Received May 5, 2004
Accepted July 6, 2004
Phytochrome Phosphorylation Modulates Light Signaling by Influencing the Protein-Protein Interaction
Jeong-Il Kim 1, Yu Shen 2, Yun-Jeong Han 2, Joung-Eun Park 3, Daniel Kirchenbauer 4, Moon-Soo Soh 5, Ferenc Nagy 6, Eberhard Schäfer 4, and Pill-Soon Song 1*
1 Kumho Life and Environmental Science Laboratory, Gwangju 500-712, Korea; Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304; Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea
2 Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304
3 Kumho Life and Environmental Science Laboratory, Gwangju 500-712, Korea; Environmental Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea
4 Institut für Biologie II/Botanik, Universität Freiburg, D-79104 Freiburg, Germany
5 Kumho Life and Environmental Science Laboratory, Gwangju 500-712, Korea
6 Institute of Plant Biology, Biological Research Center, H6701 Szeged, Hungary
* To whom correspondence should be addressed. E-mail: pssong{at}kkpc.com.
Plant photoreceptor phytochromes are phosphoproteins, but the question as to the functional role of phytochrome phosphorylation has remained to be elucidated. We investigated the functional role of phytochrome phosphorylation in plant light signaling using a Pfr-specific phosphorylation site mutant, Ser598Ala of oat (Avena sativa) phytochrome A (phyA). The transgenic Arabidopsis thaliana (phyA-201 background) plants with this mutant phyA showed hypersensitivity to light, suggesting that phytochrome phosphorylation at Serine-598 (Ser598) in the hinge region is involved in an inhibitory mechanism. The phosphorylation at Ser598 prevented its interaction with putative signal transducers, Nucleoside Diphosphate Kinase-2 and Phytochrome-Interacting Factor-3. These results suggest that phosphorylation in the hinge region of phytochromes serves as a signal-modulating site through the protein-protein interaction between phytochrome and its putative signal transducer proteins.
