Genome-wide analysis and metabolic profiling unveil the role of peroxidase CsGPX3 in theaflavin production in black tea processing

Lipidomics, transcription analysis, and hormone profiling unveil the role of CsLOX6 in MeJA biosynthesis during black tea processing

Jasmonates, such as jasmonic acid (JA) and methyl jasmonate (MeJA), are crucial aspect of black tea quality. However, lipids species, hormones, and genes regulated mechanism in the jasmonate biosynthesis during black tea processing are lacking. In this study, we employed lipidomics, hormone metabolism analysis, and transcriptome profiling of genes associated with the MeJA biosynthesis pathway to investigate these factors. The contents of lipids GLs, PLs, and TAG are decreased, accompanied by the main lipids species reduced during black tea processing. Galactolipids, primarily 34:3/36:6/36:3 DGDG and 36:6/36:5/36:4 MGDG, are transformed into massive MeJA and JA in black tea processing, accompanied by the decreased SA, MeSA, IAA, and BA and increased zeatin. Additionally, the transcriptional activity of the primary genes in MeJA biosynthesis pathway exhibited downregulated trends except for AOS and OPR and non-primary genes tend to be a little high or have fluctuation of expression. Coordinated expression of main CsHPL (TEA008699), CsAOS (TEA001041), and CsJMT (TEA015791) control the flow of lipids degradation and MeJA production. A strong infected reduction of a key lipoxygenase gene, CsLOX6 (TEA009423), in tea buds significantly reduced the level of jasmonates and expression of downstream genes, accompanied by SA, MeSA level rising, and ABA declining. We have identified a key CsLOX6, as well as established galactolipids, mainly 34:3/36:6/36:3 DGDG and 36:6/36:5/36:4 MGDG, sources for MeJA biosynthesis regulated by dynamics hormone and controlled by coordinated expressed CsHPL (TEA008699), CsAOS (TEA001041), and CsJMT (TEA015791). Our findings provide a theoretical basis for breeding high-quality black tea and offer valuable insights for improving processing methods.

Comparison of fresh and browning lotus roots (Nelumbo nucifera Gaertn.) on modulating cholesterol metabolism via decreasing hepatic cholesterol deposition and increasing fecal bile acid excretion

Lotus root (LR) is prone to browning after harvest due to the oxidation of phenolic compounds by polyphenol oxidase (PPO). This study compared the effects of LR extract and BLR extract on cholesterol metabolism in high-fat diet (HFD) mice. Our findings highlighted the innovative potentiality of BLR extract in effectively regulating cholesterol metabolism via inhibiting the intestinal FXR-FGF15 signaling pathway and boosting probiotics in gut microbiota, offering valuable insights for hypercholesterolemia and metabolic disorders. In detail, catechin was the main phenolic compound in LR, while after browning, theaflavin was the main oxidation product of phenolic compounds in BLR. Both the intake of LR extract and BLR extract regulated the disorder of cholesterol metabolism induced by HFD. In particular, BLR extract intake exhibited more robust effects on increasing the BAs contents synthesized in the liver and excreted in feces compared with LR extract intake. Furthermore, the consumption of BLR extract was more effective than that of LR extract in reducing the ileal protein expressions of FXR and FGF15 and shifting BAs biosynthesis from the classical pathway to the alternative pathway. Moreover, LR extract and BLR extract had distinct effects on the gut microbiota in HFD-fed mice: BLR extract significantly elevated probiotics Akkermansia abundance, while LR extract increased Lactobacillus abundance. Therefore, both LR extract and BLR extract improved the cholesterol deposition effectively and BLR extract even showed a stronger effect on regulating key gene and protein expressions of cholesterol metabolism.

