Transgressive segregation of primary and secondary metabolites in F(2) hybrids between Jacobaea aquatica and J. vulgaris

Application of methyl jasmonate and salicylic acid lead to contrasting effects on the plant's metabolome and herbivory

Phytohormone applications are used to mimic herbivory and can induce plant defences. This study investigated (i) metabolomic changes in leaf tissues of Jacobaea vulgaris and J. aquatica after methyl jasmonate (MeJA) and salicylic acid (SA) applications and (ii) the effects on a leaf-chewing, a leaf-mining and a piercing-sucking herbivore. MeJA treated leaves showed clearly different metabolomic profiles than control leaves, while the differences in metabolomic profiles between SA treated leaves and control leaves were less clear. More NMR peaks increased than decreased after MeJA treatment while this pattern was reversed after SA treatment. The leaf-chewing (Mamestra brassicae) and the leaf-mining herbivores (Liriomyza trifolii) fed less on MeJA-treated leaves compared to control and SA-treated leaves while they fed equally on the latter two. In J. aquatica but not in J. vulgaris, SA treatment reduced feeding damage by the piercing-sucking herbivore (Frankliniella occidentalis). Based on the herbivory and metabolomic data after phytohormone application, we made speculations as follows: For all three herbivore species, plants with high levels of threonine and citric acid showed less herbivory while plants with high levels of glucose showed more herbivory. Herbivory by thrips was lower on plants with high levels of alanine while it was higher on plants with high levels of 3,5-dicaffeoylquinic acid. The plant compounds that related to feeding of piercing-sucking herbivore were further verified with previous independent experiments.

Compositional differences in hybrids between protoporphyrinogen IX oxidase (PPO)-inhibiting herbicide-resistant transgenic rice and weedy rice accessions

We characterized the metabolites in grains of transgenic protoporphyrinogen IX oxidase-inhibiting herbicide-resistant rice and weedy accessions using GC-MS and examined whether the chemical composition of their hybrids differed from that of the parents. We found that the metabolite profiles of transgenic rice and weedy rice were clearly separated. Although the metabolite profiles of F₂ progeny were partially separated from their parents, zygosity did not affect the profiles. The F₂ progeny had similar or intermediate levels of most major nutritional components compared with their parents. However, levels of galactopyranose, trehalose, xylofuranose, mannitol, and benzoic acid were higher in the F₂ progeny. Some fatty acids and organic acids also showed prominent quantitative differences between the F₂ progeny and the parents. Changes in the metabolite levels of transgenic crop-weed hybrids compared to their parents might influence not only the ecological consequences of the hybrids, but also the nutritional quality and food safety.

Characterization of Metabolite Profile in Phyllanthus niruri and Correlation with Bioactivity Elucidated by Nuclear Magnetic Resonance Based Metabolomics

Phyllanthus niruri is an important medicinal plant. To standardize the extract and guarantee its maximum benefit, processing methods optimization ought to be amenable and beneficial. Herein, three dried P. niruri samples, air (AD), freeze (FD) and oven (OD), extracted with various ethanol to water ratios (0%, 50%, 70%, 80% and 100%) were evaluated for their metabolite changes using proton nuclear magnetic resonance (¹H-NMR)-based metabolomics approach. The amino acids analysis showed that FD P. niruri exhibited higher content of most amino acids compared to the other dried samples. Based on principal component analysis (PCA), the FD P. niruri extracted with 80% ethanol contained higher amounts of hypophyllanthin and phenolic compounds based on the loading plot. The partial least-square (PLS) results showed that the phytochemicals, including hypophyllanthin, catechin, epicatechin, rutin, quercetin and chlorogenic, caffeic, malic and gallic acids were correlated with antioxidant and α-glucosidase inhibitory activities, which were higher in the FD material extracted with 80% ethanol. This report optimized the effect of drying and ethanol ratios and these findings demonstrate that NMR-based metabolomics was an applicable approach. The FD P. niruri extracted with 80% ethanol can be used as afunctional food ingredient for nutraceutical or in medicinal preparation.

Genomics-based strategies for the use of natural variation in the improvement of crop metabolism

Next-generation genomics holds great potential in the study of plant phenotypic variation. With several crop reference genomes now available, the affordable costs of de novo genome assembly or target resequencing offer the opportunity to mine the enormous amount of genetic diversity hidden in crop wild relatives. Wide introgressions from these wild ancestors species or land races represent a possible strategy to improve cultivated varieties. In this review, we discuss the mechanisms underlying metabolic diversity within plant species and the possible strategies (and barriers) to introgress novel metabolic traits into cultivated varieties. We show how deep genomic surveys uncover various types of structural variants from extended gene pools of major crops and highlight how this variation may be used for the improvement of crop metabolism.

