CeBiTec Distinguished Lecture
Monday, June 12th 2017, 17 c.t.
Plenary Hall, ZiF building
Prof. Dr. Dierk Scheel
Leibniz Institute of Plant Biochemistry, Department for Stress and Developmental Biology, Halle (Saale)
Molecular mechanisms of 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 bacterial flagellin-derived flg22 peptide, the elf18 peptide of the bacterial elongation factor EF-Tu, bacterial peptidoglycans and lipopolysaccharides, as well as fungal chitin oligomers and glucan fragments from oomycetes. 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. Among several receptor complex components, a lectin S-domain receptor kinase was identified, which mediates lipopolysaccharide sensing in Arabidopsis thaliana.
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.
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.
Host: Prof. Dr. Bernd Weisshaar