Transcriptome Analysis Reveals the Molecular Mechanism of GABA Accumulation during Quinoa (Chenopodium quinoa Willd.) Germination

γ-Aminobutyric Acid (GABA)-enriched Hemp Milk by Solid-state Co-fermentation and Germination Bioprocesses

This study introduces the concept of developing a functional hemp drink enriched with γ-Aminobutyric acid (GABA) to enhance its nutritional value and functional properties utilizing Solid-State (SSF) co-Fermentation by Lactobacillus casei and Bacillus subtilis and germination bioprocesses. Bioprocesses may offer an alternative solution to challenges in hemp milk, such as product instability and the use of additives. Notably, the hemp milk produced through the germination for three days or co-fermentation processes yielded the highest GABA content of 79.84 and 102.45 mg/100 mL, respectively, compared to the untreated milk. These bioactive milk samples exhibited higher zeta potential and soluble protein content and also reduced solid particle sedimentation and droplet sizes (D4,3 and D3,2) compared to the untreated milk. Furthermore, the peptide, total phenolic content, and antioxidant activity of the produced GABA-enriched kinds of milk surpassed those of the untreated milk. Overall, the SSF and germination processes present a promising alternative for producing stable milk analogs with enhanced health-boosting properties.

Metabolome and Transcriptome Association Analysis Reveals Mechanism of Synthesis of Nutrient Composition in Quinoa (Chenopodium quinoa Willd.) Seeds

Quinoa (Chenopodium quinoa Willd.) seeds are rich in nutrition, superior to other grains, and have a high market value. However, the biosynthesis mechanisms of protein, starch, and lipid in quinoa grain are still unclear. The objective of this study was to ascertain the nutritional constituents of white, yellow, red, and black quinoa seeds and to employ a multi-omics approach to analyze the synthesis mechanisms of these nutrients. The findings are intended to furnish a theoretical foundation and technical support for the biological breeding of quinoa in China. In this study, the nutritional analysis of white, yellow, red, and black quinoa seeds from the same area showed that the nutritional contents of the quinoa seeds were significantly different, and the protein content increased with the deepening of color. The protein content of black quinoa was the highest (16.1 g/100 g) and the lipid content was the lowest (2.7 g/100 g), among which, linoleic acid was the main fatty acid. A combined transcriptome and metabolome analysis exhibited that differentially expressed genes were enriched in "linoleic acid metabolism", "unsaturated fatty acid biosynthesis", and "amino acid biosynthesis". We mainly identified seven genes involved in starch synthesis (LOC110716805, LOC110722789, LOC110738785, LOC110720405, LOC110730081, LOC110692055, and LOC110732328); five genes involved in lipid synthesis (LOC110701563, LOC110699636, LOC110709273, LOC110715590, and LOC110728838); and nine genes involved in protein synthesis (LOC110710842, LOC110720003, LOC110687170, LOC110716004, LOC110702086, LOC110724454 LOC110724577, LOC110704171, and LOC110686607). The data presented in this study based on nutrient, transcriptome, and metabolome analyses contribute to an enhanced understanding of the genetic regulation of seed quality traits in quinoa, and provide candidate genes for further genetic improvements to improve the nutritional value of quinoa seeds.

Impacts of Arbuscular Mycorrhizal Fungi on Metabolites of an Invasive Weed Wedelia trilobata

