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Transcriptome and metabolome profiling of the medicinal plant Dictamnus dasycarpus reveal key genes involved in quinoline alkaloids biosynthesis and limonoids biosynthesis.

BACKGROUND: As a member of Rutaceae family, Dictamnus dasycarpus Turcz. represents a prominent medicinal plant and economically valuable crop in traditional Chinese medicine, and is renowned for its therapeutic efficacy in treating dermatological conditions. The pharmacological activity of this species primarily stems from quinoline alkaloids and limonoids, which predominantly accumulate in the taproots. These bioactive compounds serve as critical determinants of both medicinal quality and crop yield. Nevertheless, the molecular mechanisms governing their dynamic accumulation patterns in D. dasycarpus taproots remain uncertain, and the fundamental biochemical basis underlying this process has yet to be elucidated. RESULTS: Metabolomic and transcriptomic analyses were carried out to investigate metabolites and gene expression during the development of D. dasycarpus taproots. The differentially accumulated secondary metabolites (DAMs) mainly included quinoline alkaloids and limonoids, and the accumulation of total alkaloids and total limonoids primarily occurred during 2- and 4-year-old. The differentially expressed genes (DEGs) are related to Glycolysis/Gluconeogenesis, Phenylalanine, tyrosine and tryptophan biosynthesis, Tryptophan metabolism, Terpenoid backbone biosynthesis, Sesquiterpenoid and triterpenoid biosynthesis, which had a close relationship with the accumulation of quinoline alkaloids and limonoids. Furthermore, we identified that some CYP450s, acetyltransferase, isomerase, 2-ODDs and others may play an important role in the process of producing quinoline alkaloids and limonoids. CONCLUSION: These results elucidated the molecular mechanisms and metabolic changes underlying the dynamic accumulation process occurring in the taproots of D. dasycarpus. These findings provide a theoretical basis for the planting and harvesting of D. dasycarpus.

Limonins

[Riboflavin biosynthesis operon of Bacillus subtilis. XIII. Genetic and biochemical study of mutants with regard to intermediate stages of biosynthesis].

New riboflavin dependent mutants of Bacillus subtilis accumulating different pteridines were studied. The data obtained show that the formation of ribityl side chain proceeds in a few steps at least on a part of riboflavin precursors. The oxidation of connected ribosyl into ribulose with subsequent restoration of it into ribityl proceeds at first. The corresponding genes are located on terminal part of riboflavin operon, as show the results of two-factor transformational crosses with different donors and recipients.

Bacillus subtilis

Initiation of Hybrid Polyketide-Nonribosomal Peptide Biosynthesis via Two Distinct Pathways in C. elegans.

Nemamide A and B are hybrid polyketide-nonribosomal peptides that are produced by the PKS-1-NRPS-1 enzymatic assembly line in the canal-associated neurons (CANs) of the nematode Caenorhabditis elegans. These signaling molecules promote survival during and recovery from starvation-induced larval arrest. Here, using genome editing and targeted metabolomics, we probed the roles of the different domains of PKS-1 in the initiation of nemamide biosynthesis. We showed that the first four domains of PKS-1 are not required for the biosynthesis of the triene-containing nemamide A, but are required for the biosynthesis of the tetraene-containing nemamide B. By targeting genes that are highly expressed in the CANs, we identified two additional enzymes that participate in the biosynthetic pathway: the peroxisomal carnitine O-octanoyl transferase CROT-1, which is required for the biosynthesis of nemamide A, and the enoyl-CoA hydratase ECH-7, which is required for the biosynthesis of nemamide B. We heterologously expressed CROT-1 and showed that it prefers hexanoyl-CoA and octanoyl-CoA as substrates, converting them to the corresponding carnitine esters. According to our model, ECH-7 is needed to supply the starter unit for nemamide B biosynthesis, which is loaded onto the first carrier protein of PKS-1 and extended by the first module, thereby installing the double bond that is unique to nemamide B. Meanwhile, CROT-1 is needed to supply the starter unit for nemamide A biosynthesis, which is loaded onto the second carrier protein of PKS-1. Our data suggest that the biosynthetic pathways of nemamide A and B are under the control of two different initiation mechanisms and, thus, that the production of these two secondary metabolites may be independently regulated.

