Engineering the expression of plant secondary metabolites-genistein and scutellarin through an efficient transient production platform in Nicotiana benthamiana L

sCentInDB: a database of essential oil chemical profiles of Indian medicinal plants

Essential oils are complex mixtures of volatile compounds produced by aromatic plants and widely used in personal care, food flavoring, and pharmaceutical industry due to their odor and therapeutic properties. As a high-value and low-volume organic product, optimizing plant yield and modifying composition by leveraging knowledge on chemical profiles of essential oils can lead to enhanced bioproducts. Additionally, overharvesting of wild medicinal plants, especially in India, threatens biodiversity. Essential oil profiles of such plants can help regulate their exploitation. Here, we present sCentInDB, a manually curated FAIR-compliant DataBase of Essential oil Chemical profiles of Medicinal plants of India, compiled from published literature. sCentInDB contains data on 554 Indian medicinal plants at the plant part level, encompassing 2170 essential oil profiles, 3420 chemicals, 471 plant-part-therapeutic use associations, 120 plant-part-odor associations, and 218 plant-part-color associations. sCentInDB also compiles metadata such as sample location, isolation, and analysis methods. Subsequently, an extensive analysis of the chemical space in sCentInDB was performed. By constructing a chemical similarity network, terpenoids were found to be distributed across the network, indicating greater structural diversity. Moreover, a comparison of the scaffold diversity of chemicals in sCentInDB was performed against three other aroma libraries using cyclic system retrieval curves. Altogether, sCentInDB will serve as a valuable resource for researchers working on plant volatiles and employing genetic engineering to enhance oil yield and composition. Further, sCentInDB will aid in the establishment of quality standards for essential oils and provide vital insights for therapeutic and perfumery applications. sCentInDB is accessible at https://cb.imsc.res.in/scentindb/ .

Localising enzymes to biomolecular condensates increase their accumulation and benefits engineered metabolic pathway performance in Nicotiana benthamiana

The establishment of Nicotiana benthamiana as a robust biofactory is complicated by issues such as product toxicity and proteolytic degradation of target proteins/introduced enzymes. Here we investigate whether biomolecular condensates can be used to address these problems. We engineered biomolecular condensates in N. benthamiana leaves using transient expression of synthetic modular scaffolds. The in vivo properties of the condensates that resulted were consistent with them being liquid-like bodies with thermodynamic features typical of multicomponent phase-separating systems. We show that recruitment of enzymes to condensates in vivo led to several-fold yield increases in one- and three-step metabolic pathways (citramalate biosynthesis and poly-3-hydroxybutyrate (PHB) biosynthesis, respectively). This enhanced yield could be for several reasons including improved enzyme kinetics, metabolite channelling or avoidance of cytotoxicity by retention of the pathway product within the condensate, which was demonstrated for PHB. However, we also observed a several-fold increase in the amount of the enzymes that accumulated when they were targeted to the condensates. This suggests that the enzymes were more stable when localised to the condensate than when freely diffusing in the cytosol. We hypothesise that this stability is likely the main driver for increased pathway product production. Our findings provide a foundation for leveraging biomolecular condensates in plant metabolic engineering and advance N. benthamiana as a versatile biofactory for industrial applications.

Engineering scutellarin biosynthesis in Artemisia annua

KEY MESSAGE

Heterologous synthesis of scutellarin was successfully achieved in Artemisia annua by supplementing missing enzymes and optimizing flavone 6 hydroxylase in the biosynthetic pathway after identifying two crucial precursors in wild type plants. Artemisia annua, a plant renowned for its antimalarial properties, harbors a diverse array of terpenoids, phenols and other natural products along with their respective precursors. Engineering A. annua plants through synthetic biology holds significant promise to produce drugs in scarcity. Herein, we identified two essential precursors of scutellarin, an ingredient known for its remarkable therapeutic efficacy in treating cerebrovascular and cardiovascular diseases, within wild-type A. annua plants. To facilitate the heterologous synthesis of this bioactive compound in A. annua, we co-expressed three key genes derived from the original host, Erigeron breviscapus: the flavone synthase II gene (EbFSII), the flavonoid-7-O-glucuronosyltransferase gene (EbF7GAT), and the flavone-6-hydroxylase gene (EbF6H). These engineered plants successfully synthesized scutellarin at levels ranging from 0.18 to 0.24 mg/g DW. Furthermore, the introduction of the flavone-6-hydroxylase gene from Scutellaria baicalensis (SbF6H), which demonstrated superior catalytic activity, significantly increased scutellarin generation, achieving concentrations of up to 0.64 mg/g DW. Notably, the insertion of these exogenous genes did not negatively affect the synthesis of artemisinin and its derivatives in A. annua. These findings suggest that A. annua offers a formidable foundation for the biosynthesis of scutellarin. Additionally, the results imply that enhancing the activity of critical enzymes boosts the yield of the valuable terminal products.

