A field-grown transgenic tomato line expressing higher levels of polyamines reveals legume cover crop mulch-specific perturbations in fruit phenotype at the levels of metabolite profiles, gene expression, and agronomic characteristics.

Genetic modification of crop plants to introduce desirable traits such as nutritional enhancement, disease and pest resistance, and enhanced crop productivity is increasingly seen as a promising technology for sustainable agriculture and boosting food production in the world. Independently, cultural practices that utilize alternative agriculture strategies including organic cultivation subscribe to sustainable agriculture by limiting chemical usage and reduced tillage. How the two together affect fruit metabolism or plant growth in the field or whether they are compatible has not yet been tested. Fruit-specific yeast S-adenosylmethionine decarboxylase (ySAMdc) line 579HO, and a control line 556AZ were grown in leguminous hairy vetch (Vicia villosa Roth) (HV) mulch and conventional black polyethylene (BP) mulch, and their fruit analysed. Significant genotypexmulch-dependent interactions on fruit phenotype were exemplified by differential profiles of 20 fruit metabolites such as amino acids, sugars, and organic acids. Expression patterns of the ySAMdc transgene, and tomato SAMdc, E8, PEPC, and ICDHc genes were compared between the two lines as a function of growth on either BP or HV mulch. HV mulch significantly stimulated the accumulation of asparagine, glutamate, glutamine, choline, and citrate concomitant with a decrease in glucose in the 556AZ fruits during ripening as compared to BP. It enables a metabolic system in tomato somewhat akin to the one in higher polyamine-accumulating transgenic fruit that have higher phytonutrient content. Finally, synergism was found between HV mulch and transgenic tomato in up-regulating N:C indicator genes PEPC and ICDHc in the fruit.

Strong increase of foliar inulin occurs in transgenic lettuce plants (Lactuca sativa L.) overexpressing the Asparagine Synthetase A gene from Escherichia coli.

Transgenic lettuce (Lactuca sativa L. cv. 'Cortina') lines expressing the asparagine synthetase A gene from Escherichia coli were produced to alter the plant nitrogen status and eventually enhance growth. The relative molecular abundance of water-soluble metabolites was measured by 1H NMR in transgenic and conventional plants at early developmental stages and grown under the same conditions. NMR metabolic profiles assessed that a transgenic line and the wild-type counterpart shared the same compounds, but it also revealed side effects on the carbon metabolism following genetic modification. Concerning the nitrogen status, the amino acid content did not vary significantly, except for glutamic acid and gamma-aminobutyric acid, which diminished in the transgenics. As for the carbon metabolism, in transgenic leaves the contents of sucrose, glucose, and fructose decreased, whereas that of inulin increased up to 30 times, accompanied by the alteration of most Krebs's cycle organic acids and the rise of tartaric acid compared to nontransformed controls. Lettuce leaf inulins consisted of short oligomeric chains made of one glucose unit bound to two/four fructose units. Inulins are beneficial for human health, and they are extracted from plants and commercialized as long-chain types, whereas the short forms are synthesized chemically. Hence, lettuce genotypes with high content of foliar short-chain inulin represent useful materials for breeding strategies and a potential source for low molecular weight inulin.

Nuclear magnetic resonance spectroscopy-based metabolite profiling of transgenic tomato fruit engineered to accumulate spermidine and spermine reveals enhanced anabolic and nitrogen-carbon interactions.

Polyamines are ubiquitous aliphatic amines that have been implicated in myriad processes, but their precise biochemical roles are not fully understood. We have carried out metabolite profiling analyses of transgenic tomato (Solanum lycopersicum) fruit engineered to accumulate the higher polyamines spermidine (Spd) and spermine (Spm) to bring an insight into the metabolic processes that Spd/Spm regulate in plants. NMR spectroscopic analysis revealed distinct metabolite trends in the transgenic and wild-type/azygous fruits ripened off the vine. Distinct metabolites (glutamine, asparagine, choline, citrate, fumarate, malate, and an unidentified compound A) accumulated in the red transgenic fruit, while the levels of valine, aspartic acid, sucrose, and glucose were significantly lower as compared to the control (wild-type and azygous) red fruit. The levels of isoleucine, glucose, gamma-aminobutyrate, phenylalanine, and fructose remained similar in the nontransgenic and transgenic fruits. Statistical treatment of the metabolite variables distinguished the control fruits from the transgenic fruit and provided credence to the pronounced, differential metabolite profiles seen during ripening of the transgenic fruits. The pathways involved in the nitrogen sensing/signaling and carbon metabolism seem preferentially activated in the high Spd/Spm transgenics. The metabolite profiling analysis suggests that Spd and Spm are perceived as nitrogenous metabolites by the fruit cells, which in turn results in the stimulation of carbon sequestration. This is seen manifested in higher respiratory activity and up-regulation of phosphoenolpyruvate carboxylase and NADP-dependent isocitrate dehydrogenase transcripts in the transgenic fruit compared to controls, indicating high metabolic status of the transgenics even late in fruit ripening.

Metabolic profile of lettuce leaves by high-field NMR spectra.

A detailed analysis of the proton high-field NMR spectra of aqueous and organic extracts of lettuce leaves is reported for the first time. A combination of COSY, TOCSY, (1)H-(13)C HSQC, (1)H-(13)C HMBC bidimensional sequences and DOSY was used to assign each spin system and to separate the components of the complex patterns. A large number of water-soluble metabolites belonging to different classes such as carbohydrates, polyols, organic acids and amino acids were fully assigned. Moreover, the complex spectra of metabolites extracted in organic solvents belonging to sterols, fatty acids, diacylglycerophospholipids, galactosyldiacylglycerols, sulpholipids, pheophytins, carotenoids and hydrocarbons were also assigned.