Comparative transcriptome analysis reveals the key genes and pathways involved in drought stress response of two wheat (Triticum aestivum L) varieties.

Drought stress results in significant yield losses in wheat production. Although studies have reported a number of wheat drought tolerance genes, a deeper understanding of the tolerance mechanisms is required for improving wheat tolerance against drought stress. In this study, we found that "Deguo 2" exhibited higher tolerance to drought than "Truman". Transcriptomics analysis enabled identification of 6084 and 7146 differentially expressed genes (DEGs), mainly mapping flavonoid biosynthesis, plant hormone, phenolamides and antioxidant pathways and revealed altered expression levels of about 700 genes. Exogenous melatonin application enhanced wheat tolerance against drought stress. Co-expression analysis showed that bHLH and bZIP transcription factors may be involved in the regulation of various pathway genes. Take together, these results provide new insights for us on exploring the crosstalk between phytohormones and secondary metabolites, and will deepen the understanding of the complex tolerance mechanisms against drought stress in wheat.

A case study of the diet-microbiota-parasite interplay in bumble bees.

AIMS: Diets and parasites influence the gut bacterial symbionts of bumble bees, but potential interactive effects remain overlooked. The main objective of this study was to assess the isolated and interactive effects of sunflower pollen, its phenolamides, and the widespread trypanosomatid Crithidia sp. on the gut bacterial symbionts of Bombus terrestris males. METHODS AND RESULTS: Bumble bee males emerged in microcolonies fed on either (i) willow pollen (control), (ii) sunflower pollen, or (iii) willow pollen spiked with phenolamide extracts from sunflower pollen. These microcolonies were infected by Crithidia sp. or were pathogen-free. Using 16S rRNA amplicon sequencing (V3-V4 region), we observed a significant alteration of the beta diversity but not of the alpha diversity in the gut microbial communities of males fed on sunflower pollen compared to males fed on control pollen. Similarly, infection by the gut parasite Crithidia sp. altered the beta diversity but not the alpha diversity in the gut microbial communities of males, irrespective of the diet. By contrast, we did not observe any significant alteration of the beta or alpha diversity in the gut microbial communities of males fed on phenolamide-enriched pollen compared to males fed on control pollen. Changes in the beta diversity indicate significant dissimilarities of the bacterial taxa between the treatment groups, while the lack of difference in alpha diversity demonstrates no significant changes within each treatment group. CONCLUSIONS: Bumble bees harbour consistent gut microbiota worldwide, but our results suggest that the gut bacterial communities of bumble bees are somewhat shaped by their diets and gut parasites as well as by the interaction of these two factors. This study confirms that bumble bees are suitable biological surrogates to assess the effect of diet and parasite infections on gut microbial communities.

Ethylene is a local modulator of jasmonate-dependent phenolamide accumulation during Manduca sexta herbivory in Nicotiana attenuata.

Rapid reconfigurations of interconnected phytohormone signalling networks allow plants to tune their physiology to constantly varying ecological conditions. During insect herbivory, most of the induced changes in defence-related leaf metabolites are controlled by jasmonate (JA) signalling, which, in the wild tobacco Nicotiana attenuata, recruits MYB8, a transcription factor controlling the accumulation of phenolic-polyamine conjugates (phenolamides). In this and other plant species, herbivory also locally triggers ethylene (ET) production but the outcome of the JA-ET cross-talk at the level of secondary metabolism regulation has remained only superficially investigated. Here, we analysed local and systemic herbivory-induced changes by mass spectrometry-based metabolomics in leaves of transgenic plants impaired in JA, ET and MYB8 signalling. Parsing deregulations in this factorial data-set identified a network of JA/MYB8-dependent phenolamides for which impairment of ET signalling attenuated their accumulation only in locally damaged leaves. Further experiments revealed that ET, albeit biochemically interrelated to polyamine metabolism via the intermediate S-adenosylmethionine, does not alter the free polyamine levels, but instead significantly modulates phenolamide levels with marginal modulations of transcript levels. The work identifies ET as a local modulator of phenolamide accumulations and provides a metabolomics data-platform with which to mine associations among herbivory-induced signalling and specialized metabolites in N. attenuata.

