The shikimate pathway and aromatic amino Acid biosynthesis in plants

Plant secondary metabolites against biotic stresses for sustainable crop protection

Sustainable agriculture practices are indispensable for achieving a hunger-free world, especially as the global population continues to expand. Biotic stresses, such as pathogens, insects, and pests, severely threaten global food security and crop productivity. Traditional chemical pesticides, while effective, can lead to environmental degradation and increase pest resistance over time. Plant-derived natural products such as secondary metabolites like alkaloids, terpenoids, phenolics, and phytoalexins offer promising alternatives due to their ability to enhance plant immunity and inhibit pest activity. Recent advances in molecular biology and biotechnology have improved our understanding of how these natural compounds function at the cellular level, activating specific plant defense through complex biochemical pathways regulated by various transcription factors (TFs) such as MYB, WRKY, bHLH, bZIP, NAC, and AP2/ERF. Advancements in multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, have significantly improved the understanding of the regulatory networks that govern PSM synthesis. These integrative approaches have led to the discovery of novel insights into plant responses to biotic stresses, identifying key regulatory genes and pathways involved in plant defense. Advanced technologies like CRISPR/Cas9-mediated gene editing allow precise manipulation of PSM pathways, further enhancing plant resistance. Understanding the complex interaction between PSMs, TFs, and biotic stress responses not only advances our knowledge of plant biology but also provides feasible strategies for developing crops with improved resistance to pests and diseases, contributing to sustainable agriculture and food security. This review emphasizes the crucial role of PSMs, their biosynthetic pathways, the regulatory influence of TFs, and their potential applications in enhancing plant defense and sustainability. It also highlights the astounding potential of multi-omics approaches to discover gene functions and the metabolic engineering of genes associated with secondary metabolite biosynthesis. Taken together, this review provides new insights into research opportunities for enhancing biotic stress tolerance in crops through utilizing plant secondary metabolites.

Transcriptomic, metabonomic and proteomic analyses reveal that terpenoids and flavonoids are required for Pinus koraiensis early defence against Bursaphelenchus xylophilus infection

Pine wilt disease (PWD), caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus, threatens Pinus seriously. Pinus koraiensis is one of the most important pine species in China and is the host for PWN. However, our understanding of the defence-regulating process following infection by B. xylophilus at the molecular level remains limited. To understand the mechanisms that P. koraiensis responds to B. xylophilus invasion, P. koraiensis was inoculated with B. xylophilus solutions and observed no obvious symptoms during the early stage; symptoms began to appear at 5 dpi. Therefore, we conducted comparative transcriptomic, metabonomic and proteomic analyses between P. koraiensis 5dpi and 0 dpi. In infected plants, 1574 genes were significantly up-regulated, including 17 terpenoid-, 41 phenylpropanoid- and 22 flavonoid-related genes. According to GO and KEGG enrichment analyses of significantly up-regulated genes, 86 GO terms and 16 KEGG pathways were significantly enriched. Most terms and pathways were associated with terpenoid-, phenylpropanoid-, flavonoid- and carbohydrate-related events. Similarly, the abundance of 36 and 30 metabolites, significantly increased in positive and negative polarity modes, respectively. Among them, naringenin and 3-methyl-2-oxovaleric acid exhibited significant toxic effects on B. xylophilus. According to functional analysis of significantly up-regulated metabolites, most terms were enriched in above pathways, in addition to alkaloid biosynthesis. Although the abundance of few proteins changed, response to stress term was significantly enriched in significant up-regulated proteins. Furthermore, plant receptor-like serine/threonine kinases, pectin methylation modulators, pinosylvin O-methyltransferase and arabinogalactan/proline-rich proteins were significantly up-regulated in the infected P. koraiensis compared to healthy plants. These proteins were not abundant in the healthy plant. Overall, these results indicate that P. koraiensis can actively response to PWN via various defense strategies, including events related to terpenoids, flavonoids, phenylpropanoids, lipids and alkaloids. Particularly, terpenoids and flavonoids are required for the early defence of P. koraiensis against B. xylophilus infection.

Phenylalanine metabolism-dependent lignification confers rhizobacterium-induced plant resistance

Phenylalanine metabolism serves as an important route for the production of diverse secondary metabolites including phenylpropanoids. The phenylpropanoid pathway is involved in plant immunity, but whether it can regulate rhizobacteria-induced resistance is poorly understood. In this study, we confirmed a growth-promoting rhizobacterium strain JR48 could induce resistance, strengthen salicylic acid (SA) signaling, and increase lignin content during Phytophthora capsici infection. We conducted transcriptome sequencing to analyze the effect of JR48 on the expression of pepper (Capsicum annuum L.) genes, generated transgenes and loss-of-function genetic materials to specify the function of peroxidase genes, and implemented metabolomics analysis to uncover the resistance-inducing metabolites of JR48. JR48 activated expression of several pepper peroxidase genes in the phenylpropanoid pathway during pathogen infection. These peroxidases positively regulated lignification-mediated pathogen resistance, and the phenylpropanoid pathway acted downstream of SA signaling to confer JR48-induced resistance. Further, JR48 was capable of producing phenylpyruvate to enhance phenylalanine accumulation, thereby reinforcing phenylalanine metabolism-dependent lignification and resistance. Our results revealed that JR48 produces phenylpyruvate to refuel phenylalanine metabolism and reinforces SA signaling to further activate expression of peroxidase genes. This study uncovers immune components previously hidden in metabolic pathways and a recent mechanism underlying rhizobacteria-induced plant resistance.

Proteomics analysis of round and wrinkled pea (Pisum sativum L.) seeds during different development periods

Seed development is complex, influenced by genetic and environmental factors. Understanding proteome profiles at different seed developmental stages is key to improving seed composition and quality. We used label-free quantitative proteomics to analyze round and wrinkled pea seeds at five growth stages: 4, 7, 12, 15, and days after anthesis (DAA), and at maturity. Wrinkled peas had lower starch content (30%) compared to round peas (47%-55%). Proteomic analysis identified 3659 protein groups, with 21%-24% shared across growth stages. More proteins were identified during early seed development than at maturity. Statistical analysis found 735 significantly different proteins between wrinkled and round seeds, regardless of the growth stage. The detected proteins were categorized into 31 functional classes, including metabolic enzymes, proteins involved in protein biosynthesis and homeostasis, carbohydrate metabolism, and cell division. Cell division-related proteins were more abundant in early stages, while storage proteins were more abundant later in seed development. Wrinkled seeds had lower levels of the starch-branching enzyme (SBEI), which is essential for amylopectin biosynthesis. Seed storage proteins like legumin and albumin (PA2) were more abundant in round peas, whereas vicilin was more prevalent in wrinkled peas. This study enhances our understanding of seed development in round and wrinkled peas. The study highlighted the seed growth patterns and protein profiles in round and wrinkled peas during seed development. It showed how protein accumulation changed, particularly focusing on proteins implicated in cell division, seed reserve metabolism, as well as storage proteins and protease inhibitors. These findings underscore the crucial role of these proteins in seed development. By linking the proteins identified to Cameor-based pea reference genome, our research can open avenues for deeper investigations into individual proteins, facilitate their practical application in crop improvement, and advance our knowledge of seed development.

Integrated analysis of the transcriptome and hormone metabolome elucidates the regulatory mechanisms governing walnut bud germination

The walnut (Juglans regia) is an important oilseed tree species characterized by its extensive distribution, high oil yield, and nutrient-dense kernels, which provide substantial economic benefits. However, the rising incidence of late-spring frosts, exacerbated by global climate change, has adversely affected walnut yields. A comprehensive understanding of the regulatory mechanisms involved in bud dormancy, germination, and development is essential for developing strategies to mitigate the effects of late-spring frosts and for breeding frost-resistant cultivars. This study focused on W13, a protogynous walnut variety with early germination of dormant buds in spring, employing a combination of transcriptomic and hormone metabolomic analyses. Our results emphasized four key biological processes-cellular response to ethylene stimulus, phenylpropanoid metabolic process, ethylene-activated signaling pathway, and monooxygenase activity-along with several relevant pathways, including plant hormone signal transduction, flavone and flavonol biosynthesis, biosynthesis of secondary metabolites, and MAPK signaling pathway, all crucial for walnut bud germination. Additionally, bud germination is closely associated with alterations in various hormone signaling pathways, including abscisic acid, auxin, cytokinin, ethylene, gibberellins, jasmonic acid, and salicylic acid. By assessing hormone levels and gene expression at different developmental stages, we pinpointed potential regulatory genes and critical hormones associated with bud germination. Furthermore, through weighted correlation network analysis, we constructed a co-expression network, identifying gene modules specifically expressed during dormancy, germination, budding, and leafing phases. The hub genes within these modules are likely pivotal in regulating walnut bud germination. Our analysis also revealed that genes from various transcription factor families are central within the co-expression network, indicating their significant roles in the bud germination process. Correlation network analysis of hormone and gene further illuminated the mechanisms through which genes and hormones jointly influence walnut bud germination. These findings establish a crucial molecular basis for a more comprehensive understanding of the mechanisms governing germination and development in dormant walnut buds.

Aromatic Amino Acids: Exploring Microalgae as a Potential Biofactory

In recent times, microalgae have emerged as powerful hosts for biotechnological applications, ranging from the production of lipids and specialized metabolites (SMs) of pharmaceutical interest to biofuels, nutraceutical supplements, and more. SM synthesis through bioengineered pathways relies on the availability of aromatic amino acids (AAAs) as an essential precursor. AAAs, phenylalanine, tyrosine, and tryptophan are also the building blocks of proteins, maintaining the structural and functional integrity of cells. Hence, they are crucial intermediates linking the primary and specialized metabolism. The biosynthesis pathway of AAAs in microbes and plants has been studied for decades, but not much is known about microalgae. The allosteric control present in this pathway has been targeted for metabolic engineering in microbes. This review focuses on the biosynthesis of AAAs in eukaryotic microalgae and engineering techniques for enhanced production. All the putative genes involved in AAA pathways in the model microalgae Chlamydomonas reinhardtii and Phaeodactylum tricornutum are listed in this review.

