Subcellular localization of phototropin 2

Abstract

Phototropins (phot1 and phot2) are plasma membrane-associated protein kinases and function as blue light photoreceptors for phototropism, chloroplast movements, and stomatal opening in Arabidopsis. To understand the mechanisms by which phot2 initiates these responses, we transformed a phot1/phot2 double mutant of Arabidopsis with constructs encoding translationally fused phot2-green fluorescent protein (GFP), which was fully active in the transgenic plants, under the control of the endogenous PHOT2 or the 35S promoter and investigated its cellular and subcellular distribution. The fusion protein was uniformly distributed in the plasma membrane in darkness, and appeared as punctate stains rapidly after blue light illumination. The punctate stains disappeared gradually after turning off the light. The kinase domain of phot2, when transiently expressed in protoplasts, showed similar subcellular localization as the light-activated phot2-GFP. Furthermore, the punctate stain was merged with a golgi marker. Hence, phot2 may translocate to golgi apparatus light-dependently.