Phenolamides in plants: an update on their function, regulation, and origin of their biosynthetic enzymes.

Phenolamides represent a family of specialized metabolites, consisting of the association of hydroxycinnamic acid derivatives with aliphatic or aromatic amines. Since the discovery of the first phenolamide in the late 1940s, decades of phytochemical analyses have revealed a high structural diversity for this family and a wide distribution in the plant kingdom. The occurrence of structurally diverse phenolamides in almost all plant organs has led to early hypotheses on their involvement in floral initiation and fertility, as well as plant defense against biotic and abiotic stress. In the present work, we critically review the literature ascribing functional hypotheses to phenolamides and recent evidence on the control of their biosynthesis in response to biotic stress. We additionally provide a phylogenetic analysis of the numerous N-hydroxycinnamoyltransferases involved in the synthesis of phenolamides and discuss the potential role of other enzyme families in their diversification. The data presented suggest multiple evolutionary events that contributed to the extension of the taxonomic distribution and diversity of phenolamides.

Systematic analysis of rice (Oryza sativa) metabolic responses to herbivory.

Plants defend against attack from herbivores by direct and indirect defence mechanisms mediated by the accumulation of phytoalexins and release of volatile signals, respectively. While the defensive arsenals of some plants, such as tobacco and Arabidopsis are well known, most of rice's (Oryza sativa) defence metabolites and their effectiveness against herbivores remain uncharacterized. Here, we used a non-biassed metabolomics approach to identify many novel herbivory-regulated metabolic signatures in rice. Most were up-regulated by herbivore attack while only a few were suppressed. Two of the most prominent up-regulated signatures were characterized as phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine. PAs accumulated in response to attack by both chewing insects, i.e. feeding of the lawn armyworm (Spodoptera mauritia) and the rice skipper (Parnara guttata) larvae, and the attack of the sucking insect, the brown planthopper (Nilaparvata lugens, BPH). In bioassays, BPH insects feeding on 15% sugar solution containing p-coumaroylputrescine or feruloylputrescine, at concentrations similar to those elicited by heavy BPH attack in rice, had a higher mortality compared to those feeding on sugar diet alone. Our results highlight PAs as a rapidly expanding new group of plant defence metabolites that are elicited by herbivore attack, and deter herbivores in rice and other plants.

Molecular evidence for biochemical diversification of phenolamide biosynthesis in rice plants.

Two phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine strongly accumulate in rice (Oryza sativa cv. Nipponbare) leaves subjected to attack of chewing and sucking herbivores. Here we identified and characterized in vitro three novel rice genes that mediated coumaroyl-CoA/feruloyl-CoA conjugation to polyamines, putrescine and agmatine. Interestingly, two genes were highly specific for their polyamine substrates, encoding putrescine N-hydroxycinnamoyltransferase and agmatine N-hydroxycinnamoyltransferase, while the third enzyme could use both polyamines and it was therefore annotated as putrescine/agmatine N-hydroxycinnamoyltransferase. All genes were preferentially expressed in rice roots and developing flowers, and in addition, the putrescine/agmatine N-hydroxycinnamoyltransferase transcripts were strongly induced by wounding in the young rice leaves. Because the wound response of this gene was only partially suppressed in the jasmonoyl-L-isoleucine deficient plants (Osjar1), it suggests that its upregulation (as well as inducible PAs in rice) may be largely independent of jasmonoyl-L-isoleucine signaling pathway. The finding of three closely related genes with a similar and/or overlapping activity in PA biosynthesis provides another striking example of rapid diversification of plant metabolism in response to environmental stresses in nature.

Revealing insect herbivory-induced phenolamide metabolism: from single genes to metabolic network plasticity analysis.