The invasive plant Wedelia trilobata benefits in various aspects, such as nutrient absorption and environmental adaptability, by establishing a close symbiotic relationship with arbuscular mycorrhizal fungi (AMF). However, our understanding of whether AMF can benefit W. trilobata by influencing its metabolic profile remains limited. In this study, Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted to analyze the metabolites of W. trilobata under AMF inoculation. Metabolomic analysis identified 119 differentially expressed metabolites (DEMs) between the groups inoculated with AMF and those not inoculated with AMF. Compared to plants with no AMF inoculation, plants inoculated with AMF showed upregulation in the relative expression of 69 metabolites and downregulation in the relative expression of 50 metabolites. AMF significantly increased levels of various primary and secondary metabolites in plants, including amino acids, organic acids, plant hormones, flavonoids, and others, with amino acids being the most abundant among the identified substances. The identified DEMs mapped 53 metabolic pathways, with 7 pathways strongly influenced by AMF, particularly the phenylalanine metabolism pathway. Moreover, we also observed a high colonization level of AMF in the roots of W. trilobata, significantly promoting the shoot growth of this plant. These changes in metabolites and metabolic pathways significantly affect multiple physiological and biochemical processes in plants, such as free radical scavenging, osmotic regulation, cell structure stability, and material synthesis. In summary, AMF reprogrammed the metabolic pathways of W. trilobata, leading to changes in both primary and secondary metabolomes, thereby benefiting the growth of W. trilobata and enhancing its ability to respond to various biotic and abiotic stressors. These findings elucidate the molecular regulatory role of AMF in the invasive plant W. trilobata and provide new insights into the study of its competitive and stress resistance mechanisms.

Recent advances in the biosynthesis and industrial biotechnology of Gamma-amino butyric acid

GABA (Gamma-aminobutyric acid), a crucial neurotransmitter in the central nervous system, has gained significant attention in recent years due to its extensive benefits for human health. The review focused on recent advances in the biosynthesis and production of GABA. To begin with, the investigation evaluates GABA-producing strains and metabolic pathways, focusing on microbial sources such as Lactic Acid Bacteria, Escherichia coli, and Corynebacterium glutamicum. The metabolic pathways of GABA are elaborated upon, including the GABA shunt and critical enzymes involved in its synthesis. Next, strategies to enhance microbial GABA production are discussed, including optimization of fermentation factors, different fermentation methods such as co-culture strategy and two-step fermentation, and modification of the GABA metabolic pathway. The review also explores methods for determining glutamate (Glu) and GABA levels, emphasizing the importance of accurate quantification. Furthermore, a comprehensive market analysis and prospects are provided, highlighting current trends, potential applications, and challenges in the GABA industry. Overall, this review serves as a valuable resource for researchers and industrialists working on GABA advancements, focusing on its efficient synthesis processes and various applications, and providing novel ideas and approaches to improve GABA yield and quality.

Transcriptome Analysis Reveals the Mechanisms of Accumulation and Conversion of Folate Derivatives during Germination of Quinoa (Chenopodium quinoa Willd.) Seeds

Folate was enriched during quinoa germination, while molecular mechanisms were not well understood. In this study, three quinoa varieties were selected for germination, and changes in substrate content and enzyme activity of the folate biosynthesis pathway were monitored. 5-Methyltetrahydrofolate (5-CH3-THF) and 5-formyltetrahydrofolate (5-CHO-THF) were significantly enriched in quinoa sprouts. Among the selected varieties, QL-2 exhibited the lowest content of the oxidation product MeFox and the highest total folate content. Based on transcriptome analysis, the p-ABA branch was found to be crucial for folate accumulation, while the pterin branch served as a key control point for the one carbon pool by folate pathway, which limited further folate biosynthesis. In the one carbon pool by folate pathway, genes CqMTHFR and CqAMT significantly contributed to the enrichment of 5-CH3-THF and 5-CHO-THF. Findings gained here would facilitate the potential application of quinoa sprouts as an alternative strategy for folate supplementation.

