1. Bacterium-induced basal resistance inhibits viral infection in tobacco plants László ZSIROS 1,2, Ágnes SZATMÁRI 1, László PALKOVICS 2, Zoltán KLEMENT 1 Zoltán BOZSÓ 1 1 Plant Protection Institute of the HAS 2 Corvinus University of Budapest Dept. of Plant Pathology

2. Main types of resistance in plants Preformed Microorganism-induced Hypersensitive response (HR) Basal resistance (BR) Early basal resistance (EBR) Late basal resistance (LBR)

3. Comparison of basal and hypersensitive defense Type of resistanceHypersensitiveBasal Plant-bacterium interaction SpecificNon-specific Inducer bacteriumMetabolically active pathogen Pathogen, saprotroph, heat killed, etc. SymptomCell necrosisSymptomless (detection with superinfection)

4. Induction of basal resistance (BR) and hypersensitive response (HR) Plant cell Basal resistance Flagellin, LPS Avr proteins Hypersensitive response Intercellular space

5. Tobacco mosaic virus (TMV) Resistance in tobacco HR – 78 hours N gene Plant-TMV interaction incompatible (HR) compatible (mosaic leaves)

6. Changes at cell level during basal resistance (BR) change in pH level cell wall fortification papilla formation active oxygen forms (eg. hydrogen peroxide) bacterium envelopment

7. Aims of research Does a bacterial infection impede the symptoms/HR of a viral superinfection? Is symptom/HR inhibition attached to bated virus replication? How do some defense-related genes change in their transcription activity?

8. Materials and methods Plants –N. tabacum L. ‘Samsun’ nn (compatible) –N. tabacum L. ‘Xanthi’ NN (incompatible) Bacterial inoculation –Pseudomonas syringae pv. syringae hrcC mutant Viral inoculation –TMV Virus quantity and gene activity assay –Real-Time PCR

9. Inoculation method to assay early basal resistance (EBR) Bacterial inoculation Water infiltration (mock) Viral inoculation 6 hours TMV

10. HR-inhibition assay (‘Xanthi’ NN plant, incompatible tobacco-TMV interaction) Bacterium (hrcC) + TMV Water + TMV Positive control (TMV only)

11. HR-inhibition assay (‘Xanthi’ NN plant, incombatible tobacco – TMV interaction) PlantPre-treatmentNumber of lesions Size of lesions Positive control (TMV only) -2282-3 mm Early basal resistance Water1882-3 mm Bacterium671 mm Average results of repeated treatments

12. Inhibition of virus replication (‘Xanthi’ NN plant, incombatible tobacco – TMV interaction) Representative results of repeated treatments hrcC = Pseudomonas syringae pv. syringae hrcC mutáns

13. Defense-related genes (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction) Epoxide hydrolase – epoxide neutralization Ortho-methyl trasferase – cell wall synthesis Superoxide dismutase – superoxide degradation

14. Defense-related genes 1 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction) Representative results of repeated treatments hrcC = Pseudomonas syringae pv. syringae hrcC mutant

15. Defense-related genes 2 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction) Representative results of repeated treatments hrcC = Pseudomonas syringae pv. syringae hrcC mutant

16. Defense-related genes 3 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction) Representative results of repeated treatments hrcC = Pseudomonas syringae pv. syringae hrcC mutant

17. Symptom inhibition of EBR (‘Samsun’ nn plant, compatible tobacco – TMV interaction) Water + TMVBacterium + TMVTMV

18. Inhibition of virus replication (‘Samsun’ nn plant, compatible tobacco – TMV interaction) Representative results of repeated treatments hrcC = Pseudomonas syringae pv. syringae hrcC mutant

19. Summary Related to EBR, there was inhibition observed in –mosaic leaf symptom development; –virus-induced HR development; –the rate of virus replication; –change in activity of some defense-related genes

20. Conclusions Possible reasons for HR or mosaic symptom inhibition during basal resistance: –blocking of virus translocation in plant –inhibition of virus replication (RNA silencing? priming?) –non-specific defense –hydrogen peroxide  symptoms