The phenylpropanoid metabolic space comprises a network of interconnected metabolic branches that contribute to the biosynthesis of a large array of compounds with functions in plant development and stress adaptation. During biotic challenges, such as insect attack, a major rewiring of gene networks associated with phenylpropanoid metabolism is observed. This rapid reconfiguration of gene expression allows prioritized production of metabolites that help the plant solve ecological problems. Phenolamides are a group of phenolic derivatives that originate from diversion of hydroxycinnamoyl acids from the main phenylpropanoid pathway after N-acyltransferase-dependent conjugation to polyamines or aryl monoamines. These structurally diverse metabolites are abundant in the reproductive organs of many plants, and have recently been shown to play roles as induced defenses in vegetative tissues. In the wild tobacco, Nicotiana attenuata, in which herbivory-induced regulation of these metabolites has been studied, rapid elevations of the levels of phenolamides that function as induced defenses result from a multi-hormonal signaling network that re-shapes connected metabolic pathways. In this review, we summarize recent findings in the regulation of phenolamides obtained by mass spectrometry-based metabolomics profiling, and outline a conceptual framework for gene discovery in this pathway. We also introduce a multifactorial approach that is useful in deciphering metabolic pathway reorganizations among tissues in response to stress.

Characterization of a spermidine hydroxycinnamoyltransferase in Malus domestica highlights the evolutionary conservation of trihydroxycinnamoyl spermidines in pollen coat of core Eudicotyledons.

Phenolamides, so called hydroxycinnamic acid amides, are specialized metabolites produced in higher plants, involved in development, reproduction and serve as defence compounds in biotic interactions. Among them, trihydroxycinnamoyl spermidine derivatives were initially found to be synthetized by a spermidine hydroxycinnamoyltransferase (AtSHT) in Arabidopsis thaliana and to accumulate in the pollen coat. This study reports the identification, in Malus domestica, of an acyltransferase able to complement the sht mutant of Arabidopsis. The quantitative RT-PCR expression profile of MdSHT reveals a specific expression in flowers coordinated with anther development and tapetum cell activities. Three phenolamides including N (1),N (5),N (10)-tricoumaroyl spermidine and N (1),N (5)-dicoumaroyl-N (10)-caffeoyl spermidine identified by LC/MS, were shown to accumulate specifically in pollen grain coat of apple tree. Moreover, in vitro biochemical characterization confirmed MdSHT capacity to synthesize tri-substituted spermidine derivatives with a substrate specificity restricted to p-coumaroyl-CoA and caffeoyl-CoA as an acyl donor. Further investigations of the presence of tri-substituted hydroxycinnamoyl spermidine conjugates in higher plants were performed by targeted metabolic analyses in pollens coupled with bioinformatic analyses of putative SHT orthologues in a wide range of available plant genomes. This work highlights a probable early evolutionary appearance in the common ancestral core Eudicotyledons of a novel enzyme from the BAHD acyltransferase superfamily, dedicated to the synthesis of trihydroxycinnamoyl spermidines in pollen coat. This pathway was maintained in most species; however, recent evolutionary divergences have appeared among Eudicotyledons, such as an organ reallocation of SHT gene expression in Fabales and a loss of SHT in Malvales and Cucurbitales.

Two gene clusters and their positive regulator SlMYB13 that have undergone domestication-associated negative selection control phenolamide accumulation and drought tolerance in tomato.

