Enhancement of rutin in Fagopyrum esculentum hairy root cultures by the Arabidopsis transcription factor AtMYB12

Buckwheat OMICS: present status and future prospects

Buckwheat (Fagopyrum spp.) is an underutilized resilient crop of North Western Himalayas belonging to the family Polygonaceae and is a source of essential nutrients and therapeutics. Common Buckwheat and Tatary Buckwheat are the two main cultivated species used as food. It is the only grain crop possessing rutin, an important metabolite with high nutraceutical potential. Due to its inherent tolerance to various biotic and abiotic stresses and a short life cycle, Buckwheat has been proposed as a model crop plant. Nutritional security is one of the major concerns, breeding for a nutrient-dense crop such as Buckwheat will provide a sustainable solution. Efforts toward improving Buckwheat for nutrition and yield are limited due to the lack of available: genetic resources, genomics, transcriptomics and metabolomics. In order to harness the agricultural importance of Buckwheat, an integrated breeding and OMICS platforms needs to be established that can pave the way for a better understanding of crop biology and developing commercial varieties. This, coupled with the availability of the genome sequences of both Buckwheat species in the public domain, should facilitate the identification of alleles/QTLs and candidate genes. There is a need to further our understanding of the molecular basis of the genetic regulation that controls various economically important traits. The present review focuses on: the food and nutritional importance of Buckwheat, its various omics resources, utilization of omics approaches in understanding Buckwheat biology and, finally, how an integrated platform of breeding and omics will help in developing commercially high yielding nutrient rich cultivars in Buckwheat.

Overexpression of AtMYB12 transcription factor simultaneously enhances quercetin-dependent metabolites in radish callus

The study aimed to enhance quercetin production in radish by optimizing Agrobacterium tumefaciens-mediated in-planta transformation. This protocol involved infecting radish seed embryo axis with A. tumefaciens EHA105 strain carrying the 35S::AtMYB12. Radish seeds were infected with the Agrobacterium suspension (0.8 OD600) for 30 min, followed by sonication for 60 s and vacuum infiltration for 90 s at 100 mm Hg. A 3-day co-cultivation in Murashige and Skoog medium with 150 μM acetosyringone yielded a transformation efficiency of 59.6% and a transgenic callus induction rate of 32.3%. Transgenic plant and callus lines were confirmed by GUS histochemical assay, PCR, and qRT-PCR. The transgenic lines showed an increased expression of flavonoid pathway genes (AtMYB12, CHS, F3H, and FLS) and antioxidant genes (GPX, APX, CAT, and SOD) compared to WT plants. Overexpression of AtMYB12 in transgenic callus increased enzyme activity of phenylalanine ammonia lyase, catalase, and ascorbate peroxidase. In half-strength MS medium with 116.8 mM sucrose, the highest growth index (7.63) was achieved after 20 days. In AtMYB12 overexpressed callus lines, phenolic content (357.31 mg g-1 dry weight), flavonoid content (463 mg g-1 dry weight), and quercetin content (48.24 mg g-1 dry weight) increased significantly by 9.41-fold. Micro-wounding, sonication, and vacuum infiltration improved in-planta transformation in radishes. These high-quercetin-content transgenic callus lines hold promise as valuable sources of flavonoids.

Simultaneous Promotion of Salt Tolerance and Phenolic Acid Biosynthesis in Salvia miltiorrhiza via Overexpression of Arabidopsis MYB12

Transcription factors play crucial roles in regulating plant abiotic stress responses and physiological metabolic processes, which can be used for plant molecular breeding. In this study, an R2R3-MYB transcription factor gene, AtMYB12, was isolated from Arabidopsis thaliana and introduced into Salvia miltiorrhiza under the regulation of the CaMV35S promoter. The ectopic expression of AtMYB12 resulted in improved salt tolerance in S. miltiorrhiza; transgenic plants showed a more resistant phenotype under high-salinity conditions. Physiological experiments showed that transgenic plants exhibited higher chlorophyll contents, and decreased electrolyte leakage and O2- and H2O2 accumulation when subjected to salt stress. Moreover, the activity of reactive oxygen species (ROS)-scavenging enzymes was enhanced in S. miltiorrhiza via the overexpression of AtMYB12, and transgenic plants showed higher superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities compared with those of the wild type (WT) under salt stress, coupled with lower malondialdehyde (MDA) levels. In addition, the amount of salvianolic acid B was significantly elevated in all AtMYB12 transgenic hair roots and transgenic plants, and qRT-PCR analysis revealed that most genes in the phenolic acid biosynthetic pathway were up-regulated. In conclusion, these results demonstrated that AtMYB12 can significantly improve the resistance of plants to salt stress and promote the biosynthesis of phenolic acids by regulating genes involved in the biosynthetic pathway.

