MAIN CONCLUSION: 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.
- 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
BACKGROUND AND AIMS: Nitric oxide (NO) is involved in the signalling and regulation of plant growth and development and responses to biotic and abiotic stresses. The photoperiod-sensitive mutant 7B-1 in tomato (Solanum lycopersicum) showing abscisic acid (ABA) overproduction and blue light (BL)-specific tolerance to osmotic stress represents a valuable model to study the interaction between light, hormones and stress signalling. The role of NO as a regulator of seed germination and ABA-dependent responses to osmotic stress was explored in wild-type and 7B-1 tomato under white light (WL) and BL. METHODS: Germination data were obtained from the incubation of seeds on germinating media of different composition. Histochemical analysis of NO production in germinating seeds was performed by fluorescence microscopy using a cell-permeable NO probe, and endogenous ABA was analysed by mass spectrometry. KEY RESULTS: The NO donor S-nitrosoglutathione stimulated seed germination, whereas the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) had an inhibitory effect. Under WL in both genotypes, PTIO strongly suppressed germination stimulated by fluridone, an ABA inhibitor. The stimulatory effect of the NO donor was also observed under osmotic stress for 7B-1 seeds under WL and BL. Seed germination inhibited by osmotic stress was restored by fluridone under WL, but less so under BL, in both genotypes. This effect of fluridone was further modulated by the NO donor and NO scavenger, but only to a minor extent. Fluorescence microscopy using the cell-permeable NO probe DAF-FM DA (4-amino-5-methylamino-2',7'-difluorofluorescein diacetate) revealed a higher level of NO in stressed 7B-1 compared with wild-type seeds. CONCLUSIONS: As well as defective BL signalling, the differential NO-dependent responses of the 7B-1 mutant are probably associated with its high endogenous ABA concentration and related impact on hormonal cross-talk in germinating seeds. These data confirm that light-controlled seed germination and stress responses include NO-dependent signalling.
- MeSH
- Models, Biological MeSH
- Cyclic N-Oxides pharmacology MeSH
- Nitric Oxide Donors pharmacology MeSH
- Fluoresceins analysis MeSH
- Stress, Physiological * drug effects radiation effects MeSH
- Imidazoles pharmacology MeSH
- Kinetics MeSH
- Germination * drug effects radiation effects MeSH
- Abscisic Acid metabolism MeSH
- Mutation MeSH
- Osmosis drug effects radiation effects MeSH
- Nitric Oxide pharmacology MeSH
- Pyridones pharmacology MeSH
- Gene Expression Regulation, Plant drug effects radiation effects MeSH
- Plant Growth Regulators metabolism MeSH
- S-Nitrosoglutathione pharmacology MeSH
- Free Radical Scavengers pharmacology MeSH
- Seeds drug effects genetics physiology radiation effects MeSH
- Signal Transduction drug effects radiation effects MeSH
- Solanum lycopersicum drug effects genetics physiology radiation effects MeSH
- Light * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Protoplast cultures are remarkable examples of plant cell dedifferentiation. The state of dedifferentiation is evidenced by changes in cell morphology, genome organization, as well as by the capability of protoplasts to differentiate into multiple types of cells (depending on the type of the stimulus applied). The first change in the genome structure is connected with large-scale chromatin decondensation, affecting chromocentres involving various types of these repetitive sequences. This paper describes not only the de- and recondensation of satellite DNA type I and 5S rDNA repetitive sequences, but it also compares the recondensation level of chromatin with the levels of oxidative stress which were decreased by using an antioxidant, as well as the capabilities of the antioxidative systems within protoplasts, during the first 72 h of their culture. It is demonstrated that the treatment of protoplasts with ascorbic acid not only decreased the level of oxidative stress but also positively stimulated the expression of the ascorbate peroxidase and catalase. It also led to a greater recondensation of the chromatin (when compared to the untreated protoplasts); in addition, it supported cell proliferation. It is concluded that large-scale genome relaxation is more directly connected with oxidative stress than with large changes in the expression of genes; and further, that its recondensation is related to the start of (as well as the level of) protection by the antioxidative systems.
- MeSH
- Ascorbate Peroxidases MeSH
- Cell Nucleus enzymology genetics metabolism MeSH
- Cucumis sativus enzymology genetics metabolism MeSH
- Catalase genetics metabolism MeSH
- Microsatellite Repeats MeSH
- Oxidative Stress MeSH
- Peroxidases genetics metabolism MeSH
- Protoplasts enzymology metabolism MeSH
- Plant Proteins genetics metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Similarly to animals, nitrous oxide (NO) has emerged recently as a key signalling molecule in many physiological and pathological processes in plants. This review summarizes the current knowledge and understanding of the molecular mechanisms of NO synthesis and signalling in plant cells.
- MeSH
- Financing, Organized MeSH
- Publication type
- Abstracts MeSH
- MeSH
- Financing, Organized MeSH
- Publication type
- Abstracts MeSH
