The effect of developmental and environmental factors on secondary metabolites in medicinal plants.

Nanoparticles (NPs) are submicron particles with 1- 100 nm lengths in two or three dimensions NPs released as nanomaterial-containing wastes from household, industrial and medical products are emerging as a new threat to the environment Plants, being fixed to the two major environmental sinks where NPs accumulate ¬— namely water and soil, cannot escape the impact of nanopollution Recent studies have shown that plant growth, development and physiology are significantly affected by NPs But, the effect of NPs on plant secondary metabolism is still obscure The induction of reactive oxygen species (ROS) following interactions with NPs has been observed consistently across plant species Taking into account the existing link between ROS and secondary signaling messengers that lead to transcriptional regulation of secondary metabolism, in this perspective we put forward the argument that ROS induced in plants upon their interaction with NPs will likely interfere with plant secondary metabolism As plant secondary metabolites play vital roles in plant performance, communication and adaptation, a comprehensive understanding of plant secondary metabolism in response to NPs is an utmost priority

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Nanoparticles Alter Secondary Metabolism in Plants via ROS Burst

Plant tissue culture as a perpetual source for production of industrially important bioactive compounds

Multi-walled carbon nanotubes stimulate callus induction, secondary metabolites biosynthesis and antioxidant capacity in medicinal plant Satureja khuzestanica grown in vitro

Plant tissue cultures are the core of plant biology, which is important for conservation, mass propagation, genetic manipulation, bioactive compound production and plant improvement. In recent years, the application of nanoparticles (NPs) has successfully led to the elimination of microbial contaminants from explants and demonstrated the positive role of NPs in callus induction, organogenesis, somatic embryogenesis, somaclonal variation, genetic transformation and secondary metabolite production. This review aims to consolidate all of the current achievements made through the integration of nanotechnology into plant tissue culture and highlight the positive attributes of using NPs in plant tissue culture. Both the positive and adverse effects of using NPs in the culture medium are discussed and presented. The toxicity aspects and the safety concerns of exposing plants and the associated environment to NPs are recorded. Finally, future prospects through the involvement of not merely Ag, TiO2, and ZnO NPs, but more recent innovations such as graphene, carbon nanotubes, SiO2, quantum dots, and dendrimers are proposed. The undisclosed shadows hanging in the background, including the repercussions of using nanomaterials without proper awareness, as well as dosage-based adverse effects and nanotoxicity aspects, are highlighted. The need for more research in the pursuit of discrete answers to unresolved questions regarding mechanisms is emphasized as the key to real progress in plant nanobiotechnology.

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Nanomaterials in plant tissue culture: the disclosed and undisclosed

Silver nanoparticles, exhibiting unusual properties of ionic ability associated with the particle suspension, have been extensively used as the anti-microbial agent in medicine. The present study addressed the elicitation potential of nanosilver particles for the enhancing plant secondary metabolite production. Ag-SiO2 core–shell nanoparticles (AgNPs) with an average size of 101.8 ± 8.9 nm were prepared as elicitor to the hairy root cultures of Artemisia annua. Artemisinin content in the cultures was increased from 1.67 mg/g dry wt to 2.86 mg/g dry wt by the stimulation of AgNPs at 900 mg/L for 3 d. AgNP elicitation was related to the released dissolved Ag+ and nanoparticulate nature of AgNPs introduced to the cultures. AgNP treatment induced oxidative stress (H2O2 production) resulting in lipid peroxidation (increased malonyldialdehyde (MDA) accumulation), enhanced activities of catalase (CAT) and increased artemisinin content in hairy roots. The elicitor stimulated artemisinin production in 20-day-old hairy root cultures up to 13.3 mg/L, a 3.9-fold increase over the control. These results suggest that Ag nanoparticles can be used as a novel effective elicitor in plant biotechnology for the production of plant secondary metabolites.

