Related Experiment Video
Updated: Aug 8, 2026
07:42
Rapid Analysis of Circadian Phenotypes in Arabidopsis Protoplasts Transfected with a Luminescent Clock Reporter
Published on: September 17, 2016
Cytokinins regulate a bidirectional phosphorelay network in Arabidopsis
Ari Pekka Mähönen1, Masayuki Higuchi, Kirsi Törmäkangas
1Plant Molecular Biology Laboratory, Institute of Biotechnology, University of Helsinki, Post office box 56, FIN-00014 Helsinki, Finland.
Current Biology : CB
|June 7, 2006
Summary
Arabidopsis cytokinin receptors, like CRE1, act as both kinases and phosphatases. This dual activity regulates plant hormone signaling by controlling phosphate transfer to histidine phosphotransfer proteins.
Area of Science:
- Plant Biology
- Molecular Signaling
- Hormone Regulation
Background:
- Cytokinins are essential plant hormones regulating growth and development.
- Arabidopsis utilizes three histidine kinase (HK) receptors: CRE1, AHK2, and AHK3.
- Hormone perception typically involves a phosphorelay cascade: HK -> histidine phosphotransfer protein (HPt) -> response regulator (RR).
Purpose of the Study:
- To investigate the dual kinase/phosphatase activity of the cytokinin receptor CRE1.
- To elucidate the role of CRE1's phosphatase activity in cytokinin signaling.
- To understand how CRE1's activity impacts plant sensitivity to cytokinins.
Main Methods:
- In vitro biochemical assays and yeast-based systems were used to test CRE1's enzymatic activity.
- In planta experiments involved replacing the native CRE1 gene with modified versions (CRE1(T278I) mutant, AHK2).
- Plant cytokinin sensitivity was assessed following gene replacement.
Main Results:
- CRE1 functions as a kinase in the presence of cytokinin, phosphorylating HPt proteins.
- CRE1 acts as a phosphatase in the absence of cytokinin, dephosphorylating HPt proteins.
- Mutating CRE1 to a phosphatase-dominant form (CRE1(T278I)) reduced cytokinin sensitivity.
- Replacing CRE1 with a kinase-dominant receptor (AHK2) increased cytokinin sensitivity.
Conclusions:
- Arabidopsis cytokinin receptors possess dual kinase and phosphatase activities.
- This dual function dynamically regulates the phosphorelay system based on cytokinin availability.
- CRE1's phosphatase activity serves to decrease signaling phosphoload in cytokinin-absent conditions.
Related Concept Videos
01:25Cell Signaling in Plants
Plant cells communicate to coordinate their cycle of growth, flowering and fruiting, and activities in roots, shoots, and leaves in response to the changing environmental conditions. Plant signaling is distinct from animal signaling. Plants primarily utilize enzyme-linked receptors, whereas the largest class of cell-surface receptors in animals are G-protein coupled receptors (GPCRs). Unlike animals, receptor tyrosine kinases are rare in plants. Instead, plants have a diverse class of...
02:45Biological Clocks and Seasonal Responses
The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
01:56Riboswitches
Riboswitches are non-coding mRNA domains that regulate the transcription and translation of downstream genes without the help of proteins. Riboswitches bind directly to a metabolite and can form unique stem-loop or hairpin structures in response to the amount of the metabolite present. They have two distinct regions – a metabolite-binding aptamer and an expression platform.
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
01:32Cytoskeletal Coordination in Cell Migration
A migrating cell changes its shape during the cyclic events of attachment and detachment from the substratum and repositions the cell organelles correspondingly. These complex events are orchestrated by the dynamic cytoskeletal network comprising actin filaments, intermediate filaments, and microtubules. Cytoskeletal crosstalk — the direct and indirect communication between the different components — is crucial for this coordination. Direct communication involves various linker proteins that...
01:56Plant Hormones
Plant hormones—or phytohormones—are chemical molecules that modulate one or more physiological processes of a plant. In animals, hormones are often produced in specific glands and circulated via the circulatory system. However, plants lack hormone-producing glands.
01:56Plant Hormones
Plant hormones—or phytohormones—are chemical molecules that modulate one or more physiological processes of a plant. In animals, hormones are often produced in specific glands and circulated via the circulatory system. However, plants lack hormone-producing glands.