Among plant metabolites, phenolamides, which are conjugates of hydroxycinnamic acid derivatives and polyamines, play important roles in plant adaptation to abiotic and biotic stresses. However, the molecular mechanisms underlying phenolamide metabolism and regulation as well as the effects of domestication and breeding on phenolamide diversity in tomato remain largely unclear. In this study, we performed a metabolite-based genome-wide association study and identified two biosynthetic gene clusters (BGC7 and BGC11) containing 12 genes involved in phenolamide metabolism, including four biosynthesis genes (two 4CL genes, one C3H gene, and one CPA gene), seven decoration genes (five AT genes and two UGT genes), and one transport protein gene (DTX29). Using gene co-expression network analysis we further discovered that SlMYB13 positively regulates the expression of two gene clusters, thereby promoting phenolamide accumulation. Genetic and physiological analyses showed that BGC7, BGC11 and SlMYB13 enhance drought tolerance by enhancing scavenging of reactive oxygen species and increasing abscisic acid content in tomato. Natural variation analysis suggested that BGC7, BGC11 and SlMYB13 were negatively selected during tomato domestication and improvement, leading to reduced phenolamide content and drought tolerance of cultivated tomato. Collectively, our study discovers a key mechanism of phenolamide biosynthesis and regulation in tomato and reveals that crop domestication and improvement shapes metabolic diversity to affect plant environmental adaptation.

Combining association with linkage mapping to dissect the phenolamides metabolism of the maize kernel.

Phenolamides are important secondary metabolites in plant species. They play important roles in plant defense responses against pathogens and insect herbivores, protection against UV irradiation and floral induction and development. However, the accumulation and variation in phenolamides content in diverse maize lines and the genes responsible for their biosynthesis remain largely unknown. Here, we combined genetic mapping, protein regulatory network and bioinformatics analysis to further enhance the understanding of maize phenolamides biosynthesis. Sixteen phenolamides were identified in multiple populations, and they were all significantly correlated with one or several of 19 phenotypic traits. By linkage mapping, 58, 58, 39 and 67 QTLs, with an average of 3.9, 3.6, 3.6 and 4.2 QTLs for each trait were mapped in BBE1, BBE2, ZYE1 and ZYE2, explaining 9.47%, 10.78%, 9.51% and 11.40% phenotypic variation for each QTL on average, respectively. By GWAS, 39 and 36 significant loci were detected in two different environments, 3.3 and 2.8 loci for each trait, explaining 10.00% and 9.97% phenotypic variation for each locus on average, respectively. Totally, 58 unique candidate genes were identified, 31% of them encoding enzymes involved in amine and derivative metabolic processes. Gene Ontology term analysis of the 358 protein-protein interrelated genes revealed significant enrichment in terms relating to cellular nitrogen metabolism, amine metabolism. GRMZM2G066142, GRMZM2G066049, GRMZM2G165390 and GRMZM2G159587 were further validated involvement in phenolamides biosynthesis. Our results provide insights into the genetic basis of phenolamides biosynthesis in maize kernels, understanding phenolamides biosynthesis and its nutritional content and ability to withstand biotic and abiotic stress.

New insights into bee pollen: Nutrients, phytochemicals, functions and wall-disruption.

Bee pollen is hailed as a treasure trove of human nutrition and has progressively emerged as the source of functional food and medicine. This review conducts a compilation of nutrients and phytochemicals in bee pollen, with particular emphasis on some ubiquitous and unique phenolamides and flavonoid glycosides. Additionally, it provides a concise overview of the diverse health benefits and therapeutic properties of bee pollen, particularly anti-prostatitis and anti-tyrosinase effects. Furthermore, based on the distinctive structural characteristics of pollen walls, a substantial debate has persisted in the past concerning the necessity of wall-disruption. This review provides a comprehensive survey on the necessity of wall-disruption, the impact of wall-disruption on the release and digestion of nutrients, and wall-disruption techniques in industrial production. Wall-disruption appears effective in releasing and digesting nutrients and exploiting bee pollen's bioactivities. Finally, the review underscores the need for future studies to elucidate the mechanisms of beneficial effects. This paper will likely help us gain better insight into bee pollen to develop further functional foods, personalized nutraceuticals, cosmetics products, and medicine.

Barley-derived beer brewing by-products contain a high diversity of hydroxycinnamoylagmatines and their dimers.

