Structure and signaling mode of type-II ethylene receptors

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Genetic and biochemical studies on the ethylene signaling pathway suggest that the receptor sensor kinases involved in signal perception and signal transduction of the plant hormone ethylene are engaged in different signaling pathways and are integrated into a complex network of protein-protein interactions. The project aims to elucidate the molecular structure and signaling mode of these receptor kinases, which form two structural and functional distinct subfamilies. Members of subfamily-I are characterized by a well-conserved histidine kinase domain and a sensor domain consisting of three transmembrane helices. On the other hand, subfamily-II receptors lack conserved residues necessary for histidine kinase activity and have an additional transmembrane helix in their sensor domain. Receptors of subfamily-I have been characterized in detail in the past. In contrast, our knowledge on receptors belonging to subfamily-II carrying the degenerate histidine kinase domain is much less profound. Consequently, our project aims to functionally dissect the role of type II receptors in ethylene signaling by studying dynamic interactions of the receptors related to the binding of the plant hormone, the dimerization mode of the receptor isoforms and the interaction of the receptors with different downstream signaling partners. Besides functional characterization of the receptors by fluorescence techniques we aim to get an even more mechanistic understanding of the actions of the type-II receptor family by solving the molecular structure of recombinant type-II receptors and of their complexes or interaction domains with their downstream signaling partners.