Animals

ODR1, the key seed dormancy and germination regulator, promotes seed Proanthocyanidin biosynthesis via interaction with TTG1 and modulation of MBW complex activity.

Seed dormancy and germination are crucial for both plant survival and reproduction and for crop sowing and harvesting. Proanthocyanidins (PAs), one of the most abundant seed metabolites, play a role in enhancing dormancy and inhibiting germination. Multiple regulatory factors involved in PAs biosynthesis can alter seed dormancy or germination capacity. However, whether the dormancy or germination factors reciprocally influence the PAs biosynthesis is unclear. Here, we report that ODR1, a seed dormancy and germination key factor and a transcriptional (co-) repressor, can regulate seed PAs biosynthesis and act as a transcriptional co-activator. The odr1 mutant shows lighter seed coat color, decreased PAs contents, and reduced expression of PAs biosynthesis genes, which are restored in the ODR1 complementary lines. ODR1 interacts with TTG1 and forms a complex with TTG1/TT2/TT8 (three MBW complex components), enhancing their activation on promoters of PAs biosynthesis genes like DFR and ANS. Overexpressing TTG1 in the odr1-2 mutant rescues or even reverses PA-related phenotypes of odr1-2, confirming that ODR1-mediated regulation of PAs biosynthesis is dependent on TTG1. Moreover, three homologous copies of ODR1 in rapeseed were identified, and simultaneous knockout of them reduces the PAs contents. These results revealed the previously uncharacterized functions of ODR1 in PAs biosynthesis, suggested its conservation between Arabidopsis and rapeseed, and provided important gene resources for rapeseed variety improvement.

Proanthocyanidins

Fatty acid biosynthesis in yeast.

Fatty acid synthetase and acetyl CoA carboxylase mutants have been used to study several aspects of fatty acid biosynthesis in yeast: the contribution of the various enzymes of fatty acid biosynthesis and modification to the overall cellular fatty acid composition, the mechanism of fatty acyl chain elongation in yeast, the molecular structure and the reaction mechanism of the fatty acid synthetase complex and the genetic control of the biosynthesis of this multi-enzyme system. Genetic and biochemical evidence suggest an alpha6beta6 molecular structure of this complex, where alpha and beta are multifunctional proteins comprising, respectively, 3 and 5 of the various fatty acid synthetase component functions. The two subunits alpha and beta are synthesized on two different, unliked genes, fas 2 and fas 1. The biosynthesis of both is coordinated. The various component enzyme activities reside in distinct domains on the multifunctional chains. While most domains appear to be functionally independent, the three acyl transferases exhibit extensive mutual interactions. It is suggested that the biosynthesis of a multifunctional protein is favoured on the grounds of kinetics and regulation as compared with the formation of a complex of the corresponding individual enzymes.

Acetyl-CoA Carboxylase

Coordinated use of three homocysteine methyltransferases supports l-methionine biosynthesis and environmental adaptation among plant-associated bacteria.

Plant pathogens colonize multiple plant-associated habitats throughout their life cycle, encountering distinct nutrient conditions and microbial communities. l-methionine is required for bacterial growth and environmental adaptation. However, how plant pathogens coordinate l-methionine biosynthetic pathways to adapt to different plant-associated environments remains poorly understood. Here, using the plant pathogen Xanthomonas campestris pv. campestris strain XC1 as a model, we show that three homocysteine methyltransferase pathways allow XC1 to catalyze the final step of l-methionine biosynthesis using different methyl donors and cofactors under different environmental conditions. Bioinformatic and transcriptional analyses identified three homocysteine methyltransferase-associated operons in XC1, mesMXD, mmuPM, and metHRHaHb, corresponding to the MesD-, MmuM-, and MetHaHb-dependent pathways, respectively. MesD uses an endogenously synthesized methyl donor and functions as the dominant homocysteine methyltransferase under l-methionine-limiting conditions, supporting bacterial growth, intracellular l-methionine accumulation, and full virulence. Furthermore, MmuM enables XC1 to use plant-derived S-methylmethionine for l-methionine biosynthesis, whereas MetHaHb enables XC1 to use vitamin B12 supplied by a neighboring bacterium for l-methionine biosynthesis in co-culture. Expression analyses showed that mesMXD was the only homocysteine methyltransferase-associated operon that responded to l-methionine availability, and its expression also decreased when S-methylmethionine- or vitamin B12-dependent pathways supported l-methionine biosynthesis. Comparative genomic analysis further showed that the three-homocysteine methyltransferase configuration is conserved in Xanthomonas and is also present in other plant-associated bacteria. Together, these findings show that a plant pathogen can coordinate endogenous, plant-derived, and microbially supported homocysteine methyltransferase pathways to maintain l-methionine biosynthesis, providing a metabolic strategy for adaptation to plant-associated environments.

