The level of resistance induced in different tomato genotypes after β-CRY treatment correlated with the upregulation of defence genes, but not sterol binding and involved ethylene and jasmonic acid signalling. Elicitins, a family of small proteins secreted by Phytophthora and Pythium spp., are the most well-known microbe-associated molecular patterns of oomycetes, a lineage of fungus-like organisms that include many economically significant crop pathogens. The responses of tomato plants to elicitin INF1 produced by Phytophthora infestans have been studied extensively. Here, we present studies on the responses of three tomato genotypes to β-cryptogein (β-CRY), a potent elicitin secreted by Phytophthora cryptogea that induces hypersensitive response (HR) cell death in tobacco plants and confers greater resistance to oomycete infection than acidic elicitins like INF1. We also studied β-CRY mutants impaired in sterol binding (Val84Phe) and interaction with the binding site on tobacco plasma membrane (Leu41Phe), because sterol binding was suggested to be important in INF1-induced resistance. Treatment with β-CRY or the Val84Phe mutant induced resistance to powdery mildew caused by the pathogen Pseudoidium neolycopersici, but not the HR cell death observed in tobacco and potato plants. The level of resistance induced in different tomato genotypes correlated with the upregulation of defence genes including defensins, β-1,3-glucanases, heveins, chitinases, osmotins, and PR1 proteins. Treatment with the Leu41Phe mutant did not induce this upregulation, suggesting similar elicitin recognition in tomato and tobacco. However, here β-CRY activated ethylene and jasmonic acid signalling, but not salicylic acid signalling, demonstrating that elicitins activate different downstream signalling processes in different plant species. This could potentially be exploited to enhance the resistance of Phytophthora-susceptible crops.

• Keywords
• Defence-related genes, Elicitins, Pseudoidium neolycopersici, Resistance, Signalling, Sterol binding,
• MeSH
• Cyclopentanes metabolism   MeSH
• Ethylenes metabolism   MeSH
• Fungal Proteins metabolism   MeSH
• Host-Pathogen Interactions MeSH
• Salicylic Acid metabolism   MeSH
• Plant Leaves metabolism   microbiology   MeSH
• Plant Diseases microbiology   MeSH
• Oxylipins metabolism   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Phytophthora MeSH
• Pythium MeSH
• Reactive Oxygen Species metabolism   MeSH
• Plant Growth Regulators metabolism   MeSH
• Signal Transduction * MeSH
• Solanum lycopersicum metabolism   microbiology   physiology   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• cryptogein protein, Phytophthora cryptogea MeSH Browser
• Cyclopentanes MeSH
• ethylene MeSH Browser
• Ethylenes MeSH
• Fungal Proteins MeSH
• jasmonic acid MeSH Browser
• Salicylic Acid MeSH
• Oxylipins MeSH
• Hydrogen Peroxide MeSH
• Reactive Oxygen Species MeSH
• Plant Growth Regulators MeSH

Cryptogein is a proteinaceous elicitor secreted by Phytophthora cryptogea that can induce resistance to P. parasitica in tobacco plants. On the basis of previous computer modelling experiments, by site-directed mutagenesis a series of cryptogein variants was prepared with altered abilities to bind sterols, phospholipids or both. The sterol binding and phospholipid transfer activities corresponded well with the previously reported structural data. Induction of the synthesis of reactive oxygen species (ROS) in tobacco cells in suspension and proteomic analysis of intercellular fluid changes in tobacco leaves triggered by these mutant proteins were not proportional to their ability to bind or transfer sterols and phospholipids. However, changes in the intercellular proteome corresponded to transcription levels of defence genes and resistance to P. parasitica and structure-prediction of mutants did not reveal any significant changes in protein structure. These results suggest, contrary to previous proposals, that the sterol-binding ability of cryptogein and its mutants, and the associated conformational change in the ω-loop, might not be principal factors in either ROS production or resistance induction. Nevertheless, the results support the importance of the ω-loop for the interaction of the protein with the high affinity binding site on the plasma membrane.

• MeSH
• Phospholipids metabolism   MeSH
• Fungal Proteins genetics   metabolism   MeSH
• Plant Immunity immunology   MeSH
• Chlorogenic Acid analysis   MeSH
• Plant Leaves genetics   immunology   parasitology   physiology   MeSH
• Mutation MeSH
• Plant Diseases immunology   parasitology   MeSH
• Phytophthora genetics   metabolism   pathogenicity   MeSH
• Proteins genetics   metabolism   MeSH
• Proteomics methods   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Recombinant Proteins MeSH
• Sesquiterpenes analysis   MeSH
• Sterols metabolism   MeSH
• Nicotiana genetics   immunology   parasitology   physiology   MeSH
• Protein Binding MeSH
• Structure-Activity Relationship MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• capsidiol MeSH Browser
• cryptogein protein, Phytophthora cryptogea MeSH Browser
• elicitin, Phytophthora MeSH Browser
• Phospholipids MeSH
• Fungal Proteins MeSH
• Chlorogenic Acid MeSH
• Proteins MeSH
• Reactive Oxygen Species MeSH
• Recombinant Proteins MeSH
• Sesquiterpenes MeSH
• Sterols MeSH