RNA Methylome Reveals the m6A-mediated Regulation of Flavor Metabolites in Tea Leaves under Solar-withering

The epitranscriptomic mark N6-methyladenosine (m6A), which is the predominant internal modification in RNA, is important for plant responses to diverse stresses. Multiple environmental stresses caused by the tea-withering process can greatly influence the accumulation of specialized metabolites and the formation of tea flavor. However, the effects of the m6A-mediated regulatory mechanism on flavor-related metabolic pathways in tea leaves remain relatively uncharacterized. We performed an integrated RNA methylome and transcriptome analysis to explore the m6A-mediated regulatory mechanism and its effects on flavonoid and terpenoid metabolism in tea (Camellia sinensis) leaves under solar-withering conditions. Dynamic changes in global m6A level in tea leaves were mainly controlled by two m6A erasers (CsALKBH4A and CsALKBH4B) during solar-withering treatments. Differentially methylated peak-associated genes following solar-withering treatments with different shading rates were assigned to terpenoid biosynthesis and spliceosome pathways. Further analyses indicated that CsALKBH4-driven RNA demethylation can directly affect the accumulation of volatile terpenoids by mediating the stability and abundance of terpenoid biosynthesis-related transcripts and also indirectly influence the flavonoid, catechin, and theaflavin contents by triggering alternative splicing-mediated regulation. Our findings revealed a novel layer of epitranscriptomic gene regulation in tea flavor-related metabolic pathways and established a link between the m6A-mediated regulatory mechanism and the formation of tea flavor under solar-withering conditions.

Study on the Trend in Microbial Changes during the Fermentation of Black Tea and Its Effect on the Quality

The role of tea endophytes in black tea fermentation and their impact on black tea quality remain unclear. We collected fresh leaves of Bixiangzao and Mingfeng tea and processed them into black tea, while testing the biochemical composition of both the fresh leaves and the black tea. We also used high-throughput techniques, such as 16S rRNA, to analyze the dynamic changes in the microbial community structure and function during black tea processing in order to investigate the influence of dominant microorganisms on the quality of black tea formation. Our results showed that bacteria, such as Chryseobacterium and Sphingomonas, and Pleosporales fungi dominated the entire black tea fermentation process. Predicted functional analysis of the bacterial community indicated that glycolysis-related enzymes, pyruvate dehydrogenase, and tricarboxylic acid cycle-related enzymes were significantly elevated during the fermentation stage. Amino acids, soluble sugars, and tea pigment content also increased considerably during fermentation. Pearson's correlation analysis revealed that the relative bacterial abundance was closely related to the content of tea polyphenols and catechins. This study provides new insights into the changes in microbial communities during the fermentation of black tea and demonstrates understanding of the basic functional microorganisms involved in black tea processing.

Genome-Wide Identification and Characterization of the PPO Gene Family in Cotton (Gossypium) and Their Expression Variations Responding to Verticillium Wilt Infection

Polyphenol oxidases (PPOs) are copper-binding metalloproteinases encoded by nuclear genes, ubiquitously existing in the plastids of microorganisms, plants, and animals. As one of the important defense enzymes, PPOs have been reported to participate in the resistant processes that respond to diseases and insect pests in multiple plant species. However, PPO gene identification and characterization in cotton and their expression patterns under Verticillium wilt (VW) treatment have not been clearly studied. In this study, 7, 8, 14, and 16 PPO genes were separately identified from Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense, respectively, which were distributed within 23 chromosomes, though mainly gathered in chromosome 6. The phylogenetic tree manifested that all the PPOs from four cotton species and 14 other plants were divided into seven groups, and the analyses of the conserved motifs and nucleotide sequences showed highly similar characteristics of the gene structure and domains in the cotton PPO genes. The dramatically expressed differences were observed among the different organs at various stages of growth and development or under the diverse stresses referred to in the published RNA-seq data. Quantitative real-time PCR (qRT-PCR) experiments were also performed on the GhPPO genes in the roots, stems, and leaves of VW-resistant MBI8255 and VW-susceptible CCRI36 infected with Verticillium dahliae V991, proving the strong correlation between PPO activity and VW resistance. A comprehensive analysis conducted on cotton PPO genes contributes to the screening of the candidate genes for subsequent biological function studies, which is also of great significance for the in-depth understanding of the molecular genetic basis of cotton resistance to VW.

