Overexpression of the lemon basil α‐zingiberene synthase gene increases both mono‐ and sesquiterpene contents in tomato fruit

Abstract

Summary a-Zingiberene synthase (ZIS), a sesquiterpene synthase gene that was isolated from lemon basil (Ocimum basilicum L.), encodes an enzyme that catalyzes the formation of a-zingiberene, and other sesquiterpenes, from farnesyl diphosphate. Transgenic tomato fruits overexpressing ZIS under the control of the fruit ripeningspecific tomato polygalacturonase promoter (PG) accumulated high levels of a-zingiberene (224-1000 ng g)1 fresh weight) and other sesquiterpenes, such as a-bergamotene, 7-epi-sesquithujene, b-bisabolene and b-curcumene, whereas no sesquiterpenes were detected in non-transformed control fruits. The ZIS-transgenic fruits also produced monoterpenes, such as a-thujene, a-pinene, b-phellandrene and c-terpinene (1-22 ng g)1 fresh weight), which were either not detected or were found only in minute concentrations in control fruits. Recombinant ZIS overexpressed in Escherichia coli catalyzed the formation of these monoterpenes from geranyl diphosphate. As the ZIS protein apparently lacks a transit peptide, and is localized in the cytosol, the production of monoterpenes in the transgenic tomatoes suggests that a pool of geranyl diphosphate is available in the cytosol. The phenotype of the ZIS-transgenic tomatoes was the same as that for wild-type tomatoes, with regard to plant vigor and shape, but transgenic plants exhibited a small decrease in lycopene content. This study thus showed that the synthesis of both mono-and sesquiterpenes can be enhanced by the ectopic expression of a single transgene in tomato fruit, and it further demonstrated the interconnection between the pools of terpenoid precursors in the plastids and the cytosol.

Improved herbivore resistance in cultivated tomato with the sesquiterpene biosynthetic pathway from a wild relative

“…Importantly, purified 7-epizingiberene, when applied to the headspace of susceptible cultivated tomato, repelled whiteflies, whereas α-zingiberene isolated from ginger did not (15). Although several zingiberene synthases have been identified (16)(17)(18), including one from S. habrochaites (7), we have now unambiguously identified and characterized 7-epizingiberene synthase from S. habrochaites and modified a cultivated tomato to produce 7-epizingiberene. Moreover, plants with improved herbivore resistance were obtained by traditional breeding and these may contribute to reduced pesticide use.…”

Molecular Cloning and Characterization of a Linalool Synthase from Lemon Myrtle

“…After static culture for 30 min at 20 C, isopropyl thio--D-galactoside was added at a final concentration of 0.4 mM to induce production of BcLS. The cultures were grown for 20 h at 20 C with agitation at 100 rpm. Cells were collected and resuspended in 20 mM Tris-HCl (pH 7.4) buffer containing 500 mM NaCl and 20 mM imidazole, and were disrupted by sonication.…”

“…Monoterpenes and sesquiterpene in the glandular trichomes of the tomato are synthesized from NPP and cis-FPP, 18,19) and lemon basil -zingiberene synthase can use GPP and FPP in vitro. 20) BcLS did not form terpene products from sesquiterpene precursor FPP, but NPP can serve as an alternate substrate for BcLS (Fig. 2).…”

Application of Metabolomics to Improve Tomato Fruit Productivity and Quality

“…Expression of the geraniol synthase gene of lemon basil (Ocimum basilicum) under the tomato polygalacturonase gene promoter enhances the production of geranyl diphosphatederived volatiles (geranyl acetate, citronellol, citronellal, and rose oxide) in ripe fruit (Davidovich-Rikanati et al, 2007). Similarly, expression of the sesquiterpene synthase gene from lemon basil enhances the production of farnesyl diphosphate-derived volatiles, including α-zingiberene and α-bergamotene (Davidovich-Rikanati et al, 2008). These examples clearly demonstrate that improvement of tomato flavor is feasible by genetic engineering.…”