Integration of volatile and non-volatile metabolite profile, and in vitro digestion reveals the differences between different preparation methods on physico-chemical and biological properties of Gastrodia elata

Gastrodia elata Blume (G. elata) is a traditional medicinal and edible plant whose quality is significantly influenced by post-harvest processing. To obtain an optimal post-harvest processing method for G. elata, this study employed sensory evaluation, scanning electron microscopy (SEM), gas chromatography-ion mobility spectrometry (GC-IMS), and non-targeted metabolomics, in conjunction with an in vitro digestion model, to assess the impact of different processing and drying methods on the quality of G. elata. The findings showed that the steam treatment followed by heat pump drying resulted in the highest levels of total phenols, total flavonoids, and polysaccharides in G. elata, and caused more pronounced damage to its microstructure. This treatment also maintained the highest antioxidant activities and optimal acetylcholinesterase (AChE) inhibition capacity throughout in vitro digestion, meanwhile, effectively eliminating the unpleasant odor and achieving the highest sensory scores. Furthermore, non-targeted metabolomic analysis revealed noteworthy alterations in the metabolite profile of G. elata, mainly related to purine metabolism and the biosynthesis of amino acids pathways. This study provides valuable insights into the post-harvest processing of G. elata.

Structural and biochemical analyses reveal quinic acid inhibits DAHP synthase a key player in shikimate pathway

The shikimate pathway, essential for aromatic amino acid biosynthesis, is absent in animals, making its enzymes promising targets for developing antimicrobials. 3-Deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) catalyzes the first committed step, which serves as the primary checkpoint for regulating the flow within the pathway, regulated by its end products (Phe, Tyr and Trp). Previously, we identified chlorogenic acid (CGA), an ester of caffeic and quinic acid, as an inhibitor of DAHPS from Bacillus subtilis, prompting us to investigate quinic acid as a potential inhibitor of Providencia alcalifaciens DAHPS (PaDAHPS). Here, we report the crystal structures of phenylalanine-sensitive DAHPS from Providenciaalcalifaciens in complex with phenylalanine (Phe) and quinic acid (QA) at resolutions of 2.5 Å and 2.68 Å, respectively. Structural analysis reveals that QA binds to the same site as Phe, with biophysical assays showing a similar binding affinity (KD = 42 μM for QA and KD = 32 μM for Phe). In vitro inhibition studies demonstrated that QA and Phe inhibit PaDAHPS activity, with appKi values of 382 μM and 132 μM, respectively. Additionally, QA inhibited the growth of several bacterial species, including Pseudomonas aeruginosa, Moraxella catarrhalis, Providencia alcalifaciens, Staphylococcus aureus, Escherichia coli with minimum inhibitory concentrations (MICs) ranging from 2.5 to 5 mg/ml. These findings identify quinic acid as a promising scaffold for developing novel antimicrobial agents targeting the shikimate pathway, providing potential therapeutic strategies for bacterial infections.

Study on the mechanism of brain injury caused by acute diquat poisoning based on metabolomics

Brain injury following acute diquat poisoning has become increasingly common in moderate to severe cases, with unclear pathogenesis and high mortality. To investigate this, we conducted metabolomics on brain tissue from poisoned rats, combined with clinical biochemical and pathological analyses. In the high-dose group, 24 metabolites showed significant differences compared to the control group: 18 were upregulated, including cytosine, sedoheptulose-7-phosphate, indole, 3-dehydroshikimate, etc.; 6 were downregulated, including 6-phosphogluconic acid, 3-hydroxybenzoic acid, dAMP, etc. In the low-dose group, 10 metabolites showed significant differences: 4 were upregulated, including pentamidine, γ-tocotrienol, benzoylecgonine, etc.; and 6 were downregulated, including dAMP, glutathione, 3-hydroxybenzoic acid, etc. Enrichment analysis identified two key pathways-phenylalanine, tyrosine, and tryptophan biosynthesis, and the pentose phosphate pathway-as involved in brain injury. ROC analysis of six differential metabolites showed that sedoheptulose-7-phosphate, (2R)-2-hydroxy-3-(phosphonatooxy)propanoate, and 3-hydroxybenzoic acid had AUC values above 0.8. These findings suggest that these three metabolites demonstrate strong diagnostic potential for brain injury induced by diquat poisoning. Correlation analysis linked these biomarkers to clinical indicators such as neutrophil count and the eutrophil to lymphocyte ratio, supporting their relevance. This study provides insights into the mechanisms and biomarkers of diquat-induced brain injury, offering a foundation for future treatment and rapid detection.

Enhancing CRISPR-Cas-based gene targeting in tomato using a dominant-negative ku80

The CRISPR-Cas-based gene targeting (GT) method has enabled precise modifications of genomic DNA ranging from single base to several kilobase scales through homologous recombination (HR). In plant somatic cells, canonical non-homologous end-joining (cNHEJ) is the predominant mechanism for repairing double-stranded breaks (DSBs), thus limiting the HR-mediated GT. In this study, we implemented an approach to shift the repair pathway preference toward HR by using a dominant-negative ku80 mutant protein (KUDN) to disrupt the initiation of cNHEJ. The employment of KUDN conferred a 1.71- to 3.55-fold improvement in GT efficiency at the callus stage. When we screened transformants, there was a more remarkable increase in GT efficiency, ranging from 1.62- to 9.84-fold, at two specific tomato loci, SlHKT1;2 and SlEPSPS1. With practical levels of efficiency, this enhanced KUDN-based GT tool successfully facilitated a 9-bp addition at an additional locus, SlCAB13. These findings provide another promising method for more efficient and precise plant breeding.

New insights into the evolution and function of the UMAMIT (USUALLY MULTIPLE ACIDS MOVE IN AND OUT TRANSPORTER) gene family

UMAMIT proteins have been known as key players in amino acid transport. In Arabidopsis, functions of several UMAMITs have been characterized, but their precise mechanism, evolutionary history and functional divergence remain elusive. In this study, we conducted phylogenetic analysis of the UMAMIT gene family across key species in the evolutionary history of plants, ranging from algae to angiosperms. Our findings indicate that UMAMIT proteins underwent a substantial expansion from algae to angiosperms, accompanied by the stabilization of the EamA (the main domain of UMAMIT) structure. Phylogenetic studies suggest that UMAMITs may have originated from green algae and be divided into four subfamilies. These proteins first diversified in bryophytes and subsequently experienced gene duplication events in seed plants. Subfamily I was potentially associated with amino acid transport in seeds. Regarding subcellular localization, UMAMITs were predominantly localized in the plasma membrane and chloroplasts. However, members from clade 8 in subfamily III exhibited specific localization in the tonoplast. These members may have multiple functions, such as plant disease resistance and root development. Furthermore, our protein structure prediction revealed that the four-helix bundle motif is crucial in controlling the UMAMIT switch for exporting amino acid. We hypothesize that the specific amino acids in the amino acid binding region determine the type of amino acids being transported. Additionally, subfamily II contains genes that are specifically expressed in reproductive organs and roots in angiosperms, suggesting neofunctionalization. Our study highlights the evolutionary complexity of UMAMITs and underscores their crucial role in the adaptation and diversification of seed plants.

Harnessing controlled-environment systems for enhanced production of medicinal plants

Medicinal plants are valued for their contributions to human health. However, the growing demand for medicinal plants and the concerns regarding their quality and sustainability have prompted the reassessment of conventional production practices. Controlled-environment cropping systems, such as vertical farms, offer a transformative approach to production of medicinal plants. By enabling precise control over environmental factors, such as light, carbon dioxide, temperature, humidity, nutrients, and airflow, controlled environments can improve the consistency, concentration, and yield of bioactive phytochemicals in medicinal plants. This review explores the potential of controlled-environment systems for enhancing production of medicinal plants. First, we describe how controlled environments can overcome the limitations of conventional production in improving the quality of medicinal plants. Next, we propose strategies based on plant physiology to manipulate environmental conditions for enhancing the levels of bioactive compounds in plants. These strategies include improving photosynthetic carbon assimilation, light spectrum signalling, purposeful stress elicitation, and chronoculture. We describe the underlying mechanisms and practical applications of these strategies. Finally, we highlight the major knowledge gaps and challenges that limit the application of controlled environments, and discuss future research directions.

Arabidopsis 3-Deoxy-d-Arabino-Heptulosonate 7-Phosphate (DAHP) Synthases of the Shikimate Pathway Display Both Manganese- and Cobalt-Dependent Activities

The plant shikimate pathway directs a significant portion of photosynthetically assimilated carbon into the downstream biosynthetic pathways of aromatic amino acids (AAA) and aromatic natural products. 3-Deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase (hereafter DHS) catalyzes the first step of the shikimate pathway, playing a critical role in controlling the carbon flux from central carbon metabolism into the AAA biosynthesis. Previous biochemical studies suggested the presence of manganese- and cobalt-dependent DHS enzymes (DHS-Mn and DHS-Co, respectively) in various plant species. Unlike well-studied DHS-Mn, however, the identity of DHS-Co is still unknown. Here, we show that all three DHS isoforms of Arabidopsis thaliana exhibit both DHS-Mn and DHS-Co activities in vitro. A phylogenetic analysis of various DHS orthologs and related sequences showed that Arabidopsis 3-deoxy-D-manno-octulosonate-8-phosphate synthase (KDOPS) proteins were closely related to microbial Type I DHSs. Despite their sequence similarity, these Arabidopsis KDOPS proteins showed no DHS activity. Meanwhile, optimization of the DHS assay conditions led to the successful detection of DHS-Co activity from Arabidopsis DHS recombinant proteins. Compared with DHS-Mn, DHS-Co activity displayed the same redox dependency but distinct optimal pH and cofactor sensitivity. Our work provides biochemical evidence that the DHS isoforms of Arabidopsis possess DHS-Co activity.

