Internal conversion product of protected precursor.

<p>Internal conversion product of protected precursor.</p

Transport of ¹⁸FS and [U-¹⁴C]suc in wild-type and <i>sut1</i> mutant leaves.

<p>A: Photo of leaves collected from two wild-type (WT) and two <i>sut1</i> mutant plants. B: ^<b>18</b>F phosphor image of leaves exposed for one hour to a solution of 200 μCi ^<b>18</b>FS and 125 μCi [^<b>14</b>C]suc. C: ^<b>14</b>C phosphor image obtained after five days exposure.</p

Radiosynthesis of 6’-Deoxy-6’[¹⁸F]Fluorosucrose via Automated Synthesis and Its Utility to Study <i>In Vivo</i> Sucrose Transport in Maize (<i>Zea mays</i>) Leaves

<div><p>Sugars produced from photosynthesis in leaves are transported through the phloem tissues within veins and delivered to non-photosynthetic organs, such as roots, stems, flowers, and seeds, to support their growth and/or storage of carbohydrates. However, because the phloem is located internally within the veins, it is difficult to access and to study the dynamics of sugar transport. Radioactive tracers have been extensively used to study vascular transport in plants and have provided great insights into transport dynamics. To better study sucrose partitioning <i>in vivo</i>, a novel radioactive analog of sucrose was synthesized through a completely chemical synthesis route by substituting fluorine-18 (half-life 110 min) at the 6’ position to generate 6’-deoxy-6’[¹⁸F]fluorosucrose (¹⁸FS). This radiotracer was then used to compare sucrose transport between wild-type maize plants and mutant plants lacking the <i>Sucrose transporter1</i> (<i>Sut1</i>) gene, which has been shown to function in sucrose phloem loading. Our results demonstrate that ¹⁸FS is transported <i>in vivo</i>, with the wild-type plants showing a greater rate of transport down the leaf blade than the <i>sut1</i> mutant plants. A similar transport pattern was also observed for universally labeled [U-¹⁴C]sucrose ([U-¹⁴C]suc). Our findings support the proposed sucrose phloem loading function of the <i>Sut1</i> gene in maize, and additionally demonstrate that the ¹⁸FS analog is a valuable, new tool that offers imaging advantages over [U-¹⁴C]suc for studying phloem transport in plants.</p></div

Transport of ¹⁸F as fluoride in wild-type leaves.

<p>150 μCi of free ^<b>18</b>F was applied to wild-type leaves and allowed to transport for two hours before a one hour image was obtained. Levels close to background were observed in the leaves with very low levels of transport.</p

Identification of the First Diketomorpholine Biosynthetic Pathway Using FAC-MS Technology

Filamentous fungi are prolific producers of secondary metabolites with drug-like properties, and their genome sequences have revealed an untapped wealth of potential therapeutic leads. To better access these secondary metabolites and characterize their biosynthetic gene clusters, we applied a new platform for screening and heterologous expression of intact gene clusters that uses fungal artificial chromosomes and metabolomic scoring (FAC-MS). We leverage FAC-MS technology to identify the biosynthetic machinery responsible for production of acu-dioxomorpholine, a metabolite produced by the fungus, <i>Aspergilllus aculeatus.</i> The acu-dioxomorpholine nonribosomal peptide synthetase features a new type of condensation domain (designated C_R) proposed to use a noncanonical arginine active site for ester bond formation. Using stable isotope labeling and MS, we determine that a phenyllactate monomer deriving from phenylalanine is incorporated into the diketomorpholine scaffold. Acu-dioxomorpholine is highly related to orphan inhibitors of P-glycoprotein targets in multidrug-resistant cancers, and identification of the biosynthetic pathway for this compound class enables genome mining for additional derivatives

TA-G reduces larval feeding on artificial diet at ecologically relevant concentrations.

<p>A. TA-G concentration across tissues. B. <i>M</i>. <i>melolontha</i> consumed 40% less TA-G-containing diet compared to control diet in a nonchoice experiment after 24 h (Student’s <i>t</i> test, <i>n</i> = 15). Underlying data can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002332#pbio.1002332.s001" target="_blank">S1 Data</a>.</p

TA-G reduces the negative effect of <i>M</i>. <i>melolontha</i> on plant vegetative and reproductive performance in the field.