Impact of Light and Dark Treatment on Phenylpropanoid Pathway Genes, Primary and Secondary Metabolites in Agastache rugosa Transgenic Hairy Root Cultures by Overexpressing Arabidopsis Transcription Factor AtMYB12

Agastache rugosa, otherwise called Korean mint, has a wide range of medicinal benefits. In addition, it is a rich source of several medicinally valuable compounds such as acacetin, tilianin, and some phenolic compounds. The present study aimed to investigate how the Tartary buckwheat transcription factor AtMYB12 increased the primary and secondary metabolites in Korean mint hairy roots cultured under light and dark conditions. A total of 50 metabolites were detected by using high-performance liquid chromatography (HPLC) and gas chromatography-time-of-flight mass spectrometry (GC-TOFMS). The result showed that the AtMYB12 transcription factor upregulated the phenylpropanoid biosynthesis pathway genes, which leads to the highest accumulation of primary and secondary metabolites in the AtMYB12-overexpressing hairy root lines (transgenic) than that of the GUS-overexpressing hairy root line (control) when grown under the light and dark conditions. However, when the transgenic hairy root lines were grown under dark conditions, the phenolic and flavone content was not significantly different from that of the control hairy root lines. Similarly, the heat map and hierarchical clustering analysis (HCA) result showed that most of the metabolites were significantly abundant in the transgenic hairy root cultures grown under light conditions. Principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) showed that the identified metabolites were separated far based on the primary and secondary metabolite contents present in the control and transgenic hairy root lines grown under light and dark conditions. Metabolic pathway analysis of the detected metabolites showed 54 pathways were identified, among these 30 were found to be affected. From these results, the AtMYB12 transcription factor activity might be light-responsive in the transgenic hairy root cultures, triggering the activation of the primary and secondary metabolic pathways in Korean mint.

The Paeonia qiui R2R3-MYB Transcription Factor PqMYBF1 Positively Regulates Flavonol Accumulation

Tree peony is a "spring colored-leaf" plant which has red leaves in early spring, and the red color of the leaves usually fades in late spring. Flavonols are one subgroup of flavonoids, and they affect the plant organs' color as co-pigments of anthocyanins. To investigate the color variation mechanism of leaves in tree peony, PqMYBF1, one flavonol biosynthesis-related MYB gene was isolated from Paeonia qiui and characterized. PqMYBF1 contained the SG7 and SG7-2 motifs which are unique in flavonol-specific MYB regulators. Subcellular localization and transactivation assay showed that PqMYBF1 localized to the nucleus and acted as a transcriptional activator. The ectopic expression of PqMYBF1 in transgenic tobacco caused an observable increase in flavonol level and the anthocyanin accumulation was decreased significantly, resulting in pale pink flowers. Dual-luciferase reporter assays showed that PqMYBF1 could activate the promoters of PqCHS, PqF3H, and PqFLS. These results suggested that PqMYBF1 could promote flavonol biosynthesis by activating PqCHS, PqF3H, and PqFLS expression, which leads metabolic flux from anthocyanin to flavonol pathway, resulting in more flavonol accumulation. These findings provide a new train of thought for the molecular mechanism of leaf color variation in tree peony in spring, which will be helpful for the molecular breeding of tree peony with colored foliage.

Hairy Root Cultures as a Source of Polyphenolic Antioxidants: Flavonoids, Stilbenoids and Hydrolyzable Tannins

Due to their chemical properties and biological activity, antioxidants of plant origin have gained interest as valuable components of the human diet, potential food preservatives and additives, ingredients of cosmetics and factors implicated in tolerance mechanisms against environmental stress. Plant polyphenols are the most prominent and extensively studied, albeit not only group of, secondary plant (specialized) metabolites manifesting antioxidative activity. Because of their potential economic importance, the productive and renewable sources of the compounds are desirable. Over thirty years of research on hairy root cultures, as both producers of secondary plant metabolites and experimental systems to investigate plant biosynthetic pathways, brought about several spectacular achievements. The present review focuses on the Rhizobium rhizogenes-transformed roots that either may be efficient sources of plant-derived antioxidants or were used to elucidate some regulatory mechanisms responsible for the enhanced accumulation of antioxidants in plant tissues.

