Metabolic engineering of isoflavone genistein in Brassica napus with soybean isoflavone synthase

Biosynthesis and metabolic engineering of isoflavonoids in model plants and crops: a review

Isoflavonoids, the major secondary metabolites within the flavonoid biosynthetic pathway, play important roles in plant defense and exhibit free radical scavenging properties in mammals. Recent advancements in understanding the synthesis, transport, and regulation of isoflavonoids have identified their biosynthetic pathways as promising targets for metabolic engineering, offering potential benefits such as enhanced plant resistance, improved biomass, and restoration of soil fertility. This review provides an overview of recent breakthroughs in isoflavonoid biosynthesis, encompassing key enzymes in the biosynthetic pathway, transporters influencing their subcellular localization, molecular mechanisms regulating the metabolic pathway (including transcriptional and post-transcriptional regulation, as well as epigenetic modifications). Metabolic engineering strategies aimed at boosting isoflavonoid content in both leguminous and non-leguminous plants. Additionally, we discuss emerging technologies and resources for precise isoflavonoid regulation. This comprehensive review primarily focuses on model plants and crops, offering insights for more effective and sustainable metabolic engineering approaches to enhance nutritional quality and stress tolerance.

Metabolic profiling and expression analysis of key genetic factors in the biosynthetic pathways of antioxidant metabolites in mungbean sprouts

Mungbeans (Vigna radiata L.), a major legume crop in Asia, contain higher amounts of functional substances than other legumes, such as catechin, chlorogenic acid, and vitexin. Germination can improve the nutritional value of legume seeds. Here, 20 functional substances were profiled in germinated mungbeans and the expression levels of the transcripts of key enzymes in targeted secondary metabolite biosynthetic pathways were identified. VC1973A, a reference mungbean elite cultivar, had the highest amount of gallic acid (99.93 ± 0.13 mg/100 g DW) but showed lower contents of most metabolites than the other genotypes. Wild mungbeans contained a large amount of isoflavones compared with cultivated genotypes, especially for daidzin, genistin and glycitin. The expression of key genes involved in biosynthetic pathways had significant positive or negative correlations with the target secondary metabolite contents. The results indicate that functional substance contents are regulated at the transcriptional level, which can be applied to improve the nutritional value of mungbean sprouts in molecular breeding or genetic engineering, and wild mungbeans are a useful resource to improve the quality of mungbean sprouts.

Chemosystematic and evolutionary trends of the genistoid clade sensu stricto (Papilionoideae, Fabaceae)

The Papilionoideae, which comprises 503 genera and approximately 14,000 species, is the largest and most diverse subfamily of the Fabaceae family. In this subfamily, the Crotalarieae, Genisteae, Podalyrieae, Thermopsideae, Sophoreae and Euchresteae tribes are closely related by micro and macromolecular features, thus forming the genistoid clade. This group combines well-known genera, whereas other genera lack phytochemical and chemotaxonomic studies. Thus, this work aimed to characterize the special metabolites in these genera in order to define the chemical profile, the micromolecular markers and the chemical diversity, as well as to evaluate the group evolutionary trends. Flavonoids and alkaloids were identified as chemosystematic markers for the studied tribes due to high occurrence number and structural diversity. Among flavonoids, the flavones and isoflavones predominated. Low protection indexes of flavonoid hydroxyls by O-glycosylation or O-methylation were observed, whereas C-prenylation and C-glycosylation were frequent, mainly at C-6 and C-8 positions. The flavone/flavonol ratio shows the predominance of the flavones. Quinolizidine and piperidine alkaloids were present in most genera. Pyrrolizidine alkaloids were found in a few genera from Thermopsideae, Genisteae and Crotalarieae, which suggests a mechanism of adaptive convergence. Cluster analysis allowed separation of genera for each tribe by chemical similarities. The micromolecular trends of protection of flavonoid hydroxyls and alkaloid oxidation indicate the genistoid clade is through evolutionary transition, which is consistent with its phylogenetic position in the Papilionoideae subfamily.

Metabolic Engineering of Isoflavones: An Updated Overview

Isoflavones are ecophysiologically active secondary metabolites derived from the phenylpropanoid pathway. They were mostly found in leguminous plants, especially in the pea family. Isoflavones play a key role in plant-environment interactions and act as phytoalexins also having an array of health benefits to the humans. According to epidemiological studies, a high intake of isoflavones-rich diets linked to a lower risk of hormone-related cancers, osteoporosis, menopausal symptoms, and cardiovascular diseases. These characteristics lead to the significant advancement in the studies on genetic and metabolic engineering of isoflavones in plants. As a result, a number of structural and regulatory genes involved in isoflavone biosynthesis in plants have been identified and characterized. Subsequently, they were engineered in various crop plants for the increased production of isoflavones. Furthermore, with the advent of high-throughput technologies, the regulation of isoflavone biosynthesis gains attention to increase or decrease the level of isoflavones in the crop plants. In the review, we begin with the role of isoflavones in plants, environment, and its benefits in human health. Besides, the main theme is to discuss the updated research progress in metabolic engineering of isoflavones in other plants species and regulation of production of isoflavones in soybeans.

