Phenolic compound production by different morphological phenotypes in hairy root cultures of Fagopyrum tataricum Gaertn

Tartary buckwheat rutin: Accumulation, metabolic pathways, regulation mechanisms, and biofortification strategies

Rutin is a significant flavonoid with strong antioxidant property and various therapeutic effects. It plays a crucial role in disease prevention and human health maintenance, especially in anti-inflammatory, antidiabetic, hepatoprotective and cardiovascular effects. While many plants can synthesize and accumulate rutin, tartary buckwheat is the only food crop possessing high levels of rutin. At present, the rutin content (RC) is regarded as the key index for evaluating the nutritional quality of tartary buckwheat. Consequently, rutin has become the focus for tartary buckwheat breeders and has made considerable progress. Here, we summarize research on the rutin in tartary buckwheat in the past two decades, including its accumulation, biosynthesis and breakdown pathways, and regulatory mechanisms. Furthermore, we propose several strategies to increase the RC in tartary buckwheat seeds based on current knowledge. This review aims to provide valuable references for elevating the quality of tartary buckwheat in the future.

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.

Comparison of Secondary Metabolite Contents and Metabolic Profiles of Six Lycoris Species

Quantitative HPLC analysis was performed on six different species of Lycoris herbs to investigate variation in phytochemical content, especially galantamine and phenylpropanoid-derived compounds. The contents of these compounds differed widely among the Lycoris species, with L. radiata and L. chinensis containing the lowest and highest galantamine contents, respectively. Specifically, the galantamine content of L. radiata was 62.5% higher than that of L. chinensis. Following L. radiata, L. sanguinea contained the next highest galantamine content, which was 59.1% higher than that of L. chinensis. Furthermore, a total of 12 phenylpropanoid-derived compounds were found in the different Lycoris species, where L. sanguinea, L. squamigera, and L. uydoensis had the largest accumulation of these compounds. The total phenylpropanoid content of L. sanguinea was the highest, while that of L. radiata was the lowest. Seven of the phenylpropanoid-derived compounds, rutin, quercetin, catechin, epicatechin gallate, chlorogenic acid, benzoic acid, and kaempferol, were dominant. L. sanguinea, L. uydoensis, and L. squamigera showed amounts of these seven compounds that were 5–6 times greater than those of the other species in the study. To the best of our knowledge, our results provide the most detailed phytochemical information on these species to date, which is valuable for future applications using these medicinal plants.

Caffeoylquinic Acids with Potential Biological Activity from Plant In vitro Cultures as Alternative Sources of Valuable Natural Products

BACKGROUND

For a long time, the researchers have been looking for new efficient methods to enhance production and obtain valuable plant secondary metabolites, which would contribute to the protection of the natural environment through the preservation of various plant species, often rare and endangered. These possibilities offer plant in vitro cultures which can be performed under strictly-controlled conditions, regardless of the season or climate and environmental factors. Biotechnological methods are promising strategies for obtaining the valuable plant secondary metabolites with various classes of chemical compounds including caffeoylquinic acids (CQAs) and their derivatives. CQAs have been found in many plant species which are components in the daily diet and exhibit a wide spectrum of biological activities, including antioxidant, immunomodulatory, antihypertensive, analgesic, anti-inflammatory, hepato- and neuroprotective, anti-hyperglycemic, anticancer, antiviral and antimicrobial activities. They have also been found to offer protection against Alzheimer's disease, and play a role in weight reduction and lipid metabolism control, as well as modulating the activity of glucose-6-phosphatase involved in glucose metabolism.

METHODS

This work presents the review of the recent advances in use in vitro cultures of various plant species for the alternative system to the production of CQAs and their derivatives. Production of the secondary metabolites in in vitro culture is usually performed with cell suspension or organ cultures, such as shoots and adventitious or transformed roots. To achieve high production of valuable secondary metabolites in in vitro cultures, the optimization of the culture condition is necessary with respect to both biomass accumulation and metabolite content. The optimization of the culture conditions can be achieved by choosing the type of medium, growth regulators or growth conditions, selection of high-productivity lines or culture period, supplementation of the culture medium with precursors or elicitor treatments. Cultivation for large-scale in bioreactors and genetic engineering: Agrobacterium rhizogenes transformation and expression improvement of transcriptional factor or genes involved in the secondary metabolite production pathway are also efficient strategies for enhancement of the valuable secondary metabolites.

RESULTS

Many studies have been reported to obtain highly productive plant in vitro cultures with respect to CQAs. Among these valuable secondary metabolites, the most abundant compound accumulated in in vitro cultures was 5-CQA (chlorogenic acid). Highly productive cultures with respect to this phenolic acid were Leonurus sibiricus AtPAP1 transgenic roots, Lonicera macranthoides and Eucomia ulmoides cell suspension cultures which accumulated above 20 mg g-1 DW 5-CQA. It is known that di- and triCQAs are less common in plants than monoCQAs, but it was also possible to obtain them by biotechnological methods.

