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Tithonia diversifolia is an invasive weed commonly found in tropical ecosystems. In this work, we investigate the influence of different abiotic environmental factors on the plant’s metabolite profile by multivariate statistical analyses of spectral data deduced by UHPLC-DAD-ESI-HRMS and NMR methods. Different plant part samples of T. diversifolia which included leaves, stems, roots and inflorescences were collected from two Brazilian states throughout a 24-month period, along with the corresponding monthly environmental data. A metabolomic approach employing concatenated LC-MS and NMR data was utilised for the first time to study the relationships between environment and plant metabolism. A seasonal pattern was observed for the occurrence of metabolites that included sugars, sesquiterpenes lactones and phenolics in the leaf and stem parts, which can be correlated to the amount of rainfall and changes in temperature. The distribution of the metabolites in the inflorescence and root parts were mainly affected by variation of some soil nutrients such as Ca, Mg, P, K and Cu. We highlight the environment-metabolism relationship for T. diversifolia and the combined analytical approach to obtain reliable data that contributed to a holistic understanding of the influence of abiotic environmental factors on the production of metabolites in various plant parts.

Plants exude a diverse cocktail of metabolites into the soil as response to exogenous and endogenous factors. So far, root exudates have mainly been studied under artificial conditions due to methodological difficulties. In this study, each five perennial grass and forb species were investigated for polar and semi-polar metabolites in exudates under field conditions. Metabolite collection and untargeted profiling approaches combined with a novel classification method allowed the designation of 182 metabolites. The composition of exuded polar metabolites depended mainly on the local environment, especially soil conditions, whereas the pattern of semi-polar metabolites was primarily affected by the species identity. The profiles of both polar and semi-polar metabolites differed between growth forms, with grass species being generally more similar to each other and more responsive to the abiotic environment than forb species. This study demonstrated the feasibility of investigating exudates under field conditions and to identify the driving factors of exudate composition.

Background Soil chromium (Cr) contamination is escalating, and phytoremediation is optimal for its abatement. Cosmos sulphureus , an annual Asteraceae herb widely used in landscape greening and ecological restoration, has strong tolerance to heavy metals, but its Cr accumulation traits, stress response and molecular mechanisms remain unclear, limiting its application. Based on physiological measurements under four Cr concentration gradients (100–400 µM), combined with transcriptomic and metabolomic analysis at the critical stress concentration of 100 µM, this study systematically elucidated the physiological stress responses, tolerance mechanisms and early molecular expression profiles of C. sulphureus under varying Cr stress. Results Roots are the main Cr accumulation organ. 100 µM is the physiological tolerance threshold with high tolerance, low translocation and activated antioxidant system; Cell wall (CW) pectin serves as the main Cr immobilization site, and its Cr enrichment correlates strongly with PME-mediated demethylation, implying that low-esterified pectin might contribute to Cr detoxification through increased chelation sites; Transcriptome identified 26,505 upregulated and 14,791 downregulated genes: defense genes related to Cr-induced pectin modification and enzyme activity (PME29, PME2, GALE2, etc.) were induced, while growth-related genes involved in CW development and photosynthetic regulation (PMEU1, WAK1, LHCA3, etc.) were repressed. Metabolomics showed elevated defensive metabolites including organic acids, amino acids, flavonoids and sugars (GSH, Pro, AsA, etc.) and also promoted the enrichment of metabolites associated with the synthesis and modification of CW pectin and cellulose (L-arabinose, raffinose, etc.). Conclusion These findings clarify the Cr accumulation characteristics of C. sulphureus roots and its remediation potential under Cr concentration ≤ 100 µM, confirming that the antioxidant system and pectin chelation detoxification are core tolerance mechanisms. Overall, C. sulphureus adopts a molecular response pattern of growth-to-defense transition. This study provides a basis for Cr remediation landscape plant breeding and plant Cr tolerance mechanism exploration. Graphical Abstract