Methionine

Amino acids as repressors of nitrogenase biosynthesis in Klebsiella pneumoniae.

Nitrogenase biosynthesis in Klebsiella pneumoniae including mutant strains, which produce nitrogenase in the presence of NH+4 (Shanmugam, K.T., Chan, Irene, and Morandi, C. (1975) Biochim. Biophys. Acta 408, 101--111) is repressed by a mixture of L-amino acids. Biochemical analysis shows that glutamine synthetase activity in strains SK-24, SK-28, and SK-29 is also repressed by amino acids, with no detectable effect on glutamate dehydrogenase. Among the various amino acids, L-glutamine in combination with L-aspartate was found to repress nitrogenase biosynthesis completely. In the presence of high concentrations of glutamine (1 mg/ml) even NH+4 repressed nitrogenase biosynthesis in the strains SK-27, SK-37, SK-55 and SK-56. Under these conditions, increased glutamate dehydrogenase activity was also detected. Physiological studies show that nitrogenase derepressed strains are unable to utilize NH+4 as sole source of nitrogen for biosynthesis of glutamate for biosynthesis of glutamate, whereas back mutations leading to NH+4 utilization results in sensitivity to repression by NH+4. These findings suggest that amino acids play an important role as regulators of nitrogen fixation.

Amino Acids

Sphingolipid biosynthesis and vitamin K metabolism in Bacteroides melaninogenicus.

B. melaninogenicus provides a unique system for the study of the biosynthesis of an important group of lipids, the phosphosphingolipids. Sphingolipid biosynthesis can be repressed and induced by depletion and restoration of vitamin K. At least one enzyme involved in sphingolipid biosynthesis from the microorganism can be solubilized and so purified by conventional methods. Pathways involved in biosynthesis may differ from hitherto postulated pathways, for example, the incorporation of NH4+ into ethanolamine residue of ceramide phosphorylethanolamine. Moreover, the derivation of mutants defective in steps in sphingolipid biosynthesis would be of great value in these studies.

Animals

Genome-resolved analysis reveals disruption of gut microbial vitamin B and K2 biosynthesis during Toxoplasma gondii infection in mice.

UNLABELLED: Toxoplasma gondii infection remodels the gut microbiome, yet its impact on microbial vitamin biosynthetic potential and host redox metabolism remains unclear. Here, we integrated mouse gut metagenomes with publicly available metagenome-assembled genomes (MAGs) to construct a genome-resolved atlas of B-vitamin and vitamin K2 biosynthesis. From 45,697 MAGs, we curated 4,771 representative genomes, of which 2,682 met high-quality criteria (completeness &#x2265;90%, contamination <5%). Functional annotation identified 229,717 vitamin-related genes corresponding to 177 Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologs across de novo pathways for eight B vitamins, thiamine (B1), riboflavin (B2), niacin (B3), pantothenate (B5), pyridoxine (B6), biotin (B7), folate (B9), cobalamin (B12), and vitamin K2. Among the high-quality genomes, 1,665 encoded complete de novo pathways for at least one vitamin, highlighting functional specialization and community-level complementarity. Transcripts per million-normalized metagenomic read counts revealed significant differences in KEGG ortholog abundances across six of the nine vitamin pathways. Reanalysis of metagenomic data from infected mice (acute, chronic, and control; n = 10 per group) revealed a stage-dependent reduction in &#x3b1;-diversity of vitamin biosynthesis pathways during acute infection, and a clear &#x3b2;-diversity separation from chronic and control groups. Core niacin biosynthesis genes (nadB, nadA, nadC) displayed phylum-specific redistribution, indicating selective remodeling of microbial NAD+ precursor production under infection-induced metabolic stress. These results suggest that T. gondii infection disrupts cooperative vitamin biosynthetic networks while specifically modulating niacin pathways linked to host NAD+ metabolism. IMPORTANCE: Gut microbes can synthesize essential vitamins, but how infection alters this function is poorly understood. By integrating mouse gut metagenomes with genome-resolved microbial data, we show that Toxoplasma gondii infection reshapes the vitamin biosynthetic potential of the gut microbiome in a stage-dependent manner. Acute infection reduces the diversity of vitamin biosynthesis pathways and shifts the taxonomic distribution of key niacin biosynthesis genes involved in microbial NAD+ precursor production. These findings identify vitamin metabolism, especially niacin-related pathways, as a sensitive functional axis of microbiome remodeling during infection. Our work links microbial taxonomic changes to functional metabolic consequences and suggests that microbiome-mediated regulation of NAD+-related metabolism may contribute to host redox adaptation during T. gondii infection.