Identification of the key flavonoid and lipid synthesis proteins in the pulp of two sea buckthorn cultivars at different developmental stages

BACKGROUND

Sea buckthorn is an economically important woody plant for desertification control and water soil conservation. Its berry pulp is rich in flavonoids and unsaturated fatty acids. Cultivars containing high oil and flavonoid contents have higher economic value and will increase in the planting area. However, the cause of the differences in oil and flavonoid contents among cultivars is still unclear. The influence of key enzymes in the lipid and flavonoid synthesis pathways on their content needs to be explored and clarified.

RESULTS

The flavonoid content in XE (Xin'e 3) was 54% higher than that in SJ (Suiji 1). Rutin was the main flavonoid in sea buckthorn pulp, and the differences in the rutin content could cause flavonoid differences between the two cultivars. The oil content of XE was 31.58% higher than that of SJ, and the difference in oil content was highest at 50-70 DAF. High-throughput proteomics was used to quantify key enzymes of flavonoid and lipid synthesis pathways in two cultivars at three developmental stages. By functional annotation and KEGG analysis, 41 key enzymes related to phenylpropanoid biosynthesis, flavonoid biosynthesis, flavone and flavonol biosynthesis, fatty acid biosynthesis and TAG biosynthesis were quantified. CHS, F3H, ANS, fabD, FATA, FAB2, LPIN and plcC showed significant differences between the two cultivars. In addition, we quantified 6 oleosins. With the exception of a 16 kDa oleosin, the other oleosins in the two cultivars were positively correlated with oil content.

CONCLUSIONS

In the flavonoid synthesis pathway, CHS and F3H were the main enzymes responsible for the difference in flavonoid content between the two cultivars. In the lipid synthesis pathway, LPIN, plcC and MGD were the main enzymes with different contents in the middle to late stages. Higher contents of LPIN and plcC in XE than in SJ could cause DAG to generate TAG from PC, since the difference in DGAT between the two cultivars was not significant. Investigating the causes of flavonoid and oil content differences among different cultivars from the perspective of proteomics, could provide a basis for understanding the regulatory mechanism of flavonoids and lipid synthesis in sea buckthorn pulp.

Buckwheat in Tissue Culture Research: Current Status and Future Perspectives

Buckwheat is a member of a genus of 23 species, where the two most common species are Fagopyrum esculentum (common buckwheat) and Fagopyrum tataricum (Tartary buckwheat). This pseudocereal is a source of micro and macro nutrients, such as gluten-free proteins and amino acids, fatty acids, bioactive compounds, dietary fibre, fagopyrins, vitamins and minerals. It is gaining increasing attention due to its health-promoting properties. Buckwheat is widely susceptible to in vitro conditions which are used to study plantlet regeneration, callus induction, organogenesis, somatic embryogenesis, and the synthesis of phenolic compounds. This review summarises the development of buckwheat in in vitro culture and describes protocols for the regeneration of plantlets from various explants and differing concentrations of plant growth regulators. It also describes callus induction protocols as well as the role of calli in plantlet regeneration. Protocols for establishing hairy root cultures with the use of Agrobacterium rhizogens are useful in the synthesis of secondary metabolites, as well as protocols used for transgenic plants. The review also focuses on the future prospects of buckwheat in tissue culture and the challenges researchers are addressing.

Biotechnological Methods for Buckwheat Breeding

The Fagopyrum genus includes two cultivated species, namely common buckwheat (F. esculentum Moench) and Tartary buckwheat (F. tataricum Gaertn.), and more than 25 wild buckwheat species. The goal of breeders is to improve the properties of cultivated buckwheat with methods of classical breeding, with the support of biotechnological methods or a combination of both. In this paper, we reviewed the possibility to use transcriptomics, genomics, interspecific hybridization, tissue cultures and plant regeneration, molecular markers, genetic transformation, and genome editing to aid in both the breeding of buckwheat and in the identification and production of metabolites important for preserving human health. The key problems in buckwheat breeding are the unknown mode of inheritance of most traits, associated with crop yield and the synthesis of medicinal compounds, low seed yield, shedding of seeds, differential flowering and seed set on branches, and unknown action of genes responsible for the synthesis of buckwheat metabolites of pharmaceutical and medicinal interest.

