Journal Article

Inducible Trans-activation of Plastid Transgenes: Expression of the <i>R. eutropha</i> <i>phb</i> Operon in Transplastomic Tobacco

Andreas Lössl, Karen Bohmert, Hans Harloff, Christian Eibl, Stefan Mühlbauer and Hans-Ulrich Koop

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 9, pages 1462-1471
Published in print September 2005 | ISSN: 0032-0781
Published online September 2005 | e-ISSN: 1471-9053 | DOI:
Inducible Trans-activation of Plastid Transgenes: Expression of the R. eutropha phb Operon in Transplastomic Tobacco

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


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Deleterious effects of constitutive transgene expression can occur if gene products are harmful to the transformed plant. Constraints such as growth inhibition and male sterility have been observed in plastid transformants containing the phb operon encoding the genes required for the production of the polyester polyhydroxybutyric acid (PHB). In order to induce PHB synthesis in tobacco in a well-timed manner, we have constructed a trans-activation system to regulate transcription of the phb operon in plastids. This system consists of a nuclear-located, ethanol-inducible T7RNA polymerase (T7RNAP) which is targeted to plastids harboring the phb operon under control of T7 regulatory elements. Following treatment with 5% ethanol, moderate induction of PHB synthesis was found. PHB amounts reached 1,383 ppm in dry weight, and an overall background activity of 171 ppm was measured in uninduced tissues. On the transcriptional level, T7RNAP induction was proven and we found that the phb operon is transcribed into at least two mRNAs. Without ethanol induction, development of flowers and fertile seeds was possible. Thus, the main problem of inhibitory transgene expression was solved. Our results show that this inducible trans-activation system could serve as an alternative to constitutive expression of transgenes in the plastome.

Keywords: Inducible transcription; Plastid Transformation; Polyhydroxybutyrate; Regulation; Renewable resources; Trans-activation system; PHB, polyhydroxybutyric acid; T7RNAP, RNA polymerase of bacteriophage T7

Journal Article.  7902 words.  Illustrated.

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

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