Crosstalk among polyamines, phytohormones, hydrogen peroxide, and phenylethanoid glycosides responses in Scrophularia striata to Cd stress.

Plants respond to Cadmium (Cd) as a hazardous heavy metal through various mechanisms depending on their available metabolite resources. In this research, the physiological and signaling pathways mediating the responses to Cd stress in Scrophularia striata seedlings were characterized after they were exposed to different Cd concentrations at different time periods. The results showed that the polyamines (PAs), Abscisic acid (ABA) and hydrogen peroxide (H2O2) contents were significantly enhanced at 48 h. Moreover, the enzyme activity of phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) as regulator enzymes in the phenylpropanoid pathway was increased, related to the reinforcement of phenolic compounds such as phenylethanoid glycosides (as a special compound of this plant). This metabolic profiling indicates that the signal transduction of Cd stress increased the activity of different enzymes (PAL and TAL) by regulating the PAs metabolism, the modulation of ABA, and the H2O2 content. As a result, it caused the accumulation of phenolic compounds, especially echinacoside and acteoside, both of which are required to improve the response of Cd stress in S. striata.

Water stress alleviation by polyamines and phenolic compounds in Scrophularia striata is mediated by NO and H2O2.

Plants respond to water stress through a variety of mechanisms, depending on metabolites preferences and their available resources. This work was performed to elucidate the cross-talk between signaling molecules (polyamines (PAs), hydrogen peroxide (H2O2) and nitric oxide (NO)), phenolic compounds and osmolytes (phenylethanoid glycosides (PhGs), phenolic acids, flavonoids, soluble sugars and amino acids) under water stress in Scrophularia striata plants. The results revealed that PAs, NO levels were enhanced in the plants, earlier in response to polyethylene glycol-induced water stress. The antioxidative mechanisms with increased activity of catalase (CAT), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) and also phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), as key enzymes in phenolic pathway were deployed in response to the stress. Mannose, glucose, xylose/rhamnose which are involved in PhGs biosynthesis as well as in serving osmotic adjustment were modulated. The elevated content of arginine and methionine as PAs precursors and tyrosine and phenylalanine as PhGs precursors was enhanced by water stress and was significantly associated with PAs and PhGs accumulations. Metabolic profiling revealed new information about relationship between stress signal molecules; PAs, NO and H2O2, osmolytes (sugers, PhGs) and phenolic compounds which involved in the improvement of water stress tolerance in S. striata.

Induction of aromatic amino acids and phenylpropanoid compounds in Scrophularia striata Boiss. cell culture in response to chitosan-induced oxidative stress.

Manipulation of cell culture media by elicitors is one of most important strategies to inducing secondary metabolism for the production of valuable metabolites. In this investigation, inducing effect of chitosan on physiological, biochemical, and molecular parameters were investigated in cell suspension cultures of Scrophularia striata Boiss. The results showed that chitosan concentration and time of elicitation are determinants of the effectiveness of the elicitor. Accumulation of aromatic amino acids (phenylalanine [Phe] and tyrosine [Tyr]), phenylpropanoid compounds (phenolic acids [PAs] and echinacoside [ECH]), hydrogen peroxide (H2O2) production, phenylalanine ammonia-lyase (PAL) activity and gene expression, and antioxidant enzymes (superoxide dismutase [SOD], peroxidase [POX], catalase [CAT]) activities were altered by changing the exposure time of elicitation. Results showed that, upon elicitation with chitosan, oxidative events were induced, antioxidant responses of S. striata cells were boosted through enhanced activity of an effective series of scavenging enzymes (SOD, CAT, and POX), and biosynthesis of non-enzymatic antioxidants (ECH and PAs [cinnamic, p-coumaric and, caffeic acids]). The increase in amino acid content and PAL activity at early days of exposure to chitosan was related with rises in phenolic compounds. These results provide evidence that chitosan by up-regulation of PAL gene differentially improves the production of phenylpropanoid compounds, which are of medical commercial value with good biotechnological prospects.

Profiling of acidic (amino and phenolic acids) and phenylpropanoids production in response to methyl jasmonate-induced oxidative stress in Scrophularia striata suspension cells.

MAIN CONCLUSION: A metabolic profiling including calculation of energy cost of amino acids biosynthesis in cultured cells of Scrophularia striata showed that methyl jasmonate-inducible oxidative stress elicited secondary metabolites formation derived from phenylalanine and tyrosine and increased energy cost for these amino acids biosynthesis. Understanding of the metabolic pathways in cell culture of Scrophularia striata, an aromatic plant species, facilitates means of production of pharmaceutical metabolites under oxidative stress. In this study, we evaluated the effects of MeJA on the S. striata metabolic pathway and the responses to oxidative stress. Exposure to methyl jasmonate (MeJA) affects plant growth, effectively induces production of reactive oxygen species (ROS) and inserts oxidative stress at the cellular level which results in alteration of primary metabolites and production of phenylepropanoid compounds. Cells treated with MeJA indicated increase in the activities of three antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPx) as well as intracellular H2O2 and MDA contents compared with mock-treated cells. High performance liquid chromatography (HPLC)-based metabolome analysis revealed dynamic metabolic changes in oxidatively stressed S. striata cells, e.g., general phenylpropanoid pathway, phenylethanoid-glycosides, lignans, and increased energy cost of biosynthesis and accumulation of amino acids. Furthermore, principal component analysis (PCA)-derived score plots demonstrated that MeJA affects cellular metabolism in S. striata cells and significantly alters metabolite composition under MeJA-inducible oxidative stress. These observations suggest that MeJA-elicited cell suspension cultures of S. striata balanced the production of primary and secondary metabolites in coordination with ROS-scavenging system.

Inhibitory potential of naphthoquinones leached from leaves and exuded from roots of the invasive plant Impatiens glandulifera.

Exploring the effects of allelopathic plant chemicals on the growth of native vegetation is essential to understand their ecological roles and importance in exotic plant invasion. Naphthoquinones have been identified as potential growth inhibitors produced by Impatiens glandulifera, an exotic annual plant that recently invaded temperate forests in Europe. However, naphthoquinone release and inhibitory potential have not been examined. We quantified the naphthoquinone content in cotyledons, leaves, stems, and roots from plants of different ages of both the invasive I. glandulifera and native Impatiens noli-tangere as well as in soil extracts and rainwater rinsed from leaves of either plant species by using ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS). We identified the compound 2-methoxy-1,4-naphthoquinone (2-MNQ) exclusively in plant organs of I. glandulifera, in resin bags buried into the soil of patches invaded by I. glandulifera, and in rainwater rinsed from its leaves. This indicates that 2-MNQ is released from the roots of I. glandulifera and leached from its leaves by rain. Specific bioassays using aqueous shoot and root extracts revealed a strong inhibitory effect on the germination of two native forest herbs and on the mycelium growth of three ectomycorrhiza fungi. These findings suggest that the release of 2-MNQ may contribute to the invasion success of I. glandulifera and support the novel weapons hypothesis.