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Plant J. 2012 Oct;72(1):1-17. doi: 10.1111/j.1365-313X.2012.05068.x. Epub 2012 Jul 17.

Characterization of two genes for the biosynthesis of the labdane diterpene Z-abienol in tobacco (Nicotiana tabacum) glandular trichomes.

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  • 1Biogemma, Functional and Applied Cereal Group, Z.I. du Brezet, 8 Rue des Frères Lumière, 63028 Clermont-Ferrand Cedex 2, France.

Erratum in

  • Plant J. 2013 May;74(4):713.

Abstract

Leaves of tobacco (Nicotiana tabacum) are covered with glandular trichomes that produce sucrose esters and diterpenoids in varying quantities, depending on cultivar type. The bicyclic diterpene Z-abienol is the major labdanoid present in some oriental tobacco cultivars, where it constitutes a precursor of important flavours and aromas. We describe here the identification and characterization of two genes governing the biosynthesis of Z-abienol in N. tabacum. As for other angiosperm labdanoid diterpenes, the biosynthesis of Z-abienol proceeds in two steps. NtCPS2 encodes a class-II terpene synthase that synthesizes 8-hydroxy-copalyl diphosphate, and NtABS encodes a kaurene synthase-like (KSL) protein that uses 8-hydroxy-copalyl diphosphate to produce Z-abienol. Phylogenetic analysis indicates that NtABS belongs to a distinct clade of KSL proteins that comprises the recently identified tomato (Solanum habrochaites) santalene and bergamotene synthase. RT-PCR results show that both genes are preferentially expressed in trichomes. Moreover, microscopy of NtCPS2 promoter-GUS fusion transgenics demonstrated a high specificity of expression to trichome glandular cells. Ectopic expression of both genes, but not of either one alone, driven by a trichome-specific promoter in transgenic Nicotiana sylvestris conferred Z-abienol formation to this species, which does not normally produce it. Furthermore, sequence analysis of over 100 tobacco cultivars revealed polymorphisms in NtCPS2 that lead to a prematurely truncated protein in cultivars lacking Z-abienol, thus establishing NtCPS2 as a major gene controlling Z-abienol biosynthesis in tobacco. These results offer new perspectives for tobacco breeding and the metabolic engineering of labdanoid diterpenes, as well as for structure-function relationship studies of terpene synthases.

© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

PMID:
22672125
[PubMed - indexed for MEDLINE]
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