| dc.description.abstract | 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 b-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 mmol m
) 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. | en_US |
