Christina E. Turi

Inoculation with arbuscular mycorrhizal fungi improves the nutritional value of tomatoes

Arbuscular mycorrhizal (AM) fungi can affect many different micronutrients and macronutrients in plants and also influence host volatile compound synthesis. Their effect on the edible portions of plants is less clear. Two separate studies were performed to investigate whether inoculation by AM fungi (Rhizophagus irregularis, Funneliformis mosseae, or both) can affect the food quality of tomato fruits, in particular common minerals, antioxidants, carotenoids, a suite of vitamins, and flavor compounds (sugars, titratable acids, volatile compounds). It was found that AM fungal inoculation increased the nutrient quality of tomato fruits for most nutrients except vitamins. Fruit mineral concentration increased with inoculation (particularly N, P, and Cu). Similarly, inoculated plants had fruit with higher antioxidant capacity and more carotenoids. Furthermore, five volatile compounds were significantly higher in AM plants compared with non-AM controls. Taken together, these results show that AM fungi represent a promising resource for improving both sustainable food production and human nutritional needs.

Comparisons of large (Vaccinium macrocarpon ait.) and small (Vaccinium oxycoccos L., Vaccinium vitis-idaea L.) cranberry in British Columbia by phytochemical determination, antioxidant potential, and metabolomic profiling with chemometric analysis

There is a long history of use and modern commercial importance of large and small cranberries in North America. The central objective of the current research was to characterize and compare the chemical composition of 2 west coast small cranberry species traditionally used (Vaccinium oxycoccos L. and Vaccinium vitis-idaea L.) with the commercially cultivated large cranberry (Vaccinium macrocarpon Ait.) indigenous to the east coast of North America. V. oxycoccos and V. macrocarpon contained the 5 major anthocyanins known in cranberry; however, the ratio of glycosylated peonidins to cyanidins varied, and V. vitis-idaea did not contain measurable amounts of glycosylated peonidins. Extracts of all three berries were found to contain serotonin, melatonin, and ascorbic acid. Antioxidant activity was not found to correlate with indolamine levels while anthocyanin content showed a negative correlation, and vitamin C content positively correlated. From the metabolomics profiles, 4624 compounds were found conserved across V. macrocarpon, V. oxycoccoS, and V. vitis-idaea with a total of approximately 8000-10 000 phytochemicals detected in each species. From significance analysis, it was found that 2 compounds in V. macrocarpoN, 3 in V. oxycoccos, and 5 in V. vitis-idaea were key to the characterization and differentiation of these cranberry metabolomes. Through multivariate modeling, differentiation of the species was observed, and univariate statistical analysis was employed to provide a quality assessment of the models developed for the metabolomics data.

North American Artemisia species from the subgenus Tridentatae (Sagebrush): a phytochemical, botanical and pharmacological review.

The genus Artemisia consists of between 350 and 500 species with most of the North American endemic Artemisia species contained within the subgenus Tridentatae (Sagebrush). The reported uses of these species by Native American and First Nations peoples include analgesic, antiinflammatory, antiseptic, immunostimulation activity, as well as the treatment of afflictions from spiritual origins. Taxonomic revision for North American Sagebrush has created a number of synonyms that confuse the literature. The phytochemical diversity of the Tridentatae includes at least 220 distinct and important specialized metabolites. This manuscript reviews the current phytochemical, botanical and pharmacological understanding for the subgenus Tridentatae, and provides a foundation for future studies of the metabolomes of the Tridentatae. Modern approaches to phytochemical analysis and drug discovery are likely to provide interesting lead compounds in the near future.

Circadian changes in endogenous concentrations of indole-3-acetic acid, melatonin, serotonin, abscisic acid and jasmonic acid in Characeae (Chara australis Brown)

Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to “light on.” The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The “dark” IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways.

Metabolomics for phytochemical discovery: development of statistical approaches using a cranberry model system.

Metabolomics is the qualitative and quantitative analysis of all of the small molecules in a biological sample at a specific time and influence. Technologies for metabolomics analysis have developed rapidly as new analytical tools for chemical separations, mass spectrometry, and NMR spectroscopy have emerged. Plants have one of the largest metabolomes, and it is estimated that the average plant leaf can contain upward of 30 000 phytochemicals. In the past decade, over 1200 papers on plant metabolomics have been published. A standard metabolomics data set contains vast amounts of information and can either investigate or generate hypotheses. The key factors in using plant metabolomics data most effectively are the experimental design, authentic standard availability, extract standardization, and statistical analysis. Using cranberry (Vaccinium macrocarpon) as a model system, this review will discuss and demonstrate strategies and tools for analysis and interpretation of metabolomics data sets including eliminating false discoveries and determining significance, metabolite clustering, and logical algorithms for discovery of new metabolites and pathways. Together these metabolomics tools represent an entirely new pipeline for phytochemical discovery.

