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First published online July 7, 2006; 10.1104/pp.106.081489 Plant Physiology 142:75-87 (2006) © 2006 American Society of Plant Biologists Differential Expression and Localization of Early Light-Induced Proteins in Arabidopsis1Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE–10691 Stockholm, Sweden (M.H., H.N., M.D., B.A., I.A.); Department of Molecular Biology, University of Geneva, 1211 Geneva 4, Switzerland (M.H.); Bio-Rad Laboratories AB, SE–17222 Sundbyberg, Sweden (H.N.); Department of Physiology and Plant Biochemistry, University of Konstanz, DE–78457 Konstanz, Germany (V.R., I.A.); Department of Cardiology, University of Maastricht-Cardiovascular Research Institute of Maastricht, 6229 ER Maastricht, The Netherlands (M.D.); Division of Cell Biology, Linköping University, S–58185 Linkoeping, Sweden (B.A.); and European Science Foundation, F–67080 Strasbourg cedex, France (B.A.)
The early light-induced proteins (Elips) in higher plants are nuclear-encoded, light stress-induced proteins located in thylakoid membranes and related to light-harvesting chlorophyll (LHC) a/b-binding proteins. A photoprotective function was proposed for Elips. Here we showed that after 2 h exposure of Arabidopsis (Arabidopsis thaliana) leaves to light stress Elip1 and Elip2 coisolate equally with monomeric (mLhcb) and trimeric (tLhcb) populations of the major LHC from photosystem II (PSII) as based on the Elip:Lhcb protein ratio. A longer exposure to light stress resulted in increased amounts of Elips in tLhcb as compared to mLhcb, due to a reduction of tLhcb amounts. We demonstrated further that the expression of Elip1 and Elip2 transcripts was differentially regulated in green leaves exposed to light stress. The accumulation of Elip1 transcripts and proteins increased almost linearly with increasing light intensities and correlated with the degree of photoinactivation and photodamage of PSII reaction centers. A stepwise accumulation of Elip2 was induced when 40% of PSII reaction centers became photodamaged. The differential expression of Elip1 and Elip2 occurred also in light stress-preadapted or senescent leaves exposed to light stress but there was a lack of correlation between transcript and protein accumulation. Also in this system the accumulation of Elip1 but not Elip2 correlated with the degree of PSII photodamage. Based on pigment analysis, measurements of PSII activity, and assays of the oxidation status of proteins we propose that the discrepancy between amounts of Elip transcripts and proteins in light stress-preadapted or senescent leaves is related to a presence of photoprotective anthocyanins or to lower chlorophyll availability, respectively.
1 This work was supported by research grants from the Swedish Research Council, the Swedish Strategic Foundation and the Carl Tryggers Foundation (to I.A. and B.A.), the Deutsche Forschungsgemeinschaft (grant nos. AD92/7–1 and AD92/7–2 to I.A.), and the Konstanz University grant (to I.A.). 2 These authors contributed equally to the paper. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Iwona Adamska (iwona.adamska{at}uni-konstanz.de). www.plantphysiol.org/cgi/doi/10.1104/pp.106.081489 * Corresponding author; e-mail iwona.adamska{at}uni-konstanz.de; fax 49–7531–88–3042. Received April 4, 2006; accepted June 30, 2006. This article has been cited by other articles:
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