A His-to-Asp phosphorelay modifies the activity of ARR4 on phytochrome signaling.
| Authors | |
|---|---|
| Year of publication | 2002 |
| Type | Article in Proceedings |
| Conference | XIII International Conference on Arabidopsis Research |
| MU Faculty or unit | |
| Citation | |
| Field | Genetics and molecular biology |
| Keywords | phytochrome signaling; two-component system; response regulator; photomorphogenesis; Arabidopsis thaliana |
| Description | The Arabidopsis thaliana response regulator 4 (ARR4), expressed in response to phytochrome B (phyB) action, specifically interacts with the extreme N-terminus of the photoreceptor. ARR4 stabilizes the active Pfr form of phyB in yeast and in planta, thus elevates the level of the active photoreceptor in vivo. Accordingly, transgenic Arabidopsis plants overexpressing ARR4 display hypersensitivity to red light but not to light of other wavelengths. We therefore propose that ARR4 acts as an output element of a two-component system that modulates red light signaling on the level of the phyB photoreceptor. The two-component system is a signal transduction mechanism that requires a His-to-Asp phosphorelay to modulate the activity of a response regulator (e.g. ARR4). Consequently, we generated transgenic Arabidopsis lines expressing a non-phosphorylable form of ARR4 (ARR4D95N). These lines show hyposensitivity to light observed also for an ARR4 loss-of-function mutant. These results suggest that the action of ARR4 on phyB requires a His-to-Asp phosphorelay. By yeast two-hybrid approach and co-immunoprecipitation assays we identified the histidine phosphotransfer protein 1 (AHP1) to specifically interact with ARR4. Thus, AHP1 may mediate a phosphotransfer from different sensor histidine kinases to ARR4. Because the activities of multiple sensor histidine kinases are integrated at the level of AHPs, ARR4 may be a target of a complex two-component signaling network, which in turn regulates phy-dependent signal transduction. To understand, how this network functions, it is essential to identify the stimuli, and therefore, the sensor histidine kinases that initiate the AHP1-to-ARR4 phosphotransfer process. |
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