Assessment and comparison of nutritional qualities of thirty quinoa (Chenopodium quinoa Willd.) seed varieties

Quinoa (Chenopodium quinoa Willd.) is an ancient crop with perfect nutritional composition and antioxidants substances. However, the current research on the nutritional quality of quinoa is limited to a small number of varieties or a single origin. In this study, we aimed at providing a detailed evaluation of abundant nutrients of quinoa seeds from thirty varieties with different color in different origins, including soluble protein, soluble sugar, amino acid, vitamin, fatty acid and saponin. Results showed that there were significant differences in the contents of γ-aminobutyric acid (6.67-78.67 mg/100 g DW) and vitamin C (11.675-105.135 mg/100 g DW) in quinoa seeds. Here, we scored thirty quinoa seeds using a weighted average score system first time and identified four varieties, black quinoa JQ-00145, red quinoa JQ-00125 and two white quinoa JQ-00005/JQ-00077, with superior nutritional quality and oxidation resistance. The results of this study will provide theoretical guidance for consumption of quinoa.

Microbial-Derived γ-Aminobutyric Acid: Synthesis, Purification, Physiological Function, and Applications

γ-Aminobutyric acid (GABA) is an important nonprotein amino acid that extensively exists in nature. At present, GABA is mainly obtained through chemical synthesis, plant enrichment, and microbial production, among which microbial production has received widespread attention due to its safety and environmental benefits. After using microbial fermentation to obtain GABA, it is necessary to be isolated and purified to ensure its quality and suitability for various industries such as food, agriculture, livestock, pharmaceutics, and others. This article provides a comprehensive review of the different sources of GABA, including its presence in nature and the synthesis methods. The factors affecting the production of microbial-derived GABA and its isolation and purification methods are further elucidated. Moreover, the main physiological functions of GABA and its application in different fields are also reviewed. By advancing our understanding of GABA, we can unlock its full potential and further utilize it in various fields to improve human health and well-being.

Multi-omics analysis provides insights intro lysine accumulation in quinoa (Chenopodium quinoa Willd.) sprouts

Lysine, the first limiting essential amino acid, the deficiency of which seriously affects the health of human and animals. In this study, quinoa germination significantly increased the nutrients, especially lysine content. To better understanding the underlying molecular mechanism of lysine biosynthesis, isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics, RNA-sequencing (RNA-Seq) technology and liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) platform-based phytohormones analyses were conducted. Through proteome analyses, a total of 11,406 differentially expressed proteins were identified, which were mainly related to secondary metabolites. The lysine-rich storage globulins and endogenous phytohormones probably contributed the increased lysine content in quinoa during germination. Furthermore, aspartic acid semialdehyde dehydrogenase is essential for lysine synthesis in addition to aspartate kinase and dihydropyridine dicarboxylic acid synthase. Protein-protein interaction analysis indicated lysine biosynthesis is associated with "amino metabolism" and "starch and sucrose metabolism". Above all, our study screens the candidate genes participated in lysine accumulation and explores the factors affected lysine biosynthesis by multi-omics analysis. These information not only paves a foundation for breeding lysine-rich quinoa sprouts but also provides valuable multi-omics resource to explore the characteristic of nutrients during quinoa germination.

Recent advances in physiochemical changes, nutritional value, bioactivities, and food applications of germinated quinoa: A comprehensive review

The production and consumption of functional foods has become an essential food industry trend. Due to its high nutritional content, quinoa is regarded as a super pseudocereal for the development of nutritious foods. However, the presence of antinutritional factors and quinoa's distinctive grassy flavor limit its food applications. Due to its benefits in enhancing the nutritional bioavailability and organoleptic quality of quinoa, germination has garnered significant interest. To date, there is no systematic review of quinoa germination and the health benefits of germinated quinoa. This review details the nutritional components and bioactivities of germinated quinoa, as well as the potential mechanisms for the accumulation of bioactive compounds during the germination process. Additionally, evidence supporting the health benefits of germinated quinoa, the current status of related product development, and perspectives for future research are presented. Thus, our research is likely to provide theoretical support for the use of germinated quinoa resources.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Quinoa (Chenopodium quinoa Willd) Bran Saponins Alleviate Hyperuricemia and Inhibit Renal Injury by Regulating the PI3K/AKT/NFκB Signaling Pathway and Uric Acid Transport