B vitamins

A Comprehensive Review on the Biosynthesis of Tropane Alkaloids.

Tropane alkaloids (TA) constitute a class of plant specialized metabolites with important pharmaceutical applications, including the anticholinergic agents hyoscyamine and scopolamine and the local anesthetic cocaine. Over the past decade, advances in genomics, structural biology, and synthetic biology have substantially revised our understanding of TA biosynthesis, leading to the identification of numerous key biosynthetic enzymes and evolutionary mechanisms. This review comprehensively summarizes current knowledge of TA biosynthesis from precursor formation to structurally diverse end products. We describe the pathway from putrescine to tropinone, the stereoselective metabolic branching mediated by Tropinone Reductases, and the downstream biosynthesis of medicinal tropane alkaloids, calystegines, and cocaine. Particular emphasis is placed on recent discoveries concerning catalytic mechanisms, structural determinants of substrate specificity, metabolic compartmentalization, and the convergent evolution of TA biosynthesis in Solanaceae and Erythroxylaceae. We further integrate advances in genomics, evolutionary biology, and metabolic engineering to highlight emerging strategies for microbial production and pathway redesign. By providing a comprehensive synthesis of recent progress and critical perspectives on unresolved questions, this review offers an updated framework for understanding TA biosynthesis and supports future research in plant specialized metabolism, synthetic biology, and natural product engineering.

Tropanes

Inhibition of prostaglandin biosynthesis by non-narcotic analgesic drugs.

The existence of a relationship between inhibition of prostaglandin biosynthesis and analgesic or anti-inflammatory activity was investigated in the case of the non-narcotic analgesics glafenine, floctafenine and clometacine, in comparison to indomethacin and acetylsalicylic acid. These compounds inhibit prostaglandin biosynthesis from arachidonic acid in a guinea-pig lung homogenate as strongly as indomethacin. On its biosynthesis in rat epididymal tissue stimulated by noradrenaline, glafenine equals indomethacin inhibitory potency, whereas floctafenine and clometacine are less active. Acetylsalicylic acid is the least active in both preparations. In vivo, prostaglandin biosynthesis induced in rat peritoneal fluid by injection of acetic acid is inhibited by the 5 drugs, ranked as follows: floctafenine greater than indomethacin greater than glafenine greater than clometacine greater than acetylsalicylic acid. The pharmacological profile of glafenine, floctafenine and clometacine is characterized by a relatively strong effect on acetic acid writhing and a relatively weak effect on carrageenin oedema, U.V. erythema and adjuvant arthritis. The inhibition of prostaglandin biosynthesis seems better correlated with their analgesic activity than with their anti-inflammatory effects. The results show that prostaglandins could play an important role in the genesis of tissulary pain in animals.

Acetates

Light regulates capsaicinoid biosynthesis via the CaHY5-CaBBX2-CaACS8 module in pepper.

