Wan, Yinglang: Blue-Light Sensing in Arabidopsis : In Vivo Microscopy of Subcellular Localization, Endocytosis, and Vesicular Recycling of the Blue-Light Receptor Phototropin 1. - Bonn, 2009. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-16949
@phdthesis{handle:20.500.11811/4049,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-16949,
author = {{Yinglang Wan}},
title = {Blue-Light Sensing in Arabidopsis : In Vivo Microscopy of Subcellular Localization, Endocytosis, and Vesicular Recycling of the Blue-Light Receptor Phototropin 1},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2009,
month = mar,

note = {In this thesis, the subcellular localization and possible functions of the blue light receptor, PHOT1, is examined. Results are presented, which indicate that blue lightinduced relocalization of auxin efflux carriers (PIN-proteins) is adjusted by PHOT1 via ARF-mediated and BFA-sensitive vesicle trafficking pathways.
PHOT1 was visualized by expressing the PHOT1::GFP reporter in Arabidopsis mutants which contain a dysfunctional copy of the endogenous PHOT1-gene. It is shown that the subcellular localization of PHOT1 in plant cells reflects the physiological functions and development stages of special kinds of cells. For example in guard cells, PHOT1 appears only in the mature developmental stage, when these cells begin to react to blue light signals. Especially, the specific roles of PHOT1 were addressed in root and shoot apical meristems. The obtained data suggest that PHOT1 has different roles in root and shoot phototropic responses. PHOT1 in root tissues acts to adjust the polar auxin transport, while PHOT1 in shoot tissues has more abundant roles. It is also suggested that the mechanism of phototropic responses in shoots and roots might be different from each other.
Interestingly, the PHOT1::GFP signals are quickly released from the plasma membrane and appear in intracellular vesicles, when cells are irradiated with blue laser light in the process of scanning in the confocal microscope. The level of PHOT1 relocalization reflects the amount of photons reaching the surface of the Arabidopsis cells. PHOT1-positive vesicles colocalize with the endosomal tracer, FM4-64, indicating that that light-induced movements of PHOT1-positive endosome are analogous to the ligand-induced receptor mediated endocytosis. PHOT1-mediated blue light sensing is sensitive to inhibitors of exocytosis and endocytosis and is also dependent on intact actin filaments.
Endosomal recycling of PIN proteins is considered as the mechanism to adjust the levels of polar auxin transport. Here it is demonstrated that blue light affects the recycling of PIN1 and PIN2 between the plasma membrane and the endosomal compartment. The pin2 null mutant lacks phototropic responses in roots, while the shoot phototropism in this mutant is independent on PIN2. By taking into account the polar transport of auxin under asymmetric illumination at the root tip, a testable model for the mechanism of root phototropism is proposed, which will helpful in guiding future phototropism research.},

url = {http://hdl.handle.net/20.500.11811/4049}
}

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