Engineering Nicotiana benthamiana as a platform for natural product biosynthesis

Nicotiana benthamiana is a model plant, widely used for research. The susceptibility of young plants to Agrobacterium tumefaciens has been utilised for transient gene expression, enabling the production of recombinant proteins at laboratory and commercial scales. More recently, this technique has been used for the rapid prototyping of synthetic genetic circuits and for the elucidation and reconstruction of metabolic pathways. In the last few years, many complex metabolic pathways have been successfully reconstructed in this species. In addition, the availability of improved genomic resources and efficient gene editing tools have enabled the application of sophisticated metabolic engineering approaches to increase the purity and yield of target compounds. In this review, we discuss recent advances in the use of N. benthamiana for understanding and engineering plant metabolism, as well as efforts to improve the utility of this species as a production chassis for natural products.

Improvement and application of vacuum-infiltration system in tomato

The Agrobacterium-mediated transient expression system has been developed and applied to various plants as an alternative to stable transformation. However, its application in tomatoes is still limited due to low expression efficiency. In this study, we describe an improved vacuum-infiltration system that can be used in both tomato fruits and leaves. Notably, this study is the first report of vacuum infiltration in attached tomato fruits. The feasibility of the improved vacuum-infiltration system in Micro-Tom tomato was confirmed by various assays, including multiple fluorescent protein expression analysis, β-glucuronidase activity analysis, and RUBY reporter visualization. Subsequently, the improved vacuum-infiltration system was successfully applied to tomato biotechnology research. Herein, a trichome-specific promoter in tomato was identified that can drive the directional synthesis of specific plant natural products (PNPs). Additionally, based on the assessment results of the improved vacuum-infiltration system, we obtained a flavonoid-rich tomato variety through the stable transformation of AmRosea and AmDelila. In a significant practical application, we successfully synthesized the high-value scutellarin in tomato, which provides an alternative route for the production of PNPs from plants. In addition, the improved vacuum-infiltration system has been demonstrated to be suitable for commercial tomato varieties ('Emerald' and 'Provence') as well. The improved vacuum-infiltration system not only speeds up fundamental and applied research in tomato but also offers an additional powerful tool for advancing tomato synthetic biology research.

Metabolomic analysis reveals the effect of ultrasonic-microwave pretreatment on flavonoids in tribute Citrus powder

In this study, the ultrasonic-microwave pretreatment was defined as a processing technology in the production of tribute citrus powder, and it could increase the flavonoid compounds in the processing fruit powder. A total of 183 upregulated metabolites and 280 downregulated metabolites were obtained by non-targeted metabolomics, and the differential metabolites was mainly involved in the pathways of flavonoid biosynthesis, flavone and flavonol biosynthesis. A total of 8 flavonoid differential metabolites were obtained including 5 upregulated metabolites (6"-O-acetylglycitin, scutellarin, isosakuranin, rutin, and robinin), and 3 downregulated metabolites (astragalin, luteolin, and (-)-catechin gallate) by flavonoids-targeted metabolomics. The 8 flavonoid differential metabolites participated in the flavonoid biosynthesis pathways, flavone and flavonol biosynthesis pathways, and isoflavonoid biosynthesis pathways. The results provide a reference for further understanding the relationship between food processing and food components, and also lay a basis for the development of food targeted-processing technologies.