title: The histidine kinases CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3 regulate vascular tissue development in Arabidopsis shoots.
abstract: The development and activity of the procambium and cambium, which ensure vascular tissue formation, is critical for overall plant architecture and growth. However, little is known about the molecular factors affecting the activity of vascular meristems and vascular tissue formation. Here, we show that the His kinase CYTOKININ-INDEPENDENT1 (CKI1) and the cytokinin receptors ARABIDOPSIS HISTIDINE KINASE2 (AHK2) and AHK3 are important regulators of vascular tissue development in Arabidopsis thaliana shoots. Genetic modifications of CKI1 activity in Arabidopsis cause dysfunction of the two-component signaling pathway and defects in procambial cell maintenance. CKI1 overexpression in protoplasts leads to cytokinin-independent activation of the two-component phosphorelay, and intracellular domains are responsible for the cytokinin-independent activity of CKI1. CKI1 expression is observed in vascular tissues of inflorescence stems, and CKI1 forms homodimers both in vitro and in planta. Loss-of-function ahk2 and ahk3 mutants and plants with reduced levels of endogenous cytokinins show defects in procambium proliferation and an absence of secondary growth. CKI1 overexpression partially rescues ahk2 ahk3 phenotypes in vascular tissue, while the negative mutation CKI1H405Q further accentuates mutant phenotypes. These results indicate that the cytokinin-independent activity of CKI1 and cytokinin-induced AHK2 and AHK3 are important for vascular bundle formation in Arabidopsis.
authors.affiliation: Department of Functional Genomics and Proteomics, Institute of Experimental Biology, Faculty of Science, Masaryk University, CZ-61137, Brno, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Hejátko
authors.forename: Hojin
authors.initials: H
authors.lastname: Ryu
authors.forename: Gyung-Tae
authors.initials: GT
authors.lastname: Kim
authors.forename: Romana
authors.initials: R
authors.lastname: Dobesová
authors.forename: Sunhwa
authors.initials: S
authors.lastname: Choi
authors.forename: Sang Mi
authors.initials: SM
authors.lastname: Choi
authors.forename: Premysl
authors.initials: P
authors.lastname: Soucek
authors.forename: Jakub
authors.initials: J
authors.lastname: Horák
authors.forename: Blanka
authors.initials: B
authors.lastname: Pekárová
authors.forename: Klaus
authors.initials: K
authors.lastname: Palme
authors.forename: Bretislav
authors.initials: B
authors.lastname: Brzobohaty
authors.forename: Ildoo
authors.initials: I
authors.lastname: Hwang
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D000071677:Histidine Kinase; D015151:Immunoblotting; D047468:Immunoprecipitation; D018520:Plant Shoots / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase; C000605492:AHK2 protein, Arabidopsis; C000605493:AHK3 protein, Arabidopsis; C101990:CKI1 protein, Arabidopsis