To aid valorisation of beer brewing by-products, more insight into their composition is essential. We have analysed the phenolic compound composition of four brewing by-products, namely barley rootlets, spent grain, hot trub, and cold trub. The main phenolics detected were hydroxycinnamoylagmatines and dimers thereof. Barley rootlets contained the highest hydroxycinnamoylagmatine content and cold trub the highest dimer content. Additionally, variations in (dimeric) hydroxycinnamoylagmatine composition and content were observed in fourteen barley rootlet samples. The most abundant compound in all rootlets was the glycosylated 4-O-7'/3-8'-linked heterodimer of coumaroylagmatine and feruloylagmatine, i.e. CouAgm-4-O-7'/3-8'-(4'Hex)-DFerAgm. Structures of glycosylated and hydroxylated derivatives of coumaroylagmatine were elucidated by NMR spectroscopy after their purification from a rootlet extract. An MS-based decision tree was developed, which aids in identifying hydroxycinnamoylagmatine dimers in complex mixtures. In conclusion, this study shows that the diversity of phenolamides and (neo)lignanamides in barley-derived by-products is larger than previously reported.

Contribution of phenolamides to the quality evaluation in Lycium spp.

ETHNOPHARMACOLOGICAL RELEVANCE: Goji berry is a general term for various plant species in the genus Lycium. Goji has long been historically used in traditional Chinese medicines. Goji is a representative tonic medicine that has the effects of nourishing the liver and kidney and benefiting the essence and eyesight. It has been widely used in the treatment of various diseases, including tinnitus, impotence, spermatorrhea and blood deficiency, since ancient times. AIM OF THE REVIEW: This study aims to comprehensively summarize the quality evaluation methods of the main compounds in goji, as well as the current research status of the phenolamides in goji and their pharmacological effects, to explore the feasibility of using phenolamides as quality control markers and thus improve the quality and efficacy in goji. MATERIALS AND METHODS: Relevant literature from PubMed, Web of Science, Science Direct, CNKI and other databases was comprehensively collected, screened and summarized. RESULTS: According to the collected literature, the quality evaluation markers of goji in the Pharmacopoeia of the People's Republic of China are Lycium barbarum polysaccharide (LBP) and betaine. As a result of its structure complexity, only the total level of LBP can be determined, while betaine is not prominent in the pharmacological action of goji and lacks species distinctiveness. Neither of them can well explain the quality of goji. KuA and KuB are commonly used as quality evaluation markers of the Lycii cortex because of their high levels and suitable pharmacological activity. Goji is rich in polyphenols, carotenoids and alkaloids. Many studies have used the above compounds to establish quality evaluation methods but the results have not been satisfactory. Phenolamides have often been neglected in previous studies because of their low single compound levels and high separation difficulty. However, in recent years, the favorable pharmacological activities of phenolamides have been gradually recognized, and studies on goji phenolamides are greatly increasing. In addition, phenolamides have higher species distinctiveness than other compounds and can be combined with other compounds to better evaluate the quality of goji to improve its average quality. CONCLUSIONS: The phenolamides in the goji are rich and play a key role in antioxidation, anti-inflammation, neuroprotection and immunomodulation. As a result of their characteristics, it is suitable to evaluate the quality by quantitative analysis of multi-components by single-marker and fingerprint. This method can be combined with other techniques to improve the quality evaluation system of goji, which lays a foundation for their effectiveness and provides a reference for new quality evaluation methods of similar herbal medicines.

Barley Phenolamides Effectively Scavenge Harmful Methylglyoxal In Vitro and in Mice.

SCOPE: Methylglyoxal (MGO), a harmful reactive dicarbonyl, is involved in the pathogenesis and development of diabetes and diabetic complications. The goal of this study is to determine whether bioactive phenolamides in barley, p-coumaroylagmatine (pCAA) and feruloylagmatine (FAA), which share a similar guanidine group to diabetic drug metformin, have the capacity to detoxify MGO. METHODS AND RESULTS: In this study, the MGO-trapping abilities of these two phenolamides both in vitro and in mice are evaluated. It is found that in vitro anti-MGO capacities of pCAA and FAA are comparable to that of metformin, and both phenolamides could rapidly scavenge MGO via forming mono- and di-MGO adducts validated by in-house synthesized standards and interpretation of respective LC-MSn (n = 2-3) data. Furthermore, mono-MGO conjugates of phenolamides are detected from feces and urine of mice after oral administration of the corresponding phenolamides. CONCLUSION: These findings suggest that barley phenolamides may have the potentials to be developed as alternative therapeutics to prevent the development of MGO-associated diabetes and diabetic complications.

