Trichome specific expression of tobacco (Nicotiana sylvestris) cembratrien-ol synthase genes is controlled by both activating and repressing cis-regions

Laboratoire d'Ecologie Alpine, Université Joseph Fourier and CNRS-Unité Mixte de Recherche 5553, 2233, rue de piscine, BP 53, 38041 Grenoble Cedex 9, France.
Plant Molecular Biology (Impact Factor: 4.26). 08/2010; 73(6):673-85. DOI: 10.1007/s11103-010-9648-x
Source: PubMed


Tobacco (Nicotiana sylvestris) glandular trichomes make an attractive target for isoprenoid metabolic engineering because they produce large amounts of one type of diterpenoids, alpha- and beta-cembratrien-diols. This article describes the establishment of tools for metabolic engineering of tobacco trichomes, namely a transgenic line with strongly reduced levels of diterpenoids in the exudate and the characterization of a trichome specific promoter. The diterpene-free tobacco line was generated by silencing the major tobacco diterpene synthases, which were found to be encoded by a family of four highly similar genes (NsCBTS-2a, NsCBTS-2b, NsCBTS-3 and NsCBTS-4), one of which is a pseudogene. The promoter regions of all four CBTS genes were sequenced and found to share over 95% identity between them. Transgenic plants expressing uidA under the control of the NsCBTS-2a promoter displayed a specific pattern of GUS expression restricted exclusively to the glandular cells of the tall secretory trichomes. A series of sequential and internal deletions of the NsCBTS-2a promoter led to the identification of two cis-acting regions. The first, located between positions -589 to -479 from the transcription initiation site, conferred a broad transcriptional activation, not only in the glandular cells, but also in cells of the trichome stalk, as well as in the leaf epidermis and the root. The second region, located between positions -279 to -119, had broad repressor activity except in trichome glandular cells and is mainly responsible for the specific expression pattern of the NsCBTS-2a gene. These results establish the basis for the identification of trans-regulators required for the expression of the CBTS genes restricted to the secretory cells of the glandular trichomes.

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Available from: Gilles Vachon, Nov 20, 2014
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    • "The chimeric SSL1-3 genes and FPS gene were inserted downstream of the strong constitutive promoters Pcv (Verdaguer et al., 1996) and Pca (Benfey et al., 1990), respectively. For trichome-specific expression of triterpene biosynthesis, the trichome-specific promoters Pcbt (Ennajdaoui et al., 2010) and Pcyp16 (Wang et al., 2002a) were fused to 59 end of botryococcene synthase genes and the FPS gene, respectively. The duplicated cauliflower mosaic virus 35S enhancer elements (Benfey et al., 1990) were fused to the 59 end of each trichome promoter. "
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