Journal Article

Extracellular Calmodulin Stimulates Light-Independent <i>RbcS-GUS</i> Expression in Suspension-Cultured Cells of Transgenic Tobacco

Junli Zhou, Ligeng Ma, Suqiao Zhang, Yuxian Zhu and Daye Sun

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 10, pages 1049-1055
Published in print October 2001 | ISSN: 0032-0781
Published online October 2001 | e-ISSN: 1471-9053 | DOI:
Extracellular Calmodulin Stimulates Light-Independent RbcS-GUS Expression in Suspension-Cultured Cells of Transgenic Tobacco

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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The RbcS genes encode the small subunits of rubisco; the expression of these genes is controlled in a light-dependent and independent manner. It has been reported that intracellular calmodulin (CaM) is involved in light-dependent RbcS expression. In this report, the role of extracellular CaM in regulating expression of RbcS in darkness was examined. The time course of expression of RbcS-GUS and that of the secretion of CaM in the suspended transgenic tobacco cells in darkness were very similar. Both showed initial increase followed by decline with maximum CaM secretion preceding maximum GUS expression by 24 h. The concentration of CaM in the culture medium is regulated light independently. Purified CaM alone added to the media enhanced RbcS-GUS expression in darkness. The addition of membrane-impermeable CaM inhibitors, such as anti-CaM antiserum or W7-agarose, repressed the expression of RbcS-GUS in darkness, but this inhibitory effect was completely reversed by adding exogenous purified CaM. These results provide the first evidence that extracellular CaM is involved in the regulation of light-independent RbcS gene expression.

Keywords: Key words: Extracellular calmodulin — Light-independent RbcS expression — Transgenic tobacco.; Abbreviations: 6-BA, 6-benzyl aminopurine; CaM, calmodulin; 2,4-D, 2,4-dichlorophenoxyacetic acid; ELISA, enzyme-linked immunosorbant assay; IAA, indole-3-acetic acid.

Journal Article.  4865 words.  Illustrated.

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

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