Domain swapping to assess the mechanistic basis of Arabidopsis phototropin 1 receptor kinase activation and endocytosis by blue light

Kaiserli, E. , Sullivan, S. , Jones, M. A. , Feeney, K. A. and Christie, J. M. (2009) Domain swapping to assess the mechanistic basis of Arabidopsis phototropin 1 receptor kinase activation and endocytosis by blue light. Plant Cell, 21(10), pp. 3226-3244. (doi: 10.1105/tpc.109.067876) (PMID:19168662)

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Phototropins (phot1 and phot2) are plasma membrane-associated receptor kinases that respond specifically to blue and UV wavelengths. In addition to a C-terminal Ser/Thr kinase domain, phototropins contain two N-terminal chromophore binding LOV domains that function as photoswitches to regulate a wide range of enzymatic activities in prokaryotes and eukaryotes. Through domain swapping, we show that the photochemical properties of Arabidopsis thaliana phot1 rely on interactions between LOV1 and LOV2, which are facilitated by their intervening linker sequence. Functional analysis of domain-swap proteins supports a mechanism whereby LOV2 acts as a dark-state repressor of phot1 activity both in vitro and in vivo. Moreover, we find a photoactive role for LOV1 in arresting chloroplast accumulation at high light intensities. Unlike LOV2, LOV1 cannot operate as a dark-state repressor, resulting in constitutive receptor autophosphorylation and accelerated internalization from the plasma membrane. Coexpression of active and inactive forms of phot1 demonstrates that autophosphorylation can occur intermolecularly, independent of LOV1, via light-dependent receptor dimerization in vivo. Indeed, transphosphorylation is sufficient to promote phot1 internalization through a clathrin-dependent endocytic pathway triggered primarily by phosphorylation of Ser-851 within the kinase activation loop. The mechanistic implications of these findings in regard to light-driven receptor activation and trafficking are discussed.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Sullivan, Dr Stuart and Kaiserli, Dr Eirini and Jones, Dr Matt and Christie, Professor John
Authors: Kaiserli, E., Sullivan, S., Jones, M. A., Feeney, K. A., and Christie, J. M.
Subjects:Q Science > QH Natural history > QH301 Biology
Q Science > QK Botany
College/School:College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
Journal Name:Plant Cell
Publisher:American Society of Plant Biologists
ISSN (Online):1532-298X
Published Online:30 October 2009
Copyright Holders:Copyright © 2009 American Society of Plant Biologists
First Published:First published in Plant Cell 21(10):3226-3244
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
378561Characterisation of the phot1-interacting protein AtMRD1 and its role in regulating phototropismJohn ChristieBiotechnology and Biological Sciences Research Council (BBSRC)BB/C000366/1Institute of Molecular Cell and Systems Biology