CONCLUSION

The results indicate that the various in vitro cultures of different plant species can be a profitable approach for the production of CQAs. In particular, an efficient production of these valuable compounds is possible by Lonicera macranthoides and Eucomia ulmoides cell suspension cultures, Leonurus sibiricus transformed roots and AtPAP1 transgenic roots, Echinacea angustifolia adventitious shoots, Rhaponticum carthamoides transformed plants, Lavandula viridis shoots, Sausera involucrata cell suspension and Cichorium intybus transformed 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.

Revisiting the versatile buckwheat: reinvigorating genetic gains through integrated breeding and genomics approach

Emerging insights in buckwheat molecular genetics allow the integration of genomics driven breeding to revive this ancient crop of immense nutraceutical potential from Asia. Out of several thousand known edible plant species, only four crops-rice, wheat, maize and potato provide the largest proportion of daily nutrition to billions of people. While these crops are the primary supplier of carbohydrates, they lack essential amino acids and minerals for a balanced nutrition. The overdependence on only few crops makes the future cropping systems vulnerable to the predicted climate change. Diversifying food resources through incorporation of orphan or minor crops in modern cropping systems is one potential strategy to improve the nutritional security and mitigate the hostile weather patterns. One such crop is buckwheat, which can contribute to the agricultural sustainability as it grows in a wide range of environments, requires relatively low inputs and possess balanced amino acid and micronutrient profiles. Additionally, gluten-free nature of protein and nutraceutical properties of secondary metabolites make the crop a healthy alternative of wheat-based diet in developed countries. Despite enormous potential, efforts for the genetic improvement of buckwheat are considerably lagged behind the conventional cereal crops. With the draft genome sequences in hand, there is a great scope to speed up the progress of genetic improvement of buckwheat. This article outlines the state of the art in buckwheat research and provides concrete perspectives how modern breeding approaches can be implemented to accelerate the genetic gain. Our suggestions are transferable to many minor and underutilized crops to address the issue of limited genetic gain and low productivity.

Enhancement of silymarin and phenolic compound accumulation in tissue culture of Milk thistle using elicitor feeding and hairy root cultures

In the present study, the effects of the metabolite elicitors chitosan, methyl jasmonate (MeJA) and salicylic acid (SA) as well as the hairy root transformation were tested for silymarin and phenolic compound accumulation in in vitro cultures of Milk thistle. For callus induction, leaf explants were cultured on MS medium supplemented with 5 mg/l NAA + 2 mg/l Kin + 0.1 mg/l GA3. Chitosan, SA and MeJA were added separately in three concentrations 200, 400 and 800 mg/l; 10, 20 and 40 mg/l; 20, 40 and 80 mg/l, respectively, to hormone free B5 medium. Alternatively, cotyledons of 12 day old seedlings were transformed with Agrobacterium rhizogenes A4 strain. Overall, increasing the concentrations of the three elicitors dramatically increased the total silymarin content. Remarkably, the elicitors mainly enhanced the accumulation of silybine A&B that were not detected in un-treated callus culture (control). In addition, the hairy root culture triggered the accumulation of silybine A&B, and silydianin, which was not detected in the non-transgenic roots. The hairy root culture was superior in production of the phenolic compounds in comparison to the control and elicitor treatments. The hairy root cultures showed also higher antioxidant capacities than non-transformed cultures and/or chemically elicited-callus cultures. Thus hairy root provide instrumental in enhancing the production of economically valuable metabolite.

Efficient Rutin and Quercetin Biosynthesis through Flavonoids-Related Gene Expression in Fagopyrum tataricum Gaertn. Hairy Root Cultures with UV-B Irradiation

Transformed hairy roots had been efficiently induced from the seedlings of Fagopyrum tataricum Gaertn. due to the infection of Agrobacterium rhizogenes. Hairy roots were able to display active elongation with high root branching in 1/2 MS medium without growth regulators. The stable introduction of rolB and aux1 genes of A. rhizogenes WT strain 15834 into F. tataricum plants was confirmed by PCR analysis. Besides, the absence of virD gene confirmed hairy root was bacteria-free. After six different media and different sources of concentration were tested, the culturing of TB7 hairy root line in 1/2 MS liquid medium supplemented with 30 g l(-1) sucrose for 20 days resulted in a maximal biomass accumulation (13.5 g l(-1) fresh weight, 1.78 g l(-1) dry weight) and rutin content (0.85 mg g(-1)). The suspension culture of hairy roots led to a 45-fold biomass increase and a 4.11-fold rutin content increase in comparison with the suspension culture of non-transformed roots. The transformation frequency was enhanced through preculturing for 2 days followed by infection for 20 min. The UV-B stress treatment of hairy roots resulted in a striking increase of rutin and quercetin production. Furthermore, the hairy root lines of TB3, TB7, and TB28 were chosen to study the specific effects of UV-B on flavonoid accumulation and flavonoid biosynthetic gene expression by qRT-PCR. This study has demonstrated that the UV-B radiation was an effective elicitor that dramatically changed in the transcript abundance of ftpAL, FtCHI, FtCHS, FtF3H, and FtFLS-1 in F. tataricum hairy roots.