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BIOENERGETICS AND PHOTOSYNTHESIS

Abnormal Chloroplast Development and Growth Inhibition in Rice Thioredoxin m Knock-Down Plants^{1,[C],[W],[OA]}

Division of Applied Life Science (BK21 Program), EB-NCRC and Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660–701, Korea (Y.H.C., J.C.M., J.H.P., W.I.F., H.H.J., J.R.L., Y.M.L., S.T.K., C.O.L., J.-Y.K., D.-J.Y., K.O.L., S.Y.L.); Department of Molecular Biology, Pusan National University, Busan 609–735, Korea (H.-S.K., I.S.Z, C.-H.L.); and School of Life Sciences and Biotechnology, Korea University, Seoul 136–701, Korea (Y.-Y.C.)

Plant cells contain several thioredoxin isoforms that are characterized by subcellular localization and substrate specificity. Here, we describe the functional characterization of a rice (Oryza sativa) thioredoxin m isoform (Ostrxm) using a reverse genetics technique. Ostrxm showed green tissue-specific and light-responsive mRNA expression. Ostrxm was localized in chloroplasts of rice mesophyll cells, and the recombinant protein showed dithiothreitol-dependent insulin β-chain reduction activity in vitro. RNA interference (RNAi) of Ostrxm resulted in rice plants with developmental defects, including semidwarfism, pale-green leaves, abnormal chloroplast structure, and reduced carotenoid and chlorophyll content. Ostrxm RNAi plants showed remarkably decreased F_v/F_m values under high irradiance conditions (1,000 µmol m^–2 s^–1) with delayed recovery. Two-dimensional electrophoresis and matrix-assisted laser-desorption/ionization time-of-flight analysis showed that the levels of several chloroplast proteins critical for photosynthesis and biogenesis were significantly decreased in Ostrxm RNAi plants. Furthermore, 2-Cys peroxiredoxin, a known target of thioredoxin, was present in oxidized forms, and hydrogen peroxide levels were increased in Ostrxm RNAi plants. The pleiotropic effects of Ostrxm RNAi suggest that Ostrxm plays an important role in the redox regulation of chloroplast target proteins involved in diverse physiological functions.

² These authors contributed equally to this article.

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: Kyun Oh Lee (leeko{at}gnu.ac.kr).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.123547

^* Corresponding author; e-mail leeko{at}gnu.ac.kr.

Received May 26, 2008; accepted August 11, 2008; published August 22, 2008.