Dynamic change of tea (Camellia sinensis) leaf cuticular wax in white tea processing for contribution to tea flavor formation

Despite some studies on tea leaf cuticular wax, their component changes during dehydration and withering treatments in tea processing and suspected relation with tea flavor quality formation remain unknown. Here, we showed that tea leaf cuticular wax changed drastically in tea leaf development, dehydration, or withering treatment during tea processing, which affected tea flavor formation. Caffeine was found as a major component of leaf cuticular wax. Caffeine and inositol contents in leaf cuticular wax increased during dehydration and withering treatments. Comparisons showed that tea varieties with higher leaf cuticular wax loading produced more aroma than these with lower cuticular wax loading, supporting a positive correlation between tea leaf cuticular wax loading and degradation with white tea aroma formation. Dehydration or withering treatment of tea leaves also increased caffeine and inositol levels in leaf cuticular wax and triggered cuticular wax degradation into various molecules, that could be related to tea flavor formation. Thus, tea leaf cuticular waxes not only protect tea plants but also contribute to tea flavor formation. The study provides new insight into the dynamic changes of tea leaf cuticular waxes for tea plant protection and tea flavor quality formation in tea processing.

Role of Reactive Oxygen Species in Aging and Age-Related Diseases: A Review

Research on the role of reactive oxygen species (ROS) in the aging process has advanced significantly over the last two decades. In light of recent findings, ROS takes part in the aging process of cells along with contributing to various physiological signaling pathways. Antioxidants being cells' natural defense mechanism against ROS-mediated alteration, play an imperative role to maintain intracellular ROS homeostasis. Although the complete understanding of the ROS regulated aging process is yet to be fully comprehended, current insights into various sources of cellular ROS and their correlation with the aging process and age-related diseases are portrayed in this review. In addition, results on the effect of antioxidants on ROS homeostasis and the aging process as well as their advances in clinical trials are also discussed in detail. The future perspective in ROS-antioxidant dynamics on antiaging research is also marshaled to provide future directions for ROS-mediated antiaging research fields.

Natural products from traditional medicine as promising agents targeting at different stages of oral biofilm development

Oral cavity is an ideal habitat for more than 1,000 species of microorganisms. The diverse oral microbes form biofilms over the hard and soft tissues in the oral cavity, affecting the oral ecological balance and the development of oral diseases, such as caries, apical periodontitis, and periodontitis. Currently, antibiotics are the primary agents against infectious diseases; however, the emergence of drug resistance and the disruption of oral microecology have challenged their applications. The discovery of new antibiotic-independent agents is a promising strategy against biofilm-induced infections. Natural products from traditional medicine have shown potential antibiofilm activities in the oral cavity with high safety, cost-effectiveness, and minimal adverse drug reactions. Aiming to highlight the importance and functions of natural products from traditional medicine against oral biofilms, here we summarized and discussed the antibiofilm effects of natural products targeting at different stages of the biofilm formation process, including adhesion, proliferation, maturation, and dispersion, and their effects on multi-species biofilms. The perspective of antibiofilm agents for oral infectious diseases to restore the balance of oral microecology is also discussed.

Diverse roles of MYB transcription factors in regulating secondary metabolite biosynthesis, shoot development, and stress responses in tea plants (Camellia sinensis)

