Journal Article

Both Phototropin 1 and 2 Localize on the Chloroplast Outer Membrane with Distinct Localization Activity

Sam-Geun Kong, Noriyuki Suetsugu, Shingo Kikuchi, Masato Nakai, Akira Nagatani and Masamitsu Wada

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 54, issue 1, pages 80-92
Published in print January 2013 | ISSN: 0032-0781
Published online November 2012 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcs151
Both Phototropin 1 and 2 Localize on the Chloroplast Outer Membrane with Distinct Localization Activity

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Chloroplasts change their position to adapt cellular activities to fluctuating environmental light conditions. Phototropins (phot1 and phot2 in Arabidopsis) are plant-specific blue light photoreceptors that perceive changes in light intensity and direction, and mediate actin-based chloroplast photorelocation movements. Both phot1 and phot2 regulate the chloroplast accumulation response, while phot2 is mostly responsible for the regulation of the avoidance response. Although it has been widely accepted that distinct intracellular localizations of phototropins are implicated in the specificity, the mechanism underlying the phot2-specific avoidance response has remained elusive. In this study, we examined the relationship of the phot2 localization pattern to the chloroplast photorelocation movement. First, the fusion of a nuclear localization signal with phot2, which effectively reduced the amount of phot2 in the cytoplasm, retained the activity for both the accumulation and avoidance responses, indicating that membrane-localized phot2 but not cytoplasmic phot2 is functional to mediate the responses. Importantly, some fractions of phot2, and of phot1 to a lesser extent, were localized on the chloroplast outer membrane. Moreover, the deletion of the C-terminal region of phot2, which was previously shown to be defective in blue light-induced Golgi localization and avoidance response, affected the localization pattern on the chloroplast outer membrane. Taken together, these results suggest that dynamic phot2 trafficking from the plasma membrane to the Golgi apparatus and the chloroplast outer membrane might be involved in the avoidance response.

Keywords: Arabidopsis thaliana; Blue light; Chloroplast; Chloroplast movement; Photoreceptor; Phototropin

Journal Article.  8227 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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