Thermal Stability and Antioxidant Activity of Bioactive Compounds in Bread Enriched with Bee Pollen and Bee Bread.

Bee pollen (BP) and bee bread (BB) are natural food sources containing a wide variety of bioactive compounds, complementing their rich nutritional composition. These bee products are being explored to empower functional foods, with the term functionality being dependent on the bioactive compounds added to the food matrix. However, there is not enough evidence of the effect of heat on these compounds during food processing and production and how it impacts their biological activity. Here, we enriched traditional bread by adding BP and BB at different proportions of 1 to 5% and tested the thermal stability of their bioactive compounds through several spectroscopic and chromatographic analyses. Adding bee pollen and bee bread to bread resulted in a 4 and 5-fold increase in total phenolic content, respectively. While not all the 38 phenolic and phenolamide compounds identified in the raw BP and BB were detected in the processed bread, phenolamides were found to be more resilient to baking and heat treatment than flavonoids. Still, the enriched bread's antioxidant activity improved with the addition of BP and BB. Therefore, incorporating bee products into heat-treated products could enhance the functionality of staple foods and increase the accessibility to these natural products.

Phenolamide and flavonoid glycoside profiles of 20 types of monofloral bee pollen.

This study aimed at investigating phenolamides and flavonoid glycosides in 20 types of monofloral bee pollen. The plant origins of pollen samples were determined by DNA barcoding, with the purities to over 70 %. The 31 phenolamides and their 33 cis/trans isomers, and 25 flavonoid glycosides were identified; moreover, 19 phenolamides and 14 flavonoid glycosides as new-found compounds in bee pollen. All phenolics and flavonoids are present in the amidation or glycosylation form. The MS/MS cleavage modes of phenolamides and flavonoid glycosides were summarized. Isorhamnetin-3-O-gentiobioside presented the highest levels 23.61 mg/g in apricot pollen. Phenolamides in 11 types of pollen constituted over 1 % of the total weight, especially 3.9 % in rose and 2.8 % in pear pollen. Tri-p-coumaroyl spermidine and di-p-coumaroyl-caffeoyl spermidine respectively accounted for over 2.6 % of the total weight in pear and rose pollen. The richness in phenolamides and flavonoid glycosides can offer bee pollen more bioactivities as functional foods.

A Comprehensive Study on the Chemical Characterization and Neuroprotective Evaluation of Pracaxi Nuts Extracts Obtained by a Sustainable Approach.

The Amazonian Pentaclethra macroloba (Willd.) Kuntze nuts contain a lipidic fraction with health-promoting effects, but little is known about the bioactivity of other constituents. In this study, the lipidic fraction obtained using supercritical fluid extraction (SFE) with CO2 was chemically characterized by using lipidomics techniques. The SFE-CO2 residue, named as pracaxi cake, was re-extracted by pressurized liquid extraction following a biorefinery approach. Using a response surface methodology and based on the extraction yield and different in vitro assays, two optimum conditions were obtained: 80% and 12.5% of ethanol at 180 °C. Under these conditions, extraction yield and different in vitro measurements related to neuroprotection were assessed. Chemical characterization of these extracts suggested the presence of triterpenoid saponins and spermidine phenolamides, which were not previously reported in pracaxi nuts. These results suggest that pracaxi oil extraction by-products are a valuable source of bioactive compounds with neuroprotective potential.

Function of hydroxycinnamoyl transferases for the biosynthesis of phenolamides in rice resistance to Magnaporthe oryzae.

