Article

The histidine kinases CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3 regulate vascular tissue development in Arabidopsis shoots.

Department of Functional Genomics and Proteomics, Institute of Experimental Biology, Faculty of Science, Masaryk University, CZ-61137, Brno, Czech Republic.
The Plant Cell (impact factor: 8.99). 08/2009; 21(7):2008-21. DOI:10.1105/tpc.109.066696 pp.2008-21
Source: PubMed

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.

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Keywords

ahk3 mutants
 
Arabidopsis cause dysfunction
 
Arabidopsis thaliana shoots
 
CKI1 forms homodimers
 
CKI1 overexpression
 
cytokinin receptors ARABIDOPSIS HISTIDINE KINASE2
 
cytokinin-independent activation
 
cytokinin-induced AHK2
 
endogenous cytokinins
 
kinase CYTOKININ-INDEPENDENT1
 
Loss-of-function ahk2
 
molecular factors
 
negative mutation CKI1H405Q
 
plant architecture
 
procambial cell maintenance
 
procambium proliferation
 
two-component signaling pathway
 
vascular meristems
 
vascular tissue development
 
vascular tissue formation
 

Jan Hejátko