Capsaicinoids are a class of unique alkaloids that confer the pungent taste to pepper fruits. However, it remains largely unknown how light regulates the biosynthesis of capsaicinoids. We conducted a metabolic analysis on light- and dark-adapted pepper fruits. The results showed that dark-adapted pepper fruits had lower capsaicinoid contents and correspondingly downregulated transcription of capsaicinoid biosynthetic genes (CBGs), indicating that light plays a crucial role in capsaicinoid biosynthesis. Furthermore, silencing of CaHY5, a pivotal transcription factor gene in the light signaling pathway, decreased the content of capsaicinoid and suppressed the expression of CBGs, whereas transient overexpression of CaHY5 generated exactly opposite results. CaHY5 can bind to the G-box motif in the promoters of CaBBX2 and CaACS8, thereby enhancing their transcriptional levels. The activated CaBBX2 then binds to the T/G-box in the CaACS8 promoter to stimulate its expression. CaBBX2 or CaACS8 silencing led to decreased levels of capsaicinoids, while their transient overexpression produced increased capsaicinoid contents. Collectively, our results indicated that the light-activated CaHY5-CaBBX2-CaACS8 regulatory module plays a pivotal role in capsaicinoid biosynthesis. These findings provide new insights into the influence of light on capsaicinoid biosynthesis and potential targets for activation of this biosynthetic pathway in pepper.

Capsicum

Ethylene response factors ERF.B2 and ERF.B5 synergically regulate ascorbic acid biosynthesis at multiple sites in tomato.

Ascorbic acid (AsA) is an important growth regulator and antioxidant in plants. It is acknowledged as a quality indicator in tomato (Solanum lycopersicum). Although the AsA biosynthetic pathway has been elucidated, its regulatory mechanisms remain largely unknown. In the present study, two members of the ethylene response factor (ERF) family, SlERF.B2 and SlERF.B5, were found to be co-expressed with SlGGP1, a pivotal gene in AsA biosynthesis. These two transcription factors were biochemically confirmed to bind to the DRE motif (GCCGAC/GTCGGC) of the SlGGP1 promoter. Notably, the SlERF.B2 and SlERF.B5 functioned as a dimer to regulate SlGGP1 expression and AsA biosynthesis. Overexpression of SlERF.B2 and SlERF.B5 enhanced the AsA levels up to 149 and 140%, respectively, whereas knockout of either of them could significantly decrease the AsA levels by up to 27%. DNA affinity purification sequencing (DAP-seq) indicated that SlERF.B2 synergistically regulates AsA biosynthesis at multiple sites by targeting the promoters of SlGPI and SlDHAR1. Overexpression of SlERF.B2 or SlERF.B5 in tomato conferred a high capacity for scavenging reactive oxygen species and enhanced tolerance to oxidation and salt stress, potentially by elevating the AsA content. This study unravels novel regulators of AsA biosynthesis and elucidates a molecular network that should facilitate the improvement of this nutrient in tomato and enhance stress tolerance in plants.

Solanum lycopersicum

Quantitative proteomics of molybdenum cofactor biosynthesis and utilization in Caenorhabditis elegans.

The molybdenum cofactor (Moco) is a chemically labile prosthetic group required by a small but essential set of metazoan enzymes, including sulfite oxidase, xanthine dehydrogenase, aldehyde oxidases, and the mitochondrial amidoxime reducing components (MARC). Disruption of Moco biosynthesis in humans causes Molybdenum Cofactor Deficiency (MoCD), a severe neonatal encephalopathy. Caenorhabditis elegans is unique among animals studied so far in that it can meet its Moco requirement through both endogenous biosynthesis and direct uptake of mature Moco from its bacterial diet. However, the organism-wide abundance of the Moco biosynthetic machinery and Moco-dependent enzymes, and their response to altered Moco supply, have remained unknown. Here, using data independent acquisition proteomics with histone anchored absolute quantification, we generated an organism wide quantitative atlas of Moco biosynthesis and utilization in C. elegans under standard and Moco limiting conditions. Components of the biosynthetic pathway showed a strikingly asymmetric abundance. The mitochondrial enzyme MOC-5, which catalyzes the first committed step in Moco biosynthesis, was present at only about 120 copies per genome equivalent, roughly fifty-fold below the downstream cytoplasmic biosynthetic machinery, which ranged from about 5,000 to 8,500 copies per genome equivalent, identifying MOC-5 as a stoichiometric bottleneck. On the utilization side, the MARC paralogs were the dominant Moco consumers, with MARC-1 exceeding 20,000 copies per genome equivalent. Loss of dietary or endogenous Moco selectively depleted the nonsulfurated clients SUOX-1 and MARC-1, whereas biosynthetic proteins remained unchanged, indicating that protein stability, rather than compensatory expression, is the main response to Moco limitation.