Enhancement of the flavone contents of Scutellaria baicalensis hairy roots via metabolic engineering using maize Lc and Arabidopsis PAP1 transcription factors

Baicalin, baicalein, and wogonin are valuable natural flavonoid compounds produced by Scutellaria baicalensis. In this study, we showed that the maize transcription factor Lc can enhance the production of these three flavonoids in hairy root cultures of S. baicalensis by comprehensively upregulating flavonoid biosynthesis pathway genes (SbPAL1, SbC4H, and Sb4CL) and baicalein 7-O-glucuronosyltransferase (UBGAT), ultimately yielding total flavonoid contents of up to 80.5 ± 6.15 mg g^-1 dry weight, which was 322% greater than the average value of total flavonoid contents produced by three GUS-overexpressing lines. Similarly, the Arabidopsis transcription factor PAP1 was found to enhance flavonoid accumulation by upregulating SbPAL1, SbPAL2, SbPAL3, SbC4H, Sb4CL, SbCHI, and UBGAT, ultimately yielding total flavonoid contents of up to 133 ± 7.66 mg g^-1 dry weight, which was 532% greater than the average value of total flavonoid contents produced by three GUS-overexpressing lines. These findings indicate that metabolic engineering in S. baicalensis can be achieved using Agrobacterium rhizogenes-mediated transformation and that the production of baicalin, baicalein, and wogonin can be enhanced via the overexpression of ZmLc and AtPAP1 in hairy root cultures. These results also indicate that ZmLc and AtPAP1 can be used as positive regulators of the flavonoid biosynthetic pathway of S. baicalensis hairy root cultures.

Treasure from garden: Bioactive compounds of buckwheat

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An extensive review on diverse bioactive components of buckwheat.

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Versatile beneficial phytochemicals are abundant in buckwheat.

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Buckwheat has a wide range of pharmacological and beneficial health effects.

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Huge research scope on Fagopyrum cymosum to identify the beneficial phytochemicals.

Buckwheat is a gluten-free crop under the family Polygonaceae abundant with beneficial phytochemicals that provide significant health benefits. It is cultivated and adapted in diverse ecological zones all over the world. Recently its popularity is expanding as a nutrient-rich healthy food with low-calories. The bioactive compounds in buckwheat are flavonoids (i.e., rutin, quercetin, orientin, isoorientin, vitexin, and isovitexin), fatty acids, polysaccharides, proteins, and amino acids, iminosugars, dietary fiber, fagopyrins, resistant starch, vitamins, and minerals. Buckwheat possesses high nutritional value due to these bioactive compounds. Additionally, several essential bioactive factors that have long been gaining interest because these compounds are beneficial for healing and preventing several human diseases. The present review demonstrates an overview of the recent researches regarding buckwheat phytochemicals and particularly focusing on the distinct function of bioactive components with their health benefits.

TrMYB4 transcription factor regulates the rutin biosynthesis in hairy roots of F. cymosum

Fagopyrum cymosum has been considered as a traditional medicinal plant that belongs to Fagopyrum, which has exhibited great pharmaceutical potential due to its abundant flavonoid accumulation. The hairy roots induced by Agrobacterium rhizogenes has been utilized to produce valuable specialized metabolites or reveals plant metabolic processes, whereas the underlying regulatory networks of flavonoid biosynthesis in hairy roots of F. cymosum remained unexplored. Here, the regulatory transcription factor TrMYB4 cloned from Trifolium repens with purple striped leaves was considered to investigate the mechanism of flavonoids biosynthesis in hairy roots of F. cymosum. Results showed that the expression of key genes involved in rutin biosynthesis pathway from TrMYB4 hairy roots were significantly up-regulated compared with non-transgenic hairy roots, while the content of total flavonoids and rutin in TrMYB4 hairy roots also increased consistently. It revealed the TrMYB4 transcription factor could regulate the rutin biosynthesis in F. cymosum. Meanwhile, our research provided a theoretical reference for the industrial production of rutin using F. cymosum hairy roots.

