Blue light activates a specific protein kinase in higher plants
P Reymond1, T W Short, W R Briggs
1Carnegie Institution of Washington, Stanford, California 94305.
Plant Physiology
|October 1, 1992
Summary
Blue light triggers a phosphorylation process in plant membrane proteins, a system found across diverse plant species. This light-activated kinase mechanism appears conserved in higher plants, suggesting a common signaling pathway.
Area of Science:
- Plant molecular biology
- Photobiology
- Biochemistry
Background:
- Blue light is known to influence various plant growth and developmental processes.
- Membrane proteins play crucial roles in cellular signaling and transport.
- Phosphorylation is a key post-translational modification regulating protein function.
Purpose of the Study:
- To investigate the effect of blue light on membrane protein phosphorylation in various plant species.
- To identify the molecular components involved in blue light-mediated phosphorylation.
- To determine if this phosphorylation system is conserved across different higher plants.
Main Methods:
- In vitro phosphorylation assays using [gamma-(32)P]ATP with crude microsomal membrane proteins from dark-grown seedlings of multiple plant species (pea, sunflower, zucchini, Arabidopsis, tomato, maize, barley, oat, wheat, sorghum).
- Analysis of phosphorylated proteins using gel electrophoresis to determine molecular mass.
- Experiments involving mixing irradiated and unirradiated solubilized membrane proteins from different species to assess signal transfer and kinase activity.
Main Results:
- A specific membrane protein (114-130 kD) is rapidly phosphorylated upon blue light illumination in vitro across a wide range of plant species.
- Evidence suggests a light-activated kinase phosphorylates a substrate, as unirradiated membranes show increased phosphorylation when mixed with irradiated ones.
- The light signal can be stored and transferred, indicating a mobile activated kinase or a stable activated state, and the system shows functional homology across species.
Conclusions:
- Blue light-mediated phosphorylation of a specific membrane protein is a ubiquitous system in higher plants.
- The findings support a model where blue light activates a specific kinase, which then phosphorylates its substrate.
- This conserved mechanism highlights a fundamental aspect of plant photobiology and signaling pathways.
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