title: Unraveling the evolution of cytokinin signaling.
abstract: The conquest of the land by plants required dramatic morphological and metabolic adaptations. Complex developmental programs under tight regulation evolved during this process. Key regulators of plant development are phytohormones, such as cytokinins. Cytokinins are adenine derivatives that affect various processes in plants. The cytokinin signal transduction system, which is mediated via a multistep variant of the bacterial two-component signaling system, is well characterized in the model plant Arabidopsis (Arabidopsis thaliana). To understand the origin and evolutionary pattern of this signaling pathway, we surveyed the genomes of several sequenced key plant species ranging from unicellular algae, moss, and lycophytes, to higher land plants, including Arabidopsis and rice (Oryza sativa), for proteins involved in cytokinin signal transduction. Phylogenetic analysis revealed that the hormone-binding receptor and a class of negative regulators first appeared in land plants. Other components of the signaling pathway were present in all species investigated. Furthermore, we found that the receptors evolved under different evolutionary constraints from the other components of the pathway: The number of receptors remained fairly constant, while the other protein families expanded.
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom.
authors.forename: Birgit
authors.initials: B
authors.lastname: Pils
authors.forename: Alexander
authors.initials: A
authors.lastname: Heyl
mesh_terms: D005075:Biological Evolution; D019068:Bryopsida / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism*; D020440:Gene Duplication; D008954:Models, Biological; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D003583:Cytokinins; D010940:Plant Proteins; D011956:Receptors, Cell Surface
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