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Evolution of a bacteriophytochrome from light to redox sensor
Laurie Vuillet1, Mila Kojadinovic, Sébastien Zappa
1Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, CIRAD, AGRO-M, INRA, UM2, Campus de Baillarguet, Montpellier Cedex, France.
The EMBO Journal
|June 22, 2007
Summary
Rhodopseudomonas palustris bacteriophytochromes (RpBphP4) can sense light or redox conditions. This regulates light-harvesting complex synthesis via a novel two-component system, revealing an evolutionary shift from light to redox sensing.
Area of Science:
- Microbiology
- Biochemistry
- Photosynthesis research
Background:
- Bacteriophytochromes are bacterial photoreceptors mediating environmental responses.
- Rhodopseudomonas palustris utilizes these for sensing light conditions.
Purpose of the Study:
- Investigate the diversity and function of bacteriophytochromes in Rhodopseudomonas palustris.
- Elucidate the signal transduction pathway regulating light-harvesting complex synthesis.
Main Methods:
- Phylogenetic analysis
- Biochemical assays to determine chromophore binding and kinase activity
- Analysis of gene regulation of light-harvesting complexes
Main Results:
- Identified two distinct types of RpBphP4 in Rhodopseudomonas palustris.
- One type functions as a canonical light-sensing bacteriophytochrome binding biliverdin.
- The predominant type has lost light sensing, instead exhibiting redox-sensing coupled to kinase activity.
- Both RpBphP4 types regulate light-harvesting 2 (LH2) complex synthesis via a transcription factor's phosphorylation status.
- This represents the first complete description of a bacteriophytochrome signal transduction pathway involving a two-component system.
Conclusions:
- Bacteriophytochromes in Rhodopseudomonas palustris have evolved from light to redox sensing.
- This adaptation allows regulation of light-harvesting complexes based on light or redox environments.
- A novel two-component system mediates bacteriophytochrome signal transduction.
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