Open AccessBiotechnology of Tomato Volatiles for Flavor Improvement
Author(s) -
Efraim Lewinsohn,
Eran Pichersky,
Shimon Gepstein
Publication year - 2001
Language(s) - English
Resource type - Reports
DOI - 10.32747/2001.7575277.bard
Subject(s) - linalool , eugenol , flavor , ocimum , terpenoid , biology , carotenoid , monoterpene , metabolic engineering , basilicum , genetically modified tomato , hexanal , lamiaceae , lycopene , solanum , biochemistry , enzyme , botany , chemistry , food science , genetically modified crops , gene , transgene , essential oil , organic chemistry
The main objectives of the research project were: 1. The manipulation, by genetic engineering techniques, of the terpenoid pathway in tomato fruit. Specifically, to test the hypothesis whether overexpression of linalool synthase in tomato fruits will result in the diversion of intermediates of the carotene biosynthetic pathway to linalool, demonstrating that linalool synthase is a key regulatory enzyme, and possibly improving tomato flavor. 2. The elucidation of the biochemical pathway leading to eugenol and methyl eugenol, and the manipulation of this pathway to determine key enzymes and to improve flavor in tomato. Background, conclusions and implications The different proportions of volatile components present in foods often determine their flavor properties. Two of the ten most important flavor compounds in tomatoes, linalool and eugenol, are emitted by the flowers of Clarkia breweri, (Onagraceae), a plant native to California, and are also present in sweet basil (Ocimum basilicum, Lamiaceae). We have studied the key enzymes and genes involved in the production of these flavorants. Linalool synthase, the key enzyme in linalool biosynthesis and its corresponding gene were isolated and characterized from Clarkia breweri. The gene was coupled to a fruit-specific tomato promotor (E8) and was used to transform tomatoes. The transgenic tomatoes produced S-linalool and 1-hydroxylinalool, compounds absent from the fruits of controls. The transgenesis did not adversely affect the overall appearance of the plants nor the levels of other terpenoids present such as carotenoids and vitamin E. Our work has proven that the terpenoid pathway in tomatoes can be modified by the introduction and expression of foreign genes coding for the enzymes controlling the production of monoterpenoid flavor compounds. We have also isolated novel enzymes and genes that are involved in the formation of eugenol and methyl eugenol from Clarkia breweri and basil. An EST library of basil glandular trichomes (the site of eugenol and methyl eugenol biosynthesis) was prepared. More than 1,200 genes have been preliminary characterized and a few of them have been confirmed by functional expression, to be involved in eugenol and methyl eugenol biosynthesis. These genes have augmented the still small repertoire of genes that are available to modify the aroma of agricultural produce by genetic engineering.