Triterpenoids derived from natural products can exert antihyperuricemic effects. Here, we investigated the antihyperuricemic activity and mechanism of quinoa bran saponins (QBSs) in hyperuricemic mouse and cell models. The QBS4 fraction, with the highest saponin content, was used. Fourier-transform infrared, high-performance liquid chromatography, and ultrahigh-performance liquid chromatography-mass spectrometry identified 11 individual saponins in QBS4, of which the main components were hederagenin and oleanolic acid. The QBS4 effects on hyperuricemic mice (induced by adenine and potassium oxonate) were then studied. QBS4 reduced the levels of uric acid (UA), serum urea nitrogen, creatinine, and lipids in mice with hyperuricemia (HUA) and decreased renal inflammation and renal damage. Molecular analysis revealed that QBS4 may alleviate HUA by regulating the expression of key genes involved in the transport of UA and by inhibiting the activation of the PI3K/AKT/NFκB inflammatory signaling pathway. In conclusion, QBS4 has promise for using as a natural dietary supplement to treat and prevent HUA.

Calcium Involved in the Enrichment of γ-Aminobutyric Acid (GABA) in Broccoli Sprouts under Fructose Treatment

The effect of fructose on γ-aminobutyric acid (GABA) content and its metabolic pathway in broccoli sprouts was investigated. The results demonstrated that the fructose treatment not only significantly increased the fresh weight, GABA, and glutamate contents in sprouts, but also promoted the activity of glutamic acid decarboxylase (GAD) and the expressions of BoGAD1 and BoGAD2. Meanwhile, fructose treatment inhibited the stem length of broccoli sprouts and enhanced the abscisic acid (ABA) production in comparison with the control. Ca2+, CaM contents, and BoCaM2 expression in broccoli sprouts were also stimulated after fructose treatment. Exogenous fructose increased inositol trisphosphate (IP3) content and activated the activity of phosphatidylinositol-specific phospholipase C (PI-PLC) and the expression of BoPLC2, contributing to Ca2+ influx into the cells. These results suggested that Ca2+ played an essential role in GABA enrichment under fructose treatment, which may be associated with GAD and PI-PLC.

Validation of HPLC Method for Analysis of Gamma-Aminobutyric and Glutamic Acids in Plant Foods and Medicinal Plants

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system of mammals and plays an important role in the suppression of neurons' excitability. GABA is formed from the decarboxylation of glutamic acid (Glu), and both GABA and Glu could be considered as important biologically active food components. In the current study, we validated a HPLC method for concomitant detection of GABA and Glu in plant samples after derivatization with dansyl chloride. The validated method had high precision and a high recovery rate and was successfully used for GABA and Glu quantification in 55 plant foods (fruits, vegetables, legumes, cereals, pseudocereals, and nuts) and 19 medicinal plants. Vegetables were the most important dietary source of these amino acids, with the highest quantity of GABA found in potatoes-44.86 mg/100 g fresh weight (FW) and yellow cherry tomatoes-36.82 mg/100 g FW. The highest amount of Glu (53.58 mg/100 g FW) was found in red cherry tomatoes. Analyzed fruits were relatively poor in GABA and Glu, and European gooseberry was the richest fruit with 13.18 mg/100 g FW GABA and 10.95 mg/100 g FW Glu. Cereals, pseudocereals, nuts, and legumes contain much higher amounts of Glu than GABA. The obtained results enrich the available information on the content of gamma-aminobutyric and glutamic acids in plant foods and could be used for the development of GABA-enriched functional foods.