Stimulation of Artemisinin Production in Artemisia annua Hairy Roots by Ag-SiO2 Core-shell Nanoparticles

Artemisinin, an endoperoxide sesquiterpene lactone, is an effective antimalarial drug isolated from Artemisia annua L. In this study, a low dose (1.44 kJm(-2)d(-1)) of UV-B radiation (280-320 nm) for short-term (1h per day for 10 days) was applied to A. annua seedlings to stimulate artemisinin production. UV-B treatment not only induced the generation of reactive oxygen species (ROS), enhanced peroxidase activity and endogenous content of abscisic acid (ABA), but stimulated the biosynthesis of artemisinin in the seedlings. Here, transcriptomic changes during UV-B radiation in A. annua were detected using an Agilent GeneChip with 43,692 probe sets. In total, 358 transcripts were identified as differentially expressed under UV-B stress, of which 172 transcripts increased and 186 transcripts decreased in abundance. In terms of biological processes, gene ontology (GO) terms including primary carbohydrate and nitrogen compound metabolic processes were enriched in UV-B-repressed genes. The up-regulated genes were enriched in response to stress, ROS generation, hormone (ethylene, ABA) stimulus and cell cycle control. The expression of key enzymes such as amorpha-4,11-diene synthase (ADS) and cytochrome P450 dependent monooxygenase/hydroxylase (CYP71AV1), and related WRKY transcription factors was up-regulated significantly for artemisinin biosynthesis. This profile of global gene expression patterns during UV-B stress will be valuable for further identification of the enzymes involved in artemisinin biosynthesis.

Transcriptome responses involved in artemisinin production in Artemisia annua L. under UV-B radiation

Triclosan (TCS), a widely used antimicrobial and preservative agent, is an emerging contaminant in aqueous and soil environment. Microbial degradation of TCS has not been reported frequently because of its inhibition of microbe growth. To explore the new microbial resources for TCS biodegradation, fungal endophytes were isolated and screened for the degradation potential. The endophytic strain B4 isolated from Artemisia annua L. showed higher degradation efficiency and was identified as Penicillium oxalicum based on its morphology and ITS sequences of ribosomal DNA. In both medium and synthetic wastewater, TCS (5 mg/L) was almost completely degraded within 2 h by the strain B4. The high capacity of TCS uptake (127.60 ± 8.57 mg/g dry weight, DW) of fungal mycelium was observed during the first 10 min after TCS addition. B4 rapidly reduced initial content (5.00 mg/L) of TCS to 0.41 mg/L in medium in 10 min. Then, the accumulation of TCS in mycelium was degraded from 0.45 to 0.05 mg/g DW after 1-h treatment. The degradation metabolites including 2-chlorohydroquinone, 2, 4-dichloropheno, and hydroquinone were found to be restrained in mycelia. The end products of the biodegradation in medium showed no toxicity to Escherichia coli. The new characteristics of high adsorption, fast degradation, and low residual toxicity highlight the potential of endophytic P. oxalicum B4 in TCS bioremediation.

Efficient degradation of triclosan by an endophytic fungus Penicillium oxalicum B4

Armillaria mellea, a symbiotic fungus in the underground tubers of Chinese medicinal orchid Gastrodia elata, is one of the main biological active components and pharmaceutical effects of its host gastrodia. The purpose of this review is to bring attention to the biological properties of this unique A. mellea mushroom and its constituents, as well as to suggest the potential for the development of new drugs related to this fungus. It contains various known and untapped bioactive metabolites such as polysaccharides, sesquiterpene aryl esters, steroids and fibrinolytic enzymes. It could be exploited as an important source of new biological natural products with anticonvulsant, immunomodulatory and antimicrobial functions. The batch culture is preferred as an alternative means of getting bioactive components from Armellaria fermentation. Challenges in investigations on A. mellea include the optimization of culture parameters, the further elucidation of the molecular pharmacological mechanism and relationship between structure and function of their secondary metabolites.

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Wan Yi Li

Papers

Stimulation of Artemisinin Production in Artemisia annua Hairy Roots by Ag-SiO2 Core-shell Nanoparticles

Transcriptome responses involved in artemisinin production in Artemisia annua L. under UV-B radiation

Efficient degradation of triclosan by an endophytic fungus Penicillium oxalicum B4

The cultivation, bioactive components and pharmacological effects of Armillaria mellea