A novel pathway for sesquiterpene biosynthesis from Z,Z-farnesyl pyrophosphate in the wild tomato Solanum habrochaites.

In the wild tomato Solanum habrochaites, the Sst2 locus on chromosome 8 is responsible for the biosynthesis of several class II sesquiterpene olefins by glandular trichomes. Analysis of a trichome-specific EST collection from S. habrochaites revealed two candidate genes for the synthesis of Sst2-associated sesquiterpenes.

CYP725A4 from yew catalyzes complex structural rearrangement of taxa-4(5),11(12)-diene into the cyclic ether 5(12)-oxa-3(11)-cyclotaxane.

Taxa-4(5),11(12)-diene is the first committed precursor of functionalized taxanes such as paclitaxel, a successful anticancer drug. Biosynthesis of taxanes in yew involves several oxidations, a number of which have been shown to be catalyzed by cytochrome P-450 oxygenases. Hydroxylation of the C-5alpha of taxa-4(5),11(12)-diene is believed to be the first of these oxidations, and a gene encoding a taxa-4(5),11(12)-diene 5alpha-hydroxylase (CYP725A4) was recently described (Jennewein, S.

Deficiency in phosphatidylserine decarboxylase activity in the psd1 psd2 psd3 triple mutant of Arabidopsis affects phosphatidylethanolamine accumulation in mitochondria.

Phosphatidylserine (PS) decarboxylase is involved in the synthesis of the abundant phospholipid phosphatidylethanolamine (PE), particularly in mitochondria, in many organisms, including yeast (Saccharomyces cerevisiae) and animals. Arabidopsis (Arabidopsis thaliana) contains three genes with sequence similarity to PS decarboxylases, and the respective gene products were functionally characterized after heterologous expression in yeast and Escherichia coli. While the PSD1 protein localizes to mitochondria, PSD2 and PSD3 are found in the endomembrane system.

Evidence from engineering that decarboxylation of free serine is the major source of ethanolamine moieties in plants.

Plants form ethanolamine (Etn) moieties by decarboxylating serine or phosphatidylserine (PtdSer), and use them to make phosphatidylethanolamine, phosphatidylcholine, choline, and glycine betaine. Serine decarboxylation is mediated by a serine decarboxylase (SDC) that is unique to plants and has a characteristic N-terminal extension. This extension was shown to have little influence on function of the enzyme in vitro.

Mitochondrial phosphatidylserine decarboxylase from higher plants. Functional complementation in yeast, localization in plants, and overexpression in Arabidopsis.

Plants are known to synthesize ethanolamine (Etn) moieties by decarboxylation of free serine (Ser), but there is also some evidence for phosphatidyl-Ser (Ptd-Ser) decarboxylation. Database searches identified diverse plant cDNAs and an Arabidopsis gene encoding 50-kD proteins homologous to yeast (Saccharomyces cerevisiae) and mammalian mitochondrial Ptd-Ser decarboxylases (PSDs). Like the latter, the plant proteins have putative mitochondrial targeting and inner membrane sorting sequences and contain near the C terminus a Glycine-Serine-Threonine motif corresponding to the site of proteolysis and catalytic pyruvoyl residue formation.

The metabolic architecture of plant cells. Stability of central metabolism and flexibility of anabolic pathways during the growth cycle of tomato cells.

The changes in the intermediary metabolism of plant cells were quantified according to growth conditions at three different stages of the growth cycle of tomato cell suspension. Eighteen fluxes of central metabolism were calculated from (13)C enrichments after near steady-state labeling by a metabolic model similar to that described in Dieuaide-Noubhani et al. (Dieuaide-Noubhani, M.

Metabolic engineering of osmoprotectant accumulation in plants.

Drought and salinity are among the worst scourges of agriculture. One effective mechanism to reduce damage from these stresses is the accumulation of high intracellular levels of osmoprotectant compounds. These compounds include proline, ectoine, betaines, polyols, and trehalose and have evolved in many different organisms.