Potassium (K+) is the most abundant mineral element in plants, and together with nitrogen and phosphorous, is limiting for plant production in many natural and agricultural habitats. Voltage-gated K+ channels are key players in the acquisition of K+ from the soil and in its redistribution within the plant. Interestingly, members of the family of plant voltage-gated K+ channels are structurally very similar but functionally they segregate into inward-rectifying (Kin) channels that allow plant cells to accumulate K+, outward-rectifying (Kout) channels that mediate K+ efflux, and weak-rectifying (Kweak) channels with the unique characteristic that they can act in two different gating modes. They are either inward-rectifying channels mediating K+ uptake only or non-rectifying channels transporting K+ in both directions over the plasmamembrane. This proposal aims at identifying the reasons for these divergences.
One goal is to identify the molecular basis for the opposite rectification of Kin and Kout channels. To achieve this, generation of synthetic Kin and Kout channels is accompanied by in silico structural molecular modeling and dynamics simulations. This combined approach is novel and will allow detailed structural and functional insights into the regulation of plant K+ channels.
Another goal is to identify mechanisms that regulate Kweak channel activity. Gating properties of these channels are strongly regulated by a complex spectrum of posttranslational modifications. By diverse approaches entities of the regulatory network are identified and the dynamics of this network is investigated in computational simulations. Beneficial aspects of Kweak channel regulation that were uncovered in Arabidopsis will be tested also in a crop plant species.
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