Effects of Tithonia diversifolia Extract as a Feed Additive on Digestibility and Performance of Hair Lambs

Animal production requires efficiency, safety and environmental sustainability. Bioactive compounds from tropical plants could modulate ruminal fermentation, providing an alternative method to antibiotic treatment and addressing concerns about antibiotic resistance. In this study, the aim was to determine the effects of Tithonia diversifolia extract (TDE) on performance, intake, digestibility and blood parameters [i.e., glucose, blood urea nitrogen (BUN), aspartate aminotransferase (AST), alanine aminotransferase (ALT)] in crossbreed sheep. The main biocompounds of the TDE include caffeic acid (CA), quercetin (QCT), luteolin (LT) and apigenin (AP). Experiment 1: An in vitro dry matter digestibility (IVDMD) study was conducted to determine the optimal inclusion levels. The IVDM values were 73.09a, 82.03b, 81.01b, 73.20a and 74.51a for the control, 5, 10, 15 and 20 g/kg for the DM treatments, respectively (R-Sq adj = 0.857). The levels of 5 and 10 g were selected for the in vivo experiment. Experiment 2: Twenty-eight male crossbred hair lambs were assigned to four treatments (n = 7): control, 20 mg monensin/day, 5 g TDE/day and 10 g TDE/day groups. No differences in animal performance were observed, including body weight and feed conversion (p > 0.05). The TDE at 10 g/day improved NDF digestibility) (61.32%) and reduced the ruminal acetate to propionate ratio. The total digestible nutrients (TDN) were higher in 10 g TDE treatment with 66.41% and the lowest acetate production (67.82%) (p = 0.042), and propionate production (21.07%) were observed. The TDE were safe at 5 g and 10 g/day for liver function and exhibited lower BUN levels suggesting an improvement in protein metabolism. TDE extract at 10 g/day (TDE10), showed improvements in total tract digestibility of NDF and reduced the ruminal acetate to propionate ratio. However, due to TDE10 reducing the DM intake, the improvements in digestibility and ruminal fermentation were not reflected in growth performance improvements.

Description of the first marine-isolated member of the under-represented phylum Gemmatimonadota, and the environmental distribution and ecogenomics of Gaopeijiales ord. nov

The phylum Gemmatimonadota is widespread but rarely cultured and, in fact, there are only six described species isolated from soil, freshwater, and wastewater treatment. However, no isolates of Gemmatimonadota from marine environment have been described; thus, little is known about the physiology and metabolism of members of the marine lineages. In this study, four novel facultatively anaerobic bacterial strains belonging to Gemmatimonadota were isolated from marine sediments collected from Xiaoshi Island in Weihai, China, using an aerobic enrichment method. The integrated results of phylogenetic and phenotypic characteristics supported that these four strains represent one novel species in a novel genus, for which the name Gaopeijia maritima gen. nov., sp. nov. is proposed, as the first representative of novel taxa, Gaopeijiales ord. nov., Gaopeijiaceae fam. nov. in the class Longimicrobiia. Gaopeijiales was detected in 22,884 out of 95,549 amplicon data sets, mainly from soil. However, the highest mean relative abundances were in sponge (0.7%) and marine sediment (0.35%), showing salt-related character. Most of the Gaopeijiales subgroups potentially belong to the rare bacterial biosphere. The aerobic enrichment in this study could significantly increase the relative abundance of Gaopeijiales (from 0.37% to 2.6%). Furthermore, the metabolic capabilities inferred from high-quality representative Gaopeijiales genomes/MAGs suggest that this group primarily performs chemoorganoheterotrophic metabolism with facultatively anaerobic characteristics and possesses various secondary metabolite biosynthesis gene clusters (BGCs), mirroring those observed in the four novel strains.IMPORTANCEDespite rapid advances in molecular and sequencing technologies, obtaining pure cultures remains a crucial research goal in microbiology, as it is essential for a deeper understanding of microbial metabolism. Gemmatimonadota is a widespread but rarely cultured bacterial phylum. Currently, there are only six cultured strains of this interesting group, all isolated from non-marine environments. Little is known about the physiology and metabolism of members of the marine lineages. Here we isolated and characterized four novel marine strains, and proposed a new order Gaopeijiales within Gemmatimonadota. Furthermore, the global distribution, environmental preference, and metabolic potential of Gaopeijiales are analyzed using public data. Our work enriches the resources available for the under-represented phylum Gemmatimonadota and provides insights into the physiological and metabolic characteristics of the marine lineage (Gaopeijiales) through culturology and omics.

Comparative Transcriptome Analysis Highlights the Role of NlABCG14 in the Honeydew Production of Virulent Brown Planthoppers (Nilaparvata lugens Stål) to Resistant Rice Variety

Brown planthoppers (BPHs, Nilaparvata lugens Stål) are a major threat to rice cultivation in Asia, necessitating the development of pest-resistant varieties for effective management. However, the adaptability of BPHs has resulted in the development of virulent populations, such as biotype Y BPHs, which exhibit significant virulence against the rice variety YHY15 that harbors the resistance gene Bph15. The various response mechanisms of BPH populations to resistant rice varieties are critical yet underexplored. Via RNA sequencing, the present study identified distinct transcriptional profiles in avirulent (biotype 1) and virulent (biotype Y) BPH nymphs both before and after feeding on YHY15 rice. Our findings revealed differential expression patterns of gene clusters involved in protein synthesis, hydrolysis, fatty acid biosynthesis, metabolism, cuticle composition, and translocation. Further analysis elucidated changes in the expression of genes associated with longevity and structural components of cuticles, highlighting specific disruptions in both biotype 1 and biotype Y BPHs. Moreover, the two biotypes showed differences in the expression level of genes involved in ATP-binding cassette (ABC) transporters. A functional assessment of ABC transporter genes revealed a role of NlABCG14 in the honeydew production of biotype Y BPHs to YHY15 rice, without impacting their survival and developmental dynamics. These insights deepen our understanding of the mechanisms of virulent BPHs response to resistant rice varieties and highlight potential targets for improving pest management strategies.

The Roles of Phytohormones in Plant Defense Mechanisms Against the Brown Planthopper

The brown planthopper (BPH; Nilaparvata lugens Stål) is the most significant insect pest compromising rice production globally. Phytohormones, which are small organic compounds produced by plants, play a crucial role in regulating plant growth and development. Nevertheless, extensive research has established that phytohormones are essential in modulating plant defense against BPH. Plants can achieve equilibrium between growth and defense by utilizing the intricate network of phytohormone signaling pathways to initiate optimal and efficient defensive responses to insects. In this review, we primarily address the roles of phytohormones in conferring resistance against BPH, with a focus on hormone cross-talk. We also discuss the potential value of integrating hormones with other agricultural practices to enhance plant defense and agricultural yield, which highlights the significance of novel approaches for environment-friendly insect pest management.

A simplified liquid chromatography-mass spectrometry methodology to probe the shikimate and aromatic amino acid biosynthetic pathways in plants

Plants direct substantial amounts of carbon toward the biosynthesis of aromatic amino acids (AAAs), particularly phenylalanine to produce lignin and other phenylpropanoids. Yet, we have a limited understanding of how plants regulate AAA metabolism, partially because of a scarcity of robust analytical methods. Here, we established a simplified workflow for simultaneous quantification of AAAs and their pathway intermediates from plant tissues, based on extraction at two alternative pH and analysis by Zwitterionic hydrophilic interaction liquid chromatography coupled to mass spectrometry. This workflow was then used to analyze metabolic responses to elevated or reduced carbon flow through the shikimate pathway in plants. Increased flow upon expression of a feedback-insensitive isoform of the first shikimate pathway enzyme elevated all AAAs and pathway intermediates, especially arogenate, the last common precursor within the post-chorismate pathway of tyrosine and phenylalanine biosynthesis. Additional overexpression of an arogenate dehydrogenase enzyme increased tyrosine levels and depleted phenylalanine and arogenate pools; however, the upstream shikimate pathway intermediates remained accumulated at high levels. Glyphosate treatment, which restricts carbon flow through the shikimate pathway by inhibiting its penultimate step, led to a predictable accumulation of shikimate and other precursors upstream of its target enzyme but also caused an unexpected accumulation of downstream metabolites, including arogenate. These findings highlight that the shikimate pathway and the downstream post-chorismate AAA pathways function as independently regulated modules in plants. The method developed here paves the way for a deeper understanding of the shikimate and AAA biosynthetic pathways in plants.

Transcriptome and metabolome reveal the primary and secondary metabolism changes in Larix gmelinii seedlings under abiotic stress

BACKGROUND

Larix gmelinii is an excellent stress resistant coniferous tree species with a wide distribution and important economic and ecological value. However, at seedling stage, L. gmelinii is extremely susceptible to abiotic stresses, and systematic research on the adaptation mechanisms of L. gmelinii seedlings to abiotic stress is still lacking.

