Members of a recently discovered subfamily of cytokinin receptors display differences and similarities to their classical counterparts

Cytokinins represent a group of plant hormones that have been shown to be essential for plant growth and development. A recent large-scale phylogenetic analysis of components of the cytokinin signal transduction pathway revealed, among other findings, the existence of a second, previously unknown subfamily of cytokinin receptors. Here we report that the cytokinin binding domains of the members of the 2 subfamilies contain residues that are highly conserved in either or in both subfamilies. Experiments using fluorescence microscopy hint at an ER and a plasma membrane localization for 2 members of the newly identified subfamily. These data provide new insights in the conservation of sequence and localization properties among the 2 subfamilies.