A Metabolomic Approach to Target Compounds from the Asteraceae Family for Dual COX and LOX Inhibition

The application of metabolomics in phytochemical analysis is an innovative strategy for targeting active compounds from a complex plant extract. Species of the Asteraceae family are well-known to exhibit potent anti-inflammatory (AI) activity. Dual inhibition of the enzymes COX-1 and 5-LOX is essential for the treatment of several inflammatory diseases, but there is not much investigation reported in the literature for natural products. In this study, 57 leaf extracts (EtOH-H₂O 7:3, v/v) from different genera and species of the Asteraceae family were tested against COX-1 and 5-LOX while HPLC-ESI-HRMS analysis of the extracts indicated high diversity in their chemical compositions. Using O2PLS-DA (R² > 0.92; VIP > 1 and positive Y-correlation values), dual inhibition potential of low-abundance metabolites was determined. The O2PLS-DA results exhibited good validation values (cross-validation = Q² > 0.7 and external validation = P² > 0.6) with 0% of false positive predictions. The metabolomic approach determined biomarkers for the required biological activity and detected active compounds in the extracts displaying unique mechanisms of action. In addition, the PCA data also gave insights on the chemotaxonomy of the family Asteraceae across its diverse range of genera and tribes.

Metabolomic Profiling of the Nectars of Aquilegia pubescens and A. Canadensis

To date, variation in nectar chemistry of flowering plants has not been studied in detail. Such variation exerts considerable influence on pollinator–plant interactions, as well as on flower traits that play important roles in the selection of a plant for visitation by specific pollinators. Over the past 60 years the Aquilegia genus has been used as a key model for speciation studies. In this study, we defined the metabolomic profiles of flower samples of two Aquilegia species, A. Canadensis and A. pubescens. We identified a total of 75 metabolites that were classified into six main categories: organic acids, fatty acids, amino acids, esters, sugars, and unknowns. The mean abundances of 25 of these metabolites were significantly different between the two species, providing insights into interspecies variation in floral chemistry. Using the PlantSEED biochemistry database, we found that the majority of these metabolites are involved in biosynthetic pathways. Finally, we explored the annotated genome of A. coerulea, using the PlantSEED pipeline and reconstructed the metabolic network of Aquilegia. This network, which contains the metabolic pathways involved in generating the observed chemical variation, is now publicly available from the DOE Systems Biology Knowledge Base (KBase; http://kbase.us).

Phylogenetic spectrum and analysis of antibacterial activities of leaf extracts from plants of the genus Rhododendron

BACKGROUND

Plants are traditionally used for medicinal treatment of numerous human disorders including infectious diseases caused by microorganisms. Due to the increasing resistance of many pathogens to commonly used antimicrobial agents, there is an urgent need for novel antimicrobial compounds. Plants of the genus Rhododendron belong to the woody representatives of the family Ericaceae, which are typically used in a range of ethno-medical applications. There are more than one thousand Rhododendron species worldwide. The Rhododendron-Park Bremen grows plants representing approximately 600 of the known Rhododendron species, and thus enables research involving almost two thirds of all known Rhododendron species.

METHODS

Twenty-six bacterial species representing different taxonomic clades have been used to study the antimicrobial potential of Rhododendron leaf extracts. Agar diffusion assay were conducted using 80% methanol crude extracts derived from 120 Rhododendron species. Data were analyzed using principal component analysis and the plant-borne antibacterial activities grouped according the first and second principal components.

RESULTS

The leaf extracts of 17 Rhododendron species exhibited significant growth-inhibiting activities against Gram-positive bacteria. In contrast, only very few of the leaf extracts affected the growth of Gram-negative bacteria. All leaf extracts with antimicrobial bioactivity were extracted from representatives of the subgenus Rhododendron, with 15 from the sub-section Rhododendron and two belonging to the section Pogonanthum. The use of bacterial multidrug efflux pump mutants revealed remarkable differences in the susceptibility towards Rhododendron leaf extract treatment.

CONCLUSIONS

For the first time, our comprehensive study demonstrated that compounds with antimicrobial activities accumulate in the leaves of certain Rhododendron species, which mainly belong to a particular subgenus. The results suggested that common genetic traits are responsible for the production of bioactive secondary metabolite(s) which act primarily on Gram-positive organisms, and which may affect Gram-negative bacteria in dependence of the activity of multidrug efflux pumps in their cell envelope.

