Abstract
The phototropic response of Arabidopsis thaliana seedlings is initiated by the blue-light (BL) photoreceptors, phototropin (phot) 1 and phot2, and by their signal transducers, NPH3 and RPT2. Although NPH3 and RPT2 play important roles in phototropic signaling, their biochemical functions remain unclear. Previously, we showed that the NPH3 protein is phosphorylated under dark conditions and is de-phosphorylated under BL. Phot1 is necessary for BL-dependent de-phosphorylation of NPH3. And our immunoprecipitation analysis demonstrated that RPT2 preferentially interacts with the dephpsphorylated NPH3. In this time, we report some phosphorylation sites of NPH3. We generated two polyclonal antibodies against phosphopeptide of NPH3, and analyzed NPH3 phosphorylation state. Under BL condition, two these phosphorylation sites are de-photphorylated mediated by phot1. We also report that PP2A might be involved in de-phosphorylation of NPH3 using phosphatase inhibitors. We will discuss regulation of NPH3 de-phosphorylation and function of NPH3 and RPT2 during induction of phototropism here.