Caenorhabditis elegans

Guanine nucleotide biosynthesis blockade impairs MLL complex formation and sensitizes leukemias to menin inhibition.

Targeting the dependency of MLL-rearranged (MLLr) leukemias on menin with small molecule inhibitors has opened new therapeutic strategies for these poor-prognosis diseases. However, the rapid development of menin inhibitor resistance calls for combinatory strategies to improve responses and prevent resistance. Here we show that leukemia stem cells (LSCs) of MLLr acute myeloid leukemia (AML) exhibit enhanced guanine nucleotide biosynthesis, the inhibition of which leads to myeloid differentiation and sensitization to menin inhibitors. Mechanistically, targeting inosine monophosphate dehydrogenase 2 (IMPDH2) reduces guanine nucleotides and rRNA transcription, leading to reduced protein expression of LEDGF and menin. Consequently, the formation and chromatin binding of the MLL-fusion complex is impaired, reducing the expression of MLL target genes. Inhibition of guanine nucleotide biosynthesis or rRNA transcription further suppresses MLLr AML when combined with a menin inhibitor. Our findings underscore the requirement of guanine nucleotide biosynthesis in maintaining the function of the LEDGF/menin/MLL-fusion complex and provide a rationale to target guanine nucleotide biosynthesis to sensitize MLLr leukemias to menin inhibitors.

Proto-Oncogene Proteins

Integrated genomic, transcriptomic, and metabolomic analyses of Chrysanthemum aromaticum provide insights into the volatile terpene biosynthesis.

Chrysanthemum aromaticum is renowned for its uniformly emitted strong and attractive scent, primarily attributed to volatile terpenes. Despite its commercial and horticultural significance, the molecular mechanisms underlying volatile terpene production in C. aromaticum remain largely unexplored. Here, we present the haplotype-resolved genome assembly of C. aromaticum, with a total size of 3.10&#x2009;Gb, comprising nine anchored chromosomes with a contig N50 of 30.66&#x2009;Mb and a scaffold N50 of 350.58&#x2009;Mb. Phylogenetic analyses revealed a distant relationship between C. aromaticum and C. indicum, suggesting that C. aromaticum likely represents a distinct species rather than a variety of C. indicum. Through integrated genomic, transcriptomic, metabolomic, and biochemical analyses, we identified seven TPS involved in monoterpene biosynthesis and six TPS for sesquiterpene biosynthesis. Notably, comparative genomic analysis revealed a gene cluster for &#x3b1;-bisabolol biosynthesis in C. aromaticum, which has specifically expanded in Chrysanthemum species through tandem gene duplications, contributing to the elevated accumulation of &#x3b1;-bisabolol in the leaves of C. aromaticum. Our study provides important insights into the biosynthesis of volatile terpenes, highlighting the genetic basis for C. aromaticum's unique aromatic profile.

Chrysanthemum

Regulation of uridylic acid biosynthesis in the cyanobacterium Anabaena variabilis.

The pathway of uridylic acid biosynthesis established by Leiberman, Kornberg, and Simms has been shown to be operative in the filamentous cyanobacterium Anabaena variabilis. The only enzyme of uridylic acid biosynthesis found to be lacking in two uracil-requiring strains of A. variabilis was aspartate transcarbamylase, the first enzyme in the pathway of de novo biosynthesis of uridvlic acid. Neither uracil-limited growth of a uracil-requiring mutant nor growth of the wild type in high concentrations of uracil resulted in substantial changes in the specific activities of enzymes of uridylic acid biosynthesis. It is therefore concluded that A. variabilis does not regulate all enzymes of this pathway by means of repression. However, control of the flow of intermediates through this pathway is possible by feedback inhibition of aspartate transcarbamylase by a variety of nucleotides.

Aspartate Carbamoyltransferase