BackgroundNitrogen uptake, reallocation within the plant, and between subcellular compartments involves ammonium, nitrate and peptide transporters. Ammonium transporters are separated into two distinct families (AMT1 and AMT2), each comprised of five members on average in angiosperms. Nitrate transporters also form two discrete families (NRT1 and NRT2), with angiosperms having four NRT2s, on average. NRT1s share an evolutionary history with peptide transporters (PTRs). The NRT1/PTR family in land plants usually has more than 50 members and contains also members with distinct activities, such as glucosinolate and abscisic acid transport.ResultsPhylogenetic reconstructions of each family across 20 land plant species with available genome sequences were supplemented with subcellular localization and transmembrane topology predictions. This revealed that both AMT families diverged prior to the separation of bryophytes and vascular plants forming two distinct clans, designated as supergroups, each. Ten supergroups were identified for the NRT1/PTR family. It is apparent that nitrate and peptide transport within the NRT1/PTR family is polyphyletic, that is, nitrate and/or peptide transport likely evolved multiple times within land plants. The NRT2 family separated into two distinct clans early in vascular plant evolution. Subsequent duplications occurring prior to the eudicot/monocot separation led to the existence of two AMT1, six AMT2, 31 NRT1/PTR, and two NRT2 clans, designated as groups.ConclusionPhylogenetic separation of groups suggests functional divergence within the angiosperms for each family. Distinct groups within the NRT1/PTR family appear to separate peptide and nitrate transport activities as well as other activities contained within the family, for example nitrite transport. Conversely, distinct activities, such as abscisic acid and glucosinolate transport, appear to have recently evolved from nitrate transporters.

Melatonin and serotonin have previously been described in mature wine grapes and finished wines, but the metabolism of these signalling molecules in the development of wine grapes has not previously been investigated. We harvested wine grapes at different stages of development from lag phase through véraison from eight different commercial vineyards representing a diversity of growing conditions, management practices, merlot varietals and localized ecosystems to determine whether different patterns in melatonin and serotonin can be found in wine grapes during seed development and berry maturation. Melatonin was detected in 45% of the fully developed purple, postvéraison grapes but only found in 23% of prelag phase samples. However, the actual concentration of melatonin was highest in wine grapes harvested at the early stage of véraison when the seed is developing. Serotonin was not detected in any of the prelag phase grapes but was consistently detected in 30-35% of grapes harvested during the véraison transition at consistent levels of about 8-10 mug/g. Interestingly, the nitrogen storage compound gamma-aminobutyric acid was also found at about 115 mug/g in 77% of early stage green grapes and declined in both prevalence and concentration with ripening. Together, these data are indicative of a potential role for these molecules in the development and maturation of wine grapes.

Catechol dehydroxylation is a central chemical transformation in the gut microbial metabolism of plant- and host-derived small molecules. However, the molecular basis for this transformation and its distribution among gut microorganisms are poorly understood. Here, we characterize a molybdenum-dependent enzyme from the human gut bacterium Eggerthella lenta that dehydroxylates catecholamine neurotransmitters. Our findings suggest that this activity enables E. lenta to use dopamine as an electron acceptor. We also identify candidate dehydroxylases that metabolize additional host- and plant-derived catechols. These dehydroxylases belong to a distinct group of largely uncharacterized molybdenum-dependent enzymes that likely mediate primary and secondary metabolism in multiple environments. Finally, we observe catechol dehydroxylation in the gut microbiotas of diverse mammals, confirming the presence of this chemistry in habitats beyond the human gut. These results suggest that the chemical strategies that mediate metabolism and interactions in the human gut are relevant to a broad range of species and habitats.

To fill the unmet need for improved matrixes for matrix-assisted laser desorption ionization (MALDI) tissue imaging of small molecules, dithranol (DT)--a matrix mainly used for the analysis of synthetic polymers--was evaluated for detection of lipids in rat liver and bovine calf lens, using MALDI Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). The use of DT resulted in better detection of endogenous lipids than did two other commonly used matrixes, α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), with >70 lipid entities (including phosphatidylcholines, phosphatidylethanolamines, sphingomyelins, phosphatidylserines, phosphatidylglycerol, phosphatidic acids, ceramide phosphates, sterol lipids, acyl carnitines, and glycerides) being detected in rat liver and bovine lens tissue sections, using positive-ion detection. Using saturated DT in chloroform/methanol (2:1, v/v), with 1% formic acid in the final mixture, 57 lipid entities were successfully imaged from bovine calf lens, with clear and distinct distribution patterns. In a section across the lens equatorial plane, all compounds showed concentric distributions around the lens nucleus and most showed specific abundance changes, which correlated with lens fiber cell age. As a novel finding, palmitoylcarnitine and oleoylcarnitine were found uniquely localized to the younger lens fiber cell cortex region. This work demonstrates the potential of DT as a new matrix for tissue imaging by MALDI-FTICR MS.