Adaptive evolution of enzymes benefits from catalytic promiscuity. Sesquiterpene lactones (STLs) have diverged extensively in the Asteraceae, and studies of the enzymes for two representative STLs, costunolide and artemisinin, could provide an insight into the adaptive evolution of enzymes. Costunolide appeared early in Asteraceae evolution and is widespread, whereas artemisinin is a unique STL appearing in a single Asteraceae species, Artemisia annua. Therefore, costunolide is a ubiquitous STL, while artemisinin is a specialized one. In costunolide biosynthesis, germacrene A oxidase (GAO) synthesizes germacrene A acid from germacrene A. Similarly, in artemisinin biosynthesis, amorphadiene oxidase (AMO) synthesizes artemisinic acid from amorphadiene. GAO promiscuity is suggested to drive the diversification of STLs. To examine the degree of GAO promiscuity, we expressed six sesquiterpene synthases from cotton (Gossypium arboretum), goldenrod (Solidago canadensis), valerian (Valeriana officinalis), agarwood (Aquilaria crassna), tobacco (Nicotiana tabacum), and orange (Citrus sinensis) in yeast to produce seven distinct sesquiterpene substrates (germacrene D, 5-epi-aristolochene, valencene, δ-cadinene, α- and δ-guaienes, and valerenadiene). GAO or AMO was coexpressed in these yeasts to evaluate the promiscuities of GAO and AMO. Remarkably, all sesquiterpenes tested were oxidized to sesquiterpene acids by GAO, but negligible activities were found from AMO. Hence, GAO apparently has catalytic potential to evolve into different enzymes for synthesizing distinct STLs, while the recently specialized AMO demonstrates rigid substrate specificity. Mutant GAOs implanted with active site residues of AMO showed substantially reduced stability, but their per enzyme activities to produce artemisinic acid increased by 9-fold. Collectively, these results suggest promiscuous GAOs can be developed as novel catalysts for synthesizing unique sesquiterpene derivatives.

The intensification of abiotic stresses, particularly drought and elevated temperatures driven by climate change, requires the widespread adoption of protected cultivation. A pivotal innovation within this system is the use of spectral-selective filters, which modify the solar spectrum to provide environmental protection and direct physiological control over plant growth, especially for high-value ornamental species. The application of colored shade nets in this study, positively influenced nutrient uptake and growth parameters except for stem diameter, spike length, number of flowers and plant and flower dry mass in Polianthes cut flowers. The highest concentration of potassium (2.78%), nitrogen (2.02%), and phosphorus (0.14%) was found in the green and blue shade treatments, but there was no significant difference between the treatments. Furthermore, the most substantial improvement in flower diameter was observed under the green shade net, resulting in a 20.75% increase, while the white shade net showed the smallest enhancement at 9.66% in comparison with full sunlight. Additionally, peroxidase activity and photosynthetic pigment levels were elevated in plants under green and white shading compared to those under blue nets. Proline content was significantly reduced by all colored shade treatments, with the highest accumulation observed in plants exposed to full sunlight. In conclusion, although the use of all shade nets improved some flower quality indices and somewhat increased the potassium, chlorophyll, and carotenoids contents and reduced proline in the plant, overall, the use of green shades is recommended.

The medicinal plants of the Asteraceae family are a valuable source of bioactive secondary metabolites, including polyphenols, phenolic acids, flavonoids, acetylenes, sesquiterpene lactones, triterpenes, etc. Under stressful conditions, the plants develop these secondary substances to carry out physiological tasks in plant cells. Secondary Asteraceae metabolites that are of the greatest interest to consumers are artemisinin (an anti-malarial drug from Artemisia annua L.—sweet wormwood), steviol glycosides (an intense sweetener from Stevia rebaudiana Bert.—stevia), caffeic acid derivatives (with a broad spectrum of biological activities synthesized from Echinacea purpurea (L.) Moench—echinacea and Cichorium intybus L.—chicory), helenalin and dihydrohelenalin (anti-inflammatory drug from Arnica montana L.—mountain arnica), parthenolide (“medieval aspirin” from Tanacetum parthenium (L.) Sch.Bip.—feverfew), and silymarin (liver-protective medicine from Silybum marianum (L.) Gaertn.—milk thistle). The necessity to enhance secondary metabolite synthesis has arisen due to the widespread use of these metabolites in numerous industrial sectors. Elicitation is an effective strategy to enhance the production of secondary metabolites in in vitro cultures. Suitable technological platforms for the production of phytochemicals are cell suspension, shoots, and hairy root cultures. Numerous reports describe an enhanced accumulation of desired metabolites after the application of various abiotic and biotic elicitors. Elicitors induce transcriptional changes in biosynthetic genes, leading to the metabolic reprogramming of secondary metabolism and clarifying the mechanism of the synthesis of bioactive compounds. This review summarizes biotechnological investigations concerning the biosynthesis of medicinally essential metabolites in plants of the Asteraceae family after various elicitor treatments.