<p>A. TA-G concentration was positively correlated to relative leaf growth across 17 <i>T</i>. <i>officinale</i> genotypes in a common garden experiment towards the end of the growing season. Relative leaf growth is the mean leaf growth of herbivore-infested plants of each genotype during the infestation period compared to the mean leaf growth of the control plants of each genotype (leaf growth: increase in maximal leaf length compared to maximal leaf length before infestation). Data points below the horizontal dashed line indicate reduction in leaf growth under <i>M</i>. <i>melolontha</i> attack. Each data point represents the mean of one genotype. Plants were infested at the end of June. Statistics of Pearson’s product-moment correlations based on mean values per genotype are shown. B. The relative number of flowers (number of flowers of the herbivore-infested plants expressed relative to noninfested plants of each genotype) was positively correlated with the concentration of TA-G, but not with the total concentrations of PIEs or TritAcs at the beginning of the flowering season. Only genotypes that flowered at this time point are shown (9 out of 17 genotypes). Underlying data can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002332#pbio.1002332.s001" target="_blank">S1 Data</a>.</p

<i>M</i>. <i>melolontha</i> growth correlates negatively with the concentration of the latex metabolite TA-G.

<p>A. Representative liquid chromatography-mass spectrometry (LC-MS) chromatogram of a latex methanol extract (left panel) and gas chromatography-flame ionization detector (GC-FID) chromatogram of a latex hexane extract (right panel) depicting the three major classes of latex secondary metabolites in <i>T</i>. <i>officinale</i>. LC = liquid chromatograph. MS = mass spectrometer. GC = gas chromatograph. FID = flame ionization detector. B. After 11 d of feeding, growth of <i>M</i>. <i>melolontha</i> larvae on 17 <i>T</i>. <i>officinale</i> genotypes was negatively correlated with TA-G concentration in the root latex (linear model, <i>p</i> = 0.007, left panel). <i>M</i>. <i>melolontha</i> growth was not correlated with the total concentrations of PIEs (middle panel) or TritAcs (right panel). Each data point represents the mean <i>M</i>. <i>melolontha</i> growth rate of 12 independent replicates of one <i>T</i>. <i>officinale</i> genotype. Underlying data can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002332#pbio.1002332.s001" target="_blank">S1 Data</a>.</p

Interrogation of Benzomalvin Biosynthesis Using Fungal Artificial Chromosomes with Metabolomic Scoring (FAC-MS): Discovery of a Benzodiazepine Synthase Activity

The benzodiazepine benzomalvin A/D is a fungally derived specialized metabolite and inhibitor of the substance P receptor NK1, biosynthesized by a three-gene nonribosomal peptide synthetase cluster. Here, we utilize fungal artificial chromosomes with metabolomic scoring (FAC-MS) to perform molecular genetic pathway dissection and targeted metabolomics analysis to assign the <i>in vivo</i> role of each domain in the benzomalvin biosynthetic pathway. The use of FAC-MS identified the terminal cyclizing condensation domain as BenY-C_T and the internal C-domains as BenZ-C₁ and BenZ-C₂. Unexpectedly, we also uncovered evidence suggesting BenY-C_T or a yet to be identified protein mediates benzodiazepine formation, representing the first reported benzodiazepine synthase enzymatic activity. This work informs understanding of what defines a fungal C_T domain and shows how the FAC-MS platform can be used as a tool for <i>in vivo</i> analyses of specialized metabolite biosynthesis and for the discovery and dissection of new enzyme activities

The germacrene A synthase ToGAS1 mediates the first committed step in latex TA-G biosynthesis.

<p>A. Partial biosynthetic pathway of TA-G. B. Phylogenetic tree of the newly identified <i>T</i>. <i>officinale</i> germacrene A synthases ToGAS1/2 and known Asteraceae terpene synthases (neighbor-joining method, <i>n</i> = 1,000 replicates). Bootstrap values are shown next to each node. Accession numbers can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002332#pbio.1002332.s029" target="_blank">S4 Table</a>. C. GC-MS analysis of enzyme products from recombinant ToGAS1/2 expressed in <i>Escherichia coli</i> and incubated with the substrate FDP. Germacrene A is converted to β-elemene during hot GC injection. cont, contamination. GC-MS = gas chromatograph coupled to a mass spectrometer. D. Expression of <i>T</i>. <i>officinale</i> germacrene A synthase genes (<i>ToGAS1</i> and <i>ToGAS2</i>) in the entire main root, latex, and outer main root cortex as determined by RT-qPCR. Statistics of two-way ANOVA and pairwise comparison according to Tukey’s post hoc test are shown. Mean Sq = Mean of squares. <i>n</i> = 3. E. Silencing of <i>ToGAS1</i> by RNAi generated three independently silenced lines with strongly depleted TA-G concentrations and two transformed, nonsilenced lines with similar TA-G concentrations as the parental wild type. N = 3. Underlying data can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002332#pbio.1002332.s001" target="_blank">S1 Data</a>.</p