[Seminar] Signaling in PAMP-triggered immunity

Seminar

Title: Signaling in PAMP-triggered immunity

Speaker: Dierk Scheel

Affiliation: Leibniz Institute of Plant Biochemistry, Department of Stress and Developmental Biology, Germany

Abstract:

Signaling in plant immunity

Plants detect potential pathogens in their environment via pathogen-associated molecular patterns (PAMPs) that are recognized by plant plasma membrane receptors. Typical PAMPs include the flagellin-derived flg22 peptide, the elf18 peptide of elongation factor EF-Tu, peptidoglycans and lipopolysaccharides, as well as chitin oligomers and glucan fragments. PAMP binding to their receptors initiates complex signaling networks that activate a multi-component defense response and thereby establish PAMP-triggered immunity.

One of the earliest detectable responses after PAMP perception is the activation of ion channels at the plasma membrane. Using a transgenic Arabidopsis line with the calcium reporter, aequorin, increases in cytosolic calcium levels are detected after PAMP application. To identify signaling network components, seeds of aequorin-expressing lines were mutagenized and the population screened for mutants with changed calcium elevation (cce) in response to different PAMPs (1). Besides several receptor complex components, a lectin S-domain receptor kinase was identified, which mediates lipopolysaccharide sensing (2).

MAPK cascades are essential for controlling defense responses. The elements that prevent erroneous signaling crosstalk may include expression patterns of the MAPK cascade components, the presence of pathway-specific protein complexes or the MAPK substrate diversity. Different strategies have been employed to isolate MAPK interacting proteins. Several VQ-motif containing proteins and tandem zinc finger proteins are MAPK substrates and regulate immune responses (3, 4).

Pathogen effectors interfere with PAMP recognition and signaling to suppress PAMP-triggered defense responses. Some effectors of the bacterial pathogen Pseudomonas syringae pv. tomato specifically interfere with MAPK cascades and thereby attenuate plant resistance.

This work is supported by Deutsche Forschungsgemeinschaft

1. Ranf S, Grimmer J, Pöschl Y, Pecher P, Chinchilla D, Scheel D, Lee J. (2012) Mol Plant 5, 115-130

2. Ranf S, Gisch N., Schäffer M, Illig T, Westphal L, Knirel YA, Sánchez-Carballo PM, Zähringer U, Hückelhofen R, Lee J, and Scheel D. (2015) Nat Immunol 16, 426-433

3. Pecher P, Eschen-Lippold L, Herklotz S, Kuhle K, Naumann K, Bethke G, Uhrig J, Weyhe M, Scheel D, and Lee J. (2014) New Phytol 203, 592-606

4. Maldonado-Bonilla LD, Eschen-Lippold L, Gago-Zachert S, Tabassum N, Bauer N,, Scheel D, Lee J. (2014) Plant Cell Physiol 55, 412-425