Journal Article

Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Large Subunit Translation is Regulated in a Small Subunit-Independent Manner in the Expanded Leaves of Tobacco

Katsuhiko Ichikawa, Chikahiro Miyake, Megumi Iwano, Masami Sekine, Atsuhiko Shinmyo and Ko Kato

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 2, pages 214-225
Published in print February 2008 | ISSN: 0032-0781
Published online February 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm179
Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Large Subunit Translation is Regulated in a Small Subunit-Independent Manner in the Expanded Leaves of Tobacco

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  • Biochemistry
  • Molecular and Cell Biology
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Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is composed of small subunits (SSs) encoded by rbcS on the nuclear genome and large subunits (LSs) encoded by rbcL on the chloroplast genome, and it is localized in the chloroplast stroma. Constitutive knockdown of the rbcS gene reportedly causes a reduction in LS quantity and the level of translation in tobacco and the unicellular green alga Chlamydomonas. Constitutively knockdown of the rbcS gene also causes a reduction in photosynthesis, which influences the expression of photosynthetic genes, including the rbcL gene. Here, to investigate the influence of the knockdown of the rbcS gene on the expression of the rbcL gene under normal photosynthetic conditions, we generated transgenic tobacco plants in which the amount of endogenous rbcS mRNA can be reduced by inducible expression of antisense rbcS mRNA with dexamethasone (DEX) treatment at later stages of growth. In already expanded leaves, after DEX treatment, the level of photosynthesis, RuBisCO quantity and the chloroplast ultrastructure were normal, but the amount of rbcS mRNA was reduced. An in vivo pulse labeling experiment and polysome analysis showed that LSs were translated at the same rate as in wild-type leaves. On the other hand, in newly emerging leaves, the rbcS mRNA quantity, the level of photosynthesis and the quantity of RuBisCO were reduced, and chloroplasts failed to develop. In these leaves, the level of LS translation was inhibited, as previously described. These results suggest that LS translation is regulated in an SS-independent manner in expanded leaves under normal photosynthetic conditions.

Keywords: Antisense rbcS; DEX-inducible gene expression system; LS translation; Nicotiana tabacum; Photosynthesis; RuBisCO

Journal Article.  6945 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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