Tomato, an essential crop in terms of economic importance and nutritional quality, is also used as a model species for all fleshy fruits and for genomics of Solanaceae. Tomato fruit quality at harvest is a direct function of its metabolite content, which in turn is a result of many physiological changes during fruit development. The aim of the work reported here was to develop a global approach to characterize changes in metabolic profiles in two interdependent tissues from the same tomato fruits. Absolute quantification data of compounds in flesh and seeds from 8 days to 45 days post anthesis (DPA) were obtained through untargeted (proton nuclear magnetic resonance, 1 H-NMR) and targeted metabolic profiling (liquid chromatography with diode array detection (LC-DAD) or gas chromatography with flame ionization detection (GC-FID)). These data were analyzed with chemometric approaches. Kohonen self organizing maps (SOM) analysis of these data allowed us to combine multivariate (distribution of samples on Kohonen SOMs) and univariate information (component plane representation of metabolites) in a single analysis. This strategy confirmed published data and brought new insights on tomato flesh and seed composition, thus demonstrating its potential in metabolomics. The compositional changes were related to physiological processes occurring in each tissue. They pointed to (i) some parallel changes at early stages in relation to cell division and transitory storage of carbon, (ii) metabolites participating in the fleshy trait and (iii) metabolites involved in the specific developmental patterns of the seeds.

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HighlightUsing metabolomics in tomato, we confirmed the existence of diel patterns in leaf composition and showed lower but significant diel changes in expanding fruit depending on the potential carbon supply.

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a b s t r a c t Edited by RA Street Keywords: Cadmium Mineral elements Solanum lycopersicum Seed FruitIn young tomato plants, modifications in mineral composition by short-term cadmium (Cd) treatments have been extensively examined. However, long-term Cd treatments have been fewly investigated, and little information about Cd-stress in fruiting plants is available. In the present work, we examined the changes in mineral nutrients of roots, stems, leaves, flowers, seeds and fruit pericarp of tomato plants submitted to a long-term Cd stress. After a 90-day culture period in hydroponic contaminated environment (0, 20 and 100 μM CdCl 2 ), fruit production was affected by increasing external Cd levels, with the absence of fruit set at 100 μM Cd. Meanwhile, Cd altered the plant mineral contents with an element-and organ-dependent response. At 20 μM, Cd triggered a significant increase in Ca content in roots, mature leaves, flowers and developing fruits. However, at 100 μM Cd, Ca content was reduced in shoots, and enhanced in roots. Cd stress reduced Zn and Cu contents in shoots and increased them in roots. High Cd level led to a significant decrease in K and Mg content in all plant organs. Furthermore, Fe concentration was reduced in roots, stems and leaves but increased in flowers, seeds and red ripe fruits. Our results suggest that tomato plants acclimatize during long-term exposure to 20 μM Cd, while 100 μM Cd results in drastic nutritional perturbations leading to fruit set abortion.

Summary Tomato is a model organism to study the development of fleshy fruit including ripening initiation. Unfortunately, few studies deal with the brief phase of accelerated ripening associated with the respiration climacteric because of practical problems involved in measuring fruit respiration.Because constraint‐based modelling allows predicting accurate metabolic fluxes, we investigated the respiration and energy dissipation of fruit pericarp at the breaker stage using a detailed stoichiometric model of the respiratory pathway, including alternative oxidase and uncoupling proteins. Assuming steady‐state, a metabolic dataset was transformed into constraints to solve the model on a daily basis throughout tomato fruit development.We detected a peak of CO 2 released and an excess of energy dissipated at 40 d post anthesis (DPA) just before the onset of ripening coinciding with the respiration climacteric. We demonstrated the unbalanced carbon allocation with the sharp slowdown of accumulation (for syntheses and storage) and the beginning of the degradation of starch and cell wall polysaccharides. Experiments with fruits harvested from plants cultivated under stress conditions confirmed the concept.We conclude that modelling with an accurate metabolic dataset is an efficient tool to bypass the difficulty of measuring fruit respiration and to elucidate the underlying mechanisms of ripening.

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We have developed an efficient protoplast-fusion method to produce somatic hybrid allopolyploid plants that combine Citrus with seven related genera, including four that are sexually incompatible. In this paper we report the creation of 18 new allotetraploid hybrids of Citrus, including ten among sexually incompatible related genera, that may have direct cultivar potential as improved citrus rootstocks. All hybrids were confirmed by cytological and RAPD analyses. If fertile, the attributes of these hybrids may be amenable to further genetic manipulation by breeding at the tetraploid level. Wide somatic hybridization of Citrus via protoplast fusion bypasses biological barriers to the natural allopolyploidization of Citrus, and creates new evolutionary opportunities that would be difficult or impossible to achieve by natural or conventional hybridization.