Association of healthy lifestyle behaviours with incident irritable bowel syndrome: a large population-based prospective cohort study.

OBJECTIVES: To evaluate the association between healthy lifestyle behaviours and the incidence of irritable bowel syndrome (IBS). DESIGN: Population-based prospective cohort study. SETTING: The UK Biobank. PARTICIPANTS: 64 268 adults aged 37 to 73 years who had no IBS diagnosis at baseline were enrolled between 2006 and 2010 and followed up to 2022. MAIN EXPOSURE: The five healthy lifestyle behaviours studied were never smoking, optimal sleep, high level of vigorous physical activity, high dietary quality and moderate alcohol intake. MAIN OUTCOME MEASURE: The incidence of IBS. RESULTS: During a mean follow-up of 12.6 years, 961 (1.5%) incident IBS cases were recorded. Among the 64 268 participants (mean age 55.9 years, 35 342 (55.0%) female, 7604 (11.8%) reported none of the five healthy lifestyle behaviours, 20 662 (32.1%) reported 1 behaviour, 21 901 (34.1%) reported 2 behaviours and 14 101 (21.9%) reported 3 to 5 behaviours at baseline. The multivariable adjusted hazard ratios associated with having 1, 2 and 3 to 5 behaviours for IBS incidence were 0.79 (95% confidence intervals 0.65 to 0.96), 0.64 (0.53 to 0.78) and 0.58 (0.46 to 0.72), respectively (P for trend <0.001). Never smoking (0.86, 0.76 to 0.98, P=0.02), high level of vigorous physical activity (0.83, 0.73 to 0.95, P=0.006) and optimal sleep (0.73, 0.60 to 0.88, P=0.001) demonstrated significant independent inverse associations with IBS incidence. No significant interactions were observed between these associations and age, sex, employment status, geographic location, gastrointestinal infection, endometriosis, family history of IBS or lifestyle behaviours. CONCLUSIONS: Adhering to a higher number of healthy lifestyle behaviours is significantly associated with a lower incidence of IBS in the general population. Our findings suggest the potential of lifestyle modifications as a primary prevention strategy for IBS.

Light signaling regulates root-knot nematode infection and development via HY5-SWEET signaling.

BACKGROUND: Meloidogyne incognita is one of the most important plant-parasitic nematodes and causes tremendous losses to the agricultural economy. Light is an important living factor for plants and pathogenic organisms, and sufficient light promotes root-knot nematode infection, but the underlying mechanism is still unclear. RESULTS: Expression level and genetic analyses revealed that the photoreceptor genes PHY, CRY, and PHOT have a negative impact on nematode infection. Interestingly, ELONGATED HYPOCOTYL5 (HY5), a downstream gene involved in the regulation of light signaling, is associated with photoreceptor-mediated negative regulation of root-knot nematode resistance. ChIP and yeast one-hybrid assays supported that HY5 participates in plant-to-root-knot nematode responses by directly binding to the SWEET negative regulatory factors involved in root-knot nematode resistance. CONCLUSIONS: This study elucidates the important role of light signaling pathways in plant resistance to nematodes, providing a new perspective for RKN resistance research.

Natural Allelic Variations of Bch10G006400 Controlling Seed Size in Chieh-qua (Benincasa hispida Cogn. var. Chieh-qua How).

Seeds are the most important reproductive organs of higher plants, the beginning and end of a plant's lifecycle. They are very important to plant growth and development, and also an important factor affecting yield. In this study, genetic analysis and BSA-seq of the F2 population crossed with the large-seeded material 'J16' and small-seeded material 'FJ5' were carried out, and the seed size locus was initially located within the 1.31 Mb region on chr10. In addition, 2281 F2 plants were used to further reduce the candidate interval to 48.8 Kb. This region contains only one gene encoding the N-acetyltransferase (NAT) protein (Bch10G006400). Transcriptome and expression analysis revealed that the gene was significantly more highly expressed in 'J16' than in 'FJ5'. Variation analysis of Bch10G006400 among parents and 50 chieh-qua germplasms revealed that as well as a nonsynonymous mutation (SNP_314) between parents, two mutations (SNP_400 and InDel_551) were detected in other materials. Combining these three mutations completely distinguished the seed size of the chieh-qua. GO and KEGG enrichment analyses revealed that DGEs played the most important roles in carbohydrate metabolism and plant hormone signal transduction, respectively. The results of this study provide important information for molecular marker-assisted breeding and help to reveal the molecular mechanism of seed size.

The generation of 5-N-glycolylneuraminic acid as a consequence of high levels of reactive oxygen species.

