The subcellular localization and blue-light-induced movement of phototropin 1-GFP in etiolated seedlings of Arabidopsis thaliana.
Phototropin 1 (phot1) is a photoreceptor for phototropism, chloroplast movement, stomatal opening, leaf expansion, and solar tracking in response to blue light. Following earlier work with PHOT1::GFP (Sakamoto and Briggs, 2002), we investigated the pattern of cellular and subcellular localization of phot1 in 3- 4-d-old etiolated seedlings of Arabidopsis thalinana. As expressed from native upstream sequences, the PHOT1::GFP fusion protein is expressed strongly in the abaxial tissues of the cotyledons and in the elongating regions of the hypocotyl. It is moderately expressed in the shoot/root transition zone and in cells near the root apex. A fluorescence signal is undetectable in the root epidermis, root cap, and root apical meristem itself. The plasma membranes of mesophyll cells near the cotyledon margin appear labeled uniformly but cross-walls created by recent cell divisions are more strongly labeled. The pattern of labeling of individual cell types varies with cell type and developmental stage. Blue-light treatment causes PHOT1::GFP, initially relatively evenly distributed at the plasma membrane, to become reorganized into a distinct mosaic with strongly labeled punctate areas and other areas completely devoid of fluorescence--a phenomenon best observed in cortical cells in the hypocotyl elongation region. Concomitant with or following this reorganization, PHOT1::GFP moves into the cytoplasm in all cell types investigated except for guard cells. It disappears from the cytoplasm by an unidentified mechanism after several hours in darkness. Neither its appearance in the cytoplasm nor its eventual disappearance in darkness is prevented by the translation inhibitor cycloheximide, although the latter process is retarded. We hypothesize that blue-light-induced phot1 re-localization modulates blue-light-activated signal transduction.
Wan
Ying-Lang
YL
Dept Plant Cell Biology, Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany.
Eisinger
William
W
Ehrhardt
David
D
Kubitscheck
Ulrich
U
Baluska
Frantisek
F
Briggs
Winslow
W
D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects; D018548:Cotyledon / Q000502:physiology / Q000528:radiation effects; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics; D018546:Hypocotyl / Q000528:radiation effects; D007091:Image Processing, Computer-Assisted; D008027:Light; D056949:Phototropins / Q000235:genetics* / Q000528:radiation effects*; D018517:Plant Roots / Q000235:genetics / Q000528:radiation effects; D018520:Plant Shoots / Q000235:genetics / Q000528:radiation effects; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000528:radiation effects; D036226:Seedlings / Q000235:genetics / Q000528:radiation effects; D013347:Subcellular Fractions / Q000528:radiation effects
D056949:Phototropins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins