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The particles within the size range of 1 and 100 nm are known as nanoparticles (NPs). NP-containing wastes released 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.

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology.

Background Agrobacterium -mediated transformation is a fundamental method for the genetic modification of plants. However, several important crops and medicinal plants are recalcitrant to this process, hindering the application of modern functional genomics and genetic improvement tools. Hypericum perforatum L. (St. John’s wort), a valuable medicinal plant due to its secondary metabolites, is particularly recalcitrant to transformation mediated by Agrobacterium tumefaciens , and the molecular basis for this resistance remains unclear. This study was conducted to investigate the defense responses of H. perforatum after co-cultivation with A. tumefaciens and Agrobacterium rhizogenes through an integrative transcriptomic and metabolomic approach. Results Transcriptome profiling revealed extensive reprogramming of gene expression in response to both Agrobacterium strains. Core genes for signal transduction, defense responses, transcriptional regulation and biosynthesis of secondary metabolites were strongly differentially expressed. In particular, WRKY, MYB and ERF transcription factor-encoding genes were induced, reflecting their role in triggering plant immunity. The upregulation of genes related to xanthone biosynthesis and the associated downregulation of flavonoid metabolism genes indicate a metabolic Shift towards xanthone production. Metabolomic analyses consistent with these results showed a striking increase in defense-related xanthones such as 6-deoxyisojacareubin, hyperxanthone E and gemixanthone A after treatment with Agrobacterium . Conclusions H. perforatum possesses a controlled defense response to Agrobacterium that involves the transcriptional induction of defense signals and the accumulation of antimicrobial xanthones. The suppression of flavonoid biosynthesis also indicates a redirection of resources towards more efficient defense compounds. These results are important to elucidate the molecular basis of recalcitrance of H. perforatum transformation and to identify the role of pre-existing and inducible immunity in limiting Agrobacterium -mediated gene transfer.

Hypericum perforatum (St John's wort) is a reservoir of diverse classes of biologically active and high value secondary metabolites, which captured the interest of both researchers and the pharmaceutical industry alike. Several studies and clinical trials have shown that H. perforatum extracts possess an astounding array of pharmacological properties. These properties include antidepressant, anti-inflammatory, antiviral, anti-cancer, and antibacterial activities; and are largely attributed to the naphtodianthrones and xanthones found in the genus. Hence, improving their production via genetic manipulation is an important strategy. In spite of the presence of contemporary genome editing tools, genetic improvement of this genus remains challenging without robust transformation methods in place. In the recent past, we found that H. perforatum remains recalcitrant to Agrobacterium tumefaciens mediated transformation partly due to the induction of plant defense responses coming into play. However, H. perforatum transformation is possible via a non-biological method, biolistic bombardment. Some research groups have observed the induction of hairy roots in H. perforatum after Agrobacterium rhizogenes co-cultivation. In this review, we aim at updating the available methods for regeneration and transformation of H. perforatum. In addition, we also propose a brief perspective on certain novel strategies to improve transformation efficiency in order to meet the demands of the pharmaceutical industry via metabolic engineering.

We report on the antimicrobial activity of a cream formulation of silver nanoparticles (AgNPs), biosynthesized using Withania somnifera extract. Aqueous extracts of leaves promoted efficient green synthesis of AgNPs compared to fruits and root extracts of W. somnifera. Biosynthesized AgNPs were characterized for their size and shape by physical-chemical techniques such as UV-visible spectroscopy, laser Doppler anemometry, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray energy dispersive spectroscopy. After confirming the antimicrobial potential of AgNPs, they were incorporated into a cream. Cream formulations of AgNPs and AgNO3 were prepared and compared for their antimicrobial activity against human pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Escherichia coli, and Candida albicans) and a plant pathogen (Agrobacterium tumefaciens). Our results show that AgNP creams possess significantly higher antimicrobial activity against the tested organisms.

Albendazole (ABZ) is an antihelminthic drug used for the treatment of several parasitic infestations. In addition to this, there are reports on the anticancer activity of ABZ against a wide range of cancer types. However, its effect on glioma has not yet been reported. In the present study, cytotoxicity of ABZ and ABZ loaded solid lipid nanoparticles (ASLNs) was tested in human glioma/astrocytoma cell line (U-87 MG). Using glyceryl trimyristate as lipid carrier and tween 80 as surfactant spherical ASLNs with an average size of 218.4 ± 5.1 nm were prepared by a combination of high shear homogenization and probe sonication methods. A biphasic in vitro release pattern of ABZ from ASLNs was observed, where 82% of ABZ was released in 24 h. In vitro cell line studies have shown that ABZ in the form of ASLNs was more cytotoxic (IC50 = 4.90 µg/mL) to U-87 MG cells compared to ABZ in the free form (IC50 = 13.30 µg/mL) due to the efficient uptake of the former by these cells.

Hypericum is a large genus that includes more than 500 species of pharmacological, ecological and conservation value. Although latest advances in sequencing technologies were extremely exploited for generating and assembling genomes of many living organisms, annotated whole genome sequence data is not publicly available for any of the Hypericum species so far. Bioavailability of secondary metabolites varies for different tissues and the data derived from different cultures will be a valuable tool for comparative studies. Here, we report the single molecule real-time sequencing (SMRT) data sets of Hypericum perforatum L. plantlets and cell suspension cultures for the first time. Sequencing data from cell suspension cultures yielded more than 33,000 high-quality transcripts from 20 Gb of raw data, while more than 55,000 high-quality transcripts were obtained from 35 Gb of raw data from plantlets. This dataset is a valuable tool for comparative transcriptomic analysis and will help to understand the unknown biosynthetic pathways of high medicinal value in the Hypericum genus.

One of the major challenges of nano-biotechnology is to engineer potent antimicrobial nanostructures (NS) with high biocompatibility. Keeping this in view, we have performed aqueous olive leaf extract mediated one pot facile synthesis of CuO-NS and CeO2-NS. Prepared NS were homogenous, less than 26 nm in size, and small crystallite units as revealed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. Fourier transform infrared spectroscopy (FTIR) of CuO-NS and CeO2-NS showed typical Cu-O prints around 592-660 cm-1 and Ce-O bond vibrations at 453 cm-1. The successful capping of CuO-NS and CeO2-NS by compounds present in the plant extract was further validated by high performance liquid chromatography (HPLC) and thermal gravimetric analysis (TGA). Active phyto-chemicals from the leaf extract simultaneously acted as strong reducing as well as capping agent in the NS synthesis. NS engineered in the present study showed antibacterial potential at extremely low concentration against highly virulent multidrug-resistant (MDR) gram-negative strains (Escherichia coli, Enterobacter cloacae, Acinetobacter baumannii and Pseudomonas aeruginosa), alarmed by World Health Organization (WHO). Furthermore, CuO-NS and CeO2-NS did not show any cytotoxicity on HEK-293 cell lines and Brine shrimp larvae indicating that the NS green synthesized in the present study are biocompatible.One of the major challenges of nano-biotechnology is to engineer potent antimicrobial nanostructures (NS) with high biocompatibility. Keeping this in view, we have performed aqueous olive leaf extract mediated one pot facile synthesis of CuO-NS and CeO2-NS. Prepared NS were homogenous, less than 26 nm in size, and small crystallite units as revealed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. Fourier transform infrared spectroscopy (FTIR) of CuO-NS and CeO2-NS showed typical Cu-O prints around 592-660 cm-1 and Ce-O bond vibrations at 453 cm-1. The successful capping of CuO-NS and CeO2-NS by compounds present in the plant extract was further validated by high performance liquid chromatography (HPLC) and thermal gravimetric analysis (TGA). Active phyto-chemicals from the leaf extract simultaneously acted as strong reducing as well as capping agent in the NS synthesis. NS engineered in the present study showed antibacterial potential at extremely low concentration against highly virulent multidrug-resistant (MDR) gram-negative strains (Escherichia coli, Enterobacter cloacae, Acinetobacter baumannii and Pseudomonas aeruginosa), alarmed by World Health Organization (WHO). Furthermore, CuO-NS and CeO2-NS did not show any cytotoxicity on HEK-293 cell lines and Brine shrimp larvae indicating that the NS green synthesized in the present study are biocompatible.

We report for the first time the isolation and functional characterization of a novel promoter inducible by Agrobacterium tumefaciens, the causative agent of crown gall disease, which leads to significant crop losses. Chemical control of this neoplastic disease is ineffective, since bacterial presence is not essential for T-DNA mediated tumor development. Moreover, A. tumefaciens-mediated transformation, a cornerstone of plant biotechnology, fails in many recalcitrant species due to poorly understood mechanisms. A unique 1086 bp promoter (HyPRO) sharing only ~ 7% similarity with known sequences in NCBI was isolated upstream of the hyp1 gene from Hypericum perforatum. In silico analysis revealed multiple cis regulatory elements (CREs), including WRKY710S, W box, PALBOX, GT1, and VRE, associated with biotic stress responses. Transgenic tobacco plants expressing β glucuronidase (GUS) under HyPRO showed strong induction by A. tumefaciens, significantly higher than induction by Pseudomonas syringae. Upstream truncation of the promoter significantly reduced GUS expression, indicating essential regulatory elements lie upstream of position - 728. This A. tumefaciens responsive promoter offers a valuable tool to dissect plant defense and could enable innovative transgenic strategies for crop improvement and resistance to neoplastic diseases. Characterization of A. tumefaciens-specific CREs using the truncation approach is currently underway in our laboratory.

Agrobacterium -mediated transformation is a fundamental method for the genetic modification of plants. However, several important crops and medicinal plants are recalcitrant to this process, hindering the application of modern functional genomics and genetic improvement tools. Hypericum perforatum L. (St. John's wort), a valuable medicinal plant due to its secondary metabolites, is particularly recalcitrant to transformation mediated by Agrobacterium tumefaciens, and the molecular basis for this resistance remains unclear. This study was conducted to investigate the defense responses of H. perforatum after co-cultivation with A. tumefaciens and Agrobacterium rhizogenes through an integrative transcriptomic and metabolomic approach. Transcriptome profiling revealed extensive reprogramming of gene expression in response to both Agrobacterium strains. Core genes for signal transduction, defense responses, transcriptional regulation and biosynthesis of secondary metabolites were strongly differentially expressed. In particular, WRKY, MYB and ERF transcription factor-encoding genes were induced, reflecting their role in triggering plant immunity. The upregulation of genes related to xanthone biosynthesis and the associated downregulation of flavonoid metabolism genes indicate a metabolic Shift towards xanthone production. Metabolomic analyses consistent with these results showed a striking increase in defense-related xanthones such as 6-deoxyisojacareubin, hyperxanthone E and gemixanthone A after treatment with Agrobacterium. H. perforatum possesses a controlled defense response to Agrobacterium that involves the transcriptional induction of defense signals and the accumulation of antimicrobial xanthones. The suppression of flavonoid biosynthesis also indicates a redirection of resources towards more efficient defense compounds. These results are important to elucidate the molecular basis of recalcitrance of H. perforatum transformation and to identify the role of pre-existing and inducible immunity in limiting Agrobacterium-mediated gene transfer.