RESULTS

Phenotypic observation and physiological index detection showed that L. gmelinii seedlings wilted with needles withered and yellowish at later stages of drought and salt stress; Under low temperature, the seedlings grew slowly and turned red at later stage. Under all 3 abiotic stresses, the chlorophyll content in seedlings significantly decreased, while the MDA content significantly increased; The activity of SOD and CAT showed a trend of increasing first and then decreasing. Transcriptome analysis revealed that DEGs were mainly involved in carbohydrate and amino acid metabolism, phenylpropanoid biosynthesis, and flavonoid synthesis metabolism. Metabolomic analysis found unique DAMs under 3 stress treatments. The combined analysis of transcriptome and metabolome showed that the changing patterns of DEGs and DAMs in primary and secondary metabolism were consistent: carbohydrate were significantly accumulated under low temperature stress; amino acids showed the most significant changes under salt stress. The variation pattern of secondary metabolism was similar under both drought and salt stress, while anthocyanin accumulation was the most obvious only under low temperature stress.

CONCLUSION

Our study provides insightful information about the different mechanisms that L. gmelinii seedlings employ in response to drought, low temperature or salt stress.

Pharmacokinetic-Pharmacodynamic Modeling of the Immune-Enhancing Effect of Shikimic Acid in Growing Pigs

Shikimic acid (SA), extracted from the fruit of shikimi-no-ki, is used both as a preservative in the food industry and as an intermediate for a variety of active ingredients with a wide range of pharmacological functions. A deeper understanding of the pharmacokinetic process of SA in pigs and its impact on humoral immunity could prove invaluable in facilitating its clinical application in veterinary and human medicine. The pharmacokinetic study employed a two-period, two-sequence, crossover design to animal experiments and developed a novel method of pig plasma preparation using water as an extractant and ionization promoter, followed by purification and enrichment on a MAX solid phase extraction (SPE) column. The results showed that SA is rapidly absorbed after intragastric administration (50 mg/kg BW), reaching a plasma Cmax of 10,823.44 ng/mL at 1.78 h, followed by rapid elimination, with a t1/2 of 1.81 h, consistent with a one-compartment model. The results for intravenous administration (2 mg/kg BW) were consistent with a two-compartment open model with a t1/2 of 3.66 h, with concentrations below the limit of quantification (LOQ) observed beyond 12 h postdose. The absolute bioavailability of SA in pigs was calculated to be 21.68%. Furthermore, the Pearson's correlation analysis demonstrated a strong positive correlation between SA concentration in pig plasma and the changes of C3, C4 and IgG, IgA, and IgM (0.6 < R < 1, P < 0.0001). A more detailed pharmacokinetic-pharmacodynamic (PK-PD) modeling analysis of the intravenous group revealed the EC50/Cmax values of approximately 10%, with all γ values exceeding 3. This study was the inaugural investigation into the pharmacokinetics of SA in growing pigs, and it also revealed that SA has the potential to act as an immunopotentiator.

An ideal leaf spraying strategy of brown sugar for edible medicinal plants of Viola inconspicua

The typical edible medicinal plants of Viola inconspicua were compared with leaf-green, biomass, metabolomes, and bacterial communities, after leaf-spraying water (A), brown sugar water (B), brown sugar, urea, and KH2PO4 water (C), or KH2PO4 and urea water (D). The plants sprayed with C solution presented relatively normal leaf-green and the highest biomass. In contrast of A group, B, C, and D groups were found with 72, 94, and 104 leaf differently accumulated metabolites (DAMs) and 105, 88, and 92 root DAMs, respectively. Typically, relative abundances of amino acids were elevated in C and D groups, while those of leaf flavonoids were increased in B group. Noticeably, leaf DAMs of C group versus A group had strong correlations with one to more phylum- or/and genus-dominant bacteria of C group. Taken together, leaf-spraying brown sugar, urea, and KH2PO4 water are ideal for holding leaf-green and biomass in V. inconspicua plants.

Development of an HPPD-Inhibitor Resistant Wheat and Multiomics Integrative Analysis of Herbicide Toxicity and OsHIS1 Detoxification in Wheat

Weed infestation in agricultural fields significantly diminishes crop yields. Herbicides are widely used as a primary method of weed control. Developing herbicide-resistant crops through the expression of resistant genes represents a sustainable approach. This study generated wheat germplasms highly resistant to 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides by transforming the rice HPPD INHIBITOR SENSITIVE 1 (OsHIS1) gene into Xinong 511, conferring resistance to mesotrione at levels up to nine times the typical field application rate (1350 g ai ha-1). Agronomic trait evaluations under greenhouse and field conditions showed no additional effects on wheat. Herbicide susceptibility assays confirmed the specific resistance to different HPPD inhibitors. Transcriptome and metabolome analyses revealed regulation of flavonoid and photosynthesis-antenna protein pathways in the herbicide functional. Collectively, OsHIS1 could be applied in the production of herbicide-resistant wheat.

Impact of Pristine and Aged Tire Wear Particles on Ipomoea aquatica and Rhizospheric Microbial Communities: Insights from a Long-Term Exposure Study

Tire wear particles (TWPs), generated from tire abrasion, contribute significantly to environmental contamination. The toxicity of TWPs to organisms has raised significant concerns, yet their effects on terrestrial plants remain unclear. Here, we investigated the long-term impact of pristine and naturally aged TWPs on water spinach (Ipomoea aquatica) and its rhizospheric soil. The results indicated that natural aging reduced the toxicity of TWPs, as evidenced by decreased levels of polycyclic aromatic hydrocarbons (PAHs) in soil and TWPs themselves. Consequently, aged TWPs were found to enhance the plant growth and chlorophyll content, whereas pristine TWPs increased the plant stress. Furthermore, aged TWPs improved soil organic matter (SOM) and total organic carbon (TOC), thereby boosting the microbial enzymes involved in nitrogen cycling. Metabolomic analysis revealed that aged TWPs upregulated key pathways related to carbon and nitrogen metabolism, enhancing plant growth and stress responses. Additionally, rhizosphere bacterial diversity was higher under aged TWPs, favoring nutrient-cycling taxa such as Acidobacteriota and Nitrospirota. Pristine TWPs may lead to overproliferation of certain dominant species, thereby reducing microbial diversity in soil, which could ultimately compromise the soil health. These findings contribute to a deeper understanding of the mechanisms underlying TWP toxicity in plants and highlight the necessity for further research on the impact of aged TWPs across various plant species over different exposure durations for comprehensive risk assessment.

Cinnamaldehyde in Focus: Antimicrobial Properties, Biosynthetic Pathway, and Industrial Applications

Trans-cinnamaldehyde (TCA), a major bioactive compound derived from cinnamon (Cinnamomum spp.), has garnered significant attention for its diverse therapeutic properties. Its broad-spectrum antimicrobial activity, targeting both Gram-positive and Gram-negative bacteria as well as various fungi, positions TCA as a potent natural antimicrobial agent. Beyond its antimicrobial effects, TCA demonstrates promising antidiabetic and anti-inflammatory activities, making it a valuable compound in medicinal and cosmetic applications. Recent studies have highlighted its role in disrupting microbial membranes, inhibiting biofilm formation, and modulating key metabolic pathways in pathogens. Furthermore, TCA has gained popularity in cosmetics due to its antimicrobial activity, antioxidant properties, and skin-friendly profile. This review provides a comprehensive overview of TCA's antimicrobial potential, focusing on its mechanisms of action and its market and industrial applications. We also discuss the biosynthetic pathway of TCA, exploring both its natural production in cinnamon and advances in biotechnological production methods. As the demand for sustainable and natural antimicrobial agents grows, TCA emerges as a promising candidate for diverse applications. Finally, this review explores future directions for optimizing TCA production through metabolic engineering and synthetic biology approaches to meet industrial-scale demands.

Plant terrestrialization: an environmental pull on the evolution of multi-sourced streptophyte phenolics

Phenolic compounds of land plants are varied: they are chemodiverse, are sourced from different biosynthetic routes and fulfil a broad spectrum of functions that range from signalling phytohormones, to protective shields against stressors, to structural compounds. Their action defines the biology of land plants as we know it. Often, their roles are tied to environmental responses that, however, impacted already the algal progenitors of land plants, streptophyte algae. Indeed, many streptophyte algae successfully dwell in terrestrial habitats and have homologues for enzymatic routes for the production of important phenolic compounds, such as the phenylpropanoid pathway. Here, we synthesize what is known about the production of specialized phenolic compounds across hundreds of millions of years of streptophyte evolution. We propose an evolutionary scenario in which selective pressures borne out of environmental cues shaped the chemodiversity of phenolics in streptophytes. This article is part of the theme issue 'The evolution of plant metabolism'.

Evolution of aromatic amino acid metabolism in plants: a key driving force behind plant chemical diversity in aromatic natural products

A diverse array of plant aromatic compounds contributes to the tremendous chemical diversity in the plant kingdom that cannot be seen in microbes or animals. Such chemodiversity of aromatic natural products has emerged, occasionally in a lineage-specific manner, to adopt to challenging environmental niches, as various aromatic specialized metabolites play indispensable roles in plant development and stress responses (e.g. lignin, phytohormones, pigments and defence compounds). These aromatic natural products are synthesized from aromatic amino acids (AAAs), l-tyrosine, l-phenylalanine and l-tryptophan. While amino acid metabolism is generally assumed to be conserved between animals, microbes and plants, recent phylogenomic, biochemical and metabolomic studies have revealed the diversity of the AAA metabolism that supports efficient carbon allocation to downstream biosynthetic pathways of AAA-derived metabolites in plants. This review showcases the intra- and inter-kingdom diversification and origin of committed enzymes involved in plant AAA biosynthesis and catabolism and their potential application as genetic tools for plant metabolic engineering. I also discuss evolutionary trends in the diversification of plant AAA metabolism that expands the chemical diversity of AAA-derived aromatic natural products in plants. This article is part of the theme issue 'The evolution of plant metabolism'.