An overview of the nutritional profile, processing technologies, and health benefits of quinoa with an emphasis on impacts of processing

Consumers are becoming increasingly conscious of adopting a healthy lifestyle and demanding food with high nutritional values. Quinoa (Chenopodium quinoa Willd.) has attracted considerable attention and is consumed worldwide in the form of a variety of whole and processed products owing to its excellent nutritional features, including richness in micronutrients and bioactive phytochemicals, well-balanced amino acids composition, and gluten-free properties. Recent studies have indicated that the diverse utilization and final product quality of this pseudo-grain are closely related to the processing technologies used, which can result in variations in nutritional profiles and health benefits. This review comprehensively summarizes the nutritional properties, processing technologies, and potential health benefits of quinoa, suggesting that quinoa plays a promising role in enhancing the nutrition of processed food. In particular, the effects of different processing technologies on the nutritional profile and health benefits of quinoa are highlighted, which can provide a foundation for the updating and upgrading of the quinoa processing industry. It further discusses the present quinoa-based food products containing quinoa as partial or whole substitute for traditional grains.

Integrating transcriptomics and metabolomics to analyze quinoa (Chenopodium quinoa Willd.) responses to drought stress and rewatering

The crop production of quinoa (Chenopodium quinoa Willd.), the only plant meeting basic human nutritional requirements, is affected by drought stress. To better understand the drought tolerance mechanism of quinoa, we screened the drought-tolerant quinoa genotype "Dianli 129" and studied the seedling leaves of the drought-tolerant quinoa genotype after drought and rewatering treatments using transcriptomics and targeted metabolomics. Drought-treatment, drought control, rewatering-treated, and rewatered control were named as DR, DC, RW, and RC, respectively. Among four comparison groups, DC vs. DR, RC vs. RW, RW vs. DR, and RC vs. DC, we identified 10,292, 2,307, 12,368, and 3 differentially expressed genes (DEGs), and 215, 192, 132, and 19 differentially expressed metabolites (DEMs), respectively. A total of 38,670 genes and 142 pathways were annotated. The results of transcriptome and metabolome association analysis showed that gene-LOC110713661 and gene-LOC110738152 may be the key genes for drought tolerance in quinoa. Some metabolites accumulated in quinoa leaves in response to drought stress, and the plants recovered after rewatering. DEGs and DEMs participate in starch and sucrose metabolism and flavonoid biosynthesis, which are vital for improving drought tolerance in quinoa. Drought tolerance of quinoa was correlated with gene expression differences, metabolite accumulation and good recovery after rewatering. These findings improve our understanding of drought and rewatering responses in quinoa and have implications for the breeding of new drought-tolerance varieties while providing a theoretical basis for drought-tolerance varieties identification.

Heterologous Expression and Characterization of Tea (Camellia sinensis) Polyamine Oxidase Homologs and Their Involvement in Stresses

Polyamine oxidase (PAO) is a key enzyme maintaining polyamine homeostasis, which affects plant physiological activities. Until now, the gene members and function of PAOs in tea (Camellia sinenesis) have not been fully identified. Here, through the expression in Escherichia coli and Nicotiana benthamiana, we identified six genes annotated as CsPAO in tea genome and transcriptome and determined their enzyme reaction modes and gene expression profiles in tea cultivar 'Yinghong 9'. We found that CsPAO1,2,3 could catalyze spermine, thermospermine, and norspermidine, and CsPAO2,3 could catalyze spermidine in the back-conversion mode, which indicated that the precursor of γ-aminobutyric acid might originate from the oxidation of putrescin but not spermidine. We further investigated the changes of CsPAO activity with temperature and pH and their stability. Kinetic parameters suggested that CsPAO2 was the major PAO modifying polyamine composition in tea, and it could be inactivated by β-hydroxyethylhydrazine and aminoguanidine. Putrescine content and CsPAO2 expression were high in tea flowers. CsPAO2 responded to wound, drought, and salt stress; CsPAO1 might be the main member responding to cold stress; anoxia induced CsPAO3. We conclude that in terms of phylogenetic tree, enzyme characteristics, and expression profile, CsPAO2 might be the dominant CsPAO in the polyamine degradation pathway.