Phenolamide (PA) metabolites play important roles in the interaction between plants and pathogens. The putrescine hydroxycinnamoyl transferase genes OsPHT3 and OsPHT4 positively regulate rice cell death and resistance to Magnaporthe oryzae. The bZIP transcription factor APIP5, a negative regulator of cell death and rice immunity, directly binds to the OsPHT4 promoter to regulate putrescine-derived PAs. Whether other hydroxycinnamoyl transferase (HT) genes also participate in APIP5-mediated immunity remains unclear. Surprisingly, we find that genes encoding agmatine hydroxycinnamoyl transferases OsAHT1 and OsAHT2, tryptamine hydroxycinnamoyl transferases OsTBT1 and OsTBT2, and tyramine hydroxycinnamoyl transferases OsTHT1 and OsTHT2, responsible for the biosynthesis of polyamine-derived PAs are all up-regulated in APIP5-RNAi transgenic plants compared with segregated wild-type rice. Furthermore, both OsAHT1/2 and OsTBT1/2 are induced during M. oryzae infection, showing expression patterns similar to those previously reported for OsTHT1/2 and OsPHT3/4. Transgenic plants overexpressing either OsAHT2-GFP or OsTBT1-GFP show enhanced resistance against M. oryzae and accumulated more PA metabolites and lignin compared with wild-type plants. Interestingly, as demonstrated for OsPHT4, APIP5 directly binds to the promoters of OsAHT1/2, OsTBT1/2, and OsTHT1/2, repressing their transcription. Together, these results indicate that the HT genes are common targets of APIP5 and that PAs play critical roles in rice immunity.

Widely targeted metabolomics analysis reveals the effect of fermentation on the chemical composition of bee pollen.

Microbial fermentation can break the bee pollen wall. However, the global profiling of bee pollen metabolites under fermentation remains unclear. This study aims to comprehensively elucidate the changes in the composition of bee pollen after microbial fermentation. Ultra-performance liquid chromatography-electron spray ionization-mass spectrometry (UPLC-ESI-MS) based on widely targeted metabolomics analysis was used to compare the chemical composition of unfermented bee pollen (UBP) and fermented bee pollen (FBP). Among the 890 metabolites detected, a total of 668 differential metabolites (classified into 17 categories) were identified between UBP and FBP. Fermentation significantly increased the contents of primary metabolites such as 74 amino acids and derivatives, 42 polyunsaturated fatty acids and 66 organic acids, as well as some secondary metabolites such as 38 phenolic acids, 80 flavone aglycones and 22 phenolamides. The results indicate that fermentation is a promising strategy to improve the nutritional value of bee pollen.

Metabolome-Based Genome-Wide Association Study Provides Genetic Insights Into the Natural Variation of Foxtail Millet.

The plant metabolome is considered as a bridge between the genome and the phenome and is essential for the interaction between plant growth and the plant environment. Here, we used the liquid chromatography-tandem mass spectrometry method to perform a widely targeted metabolomics analysis of 150 millet germplasm and simultaneous identification and quantification of 330 annotated metabolites. Comparing the metabolic content of different millets revealed significant natural variation of both primary and secondary metabolites, including flavonoids, phenolamides, hydroxycinnamoyl derivatives, nucleotides, and lipids, in the millets from India and the north and south of China; among them, some of the flavonoids are the most prominent. A total of 2.2 TB sequence data were obtained by sequencing 150 accessions of foxtail millet using the Illumina platform. Further digging into the genetic basis of metabolites by mGWAS analysis found that cyanidin 3-O-glucoside and quercetin O-acetylhexside are concentratedly located at 43.55 Mb on chromosome 5 and 26.9 Mb on chromosome 7, and two Lc were mined as candidate genes, respectively. However, the signals of luteolin 7-O-glucoside and kaempferol 3-O-glucoside were also detected at 14.36 Mb on chromosome 3, and five glycosyltransferase genes on this loci were deemed to regulate their content. Our work is the first research to use mGWAS in millet, and it paves the way for future dissection of complex physiological traits in millet.