Tea (Camellia sinensis) is concocted from tea plant shoot tips that produce catechins, caffeine, theanine, and terpenoids, which collectively determine the rich flavors and health benefits of the infusion. However, little is known about the integrated regulation of shoot tip development and characteristic secondary metabolite biosynthesis in tea plants. Here, we demonstrate that MYB transcription factors (TFs) play key and yet diverse roles in regulating leaf and stem development, secondary metabolite biosynthesis, and environmental stress responses in tea plants. By integrating transcriptomic and metabolic profiling data in different tissues at a series of developmental stages or under various stress conditions, alongside biochemical and genetic analyses, we predicted the MYB TFs involved in regulating shoot development (CsMYB2, 98, 107, and 221), epidermal cell initiation (CsMYB184, 41, 139, and 219), stomatal initiation (CsMYB113 and 153), and the biosynthesis of flavonoids (including catechins, anthocyanins, and flavonols; CsMYB8 and 99), caffeine (CsMYB85 and 86), theanine (CsMYB9 and 49), carotenoids (CsMYB110), mono-/sesquiterpenoid volatiles (CsMYB68, 147, 148, and 193), lignin (CsMYB164 and 192), and indolic compounds (CsMYB139, 162, and 198), as well as the MYB TFs that are likely involved in hormone signaling-mediated environmental stress and defense responses. We characterized the functions of some key MYBs in regulating flavonoid and carotenoid biosynthesis for tea quality and flavor. This study provides a cross-family analysis of MYBs in tea alongside new insights into the coordinated regulation of tea plant shoot development and secondary metabolism, paving the way towards understanding of tea quality trait formation and genetic improvement of quality tea plants.

Mechanistic insights into the inhibitory effect of theaflavins on virulence factors production in Streptococcus mutans

Streptococcus mutans is the primary etiological agent associated with cariogenic process. The present study aimed to investigate the antibacterial and anti-virulence activities of theaflavins (TFs) to Streptococcus mutans UA159 as well as the underlying mechanisms. The results showed that TFs were capable of suppressing the acid production, cell adherence, water-insoluble exopolysaccharides production, and biofilm formation by S. mutans UA159 with a dosage-dependent manner while without influencing the cell growth. By a genome-wide transcriptome analysis (RNA-seq), we found that TFs attenuated the biofilm formation of S. mutans UA159 by inhibiting glucosyltransferases activity and the production of glucan-binding proteins (GbpB and GbpC) instead of directly blocking the expression of genes coding for glucosyltransferases. Further, TFs inhibited the expression of genes implicated in peptidoglycan synthesis, glycolysis, lipid synthesis, two-component system, signaling peptide transport (comA), oxidative stress response, and DNA replication and repair, suggesting that TFs suppressed the virulence factors of S. mutans UA159 by affecting the signal transduction and cell envelope stability, and weakening the ability of cells on oxidative stress resistance. In addition, an upregulated expression of the genes involved in protein biosynthesis, amino acid metabolism, and transport system upon TFs treatment indicated that cells increase the protein synthesis and nutrients uptake as one self-protective mechanism to cope with stress caused by TFs. The results of this study increase our current understanding of the anti-virulence activity of TFs on S. mutans and provide clues for the use of TFs in the prevention of dental caries.

Polymerized Luteolin Nanoparticles: Synthesis, Structure Elucidation, and Anti-Inflammatory Activity

Luteolin is an anti-inflammatory flavonoid commonly found in many edible plants. The compound is popularly consumed as a supplement regardless of its poor water solubility (27.8 μg/mL at 25 °C) and low bioavailability. Here, mild one-pot polymerization of luteolin into water-dispersible nanospheres, with an average dry size of 234.8 ± 101.6 nm, an aqueous size distribution of 379.1 ± 220.5 nm (PDI = 0.338), an average ζ-potential of -36.2 ± 0.2 mV, and an 89.3 ± 4.8% yield, is described. The nanospheres consist of polymerized luteolin (polyluteolin) with a weight-average molecular mass of around 410000 Da. The chemical structure of polyluteolin is identified through ¹H-¹H correlated spectroscopy (COSY), ¹H-¹³C heteronuclear single-quantum coherence (HSQC), and ¹H-¹³C heteronuclear multiple-bond correlation (HMBC) NMR spectroscopic analyses of the oligomers, and a polymerization mechanism is proposed. Unlike luteolin that showed both dose-dependent anti-inflammatory activity and cytotoxicity when tested in lipopolysaccharide-stimulated macrophages, the polyluteolin nanoparticles possess dose-dependent anti-inflammatory activity without causing cell death even at high concentrations.