The presence of N-glycolylneuraminic acid (Neu5Gc), a non-human sialic acid in cancer patients, is currently attributed to the consumption of red meat. Excess dietary red meat has been considered a risk factor causing chronic inflammation and for the development of cancers. However, it remains unknown whether Neu5Gc can be generated via a chemical reaction rather than via a metabolic pathway in the presence of high levels of reactive oxygen species (ROS) found in the inflammatory and tumor environments. In this study, the conversion of N-acetylneuraminic acid (Neu5Ac) to Neu5Gc has been assessed in vitro under conditions mimicking the hydroxyl radical-rich humoral environment found in inflammatory and cancerous tissues. As a result, Neu5Gc has been detected via liquid chromatography-multiple reaction monitoring mass spectrometry. Furthermore, this conversion has also been found to take place in serum biomatrix containing ROS and in cancer cell cultures with induced ROS production.

An imaging-based machine learning model outperforms clinical risk scores for prognosis of cirrhotic variceal bleeding.

OBJECTIVES: To develop and validate a machine learning model based on contrast-enhanced CT to predict the risk of occurrence of the composite clinical endpoint (hospital-based intervention or death) in cirrhotic patients with acute variceal bleeding (AVB). METHODS: This retrospective study enrolled 330 cirrhotic patients with AVB between January 2017 and December 2020 from three clinical centers. Contrast-enhanced CT and clinical data were collected. Centers A and B were divided 7:3 into a training set and an internal test set, and center C served as a separate external test set. A well-trained deep learning model was applied to segment the liver and spleen. Then, we extracted 106 original features of the liver and spleen separately based on the Image Biomarker Standardization Initiative (IBSI). We constructed the Liver-Spleen (LS) model based on the selected radiomics features. The performance of LS model was evaluated by receiver operating characteristics and calibration curves. The clinical utility of models was analyzed using decision curve analyses (DCA). RESULTS: The LS model demonstrated the best diagnostic performance in predicting the composite clinical endpoint of AVB in patients with cirrhosis, with an AUC of 0.782 (95% CI 0.650-0.882) and 0.789 (95% CI 0.674-0.878) in the internal test and external test groups, respectively. Calibration curves and DCA indicated the LS model had better performance than traditional clinical scores. CONCLUSION: A novel machine learning model outperforms previously known clinical risk scores in assessing the prognosis of cirrhotic patients with AVB CLINICAL RELEVANCE STATEMENT: The Liver-Spleen model based on contrast-enhanced CT has proven to be a promising tool to predict the prognosis of cirrhotic patients with acute variceal bleeding, which can facilitate decision-making and personalized therapy in clinical practice. KEY POINTS: • The Liver-Spleen machine learning model (LS model) showed good performance in assessing the clinical composite endpoint of cirrhotic patients with AVB (AUC ≥ 0.782, sensitivity ≥ 80%). • The LS model outperformed the clinical scores (AUC ≤ 0.730, sensitivity ≤ 70%) in both internal and external test cohorts.

Cooperative Bimetallic Catalysis via One-Metal/Two-Ligands: Mechanistic Insights of Polyfluoroarylation-Allylation of Diazo Compounds.

Metal/ligand in situ assembly is crucial for tailoring the reactivity & selectivity in transition metal catalysis. Cooperative catalysis via a single metal/two ligands is still underdeveloped, since it is rather challenging to harness the distinct reactivity profiles of the species generated by self-assembly of a single metal precursor with a mixture of different ligands. Herein, we report a catalytic system composed of a single metal/two ligands for a three-component reaction of polyfluoroarene, α-diazo ester, and allylic electrophile, leading to highly efficient construction of densely functionalized quaternary carbon centers, that are otherwise hardly accessible. Mechanistic studies suggest this reaction follows a cooperative bimetallic pathway via two catalysts with distinct reactivity profiles, which are assembled in situ from a single metal precursor and two ligands and work in concert to escort the transformation.

The critical role of B4GALT4 in promoting microtubule spindle assembly in HCC through the regulation of PLK1 and RHAMM expression.

Beta 1,4-galactosyltransferase (B4GALT)-family glycosyltransferases are involved in multiple biological processes promoting cancer progression, regulating the dynamic network of cancer cell proliferation and apoptosis, and are associated with metastasis. However, their roles in the dysregulation of expressions and functions in hepatocellular carcinoma (HCC) remain unclear. Herein, bioinformatic approaches have been applied to investigate their expression profiles, and to obtain correlations between gene expressions and clinicopathological parameters as well as downstream target genes in HCC. Multiple databases were used to screen the expressions of B4GALT family members in tumor tissues, and to evaluate their prognostic value among HCC patients in different aspects. Results indicated an overall upregulation of B4GALTs' transcription levels in tumor tissues and a strong correlation with poor prognosis. Through Gene Ontology analysis, gene set enrichment analysis, and verification of single-cell RNA sequencing data, we established a connection between the B4GALT family and microtubule spindle assembly, which particularly highlighted the role of B4GALT4 in this phenomenon. B4GALT4 knockdown downregulated the production of lumican, and repressed the expressions of polo-like kinase 1 and RHAMM by regulating the transforming growth factor-beta pathway, thus suggesting that B4GALT4 is a critical promotor for HCC. We believe that these studies will provide valuable insight into the role of B4GALT family members in HCC and lead to the development of new strategies to improve the outcomes for patients with HCC.

