Research Group Defense Physiology, PD Dr. Axel Mithöfer

Plant-Microbe Interactions

During the interactions between plants and microbes, microbe-associated molecular patterns (MAMPs,) represent highly effective signals. Upon perception by specific plant receptors, these signals induce downstream signal transduction processes including ion fluxes, Ca²+ concentration changes in the cytosol and the nucleus, phosphorylation / dephosphorylation reactions, oxylipins synthesis (including jasmonates) and finally the activation of specific cellular reactions. We are interested to identify components of signal transduction chains in both symbioses and pathogenic interactions and ask whether or not they are present in plant herbivore interactions as well.

Plant-Insect Interactions

Plants have evolved a large assortment of direct and indirect defences that cause an effective and drastic reduction in insect feeding. The activation of specific defence responses requires efficient recognition of the aggressor, conversion of the perceived signal into downstream signaling cascades and, eventually, the onset of appropriate reactions against the enemy. Signal perception in the plant cell may rely, for example, on the presence of specific receptors for insect-derived chemical signals such as herbivore associated molecular patterns (HAMPs) or on general recognition processes that rely on localized injury of the plant. Subsequent signal transduction elements are under investigation as well with a focus on calcium-mediated processes. In principle, herbivory combines two different aspects of the feeding process. First, there is mechanical wounding of the infested tissue and second, the introduction of oral secretions derived from the feeding organism into the wounded tissue. Thus, the attacked plant faces both a mechanical and a chemical challenge. Using a mechanical larva, MecWorm, we are able to mimic and study the wounding process without the chemistry of oral secretions. All aspects mentioned above are investigated to understand early signaling events in plant-herbivore interactions.

Mecworm

Carnivorous Plants

Although well known and often described in literature and textbooks, the biochemistry and molecular biology of carnivory in plants are not well understood. To obtain a more basic information of this fascinating topic, we started analyzing the composition of the digesting pitcher fluid of Nepenthes species by a proteomic approach. First results indicate the presence of either various unknown proteins or plant enzymes classified as inducible pathogenesis-related proteins.   

<span class="species">Nepenthes alata</span>
Nepenthes alata