Strategic enhancement of genetic gain for nutraceutical development in buckwheat: A genomics-driven perspective

Buckwheat (Fagopyrum spp.) under the family Polygonaceae is an ancient pseudocereal with stupendous but less studied nutraceutical properties. The gluten free nature of protein, balanced amino acid profile and health promoting bioactive flavonoids make it a golden crop of future. Besides a scanty basic research, not much attention has been paid to the improvement of plant type and breeding of nutraceutical traits. Scanning of scientific literature indicates that adequate genetic variation exists for agronomic and nutritional traits in mainstream and wild gene pool of buckwheat. However, the currently employed conventional approaches together with poorly understood genetic mechanisms restrict effective utilization of the existing genetic variation in nutraceutical breeding of buckwheat. The latest trends in buckwheat genomics, particularly avalilabity of draft genome sequences for both the cultivated species (F. esculentum and F.tataricum) hold immense potential to overcome these limitations. Utilizing the transgenic hairy rot cultures, role of various transcription factors and gene families have been deduced in production and biosynthesis of bioactive flavonoids. Further, the acquisition of high-density genomics data coupled with the next-generation phenotyping will certainly improve our understanding of underlying genetic regulation of nutraceutical traits. The present paper highlights the application of multilayered omics interventions for tailoring a nutrient rich buckwheat cultivar and nutraceutical product development.

The R2R3 transcription factor HlMYB8 and its role in flavonoid biosynthesis in hop (Humulus lupulus L.)

Hop is an important source of medicinally valuable secondary metabolites including bioactive prenylated chalcones. To gain in-depth knowledge of the regulatory mechanisms of hop flavonoids biosynthesis, full-length cDNA of HlMyb8 transcription factor gene was isolated from lupulin glands. The deduced amino acid sequence of HlMyb8 showed high similarity to a flavonol-specific regulator of phenylpropanoid biosynthesis AtMYB12 from Arabidopsis thaliana. Transient expression studies and qRT-PCR analysis of transgenic hop plants overexpressing HlMyb8 revealed that HlMYB8 activates expression of chalcone synthase HlCHS_H1 as well as other structural genes from the flavonoid pathway branch leading to the production of flavonols (F3H, F'3H, FLS) but not prenylflavonoids (PT1, OMT1) or bitter acids (VPS, PT1). HlMyb8 could cross-activate Arabidopsis flavonol-specific genes but to a much lesser extent than AtMyb12. Reciprocally, AtMyb12 could cross-activate hop flavonol-specific genes. Transcriptome sequence analysis of hop leaf tissue overexpressing HlMyb8 confirmed the modulation of several other genes related to flavonoid biosynthesis pathways (PAL, 4CL, ANR, DFR, LDOX). Analysis of metabolites in hop female cones confirmed that overexpression of HlMyb8 does not increase prenylflavonoid or bitter acids content in lupulin glands. It follows from our results that HlMYB8 plays role in a competition between flavonol and prenylflavonoid or bitter acid pathways by diverting the flux of CHS_H1 gene product and thus, may influence the level of these metabolites in hop lupulin.

Enhanced rutin accumulation in tobacco leaves by overexpressing the NtFLS2 gene

Rutin, one of the metabolites of the flavonoid pathway, shows great potential in industrial applications as a key component in pharmaceutical medicines and biological pesticides. Although the genetic manipulation of transcription factors (TFs) could increase rutin levels in plants, the accompanying accumulation of structurally similar chemicals complicates industrial rutin extraction. In this study, we demonstrated remarkably elevated rutin content (3.5-4.4-fold relative to controls) in transgenic tobacco plants by overexpressing NtFLS2. The levels of other intermediates in the branch pathway did not change much except for a moderate increase of kaempferol-3-O-rutinoside. Furthermore, the transcript levels of pathway genes in transgenic lines were comparable with controls, indicating genetic engineering did not significantly alter the branch pathway. Additionally, the transgenic tobacco plants appeared normal except for a flower color change from light red to white suggesting that it could be a valuable material for industrial extraction of rutin.

Development of Marker-Free Transgenic Potato Tubers Enriched in Caffeoylquinic Acids and Flavonols

Potato (Solanum tuberosum L.) is a major crop worldwide that meets human economic and nutritional requirements. Potato has several advantages over other crops: easy to cultivate and store, cheap to consume, and rich in a variety of secondary metabolites. In this study, we generated three marker-free transgenic potato lines that expressed the Arabidopsis thaliana flavonol-specific transcriptional activator AtMYB12 driven by the tuber-specific promoter Patatin. Marker-free potato tubers displayed increased amounts of caffeoylquinic acids (CQAs) (3.35-fold increases on average) and flavonols (4.50-fold increase on average). Concentrations of these metabolites were associated with the enhanced expression of genes in the CQA and flavonol biosynthesis pathways. Accumulation of CQAs and flavonols resulted in 2-fold higher antioxidant capacity compared to wild-type potatoes. Tubers from these marker-free transgenic potatoes have therefore improved antioxidant properties.