Leaf polyphenol profile and SSR-based fingerprinting of new segregant Cynara cardunculus genotypes

The dietary value of many plant polyphenols lies in the protection given against degenerative pathologies. Their in planta role is associated with the host's defense response against biotic and abiotic stress. The polyphenol content of a given plant tissue is strongly influenced by the growing environment, but is also genetically determined. Plants belonging to the Cynara cardunculus species (globe artichoke and the cultivated and wild cardoon) accumulate substantial quantities of polyphenols mainly mono and di-caffeoylquinic acid (CQA) in their foliage. Transgressive segregation for CQA content in an F1 population bred from a cross between a globe artichoke and a cultivated cardoon led to the selection of eight segregants which accumulated more CQA in their leaves than did those of either of their parental genotypes. The selections were grown over two seasons to assess their polyphenol profile (CQAs, apigenin and luteolin derivatives and narirutin), and were also fingerprinted using a set of 217 microsatellite markers. The growing environment exerted a strong effect on polyphenol content, but two of the selections were able to accumulate up to an order of magnitude more CQA than either parent in both growing seasons. Since the species is readily vegetatively propagable, such genotypes can be straightforwardly exploited as a source of pharmaceutically valuable compounds, while their SSR-based fingerprinting will allow the genetic identity of clonally propagated material to be easily verified.

Pyrrolizidine alkaloid variation in shoots and roots of segregating hybrids between Jacobaea vulgaris and Jacobaea aquatica

Hybridization can lead to novel qualitative or quantitative variation of secondary metabolite (SM) expression that can have ecological and evolutionary consequences. We measured pyrrolizidine alkaloid (PA) expression in the shoots and roots of a family including one Jacobaea vulgaris genotype and one Jacobaea aquatica genotype (parental genotypes), two F(1) hybrid genotypes, and 102 F(2) hybrid genotypes using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We detected 37 PAs in the roots and shoots of J. vulgaris, J. aquatica and the hybrids. PA concentrations and compositions differed between genotypes, and between roots and shoots. Three otosenine-like PAs that only occurred in the shoots of parental genotypes were present in the roots of F(2) hybrids; PA compositions were sometimes novel in F(2) hybrids compared with parental genotypes, and in some cases transgressive PA expression occurred. We also found that PAs from within structural groups covaried both in the roots and in the shoots, and that PA expression was correlated between shoots and roots. Considerable and novel variation present among F(2) hybrids indicates that hybridization has a potential role in the evolution of PA diversity in the genus Jacobaea, and this hybrid system is useful for studying the genetic control of PA expression.

The relationship between structurally different pyrrolizidine alkaloids and western flower thrips resistance in F(2) hybrids of Jacobaea vulgaris and Jacobaea aquatica

Segregating plant hybrids often have more ecological and molecular variability compared to parental species, and are therefore useful for studying relationships between different traits, and the adaptive significance of trait variation. Hybrid systems have been used to study the relationship between the expression of plant defense compounds and herbivore susceptibility. We conducted a western flower thrips (WFT) bioassay using a hybrid family and investigated the relationship between WFT resistance and pyrrolizidine alkaloid (PA) variation. The hybrid family consisted of two parental (Jacobaea vulgaris and Jacobaea aquatica) genotypes, two F₁ genotypes, and 94 F₂ hybrid lines. The J. aquatica genotype was more susceptible to thrips attack than the J. vulgaris genotype, the two F₁ hybrids were as susceptible as J. aquatica, and susceptibility to WFT differed among F₂ hybrid lines: 69 F₂ lines were equally susceptible compared to J. aquatica, 10 F₂ lines were more susceptible than J. aquatica and 15 F₂ lines were as resistant as J. vulgaris or were intermediate to the two parental genotypes. Among 37 individual PAs that were derived from four structural groups (senecionine-, jacobine-, erucifoline- and otosenine-like PAs), the N-oxides of jacobine, jaconine, and jacoline were negatively correlated with feeding damage caused by WFT, and the tertiary amines of jacobine, jaconine, jacoline, and other PAs did not relate to feeding damage. Total PA concentration was negatively correlated with feeding damage. Among the four PA groups, only the total concentration of the jacobine-like PAs was negatively correlated with feeding damage. Multiple regression tests suggested that jacobine-like PAs play a greater role in WFT resistance than PAs from other structural groups. We found no evidence for synergistic effects of different PAs on WFT resistance. The relationship between PA variation and WFT feeding damage in the Jacobaea hybrids suggests a role for PAs in resistance to generalist insects.