The SH3-binding domain of chorismate mutase protein of Mycobacterium tuberculosis contributes to mycobacterial virulence

Crystal structure of the secretory chorismate mutase protein of Mycobacterium tuberculosis (MtbCM) reveals presence of a proline rich region on its surface that serve as a recognition site for protein-protein interaction. This study shows that MtbCM upregulates IL-10 which favors M. tuberculosis by affecting PKCε-MKP-1-p38 MAPK signaling. MtbCM translocates to the Golgi-network where it interacts with AKAP9 via its SH3-binding domain to inhibit AKAP9-PKCε interaction and reducing PKCε phosphorylation. In the absence of phosphorylated PKCε, IRAK3 fails to stabilize MKP-1 resulting in higher p38 MAPK activation and IL-10 production. M. smegmatis expressing MtbCM survived better in infected mice. Mutation in SH3-binding domain ablated MtbCM-AKAP9 interaction resulting in IL-10 production and decreased bacterial survival. This study highlights the importance of SH3-binding domain in host-pathogen interaction and a role of MtbCM in modulation of cytokine response and mycobacterial virulence in addition to its role in shikimate pathway.

Transcriptional Profiling Analysis Providing Insights into the Harsh Environments Tolerance Mechanisms of Krascheninnikovia arborescens

Krascheninnikovia arborescens, an endemic shrub in China, thrives in desertification-prone environments due to its robust biomass, hairy leaves, and extensive root system. It is vital for ecological restoration and serves as a valuable forage plant. This study explored the molecular mechanisms underlying K. arborescens' adaptation to desert conditions, focusing on its physiological, biochemical, and transcriptomic responses to drought, salt, and alkali stresses. The results revealed that the three stresses have significant impacts on the photosynthetic, antioxidant, and ion balance systems of the plants, with the alkali stress inducing the most pronounced changes and differential gene expression. The clustering and functional enrichment analyses of differentially expressed genes (DEGs) highlighted the enrichment of the induced genes in pathways related to plant hormone signaling, phenylpropanoid biosynthesis, and transcription factors following stress treatments. In these pathways, the synthesis and signal transduction of abscisic acid (ABA) and ethylene, as well as the flavonoid and lignin synthesis pathways, and transcription factors such as MYB, AP2/ERF, bHLH, NAC, and WRKY responded actively to the stress and played pivotal roles. Through the WGCNA analysis, 10 key modules were identified, with the yellow module demonstrating a high correlation with the ABA and anthocyanin contents, while the turquoise module was enriched in the majority of genes related to hormone and phenylpropanoid pathways. The analysis of hub genes in these modules highlighted the significant roles of the bHLH and MYB transcription factors. These findings could offer new insights into the molecular mechanisms that enable the adaptation of K. arborescens to desert environments, enhancing our understanding of how other desert plants adapt to harsh conditions. These insights are crucial for exploring and utilizing high-quality forage plant germplasm resources and ecological development, with the identified candidate genes serving as valuable targets for further research on stress-resistant genes.

Integration of biological and information technologies to enhance plant autoluminescence

Autoluminescent plants have been genetically modified to express the fungal bioluminescence pathway (FBP). However, a bottleneck in precursor production has limited the brightness of these luminescent plants. Here, we demonstrate the effectiveness of utilizing a computational model to guide a multiplex five-gene-silencing strategy by an artificial microRNA array to enhance caffeic acid (CA) and hispidin levels in plants. By combining loss-of-function-directed metabolic flux with a tyrosine-derived CA pathway, we achieved substantially enhanced bioluminescence levels. We successfully generated eFBP2 plants that emit considerably brighter bioluminescence for naked-eye reading by integrating all validated DNA modules. Our analysis revealed that the luminous energy conversion efficiency of the eFBP2 plants is currently very low, suggesting that luminescence intensity can be improved in future iterations. These findings highlight the potential to enhance plant luminescence through the integration of biological and information technologies.

Exploring the Correlation Between the Molecular Structure and Biological Activities of Metal-Phenolic Compound Complexes: Research and Description of the Role of Metal Ions in Improving the Antioxidant Activities of Phenolic Compounds

We discussed and summarized the latest data from the global literature on the action of polyphenolic antioxidants and their metal complexes. The review also includes a summary of the outcomes of theoretical computations and our many years of experimental experience. We employed various methods, including spectroscopy (FT-IR, FT-Raman, NMR, UV/Vis), X-ray diffraction, thermal analysis, quantum calculations, and biological assays (DPPH, ABTS, FRAP, cytotoxicity, and genotoxicity tests). According to our research, the number and position of hydroxyl groups in aromatic rings, as well as the delocalization of electron charge and conjugated double bonds, have a major impact on the antioxidant effectiveness of the studied compounds. Another important factor is metal complexation, whereby high ionic potential metals (e.g., Fe(III), Cr(III), Cu(II)) enhance antioxidant properties by stabilizing electron charge, while the low ionic potential metals (e.g., Ag(I), Hg(II), Pb(II)) reduce efficacy by disrupting electron distribution. However, we observed no simple correlation between ionic potential and antioxidant capacity. This paper gives insights that will aid in identifying new, effective antioxidants, which are vital for nutrition and the prevention of neurodegenerative illnesses. Our results outline the connections between biological activity and molecular structure, offering a foundation for the methodical design of antioxidants. Our review also shows in detail how we use various complementary methods to assess the impact of metals on the electronic systems of ligands. This approach moves beyond the traditional "trial and error" method, allowing for the more efficient and rational development of future antioxidants.

A fungal effector suppresses plant immunity by manipulating DAHPS-mediated metabolic flux in chloroplasts

Plant secondary metabolism represents an important and ancient form of defense against pathogens. Phytopathogens secrete effectors to suppress plant defenses and promote infection. However, it is largely unknown, how fungal effectors directly manipulate plant secondary metabolism. Here, we characterized a fungal defense-suppressing effector CfEC28 from Colletotrichum fructicola. Gene deletion assays showed that ∆CfEC28-mutants differentiated appressoria normally on plant surface but were almost nonpathogenic due to increased number of plant papilla accumulation at attempted penetration sites. CfEC28 interacted with a family of chloroplast-localized 3-deoxy-d-arabinose-heptulonic acid-7-phosphate synthases (DAHPSs) in apple. CfEC28 inhibited the enzymatic activity of an apple DAHPS (MdDAHPS1) and suppressed DAHPS-mediated secondary metabolite accumulation through blocking the manganese ion binding region of DAHPS. Dramatically, transgene analysis revealed that overexpression of MdDAHPS1 provided apple with a complete resistance to C. fructicola. We showed that a novel effector CfEC28 can be delivered into plant chloroplasts and contributes to the full virulence of C. fructicola by targeting the DAHPS to disrupt the pathway linking the metabolism of primary carbohydrates with the biosynthesis of aromatic defense compounds. Our study provides important insights for understanding plant-microbe interactions and a valuable gene for improving plant disease resistance.

Metabolome and transcriptome unveil the mechanism of light on regulating beauvericin synthesis in Cordyceps chanhua

Cordyceps chanhua, an important cordycipitoid medical mushroom with wide use in Asia, has gained attention for its bioactive component beauvericin (BEA), which is of medicinal value as a drug lead, but also of food safety risk. Recent observations by our group revealed a significant decrease of BEA content in C. chanhua when exposed to light, but the underlying regulatory mechanisms remain elusive. In this study, a comprehensive approach combining metabolomics and transcriptomics was employed to investigate the effects of white light on the secondary metabolism of C. chanhua for elucidation of the influence of light on BEA biosynthesis in this fungus. The result showed that the genes and metabolites involved in the synthesis of D-hydroxyisovaleric acid, a precursor of BEA synthesis, were down-regulated under light exposure, while those associated with the synthesis of phenylalanine, another precursor of BEA synthesis, were up-regulated leading to elevated phenylalanine levels. It suggested that the suppressive effect of light on BEA synthesis in C. chanhua occurred primarily through the inhibition of D-hydroxyisovaleric acid synthesis, while the enhanced phenylalanine biosynthesis likely directed towards other metabolic pathway such as pigment synthesis. These results contributed to a better understanding on how light modulates the secondary metabolism of C. chanhua and provided valuable guidance for optimizing BEA production in cultivation practices.

6-Phosphogluconate dehydrogenase 2 bridges the OPP and shikimate pathways to enhance aromatic amino acid production in plants

The oxidative pentose phosphate (OPP) pathway provides metabolic intermediates for the shikimate pathway and directs carbon flow to the biosynthesis of aromatic amino acids (AAAs), which serve as basic protein building blocks and precursors of numerous metabolites essential for plant growth. However, genetic evidence linking the two pathways is largely unclear. In this study, we identified 6-phosphogluconate dehydrogenase 2 (PGD2), the rate-limiting enzyme of the cytosolic OPP pathway, through suppressor screening of arogenate dehydrogenase 2 (adh2) in Arabidopsis. Our data indicated that a single amino acid substitution at position 63 (glutamic acid to lysine) of PGD2 enhanced its enzyme activity by facilitating the dissociation of products from the active site of PGD2, thus increasing the accumulation of AAAs and partially restoring the defective phenotype of adh2. Phylogenetic analysis indicated that the point mutation occurred in a well-conserved amino acid residue. Plants with different amino acids at this conserved site of PGDs confer diverse catalytic activities, thus exhibiting distinct AAAs producing capability. These findings uncover the genetic link between the OPP pathway and AAAs biosynthesis through PGD2. The gain-of-function point mutation of PGD2 identified here could be considered as a potential engineering target to alter the metabolic flux for the production of AAAs and downstream compounds.