AtMYB12 regulates flavonoids accumulation and abiotic stress tolerance in transgenic Arabidopsis thaliana

In plants, transcriptional regulation is the most important tool for modulating flavonoid biosynthesis. The AtMYB12 gene from Arabidopsis thaliana has been shown to regulate the expression of key enzyme genes involved in flavonoid biosynthesis, leading to the increased accumulation of flavonoids. In this study, the codon-optimized AtMYB12 gene was chemically synthesized. Subcellular localization analysis in onion epidermal cells indicated that AtMYB12 was localized to the nucleus. Its overexpression significantly increased accumulation of flavonoids and enhanced salt and drought tolerance in transgenic Arabidopsis plants. Real-time quantitative PCR (qRT-PCR) analysis showed that overexpression of AtMYB12 resulted in the up-regulation of genes involved in flavonoid biosynthesis, abscisic acid (ABA) biosynthesis, proline biosynthesis, stress responses and ROS scavenging under salt and drought stresses. Further analyses under salt and drought stresses showed significant increases of ABA, proline content, superoxide dismutase (SOD) and peroxidase (POD) activities, as well as significant reduction of H2O2 and malonaldehyde (MDA) content. The results demonstrate the explicit role of AtMYB12 in conferring salt and drought tolerance by increasing the levels of flavonoids and ABA in transgenic Arabidopsis. The AtMYB12 gene has the potential to be used to enhance tolerance to abiotic stresses in plants.

Induction of hairy roots by Agrobacterium rhizogenes-mediated transformation of spine gourd (Momordica dioica Roxb. ex. willd) for the assessment of phenolic compounds and biological activities

An efficient protocol for hairy root induction of spine gourd (Momordica dioica) was established using Agrobacterium rhizogenes (KCTC 2703). This study evaluates the phenolic compound production, antioxidant and antimicrobial (antibacterial, antifungal and antiviral) activities of transgenic hairy root cultures in M. dioica . Hairy roots were induced from leaves, petiole, and internodal explants. Molecular analysis of PCR and gene sequencing using specific primers of rolC and aux1 revealed T-DNA integration in the hairy root clones and RT-PCR analysis confirmed the expression of hairy root inducible genes (rolC and aux1). The greatest biomass accumulation of hairy roots on MS liquid medium supplemented with 3% sucrose was observed at 22 days. Ultra-HPLC was used to compare the individual phenolic compound contents of transgenic and non-transgenic roots. Moreover, transgenic hairy roots efficiently produced several phenolic compounds, such as flavonols, hydroxycinnamic acid and hydroxybenzoic acid derivatives. The total phenolic, flavonoid contents and biological (antioxidant, antibacterial, antifungal and antiviral) activities were higher in hairy roots compared to non-transformed roots. These results demonstrate the greater potentiality of M. dioica hairy root cultures for the production of valuable phenolic compounds and for studies of their biological activity.

Heterologous expression of AtMYB12 in kale (Brassica oleracea var. acephala) leads to high flavonol accumulation

Overexpression of Arabidopsis AtMYB12 transcription factor greatly increases the total phenolic and flavonol content in transgenic kale leaves. Flavonoids are a diverse group of plant secondary metabolites exhibiting a number of health-promoting effects. There has been a growing interest to develop biotechnological methods for the enhanced production of flavonoids in crop plants. AtMYB12 is an Arabidopsis transcription factor which specifically activates flavonol synthesis and its overexpression has led to increased flavonol accumulation in several transgenic plants. In the present study, AtMYB12 was overexpressed in a commercial cultivar of kale and the transgenic plants were tested both in in vitro and in semi-field conditions in cages under natural light. Using this method, a severalfold increase in both total phenolics content and flavonol accumulation was achieved. This study provides a reliable and efficient transformation protocol for kale and suggests the potential of this flavonol-enriched vegetable for the production of kaempferol.

