Kermodul : Angeborene Immunität Innate Immunity. Uwe Sonnewald usonne@biologie.uni-erlangen.de

Transcription

1 BC Kermodul : Angeborene Immunität Innate Immunity Pathogens Invasion strategies Pathogen Host Interactions Basal Defence Uwe Sonnewald usonne@biologie.uni-erlangen.de 1

2 Pathogens and diseases Viruses Bacteria Nematodes Fungi ` 2

3 Two major types of defenses INNATE (NONSPECIFIC) IMMUNITY Rapid responses to a broad range of microbes External defenses Internal defenses ACQUIRED (SPECIFIC) IMMUNITY Slower responses to specific microbes Invading microbes (pathogens) Skin Mucous membranes Secretions Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells Humoral response (antibodies) Cell-mediated response (cytotoxic lymphocytes) 3

4 Innate (nonspecific) immunity First line: External defenses (Epithelien) 4

5 Innate immunity Second line: Internal defenses 1. Phagocytosis Microbes 1 Phagocytic cell Phagocytes Attach to and ingest invading microorganisms Initiates the inflammatory response Macrophages migrants or in lymph organs Antimicrobial proteins Complement system lysis of invading cells, triggers inflammation Interferons activate macrophages, prevent cell-to-cell spread Defensins secreted by macrophages Vacuole MACROPHAGE Lysosome containing enzymes 6 5

6 Innate immunity Second line: Internal defenses Natural killer (NK) cells Attack virus-infected body cells and cancer cells Apoptosis (cell death) in cells attacked 6

7 Innate immunity Second line: Internal defenses 2. Inflammatory response 7

8 Activation of complement proteins 8

9 Activation of complement proteins and lysis of target cells 9

10 Plants Immunity Non-host resistance Host resistance Pre-existing Induced Hypersensitive Cell death Physical or chemical barriers Basal defense Innate immunity 10

11 Pre-existing defenses Cuticle Host Cell Wall Bark Trichomes 11

12 Plant pathogenic bacteria are extracellular 12

13 How do pathogens enter the apoplast? Fungi Bacteria penetration peg Illustrated glossary of plant pathology 13

14 Infection sequence of Erysiphe cichoracearum on a susceptible Arabidopsis Stage 1 Stage 3 Stage 2 Stage 4 14

15 Pathogen-induced responses: Bacteria /Fungi Plant Cell 15

16 Signal transduction events 16

17 Vesicles carrying antimicrobial compounds can be observed under the microscope Surface view of a sorghum leaf inoculated 22 hours earlier with the fungus C. graminicola; arrows indicate appressoria 17 Snyder & Nicholson (1990) Science Vol no. 4963, pp

18 Visualization of vesicle trafficking by GFP tagging of plasma membranes Aggregation of vesicles in response to fungal infection Host plasma membrane dynamics during Erysiphe cichoracearum infectionsvisualized by green fluorescent protein (GFP)-tagged plasma membrane marker lines. Koh et al. (2005), The Plant Journal 44,

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

20 GFP labeling of Microfilaments Polarization of microfilaments in response to fungal infection Rearrangement of microfilaments in Arabidopsis epidermal cells expressing green fluorescent protein fused to the actin-binding domain of a mouse talin 8h after inoculation with Colletotrichum truncatum. Appressoria Shimada et al.(2006) MPMI 19,

21 Induced basal defenses (Innate immunity) Antimicrobial compounds, Defense proteins Bacterium Papilla Secretory pathway Golgi Hormones (Salicylic acid, jasmonic acid, ethylene) Signal transduction cascade Nucleus DNA RNA nucleus Antimicrobial compounds New proteins ER, translation 21

22 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) 22

23 Pattern recognition receptors (PRRs) 23

24 Pattern recognition receptors (PRRs) The PRR are divided in four families: Toll-like receptors (TLR) Nucleotide oligomerisation receptors (NLR) C-type lectin receptors (CLR) RIG-1 like receptors (RLR) 24

25 Pattern recognition receptors (PRRs) TLR1, 2, 4 and 6 recognise bacterial lipids TLR3, 7 and 8 recognise viral RNA TLR9 recognises bacterial DNA TLR5 and 10 recognise bacterial or parasite proteins 25

26 Pattern recognition receptors (PRRs) Three main pathways are activated by TLRs: MAP kinase pathway (ERK, p38 and JNK) NFkB pathway IRF pathway (interferon-regulatory factor) 26

27 Pattern recognition receptors (PRRs) 27

28 Recognition of pathogen associated patterns (PAMPS) Neutrophil Neutrophils are attracted by formylmethionine containing peptides Pipette containing Formyl-Met-Leu-Phe 28

29 29

30 Flagellin 30

31 Bacterial flagellin 31

32 "flg22": highly conserved domain in N-terminus QRLSTGSRINSAKDDAAGLQIA... up to now, the best "general elicitor" in plants... (Georg Felix, J. Duran, Sigrid Volko & Thomas Boller, Plant J. 18, , 1999) 32

33 Location of epitope recognized in plants and animals Smith et al., Nature Immunol

34 Flagellin-Signalling Gomez-Gomez and Boller, 2002, Trends in Plant Sci. (7) 34

35 Mutation of FLS2 Growth retardation 35

36 Mutation of FLS2 fls2 deposit less callose Growth is less affected in fls2 fls2 Col-0 III I II 36

37 How can microbes be successful pathogens? 37

38 Successful pathogens are able to: 1. Suppress or evade host basal defenses; 2. Interfere with host cell metabolism, altering it to their own advantage 38

39 Microbial effector proteins suppress immunity Microbe PAMP Receptor Signal transduction Resistance Effektoren Microbe PAMP Receptor Signal transduction Susceptebility 39

40 Strategies used by bacterial pathogens Abramovitch et al. Nature Reviews Molecular Cell Biology 7, (August 2006) doi: /nrm

41 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 & Alfano Cellular Microbiology 6 (11),

42 Speth et al. (2007) Curr. Opin. Plant Biol. 42

43 YopJ inhibition of MAPK signaling by acetylation of MKKs. Mukherjee (2007) TIBS 32,

44 Microbial effectors targetting the secretory pathway xopj:gfp Perturbed endomembrane trafficking xopj C235A xopj G2A Catalytic triade required AvrRxV XopJ XopB PM localization requires myristoylation 44

45 Resistance Susceptibility Resistance Susceptibility 45

46 46 Jones & Dangl (2006) Nature 444; Chisholm et al (2006), Cell 124