Metabolic Engineering of Isoflavonoid Biosynthesis by Expressing Glycine max Isoflavone Synthase in Allium cepa L. for Genistein Production

Isoflavonoids, the diverse group of secondary metabolites derived from the phenylpropanoid pathway, are distributed predominantly in leguminous plants and play a vital role in promoting human health. Genetic engineering of the metabolite synthesis pathway has turned out to be an attractive approach for the production of various secondary metabolites. In our study, we attempted to produce the isoflavone genistein, a well-known health-promoting metabolite, in Allium cepa L. (onion) by introducing Glycine max Isoflavone synthase (GmIFS). The GmIFS gene was cloned into the pEarleyGate 102 HA vector and transformed into onion by Agrobacterium-mediated and biolistic methods. The presence of GmIFS in transgenic onion was confirmed by PCR, dot blot, and Southern hybridization. Analysis of the transgenic onion calli lines demonstrated that the expression of the GmIFS gene led to the production of isoflavone genistein in in vitro tissues. The biolistic stable transformed calli with transformation efficiency of 73% (62.65 nM/g FW) accumulated more genistein than the Agrobacterium stable transformed calli with transformation efficiency of 56% (42.5 nM/g FW). Overall, heterologous gene expression of GmIFS was demonstrated by modifying the secondary metabolite pathway in onion tissues for the production of isoflavone genistein that can boost up human health with its health-promoting properties.

Characterization of Brassica napus Flavonol Synthase Involved in Flavonol Biosynthesis in Brassica napus L

Recently, Brassica napus has become a very important crop for plant oil production. Flavonols, an uncolored flavonoid subclass, have a high antioxidative effect and are known to have antiproliferative, antiangiogenic, and neuropharmacological properties. In B. napus, some flavonoid structural genes have been identified, such as, BnF3H-1, BnCHS, and BnC4H-1. However, no studies on FLS genes in B. napus have been conducted. Thus, in this study, we cloned and characterized the function of BnFLS gene B. napus. By overexpression of the BnFLS gene, flavonol (kaempferol and quercetin) levels were recovered in the Arabidopsis atfls1-ko mutant. In addition, we found that the higher endogenous flavonol levels of BnFLS-ox in vitro shoots correlated with slightly higher ROS scavenging activities. Thus, our results indicate that the BnFLS gene encodes for a BnFLS enzyme that can be manipulated to specifically increase flavonol accumulation in oilseed plants and other species such as Arabidopsis.

Flavonoids: biosynthesis, biological functions, and biotechnological applications

Flavonoids are widely distributed secondary metabolites with different metabolic functions in plants. The elucidation of the biosynthetic pathways, as well as their regulation by MYB, basic helix-loop-helix (bHLH), and WD40-type transcription factors, has allowed metabolic engineering of plants through the manipulation of the different final products with valuable applications. The present review describes the regulation of flavonoid biosynthesis, as well as the biological functions of flavonoids in plants, such as in defense against UV-B radiation and pathogen infection, nodulation, and pollen fertility. In addition, we discuss different strategies and achievements through the genetic engineering of flavonoid biosynthesis with implication in the industry and the combinatorial biosynthesis in microorganisms by the reconstruction of the pathway to obtain high amounts of specific compounds.

Flavonoids: biosynthesis, biological functions, and biotechnological applications

Flavonoids are widely distributed secondary metabolites with different metabolic functions in plants. The elucidation of the biosynthetic pathways, as well as their regulation by MYB, basic helix-loop-helix (bHLH), and WD40-type transcription factors, has allowed metabolic engineering of plants through the manipulation of the different final products with valuable applications. The present review describes the regulation of flavonoid biosynthesis, as well as the biological functions of flavonoids in plants, such as in defense against UV-B radiation and pathogen infection, nodulation, and pollen fertility. In addition, we discuss different strategies and achievements through the genetic engineering of flavonoid biosynthesis with implication in the industry and the combinatorial biosynthesis in microorganisms by the reconstruction of the pathway to obtain high amounts of specific compounds.

Effects of a coumarin derivative, 4-methylumbelliferone, on seed germination and seedling establishment in Arabidopsis

The root system is central for plant adaptation to soil heterogeneity and is organized primarily by root branching. To search for compounds that regulate root branching, a forward chemical genetics screen was employed, and 4-methylumbelliferone (4-MU), a coumarin derivative, was found to be a potent regulator of lateral root formation. Exogenous application of 4-MU to Arabidopsis thaliana seeds affected germination and led to reduced primary root growth, the formation of bulbous root hairs, and irregular detached root caps accompanied by reorganization of the actin cytoskeleton in root tips before seedling establishment. Abundant lateral roots formed after exposure to 125 μM 4-MU for 22 days. Molecular, biochemical, and phytochemical approaches were used to determine the effect of 4-MU on root growth and root branching. Arabidopsis seedlings grown in the presence of 4-MU accumulated this compound only in roots, where it was partially transformed by UDP-glycosyltransferases (UGTs) into 4-methylumbelliferyl-β-D-glucoside (4-MU-Glc). The presence of 4-MU-Glc in seedling roots was consistent with the upregulation of several genes that encode UGTs in the roots. This shows that UGTs play an integral role in the detoxification of 4-MU in plants. The increased expression of two auxin efflux facilitator genes (PIN2 and PIN3) in response to 4-MU and the lack of response of the auxin receptor TIR1 and the key auxin biosynthetic gene YUCCA1 suggest that auxin redistribution, rather than auxin biosynthesis, may directly or indirectly mediate 4-MU-induced root branching.