Optimization of saponin extraction from the leaves of Panax notoginseng and Panax quinquefolium and evaluation of their antioxidant, antihypertensive, hypoglycemic and anti-inflammatory activities

Panax notoginseng and Panax quinquefolium are important economic plants that utilize dried roots for medicinal and food dual purposes; there is still insufficient research of their stems and leaves, which also contain triterpenoid saponins. The extraction process was developed with a total saponin content of 12.30 ± 0.34% and 12.19 ± 0.64% for P. notoginseng leaves (PNL) and P. quinquefolium leaves (PQL) extracts, respectively. PNL and PQL saponin extracts showed good antioxidant, antihypertensive, hypoglycemic, and anti-inflammatory properties in vitro and RAW264.7 cells. A total of 699 metabolites were identified in PNL and PQL saponin extracts, with the majority being triterpenoid saponins, flavonoids and amino acids. Fourteen ginsenosides, 18 flavonoids or alkaloids, and 16 amino acids were enriched in both saponin extracts. Overall, the utilization of saponins from medicinal plants PNL and PQL has been developed to facilitate systematic research in the functional food and natural product industries.

Sugarcane (Saccharum officinarum L.) induces psychostimulant, anxiolytic-like effects and improvement of motor performance in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Sugarcane (Saccharum officinarum L.) is reported by traditional medicine as tonic, stimulating and beneficial in increasing resistance to fatigue. Previous preclinical studies in rats using aqueous extract of sugarcane leaves (AE) revealed pharmacological effects on the central nervous and cardiovascular systems involving the participation of dopaminergic pathways. This neurotransmission system is also related to motor, emotional and cognitive activities, which could, in part, justify the ethnopharmacological information.

AIM OF STUDY

The present study aimed to investigate the motor, emotional and cognitive activities of rats submitted to AE treatment using behavioral tests in order to correlate the pharmacological effects with the therapeutic benefits postulated by traditional medicine. Additionally, the chemical profile of AE was evaluated by HPLC-UV/Vis, and the presence of shikimic acid, vitexin, and ferulic acid, as possible chemical markers, was investigated through comparisons of chemical parameters with the authentic patterns, and a UV-Vis scan of known spectra.

MATERIAL AND METHODS

Rats received water (1.5 mL/kg, p.o.) and AE (0.5, 10 and 500 mg/kg, p.o.) in the absence and presence of haloperidol (0.5 mg/kg, i.p.), 90 min before open field; rotarod; elevated plus maze and inhibitory avoidance tests for investigation of motor; emotional and cognitive responses. As a positive control was used apomorphine (0.25 mg/kg, s.c.). The chemical profile of AE was evaluated by HPLC-UV/Vis and the presence of shikimic acid, vitexin and ferulic acid, as possible chemical markers, was investigated through comparisons with the retention times, an increase of the integral of the peak area determined by co-injection of AE with the authentic patterns, and a UV-Vis scan of known spectra.

RESULTS

In open field, it revealed that AE increased locomotion; reduced rearing but did not change freezing and grooming. Besides, AE increased motor performance in rotarod and reduced anxiety in elevated plus maze. A relation dose-response was observed in these tests where the lowest dose of AE was more effective in developing pharmacological responses. Previous administration of haloperidol inhibited the responses of AE. Inhibitory avoidance test revealed that AE did not modify fast-learning and associative memory.

CONCLUSIONS

Sugarcane induced psychostimulant, anxiolytic-like effects, and improvement of motor performance in rats, with the involvement of dopaminergic pathways. The present study points to AE as a potential adaptogen but, in addition to behavioral assessments, metabolic and molecular aspects, that involve the participation of a variety of regulatory systems, will be investigated in futures studies. Phytochemical analyses showed that AE is a complex matrix and revealed shikimic acid, vitexin, and ferulic acid as potential chemical markers.

Transcriptomic and metabolomic reveal OsCOI2 as the jasmonate-receptor master switch in rice root

Jasmonate is an essential phytohormone involved in plant development and stress responses. Its perception occurs through the CORONATINE INSENSITIVE (COI) nuclear receptor allowing to target the Jasmonate-ZIM domain (JAZ) repressors for degradation by the 26S proteasome. Consequently, repressed transcription factors are released and expression of jasmonate responsive genes is induced. In rice, three OsCOI genes have been identified, OsCOI1a and the closely related OsCOI1b homolog, and OsCOI2. While the roles of OsCOI1a and OsCOI1b in plant defense and leaf senescence are well-established, the significance of OsCOI2 in plant development and jasmonate signaling has only emerged recently. To unravel the role of OsCOI2 in regulating jasmonate signaling, we examined the transcriptomic and metabolomic responses of jasmonate-treated rice lines mutated in both the OsCOI1a and OsCOI1b genes or OsCOI2. RNA-seq data highlight OsCOI2 as the primary driver of the extensive transcriptional reprogramming observed after a jasmonate challenge in rice roots. A series of transcription factors exhibiting an OsCOI2-dependent expression were identified, including those involved in root development or stress responses. OsCOI2-dependent expression was also observed for genes involved in specific processes or pathways such as cell-growth and secondary metabolite biosynthesis (phenylpropanoids and diterpene phytoalexins). Although functional redundancy exists between OsCOI1a/b and OsCOI2 in regulating some genes, oscoi2 plants generally exhibit a weaker response compared to oscoi1ab plants. Metabolic data revealed a shift from the primary metabolism to the secondary metabolism primarily governed by OsCOI2. Additionally, differential accumulation of oryzalexins was also observed in oscoi1ab and oscoi2 lines. These findings underscore the pivotal role of OsCOI2 in jasmonate signaling and suggest its involvement in the control of the growth-defense trade-off in rice.

Identification of amino acid residue in the Cronobacter sakazakii LamB responsible for the receptor compatibility of polyvalent coliphage CSP1

Polyvalent bacteriophages show the feature of infecting bacteria across multiple species or even orders. Infectivity of a polyvalent phage is variable depending on the host bacteria, which can disclose differential inhibition of bacteria by the phage. In this study, a polyvalent phage CSP1 infecting both Cronobacter sakazakii ATCC 29544 and Escherichia coli MG1655 was isolated. CSP1 showed higher growth inhibition and adsorption rate in E. coli compared to C. sakazakii, and identification of host receptors revealed that CSP1 uses E. coli LamB (LamBE) as a receptor but that CSP1 requires both C. sakazakii LamB (LamBC) and lipopolysaccharide (LPS) core for C. sakazakii infection. The substitution of LamBC with LamBE in C. sakazakii enhanced CSP1 susceptibility and made C. sakazakii LPS core no more essential for CSP1 infection. Comparative analysis of LamBC and LamBE disclosed that the extra proline at amino acid residue 284 in LamBC made a structural distinction by forming a longer loop and that the deletion of 284P in LamBC aligns its structure and makes LamBC function like LamBE, enhancing CSP1 adsorption and growth inhibition of C. sakazakii. These results suggest that 284P of LamBC plays a critical role in determining the CSP1-host bacteria interaction. These findings could provide insight into the elucidation of molecular determinants in the interaction between polyvalent phages and host bacteria and help us to understand the phage infectivity for efficient phage application.

IMPORTANCE

Polyvalent phages have the advantage of a broader host range, overcoming the limitation of the narrow host range of phages. However, the limited molecular biological understanding on the host bacteria-polyvalent phage interaction hinders its effective application. Here, we revealed that the ability of the polyvalent phage CSP1 to infect Cronobacter sakazakii ATCC 29544 is disturbed by a single proline residue in the LamB protein and that lipopolysaccharide is used as an auxiliary receptor for CSP1 to support the adsorption and the subsequent infection of C. sakazakii. These results can contribute to a better understanding of the interaction between polyvalent phages and host bacteria for efficient phage application.

Histochemical and molecular analyses reveal an insight into the scent volatiles synthesis and emission in ephemeral flowers of Murraya paniculata (L.) Jack

MAIN CONCLUSION

Temporal histolocalization of floral volatiles in the petal epidermis of Murraya paniculata was found to be linked with the coordinated expression of candidate genes and successive accumulation of an internal pool of volatiles. Murraya paniculata (Rutaceae) is known for its highly fragrant ephemeral flowers that emit volatiles to attract nocturnal pollinators. To unfold the patterns of volatile emission in relation to floral life-span, we studied time-course accumulation and emission rate of scent volatiles at six timepoints of floral maturation, at an interval of 4 h starting from the bud stage to the senescence stage on the next day. This study revealed the maximum emission rate of scent volatiles at the anthesis stage at 18:00 h. This finding correlates well with the maximum accumulation of volatiles in the internal pool of the flowers at this stage. The key volatiles detected in both emitted and internal pools were benzaldehyde, benzeneacetaldehyde, linalool, caryophyllene, germacrene-D and α-farnesene. In addition, the internal pool also contained substantial amounts of indole, scopoletin, caffeine and osthole. To histochemically localize the temporal accumulation of major volatile groups in the epidermal cells, petal cross sections were stained with NaDi and ferric chloride to visualize terpenes and phenolics, respectively, under light microscope. Histolocalization studies showed a higher accumulation of terpenes at 14:00 h and 18:00 h, which subsequently was reduced as senescence approached. Significant phenolics in the abaxial and adaxial layers of the petal epidermis accumulated at 18:00 h and at the early senescence (06:00 h) stages. Furthermore, temporal localization of active shikimate dehydrogenase (SKDH) protein through in-gel activity assay demonstrated higher enzymatic activities at anthesis (18:00 h) and fully bloomed (02:00 h) stages, supporting the findings of higher accumulation of phenolic volatiles at 18:00 h and 06:00 h stages. Expression analysis of major candidate genes of floral scent volatiles pathway supported the hypothesis that the emission rate of floral fragrance reached its maximum at the anthesis (18:00 h) stage. In contrast, biosynthesis of scent compounds started at the bud (14:00 h) stage itself as indicated by the RT-PCR semi-quantitative estimation. As flowers of M. paniculata attract multiple pollinator species, this study could also serve as a springboard for pollination biology in Rutaceae, which includes important fruit crops.