Genome-wide identification, phylogenetic analysis, and expression profiles of trihelix transcription factor family genes in quinoa (Chenopodium quinoa Willd.) under abiotic stress conditions

Background

The trihelix family of transcription factors plays essential roles in the growth, development, and abiotic stress response of plants. Although several studies have been performed on the trihelix gene family in several dicots and monocots, this gene family is yet to be studied in Chenopodium quinoa (quinoa).

Results

In this study, 47 C. quinoa trihelix (CqTH) genes were in the quinoa genome. Phylogenetic analysis of the CqTH and trihelix genes from Arabidopsis thaliana and Beta vulgaris revealed that the genes were clustered into five subfamilies: SIP1, GTγ, GT1, GT2, and SH4. Additionally, synteny analysis revealed that the CqTH genes were located on 17 chromosomes, with the exception of chromosomes 8 and 11, and 23 pairs of segmental duplication genes were detected. Furthermore, expression patterns of 10 CqTH genes in different plant tissues and at different developmental stages under abiotic stress and phytohormone treatment were examined. Among the 10 genes, CqTH02, CqTH25, CqTH18, CqTH19, CqTH25, CqTH31, and CqTH36, were highly expressed in unripe achenes 21 d after flowering and in mature achenes compared with other plant tissues. Notably, the 10 CqTH genes were upregulated in UV-treated leaves, whereas CqTH36 was consistently upregulated in the leaves under all abiotic stress conditions.

Conclusions

The findings of this study suggest that gene duplication could be a major driver of trihelix gene evolution in quinoa. These findings could serve as a basis for future studies on the roles of CqTH transcription factors and present potential genetic markers for breeding stress-resistant and high-yielding quinoa varieties.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08726-y.

Transcriptomic and metabolomic landscape of quinoa during seed germination

BACKGROUND

Quinoa (Chenopodium quinoa), a dicotyledonous species native to Andean region, is an emerging crop worldwide nowadays due to its high nutritional value and resistance to extreme abiotic stresses. Although it is well known that seed germination is an important and multiple physiological process, the network regulation of quinoa seed germination is largely unknown.

RESULTS

Here, we performed transcriptomic study in five stages during transition from quinoa dry seed to seedling. Together with the GC-MS based metabolome analysis, we found that seed metabolism is reprogrammed with significant alteration of multiple phytohormones (especially abscisic acid) and other nutrients during the elongation of radicels. Cell-wall remodeling is another main active process happening in the early period of quinoa seed germination. Photosynthesis was fully activated at the final stage, promoting the biosynthesis of amino acids and protein to allow seedling growth. The multi-omics analysis revealed global changes in metabolic pathways and phenotype during quinoa seed germination.

CONCLUSION

The transcriptomic and metabolomic landscape depicted here pave ways for further gene function elucidation and quinoa development in the future.

From plant biology research to technology transfer and knowledge extension: improving food quality and mitigating environmental impacts

Academic scientists face an unpredictable path from plant biology research to real-life application. Fundamental studies of γ-aminobutyrate and carotenoid metabolism, control of Botrytis infection, and the uptake and distribution of mineral nutrients illustrate that most academic research in plant biology could lead to innovative solutions for food, agriculture, and the environment. The time to application depends on various factors such as the fundamental nature of the scientific questions, the development of enabling technologies, the research priorities of funding agencies, the existence of competitive research, the willingness of researchers to become engaged in commercial activities, and ultimately the insight and creativity of the researchers. Applied research is likely to be adopted more rapidly by industry than basic research, so academic scientists engaged in basic research are less likely to participate in science commercialization. It is argued that the merit of Discovery Grant applications to the Natural Sciences and Engineering Research Council (NSERC) of Canada should not be evaluated for their potential impact on policy and (or) technology. Matching industry funds in Canada rarely support the search for knowledge. Therefore, NSERC Discovery Grants should fund basic research in its entirety.