Histidine phosphorelay kinases and epigenetic factors controlling de novo shoot organogenesis

The success of plant tissue culture technology stems from the remarkable competence of specific
cell types to initiate cell divisions and form primordia (immature meristems) that generate organs
such as roots and shoots. De novo shoot organogenesis occurs upon administering the appropriate
sequence and dose of the hormones auxin and cytokinin. The interplay and opposing functions of
auxin and cytokinin has been enigmatic since their discovery, whereby cytokinins are linked with
shoot formation and auxins with root formation. We aim to unravel molecular processes underlying
cytokinin signalling that guides the process of de novo shoot organogenesis. To this end a small
molecule named C1 will be implemented that strongly enhances the formation of shoots from root
explants (pieces of root). In bacteria, the compound C1 has been shown to affect the activity of a
histidine phosphorelay kinase involved in osmoregulation. Similarity of this kinase with
phosphorelay kinases in plants that encompasses the cytokinin receptors AHK2, 3 and 4, suggest
that C1 mediates enhancement of shoot organogenesis through the regulation of cytokinin
signalling. This project will address the question whether phosphorelay kinases are dominating
regulators of shoot organogenesis and will investigate possible mechanisms by which compound C1
enhances de novo shoot organogenesis.