Plant metabolic responses to soil herbicide residues differ under herbivory in two woodland strawberry genotypes

The use of glyphosate-based herbicides (GBHs) to control weeds has increased exponentially in recent decades, and their residues and degradation products have been found in soils across the globe. GBH residues in soil have been shown to affect plant physiology and specialised metabolite biosynthesis, which, in turn, may impact plant resistance to biotic stressors. In a greenhouse study, we investigated the interactive effects between soil GBH residues and herbivory on the performance, phytohormone concentrations, phenolic compound concentrations and volatile organic compound (VOC) emissions of two woodland strawberry (Fragaria vesca) genotypes, which were classified as herbivore resistant and herbivore susceptible. Plants were subjected to herbivory by strawberry leaf beetle (Galerucella tenella) larvae, and to GBH residues by growing in soil collected from a field site with GBH treatments twice a year over the past eight years. Soil GBH residues reduced the belowground biomass of the susceptible genotype and the aboveground biomass of both woodland strawberry genotypes. Herbivory increased the belowground biomass of the resistant genotype and the root-shoot ratio of both genotypes. At the metabolite level, herbivory induced the emission of several VOCs. Jasmonic acid, abscisic acid and auxin concentrations were induced by herbivory, in contrast to salicylic acid, which was only induced by herbivory in combination with soil GBH residues in the resistant genotype. The concentrations of phenolic compounds were higher in the resistant genotype compared to the susceptible genotype and were induced by soil GBH residues in the resistant genotype. Our results indicate that soil GBH residues can differentially affect plant performance, phytohormone concentrations and phenolic compound concentrations under herbivore attack, in a genotype-dependent manner. Soil GBH altered plant responses to herbivory, which may impact plant resistance traits and species interactions. With ongoing agrochemical pollution, we need to consider plant cultivars with better resistance to polluted soils while maintaining plant resilience under challenging environmental conditions.

A Novel MsEOBI-MsPAL1 Module Enhances Salinity Stress Tolerance, Floral Scent Emission and Seed Yield in Alfalfa

Alfalfa (Medicago sativa L.) is an important and widely cultivated forage legume, yet its yield is constrained by salinity stress. In this study, we characterized an R2R3-MYB transcription factor MsEOBI in alfalfa. Its salt tolerance function and regulatory pathways were investigated. The nuclear-localized MsEOBI functions as a transcriptional activator, enhancing salinity tolerance by promoting the biosynthesis of flavonoids and lignin, as well as facilitating the scavenging of reactive oxygen species (ROS). Additionally, MsEOBI promotes pollinator attraction and increases seed yield by activating the biosynthesis of volatile phenylpropanoids. Yeast one-hybrid (Y1H), dual-luciferase reporter and chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) assays demonstrated that MsEOBI directly binds to the promoter regions of MsPAL1, a key gene in the phenylpropanoid pathway, thereby activating its expression. Overexpression of MsPAL1 enhances salinity tolerance in alfalfa. These findings elucidate the role of the MsEOBI-MsPAL1 regulatory module and provide valuable genetic resources for the future breeding of salt-tolerant alfalfa varieties.

Large-scale analysis of the PAC domain structure of arogenate dehydratases reveals their evolutionary patterns in angiosperms

Arogenate dehydratase (ADT) is the key limiting enzyme of plant phenylalanine biosynthesis, but some ADTs display a prephenate decarboxylase/dehydratase activity-conferring (PAC) domain. The genome resources of 70 species were employed to identify genes and outline their characteristics, especially the number and type of PAC domain structures. We obtained 522 ADTs, and their size, exon number, amino acid number and putative protein isoelectric point greatly varied from 306 to 2520 bp, 1 to 15, 101 to 839 and 4.37 to 11.18, respectively. We classified the ADTs into Class α (without a PAC domain) (115, 22.0 %), β (with a type I PAC domain) (244, 46.7 %) and γ (with a type II PAC domain) (163, 31.2 %), and their distribution frequencies exhibited large differences among various branches of angiosperms. We found that Class γ members are more conserved than Class β members, although they commonly experienced multiple duplication events and strong purifying selection, which resulted in a small number, and the putative origin order was from Class α to β and then to γ. In addition, the co-occurrence of both Class β and γ members could ensure the survival of angiosperms, while their optimized composition and strategically intertwined regulation may facilitate core eudicot success.

Global lysine succinylation analysis unveils post-translational regulation effect on phenylpropanoid metabolism remodeling during Lonicera japonica flower development

Lonicera japonica plays a significant role in traditional Chinese medicine and as a food source, making it a focus of studies on protein succinylation and its potential role in regulating secondary metabolism during flower development. This study aimed to clarify the regulatory mechanism of protein succinylation on phenylpropanoid-related phenotypic changes by conducting a global lysine succinylation proteomic analysis across different flowering stages. A total of 586 lysine succinylated peptides in 303 proteins were identified during early and late floral stages. Functional enrichment analysis revealed that succinylated proteins primarily participated in the tricarboxylic acid (TCA) cycle, amino acid metabolism, and secondary metabolism. The abundance of succinylated aspartate transaminase (AT), 4-coumarate-CoA ligase (4CL), and phenylalanine N-hydroxylase (CYP79A2) in phenylpropanoid metabolism varied during flower development. In vitro experiments demonstrated that succinylation increased AT activity while inhibited 4CL activity. Decreased levels of total flavonoids and phenolic acids indicated significant alterations in phenylpropanoid metabolism during later floral stages. These results suggest that succinylation of TCA cycle proteins not only influences flower development but also, together with AT-4CL-CYP79A2 co-succinylation, redirects phenylpropanoid metabolism during flower development in L. japonica.

Bifunctional Phenylalanine/Tyrosine Ammonia-Lyase (PTAL) Enhances Lignin Biosynthesis: Implications in Carbon Fixation in Plants by Genetic Engineering

Lignin is a key metabolite for terrestrial plants. Two types of aromatic amino acids, phenylalanine (Phe) and tyrosine (Tyr), serve as the precursors for lignin biosynthesis. In most plant species, Phe is deaminated by Phe ammonia-lyase (PAL) to initiate lignin biosynthesis, but in grass species, Phe and Tyr are deaminated by Phe/Tyr ammonia-lyase (PTAL). To understand the efficiency of PAL and PTAL, we used transgenic and non-transgenic Arabidopsis with PAL and crop-weedy rice hybrids (CWRH) with PTAL to analyze lignin-biosynthesis-associated metabolites. The transgenic plants overexpressed the exogenous 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, whereas the non-transgenic plants normally expressed the endogenous EPSPS gene. Our results show significantly increased Phe/Tyr contents in transgenic Arabidopsis and CWRH plants, leading to substantially increased lignin and biomass. In addition, the PTAL pathway promotes a much greater proportion of increased lignin and biomass in transgenic CWRH than in transgenic Arabidopsis lineages. Evidently, more efficient lignin biosynthesis characterized the grass species possessing the PTAL pathway. These findings are important for a better understanding of the PAL and PTAL's functions in the phenylpropanoid metabolic pathways in the evolution of plant species. These findings also have great value for implications such as effective carbon fixation by enhancing lignin biosynthesis through genetic engineering of their key genes in appropriately selected plant species.

Impact of External Sources of Indole Acetic Acid and 2,3,5-Triiodobenzoic Acid on Alkaloid Production and Their Relationships with Primary Metabolism and Antioxidant Activity in Annona emarginata (Schltdl.) H. Rainer

Annona emarginata is a native Brazilian species capable of producing at least ten alkaloids of ecological, agronomic, and pharmacological importance. Some studies have explored the effect of external phytoregulators on the production of alkaloids, including the effect of auxins, which, like alkaloids, derive from the shikimic acid pathway. Thus, this study aimed to evaluate how indole acetic acid (IAA) and its inhibitor 2,3,5-triiodobenzoic acid (TIBA) impact the production of alkaloids and the primary metabolism of A. emarginata, which brings advances in the understanding of the mechanisms of alkaloid synthesis and can aid in the bioprospection of molecules of interest in Annonaceae. The design was completely randomized, with three treatments (control, IAA [10-6 M] and TIBA [10-6 M]) and five collection times (12, 36, 84, 156, and 324 h). The following variables were analyzed: total alkaloids, alkaloid profile, nitrate reductase activity, gas exchange in photosynthesis, chlorophyll a fluorescence, sugars, starch, and antioxidant activity. Of the twelve alkaloids analyzed, discretine and xylopine were not detected in the control plants; however, both were detected when IAA was applied (in roots and leaves) and xylopine (in roots) when the inhibitor was applied. The alkaloid asimilobine was not detected with the use of TIBA. Variations in alkaloid concentrations occurred in a punctual manner, without significant variations in photosynthesis and nitrate reductase activity, but with variations in the antioxidant system and sugar concentrations, mainly at 156 h, when the highest alkaloid concentrations were observed with the use of TIBA. It could be concluded that IAA is capable of selectively modulating the production of alkaloids in A. emarginata, either due to an external source or by the application of its inhibitor (TIBA).

