culture tested, Sigma-Aldrich).…”

A Harpin Binding Site in Tobacco Plasma Membranes Mediates Activation of the Pathogenesis-Related Gene HIN1 Independent of Extracellular Calcium but Dependent on Mitogen-Activated Protein Kinase Activity

“…s. syringae -derived harpins and elicitins from various Phytophthora species trigger the HR, PR gene expression, and systemic acquired resistance in the nonhost plant tobacco (Ricci et al, 1989;He et al, 1993;Baillieul et al, 1995;Gopalan et al, 1996). Using harpin from P. s. phaseolicola (harpin Psph ) and the Phytophthora megasperma ␤ -elicitin ␤ -megaspermin, we have attempted a comparative analysis of signal perception and transduction mechanisms induced by bacterial and oomycete elicitors.…”

The Plant Defense Elicitor Cryptogein Stimulates Clathrin-Mediated Endocytosis Correlated with Reactive Oxygen Species Production in Bright Yellow-2 Tobacco Cells

“…This probe was used at the final concentration of 4.25 mM. Cryptogein was purified according to the method of Ricci et al (1989), prepared in distilled water, and used at the final concentration of 50 nM. Tyrphostins A23 and A51 (SigmaAldrich) were stored in DMSO as 1,000-fold stock solutions and used at a final concentration of 5 mM.…”

“…Cryptogein, produced by the oomycete Phytophthora cryptogea, belongs to a class of proteinaceous elicitors called elicitins, able to induce a HR and acquired resistance in tobacco plants (Ricci et al, 1989). The mode of action of cryptogein begins with the recognition of this elicitor by an unidentified plasma membrane receptor at a high-affinity binding site .…”