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Publications - Cell and Metabolic Biology
Publications
Diterpenoids form a diverse group of natural products, many of which are or could become pharmaceuticals or industrial chemicals. The modular character of diterpene biosynthesis and the promiscuity of the enzymes involved make combinatorial biosynthesis a promising approach to generate libraries of diverse diterpenoids. Here, we report on the combinatorial assembly in yeast of ten diterpene synthases producing (+)-copalyldiphosphate-derived backbones and four cytochrome P450 oxygenases (CYPs) in diverse combinations. This resulted in the production of over 200 diterpenoids. Based on literature and chemical database searches, 162 of these compounds can be considered new-to-Nature. The CYPs accepted most substrates they were given but remained regioselective with few exceptions. Our results provide the basis for the systematic exploration of the diterpenoid chemical space in yeast using sequence databases.
Publications
The pyrethrum plant, Tanacetum cinerariifolium (Asteraceae) synthesizes a class of compounds called pyrethrins that have strong insecticidal properties but are safe to humans. Class I pyrethrins are esters of the monoterpenoid trans-chrysanthemic acid with one of three jasmonic-acid derived alcohols. We reconstructed the trans-chrysanthemic acid biosynthetic pathway in tomato fruits, which naturally produce high levels of the tetraterpene pigment lycopene, an isoprenoid which shares a common precursor, dimethylallyl diphosphate (DMAPP), with trans-chrysanthemic acid. trans-Chrysanthemic acid biosynthesis in tomato fruit was achieved by expressing the chrysanthemyl diphosphate synthase gene from T. cinerariifolium, encoding the enzyme that uses DMAPP to make trans-chrysanthemol, under the control of the fruit specific promoter PG, as well as an alcohol dehydrogenease (ADH) gene and aldehyde dehydrogenase (ALDH) gene from a wild tomato species, also under the control of the PG promoter. Tomato fruits expressing all three genes had a concentration of trans-chrysanthemic acid that was about 1.7-fold higher (by weight) than the levels of lycopene present in non-transgenic fruit, while the level of lycopene in the transgenic plants was reduced by 68%. Ninety seven percent of the diverted DMAPP was converted to trans-chrysanthemic acid, but 62% of this acid was further glycosylated. We conclude that the tomato fruit is an alternative platform for the biosynthesis of trans-chrysanthemic acid by metabolic engineering.
Publications
In contrast to animal lectins, no evidence has indicated the occurrence of plant lectins, which recognize and bind “endogenous” receptors and accordingly are involved in recognition mechanisms within the organism itself. Here we show that the plant hormone jasmonic acid methyl ester (JAME) induces in leaves of Nicotiana tabacum (var. Samsun NN) the expression of a lectin that is absent from untreated plants. The lectin specifically binds to oligomers of N‐acetylglucosamine and is detected exclusively in the cytoplasm and the nucleus. Both the subcellular location and specificity indicate that the Nicotiana tabacum agglutinin (called Nictaba) may be involved in the regulation of gene expression in stressed plants through specific protein‐carbohydrate interactions with regulatory cytoplasmic/nuclear glycoproteins. Searches in the databases revealed that many flowering plants contain sequences encoding putative homologues of the tobacco lectin, which suggest that Nictaba is the prototype of a widespread or possibly ubiquitous family of lectins with a specific endogenous role.
This page was last modified on 27 Jan 2025 .