The main aim of this study was to compare the cytological difference between ovular mucilage cells in two Asteraceae species—Pilosella officinarum and Taraxacum officinale—in order to determine whether pectic epitopes, arabinogalactan proteins, or extensins are present. The immunocytochemical technique was used. Both the Taracacum and Pilosella genera have been used recently as models for understanding the mechanisms of apomixis. Knowledge of the presence of signal molecules (pectic epitopes, arabinogalactan proteins, and extensins) can help better understand the developmental processes in these plants during seed growth. The results showed that in Pilosella officinarum, there was an accumulation of pectins in the mucilage, including both weakly and highly esterified pectins, which was in contrast to the mucilage of Taraxacum officinale, which had low amounts of these pectins. However, Taraxacum protoplasts of mucilage cells were rich in weakly methyl-esterified pectins. While the mucilage contained arabinogalactan proteins in both of the studied species, the types of arabinogalactan proteins were different. In both of the studied species, extensins were recorded in the transmitting tissues. Arabinogalactan proteins as well as weakly and highly esterified pectins and extensins occurred in close proximity to calcium oxalate crystals in both Taraxacum and Pilosella cells.

Postmortem lignification of xylem tracheary elements (TEs) has been debated for decades. Here, we provide evidence in Zinnia elegans TE cell cultures, using pharmacological inhibitors and in intact Z. elegans plants using Fourier transform infrared microspectroscopy, that TE lignification occurs postmortem (i.e., after TE programmed cell death). In situ RT-PCR verified expression of the lignin monomer biosynthetic cinnamoyl CoA reductase and cinnamyl alcohol dehydrogenase in not only the lignifying TEs but also in the unlignified non-TE cells of Z. elegans TE cell cultures and in living, parenchymatic xylem cells that surround TEs in stems. These cells were also shown to have the capacity to synthesize and transport lignin monomers and reactive oxygen species to the cell walls of dead TEs. Differential gene expression analysis in Z. elegans TE cell cultures and concomitant functional analysis in Arabidopsis thaliana resulted in identification of several genes that were expressed in the non-TE cells and that affected lignin chemistry on the basis of pyrolysis—gas chromatography/mass spectrometry analysis. These data suggest that living, parenchymatic xylem cells contribute to TE lignification in a non-cell-autonomous manner, thus enabling the postmortem lignification of TEs.

Melatonin (MT) is a versatile signaling molecule involved in plant growth regulation and stress tolerance. This study examined the effects of MT at five concentrations (50, 100, 200, 300, and 400 µM) on neck bending (NB) and vase life of Gerbera jamesonii ‘Pink Elegance’ cut flowers. Morphological, physiological, biochemical, and signaling-related traits were evaluated. The results showed that MT, especially at 300 µM, effectively reduced NB, enhanced water uptake, improved antioxidant defense by increasing activities of SOD, CAT, APX, and GPX, and promoted lignin accumulation in stems. Moreover, MT treatment modulated nitric oxide (NO) and salicylic acid (SA) levels, suggesting a role in stress-related signaling. Overall, MT application improved postharvest quality and extended vase life, highlighting its potential as a practical strategy for maintaining the quality of gerbera cut flowers.

As a special woody vegetable, Chinese toon (Toona sinensis) has a unique flavor, which is mainly formed by a combination of volatile substances. The secretion and storage of volatile odorants in plants are often carried out in trichomes. Currently, studies on the formation of T. sinensis flavor in terms of biosynthetic processes and epidermal trichome morphology are scarce. Here, we conducted a detailed analysis of the morphology, structure, and distribution of trichomes on the leaves of T. sinensis. We identified three types of trichomes: non-glandular, sessile glandular, and stalked glandular. We found that the distribution of trichomes varies greatly in the natural populations of T. sinensis, and this may be closely related to the changes in volatile components. In order to clarify the relationship between secondary metabolism and trichome formation, we integrated the metabolic analysis of volatiles with transcriptome analysis and discovered two important (Terpene Synthase) TPS genes that may be directly involved in terpene synthesis. Through the heterologous expression in tobacco and the transient expression in T. sinensis, we showed that the TPS genes can participate in the synthesis of sesquiterpenes, among which TsTPS1262 can lead to the synthesis of elemene in T. sinensis. Our study provides insights into the synthesis pathways of complex volatile components in T. sinensis and also provides a basis for flavor breeding applications.