In vitro conservation, phytochemistry, and medicinal activity of Artemisia tridentata Nutt.: metabolomics as a hypothesis-generating tool for plant tissue culture

Artemisia tridentata Nutt. and related species in the subgenus Tridentatae are ecologically important plants with a rich history of ceremonial and medicinal use by the indigenous people of North America. With the exception of antimicrobial and insecticidal bioassays, there is limited data to support the traditional uses of A. tridentata. Additionally, wild A. tridentata populations are declining and conservation of genetic resources is warranted. The current study was designed to (a) develop in vitro protocols to conserve A. tridentata in axenic culture and to provide plant tissues for phytochemical analysis, (b) to investigate the presence of neurologically-active phytochemicals in A. tridentata and (c) to develop metabolomics as a tool for understanding secondary metabolite biosynthesis under aseptic conditions. A collection of in vitro-grown germplasm lines was established from wild-harvested seeds of A. tridentata. Neurotransmitters acetylcholine, GABA, melatonin and serotonin were identified and quantified in the plant tissues. Crude extracts of A. tridentata inhibited acetylcholinesterase in a bioassay. A metabolomics analysis with chemometric statistics quantified changes in the phytochemical profiles of wild-harvested plants and plantlets in axenic culture. A total of 1,543 phytochemicals were found in all samples of A. tridentata including 52 significant ions putatively identified as monoterpene, phenolic or sesquiterpene compounds. Together, these data provide the foundation for further investigations of the phytochemical diversity and medicinal activity of A. tridentata and demonstrate a research approach for use of metabolomics as a tool for understanding secondary metabolite biosynthesis under aseptic conditions.

Galanthamine, an anti-cholinesterase drug, effects plant growth and development in Artemisia tridentata Nutt. via modulation of auxin and neurotransmitter signaling.

Galanthamine is a naturally occurring acetylcholinesterase (AchE) inhibitor that has been well established as a drug for treatment of mild to moderate Alzheimer disease, but the role of the compound in plant metabolism is not known. The current study was designed to investigate whether galanthamine could redirect morphogenesis of Artemisia tridentata Nutt. cultures by altering concentration of endogenous neurosignaling molecules acetylcholine (Ach), auxin (IAA), melatonin (Mel), and serotonin (5HT). Exposure of axenic A. tridentata cultures to 10 µM galanthamine decreased the concentration of endogenous Ach, IAA, MEL, and AchE, and altered plant growth in a manner reminiscent of 2–4D toxicity. Galanthamine itself demonstrated IAA activity in an oat coleoptile elongation bioassay, 20 µM galanthamine showed no significant difference compared with 5 μM IAA or 5 μM 1-Naphthaleneacetic acid (NAA). Metabolomic analysis detected between 20,921 to 27,891 compounds in A. tridentata plantlets and showed greater commonality between control and 5 µM treatments. Furthermore, metabolomic analysis putatively identified coumarins scopoletin/isoscopoletin, and scopolin in A. tridentata leaf extracts and these metabolites linearly increased in response to galanthamine treatments. Overall, these data indicate that galanthamine is an allelopathic phytochemical and support the hypothesis that neurologically active compounds in plants help ensure plant survival and adaptation to environmental challenges.

Systems Biology Analysis of Changes in Potential Across Plasma Membrane: Physiological Implications

Variation of the membrane potential difference (PD) across plasma membrane is considered in terms of one or more ion transporter populations changing their conductance and activation kinetics. Slow changes occurring over minutes can be investigated by the current voltage (I/V) technique. In some cases, data are sufficient to model electrical characteristics of each transporter population and their evolution with time. The proton pump at the plasma membrane of the salt-sensitive Characeae Chara australis provides an example of single transporter changing conductance against a steady background. The rise and fall in proton pump conductance may be prompted by circadian oscillations of indoleamines IAA and melatonin, measured in growing thalli of characean plants. In response to abiotic stress, two or more transporter populations change conductance and/or PD dependence. The voltage clamp to extreme negative PD levels transiently inhibits the proton pump in C. australis, activating H+/OH− channels, increasing the background conductance, and opening inward rectifier channels at more depolarized PDs. An increase in medium salinity (after pre-treatment with isotonic sorbitol medium) results in similar response, which is preceded by a typical noise in membrane PD. In salt-tolerant Characeae Lamprothamnium sp., increase in salinity (or osmolarity) provokes an increase in proton pumping as well as increase in background conductance and opening of the inward rectifier channels at more depolarized PDs to effect turgor regulation. The hypoosmotic turgor regulation also involves a complex interaction of several transporters, initiated by the increase of turgor pressure , [Ca2+]cyt increase, and PD changes. A detailed modeling is in progress for most of these responses. The examples demonstrate the analytical and predictive power of the I/V methodology coupled with the systems biology modeling and monitoring of biochemical changes.