1 / 18

Plant basal defenses

Plant basal defenses. 1. Pre-existing. 2. Induced. Pre-existing defenses: the first barrier. Physical barriers involve properties of the plant surface, that is, the cuticle, stomata and cell walls.

janicewalsh
Download Presentation

Plant basal defenses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plant basal defenses 1. Pre-existing 2. Induced

  2. Pre-existing defenses: the first barrier • Physical barriers involve properties of the plant surface, that is, the cuticle, stomata and cell walls. • Chemical barriers include compounds, such as phytoanticipins that have antimicrobial activity, and defensins, which interfere with pathogen nutrition and retard their development.

  3. Plant pathogenic bacteria are extracellular

  4. How do pathogens enter the apoplast? Fungi Bacteria penetration peg Illustrated glossary of plant pathology www.apsnet.org/

  5. Pathogen-induced responses:It’s a race!!!! “As soon as a plant has recognized an attacking pathogen, the race is on. The plant attempts to prevent infection and to minimize potential damage, the pathogen attempts to gain access to nutrients for growth and reproduction.” Schmelzer, 2002 Question 3: On your carbonless paper, make a model that may enable us to follow the events that will occur in the plant cell during basal defense against pathogens.

  6. Signal transduction events PAMPS (Pathogen-Associated Molecular Patterns) oligosaccharides, lipids, polypeptides (flagellin), glycoproteins, etc… Espinosa, Avelina & Alfano Disabling surveillance: bacterial type III secretion system effectors that suppress innate immunity.Cellular Microbiology6 (11), 1027-1040.

  7. Cell polarization and papilla formation upon fungal infection Schmelzer (2002). Trends in Plant Science 7: 411-415

  8. Vesicles carrying antimicrobial compounds can be observed under the microscope Snyder and Nicholson, Science (1990)

  9. Aggregation of vesicles in response to fungal infection Plant proteins can be visualized by “tagging” them with fluorescent markers (GFP, YFP, etc…) Polarization of microfilaments in response to fungal infection Koh et al.,The Plant Journal(2005) Shimada et al.,MPMI (2006)

  10. Antimicrobial compounds, Defense proteins Papilla Secretory pathway Hormones (Salicylic acid, jasmonic acid, ethylene) Golgi Nucleus DNA RNA nucleus New proteins Antimicrobial compounds ER, translation Induced basal defenses (Innate immunity) Bacterium Signal transduction cascade

  11. Output of Induced basal defenses Recognition events(elicitors, receptors) • Signal transduction cascades • MAP kinases, phosphorylation cascades • Chemical changes: • Synthesis of NO, ROSs, signaling molecules (SA, JA, Ethylene), etc… • Gene expression changes (transcriptional regulation) • Synthesis of antimicrobial compounds and proteins (phytoalexins, PR proteins) • Cytoskeletal rearrangements, vesicle trafficking, secretion • Morphological changes (organelle redistribution, papilla deposition, cell wall modifications)

  12. Q4: How can microbes be successful pathogens?

  13. Successful pathogens are able to: • Suppress or evade host basal defenses; • Interfere with host cell metabolism, altering it to their own advantage

  14. Strategies used by bacterial pathogens Abramovitch et al.Nature Reviews Molecular Cell Biology7, 601–611 (August 2006) | doi:10.1038/nrm1984

  15. Plant pathogenic bacteria secrete proteins called “virulence effectors” directly into the host cell Bacteria use a sophisticated “injection” apparatus, called a Type III Secretion System, to deliver virulence effector proteins directly in the cytoplasm of the host cell. Bacterial type III effectors disable host surveillance by suppressing innate immunity. Espinosa & AlfanoCellular Microbiology6 (11), 1027-1040.

  16. Antimicrobial compounds, Defense proteins Papilla Secretory pathway Hormones (Salicylic acid, jasmonic acid, ethylene) Golgi Nucleus DNA RNA nucleus New proteins Antimicrobial compounds ER, translation Bacterial virulence effectors suppress host innate immunity Bacterium Signal transduction cascade

  17. Some of the available tools for dissecting plant-pathogen interactions: • Pathogenesis Assays • (assessing symptom development and pathogen multiplication in the host) • Microarrays • (analysis of global gene expression in the host plant) • Genetic transformation • (expression of any given plant or pathogen gene in the host plant) • Gene knock-out • (both in plant and pathogen) • Fluorescent protein tagging and microscopy • (allows visualization of protein localization and cellular dynamics)

More Related