In vivo assembly in tobacco cells to elucidate and engineer the biosynthesis of 4-hydroxydihydrocinnamaldehyde from Gloriosa superba

KEY MESSAGE

This study described the biosynthesis of 4-hydroxydihydrocinnamaldehyde sharing with monolignol pathway and supplemented the biosynthesis of colchicine in G. superba, 4-hydroxydihydrocinnamaldehyde produced in tobacco BY2 cells provided an important stepstone. The precursor, 4-hydroxydihydrocinnamaldehyde (4-HDCA), participates in the biosynthesis of the carbon skeleton of colchicine, which is derived from L-phenylalanine. However, one hypothesis proposed that 4-HDCA is synthesized by sharing the early part of the monolignol pathway in G. superba. In this study, we validated this prediction and identified the enzymatic functions involved in this pathway. GsDBR1 is a crucial enzyme to illustrate 4-HDCA diverging from monolignol pathway, we first confirmed its reductase activity on 4-coumaraldehyde, an important intermediate compound in monolignol biosynthesis. Then, the biochemical function of recombinant enzymes belonging to the other four families were verified to elucidate the entire process of 4-HDCA biosynthesis from L-phenylalanine. After reconstruction, the 4-HDCA was 78.4 ng/g with fresh weight (FW) of transgenic tobacco cells, and the yield increased to 168.22 ng/g·FW after improved treatment with methyl jasmonate (MeJA). The elucidation of 4-HDCA biosynthesis sharing the monolignol pathway supplemented the biosynthesis of colchicine in G. superba, and the production of 4-HDCA in tobacco cells provides an important step in the development of plant cell cultures as heterologous bio-factories for secondary metabolite production.

Pathway-Adapted Biosensor for High-Throughput Screening of O-Methyltransferase and its Application in Vanillin Synthesis

Vanillin is a widely used flavoring compound in the food, pharmaceutical, and cosmetics area. However, the biosynthesis of vanillin from low-cost shikimic acid is significantly hindered by the low activity of the rate-limiting enzyme, caffeate O-methyltransferase (COMT). To screen COMT variants with improved conversion rates, we designed a biosensing system that is adaptable to the COMT-mediated vanillin synthetic pathway. Through the evolution of aldehyde transcriptional factor YqhC, we obtained a dual-responsive variant, MuYqhC, which positively responds to the product and negatively responds to the substrate, with no response to intermediates. Using the MuYqhC-based vanillin biosensor, we successfully identified a COMT variant, Mu176, that displayed a 7-fold increase in the conversion rate compared to the wild-type COMT. This variant produced 2.38 mM vanillin from 3 mM protocatechuic acid, achieving a conversion rate of 79.33%. The enhanced activity of Mu176 was attributed to an enlarged binding pocket and strengthened substrate interaction. Applying Mu176 to Bacillus subtilis increased the level of vanillin production from shikimic acid by 2.39-fold. Further optimization of the production chassis, increasing the S-adenosylmethionine supply and the precursor concentration, elevated the vanillin titer to 1 mM, marking the highest level of vanillin production from shikimic acid in Bacillus. Our work highlights the significance of the MuYqhC-based biosensing system and the Mu176 variant in vanillin production.

Exploring Metabolomics to Innovate Management Approaches for Fall Armyworm (Spodoptera frugiperda [J.E. Smith]) Infestation in Maize (Zea mays L.)

The Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is a highly destructive lepidopteran pest known for its extensive feeding on maize (Zea mays L.) and other crops, resulting in a substantial reduction in crop yields. Understanding the metabolic response of maize to FAW infestation is essential for effective pest management and crop protection. Metabolomics, a powerful analytical tool, provides insights into the dynamic changes in maize's metabolic profile in response to FAW infestation. This review synthesizes recent advancements in metabolomics research focused on elucidating maize's metabolic responses to FAW and other lepidopteran pests. It discusses the methodologies used in metabolomics studies and highlights significant findings related to the identification of specific metabolites involved in FAW defense mechanisms. Additionally, it explores the roles of various metabolites, including phytohormones, secondary metabolites, and signaling molecules, in mediating plant-FAW interactions. The review also examines potential applications of metabolomics data in developing innovative strategies for integrated pest management and breeding maize cultivars resistant to FAW by identifying key metabolites and associated metabolic pathways involved in plant-FAW interactions. To ensure global food security and maximize the potential of using metabolomics in enhancing maize resistance to FAW infestation, further research integrating metabolomics with other omics techniques and field studies is necessary.

Molecular basis of one-step methyl anthranilate biosynthesis in grapes, sweet orange, and maize

Plants synthesize an array of volatile compounds, many of which serve ecological roles in attracting pollinators, deterring herbivores, and communicating with their surroundings. Methyl anthranilate (MeAA) is an anti-herbivory defensive volatile responsible for grape aroma that is emitted by several agriculturally relevant plants, including citrus, grapes, and maize. Unlike maize, which uses a one-step anthranilate methyltransferase (AAMT), grapes have been thought to use a two-step pathway for MeAA biosynthesis. By mining available transcriptomics data, we identified two AAMTs in Vitis vinifera (wine grape), as well as one ortholog in "Concord" grape. Many angiosperms methylate the plant hormone salicylic acid (SA) to produce methyl salicylate, which acts as a plant-to-plant communication molecule. Because the Citrus sinensis (sweet orange) SA methyltransferase can methylate both anthranilate (AA) and SA, we used this enzyme to examine the molecular basis of AA activity by introducing rational mutations, which identified several active site residues that increase activity with AA. Reversing this approach, we introduced mutations that imparted activity with SA in the maize AAMT, which uncovered different active site residues from those in the citrus enzyme. Sequence and phylogenetic analysis revealed that one of the Vitis AAMTs shares an ancestor with jasmonic acid methyltransferases, similar to the AAMT from strawberry (Frageria sp.). Collectively, these data demonstrate the molecular mechanisms underpinning AA activity across methyltransferases and identify one-step enzymes by which grapes synthesize MeAA.

Expression of dehydroshikimate dehydratase in poplar induces transcriptional and metabolic changes in the phenylpropanoid pathway

Modification of lignin in feedstocks via genetic engineering aims to reduce biomass recalcitrance to facilitate efficient conversion processes. These improvements can be achieved by expressing exogenous enzymes that interfere with native biosynthetic pathways responsible for the production of the lignin precursors. In planta expression of a bacterial 3-dehydroshikimate dehydratase in poplar trees reduced lignin content and altered the monomer composition, which enabled higher yields of sugars after cell wall polysaccharide hydrolysis. Understanding how plants respond to such genetic modifications at the transcriptional and metabolic levels is needed to facilitate further improvement and field deployment. In this work, we acquired fundamental knowledge on lignin-modified poplar expressing 3-dehydroshikimate dehydratase using RNA-seq and metabolomics. The data clearly demonstrate that changes in gene expression and metabolite abundance can occur in a strict spatiotemporal fashion, revealing tissue-specific responses in the xylem, phloem, or periderm. In the poplar line that exhibited the strongest reduction in lignin, we found that 3% of the transcripts had altered expression levels and ~19% of the detected metabolites had differential abundance in the xylem from older stems. The changes affected predominantly the shikimate and phenylpropanoid pathways as well as secondary cell wall metabolism, and resulted in significant accumulation of hydroxybenzoates derived from protocatechuate and salicylate.

Harnessing in vivo synthesis of bioactive multiarylmethanes in Escherichia coli via oxygen-mediated free radical reaction induced by simple phenols

BACKGROUND

Xanthenes and multi-aryl carbon core containing compounds represent different types of complex and condensed architectures that have impressive wide range of pharmacological, industrial and synthetic applications. Moreover, indoles as building blocks were only found in naturally occurring metabolites with di-aryl carbon cores and in chemically synthesized tri-aryl carbon core containing compounds. Up to date, rare xanthenes with indole bearing multicaryl carbon core have been reported in natural or synthetic products. The underlying mechanism of fluorescein-like arthrocolins with tetra-arylmethyl core were synthesized in an engineered Escherichia coli fed with toluquinol remained unclear.

RESULTS

In this study, the Keio collection of single gene knockout strains of 3901 mutants of E. coli BW25113, together with 14 distinct E. coli strains, was applied to explore the origins of endogenous building blocks and the biogenesis for arthrocolin assemblage. Deficiency in bacterial respiratory and aromatic compound degradation genes ubiX, cydB, sucA and ssuE inhibited the mutant growth fed with toluquinol. Metabolomics of the cultures of 3897 mutants revealed that only disruption of tnaA involving in transforming tryptophan to indole, resulted in absence of arthrocolins. Further media optimization, thermal cell killing and cell free analysis indicated that a non-enzyme reaction was involved in the arthrocolin biosynthesis in E. coli. Evaluation of redox potentials and free radicals suggested that an oxygen-mediated free radical reaction was responsible for arthrocolins formation in E. coli. Regulation of oxygen combined with distinct phenol derivatives as inducer, 31 arylmethyl core containing metabolites including 13 new and 8 biological active, were isolated and characterized. Among them, novel arthrocolins with p-hydroxylbenzene ring from tyrosine were achieved through large scale of aerobic fermentation and elucidated x-ray diffraction analysis. Moreover, most of the known compounds in this study were for the first time synthesized in a microbe instead of chemical synthesis. Through feeding the rat with toluquinol after colonizing the intestines of rat with E. coli, arthrocolins also appeared in the rat blood.

CONCLUSION

Our findings provide a mechanistic insight into in vivo synthesis of complex and condensed arthrocolins induced by simple phenols and exploits a quinol based method to generate endogenous aromatic building blocks, as well as a methylidene unit, for the bacteria-facilitated synthesis of multiarylmethanes.