Overexpression of Cinnamate 4-Hydroxylase and 4-Coumaroyl CoA Ligase Prompted Flavone Accumulation inScutellaria baicalensisHairy Roots

Scutellaria baicalensis Georgi, a species of the Lamiaceae family, is considered as one of the 50 fundamental herbs used in traditional Chinese medicine. In order to enhance flavone (baicalein, baicalin, and wogonin) content in S. baicalensis roots, we overexpressed a single gene of cinnamate 4-hydroxylase (C4H) and 4-coumaroyl coenzyme A ligase (4CL) using an Agrobacterium rhizogenes-mediated system. SbC4H- and Sb4CL-overexpressed hairy root lines enhanced the transcript levels of SbC4H and Sb4CL compared with those in the control and also increased flavones contents by approximately 3- and 2.5-fold, respectively. We successfully engineered the flavone biosynthesis pathway for the production of beneficial flavones in S. baicalensis hairy roots. The importance of upstream gene C4H and 4CL in flavone biosynthesis and the efficiency of metabolic engineering in promoting flavone biosynthesis in S. baicalensis hairy roots have been indicated in this study.

Comparative analysis of flavonoids and polar metabolite profiling of Tanno-original and Tanno-high rutin buckwheat

Rutin is an important indicator for evaluating the quality of buckwheat. In this study, flavonoid biosynthesis was compared between two common cultivars (an original and a high-rutin line) of buckwheat, Fagopyrum esculentum Moench. Transcriptional levels of the main flavonoid biosynthetic genes were analyzed by real-time PCR, and main flavonoid metabolites were detected by high-performance liquid chromatography (HPLC); levels of gene expression varied among organs of the two cultivars. Significantly higher transcription levels of most flavonoid biosynthetic genes, except FeFLS1, were detected in stems of the high-rutin line than in stems of the original line. FeCHI and FeFLS2 genes also showed higher expression levels in seeds of the high-rutin cultivar. In contrast, FePAL, FeC4H, Fe4CL1, FeCHS, FeF3H, FeF3'H, FeFLS2, and FeDFR were highly detected in the roots of the original line. The HPLC results indicated 1.73-, 1.62-, and 1.77-fold higher accumulation of rutin (the primary flavonoid compound) in leaves, stems, and mature seeds of the high-rutin cultivar (24.86, 1.46, and 1.36 μg/mg, respectively) compared with the original cultivar (14.40, 0.90, and 0.77 μg/mg, respectively). A total of 46 metabolites were identified from seeds by gas chromatography-time-of-flight mass spectrometry. The metabolite profiles were subjected to principal component analysis (PCA). PCA could clearly differentiate the original and high-rutin cultivars. Our results indicate that the high-rutin cultivar could be an excellent alternative for buckwheat culture, and we provide useful information for obtaining this cultivar.

Evaluation of total phenolic compounds and insecticidal and antioxidant activities of tomato hairy root extract

Tomatoes are one of the most consumed crops in the whole world because of their versatile importance in dietary food as well as many industrial applications. They are also a rich source of secondary metabolites, such as phenolics and flavonoids. In the present study, we described a method to produce these compounds from hairy roots of tomato (THRs). Agrobacterium rhizogenes strain A4 was used to induce hairy roots in the tomato explants. The Ri T-DNA was confirmed by polymerase chain reaction amplification of the rolC gene. Biomass accumulation of hairy root lines was 1.7-3.7-fold higher compared to in vitro grown roots. Moreover, THRs efficiently produced several phenolic compounds, such as rutin, quercetin, kaempferol, gallic acid, protocatechuic acid, ferulic acid, colorogenic acid, and caffeic acid. Gallic acid [34.02 μg/g of dry weight (DW)] and rutin (20.26 μg/g of DW) were the major phenolic acid and flavonoid produced by THRs, respectively. The activities of reactive oxygen species enzymes (catalase, ascorbate peroxidase, and superoxide dismutase) were quantified. The activity of catalase in THRs was 0.97 ± 0.03 mM H2O2 min(-1) g(-1), which was 1.22-fold (0.79 ± 0.09 mM H2O2 min(-1) g(-1)) and 1.59-fold (0.61 ± 0.06 mM H2O2 min(-1) g(-1)) higher than field grown and in vitro grown roots, respectively. At 100 μL/g concentration, the phenolic compound extract caused 53.34 and 40.00% mortality against Helicoverpa armigera and Spodoptera litura, respectively, after 6 days. Surviving larvae of H. armigera and S. litura on the phenolic compound extract after 6 days showed 85.43 and 86.90% growth retardation, respectively.