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Plant Physiology Preview Published on July 9, 2008; 10.1104/pp.108.124875
OPEN ACCESS ARTICLE
Received June 16, 2008 Enhanced tolerance to oxidative stress in transgenic Arabidopsis thaliana plants expressing proteins of unknown function
Department of Biochemistry and Molecular Biology, University of Nevada, Mail Stop 200, Reno NV 89557; Department of Plant Sciences, Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel * Corresponding author; email: ronm{at}unr.edu.
Over a quarter of all plant genes encode proteins of unknown function which can be further classified as Proteins with Obscure Features (POFs), that lack currently defined motifs or domains, or Proteins with Define Features (PDFs), that contain at least one previously defined domain or motif. Although empirical data in the form of transcriptome and proteome profiling suggest that many of these proteins play important roles in plants, their functional characterization remains one of the main challenges in modern biology. To begin the functional annotation of proteins with unknown function, which are involved in the oxidative stress response of Arabidopsis thaliana, we generated transgenic Arabidopsis plants that constitutively expressed 23 different POFs (of which 4 were specific to Arabidopsis), and 18 different PDFs. All previously found to be expressed in response to oxidative stress in Arabidopsis. Transgenic plants were tested for their tolerance to oxidative stress imposed by paraquat or t-butyl hydroperoxide, or subjected to osmotic, salinity, cold and heat stresses. More than 70% of all expressed proteins conferred tolerance to oxidative stress. In contrast, over 90% of the expressed proteins did not confer enhanced tolerance to the other abiotic stresses tested, and about 50% rendered plants more susceptible to osmotic or salinity stress. Two Arabidopsis-specific POFs, and an Arabidopsis and Brassica-specific protein of unknown function, conferred enhanced tolerance to oxidative stress. Our findings suggest that tolerance to oxidative stress involves mechanisms and pathways that are unknown at present, including some that are specific to Arabidopsis or the Brassicaceae.
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