N-Butyrylated Hyaluronic Acid Achieves Anti-Inflammatory Effects In Vitro and in Adjuvant-Induced Immune Activation in Rats.

Previously synthesized N-butyrylated hyaluronic acid (BHA) provides anti-inflammatory effects in rat models of acute gouty arthritis and hyperuricemia. However, the mechanism of action remains to be elucidated. Herein, the anti-inflammatory and antioxidative activities of BHA and the targeted signaling pathways were explored with LPS-induced RAW264.7 and an adjuvant-induced inflammation in a rat model. Results indicated that BHA inhibited the generation of pro-inflammatory cytokines TNFα, IL-1ß and IL-6, reduced ROS production and down-regulated JAK1-STAT1/3 signaling pathways in LPS-induced RAW264.7. In vivo, BHA alleviated paw and joint swelling, decreased inflammatory cell infiltration in paw tissues, suppressed gene expressions of p38 and p65, down-regulated the NF-κB and MAPK signaling pathways and reduced protein levels of TNFα, IL-1ß and IL-6 in joint tissues of arthritis rats. This study demonstrated the pivotal role of BHA in anti-inflammation and anti-oxidation, suggesting the potential clinical value of BHA in the prevention of inflammatory arthritis and is worthy for development as a new pharmacological treatment.

dCA1-NAc shell glutamatergic projection mediates context-induced memory recall of morphine.

Opioid relapse is generally caused by the recurrence of context-induced memory reinstatement of reward. However, the internal mechanisms that facilitate and modify these processes remain unknown. One of the key regions of the reward is the nucleus accumbens (NAc) which receives glutamatergic projections from the dorsal hippocampus CA1 (dCA1). It is not yet known whether the dCA1 projection to the NAc shell regulates the context-induced memory recall of morphine. Here, we used a common model of addiction-related behavior conditioned place preference paradigm, combined with immunofluorescence, chemogenetics, optogenetics, and electrophysiology techniques to characterize the projection of the dCA1 to the NAc shell, in context-induced relapse memory to morphine. We found that glutamatergic neurons of the dCA1 and gamma aminobutyric acidergic (GABA) neurons of the NAc shell are the key brain areas and neurons involved in the context-induced reinstatement of morphine memory. The dCA1-NAc shell glutamatergic input pathway and the excitatory synaptic transmission of the dCA1-NAc shell were enhanced via the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) when mice were re-exposed to environmental cues previously associated with drug intake. Furthermore, chemogenetic and optogenetic inactivation of the dCA1-NAc shell pathway decreased the recurrence of long- and short-term morphine-paired context memory in mice. These results provided evidence that the dCA1-NAc shell glutamatergic projections mediated the context-induced memory recall of morphine.

The expression and functional analysis of the sialyl-T antigen in prostate cancer.

Aberrant glycosylation is a featured characteristic of cancer and plays a role in cancer pathology; thus an understanding of the compositions and functions of glycans is critical for discovering diagnostic biomarkers and therapeutic targets for cancer. In this study, we used MALDI-TOF-MS analysis to determine the O-glycan profiles of prostate cancer cells metastasized to bone (PC-3), brain (DU145), lymph node (LNCaP), and vertebra (VCaP) in comparison to immortalized RWPE-1 cells derived from normal prostatic tissue. Prostate cancer (CaP) cells exhibited an elevation of simple/short O-glycans, with a reduction of complex O-glycans, increased O-glycan sialylation and decreased fucosylation. Core 1 sialylation was increased dramatically in all CaP cells, and especially in PC-3 cells. The expression of Neu5Acα2-3Galß1-3GalNAc- (sialyl-3T antigen) which is the product of α2,3-sialyltransferase-I (ST3Gal-I) was substantially increased. We therefore focused on exploring the possible function of ST3Gal-I in PC-3 cells. ST3Gal-I silencing studies showed that ST3Gal-I was associated with PC-3 cell proliferation, migration and apoptosis. Further in vivo studies demonstrated that down regulation of ST3Gal-I reduced the tumor size in xenograft mouse model, indicating that sialyl-3T can serve as a biomarker for metastatic prostate cancer prognosis, and that ST3Gal-I could be a target for therapeutic intervention in cancer treatment.

Recent advances in single-cell analysis by mass spectrometry.

Cells are the most basic structural units that play vital roles in the functioning of living organisms. Analysis of the chemical composition and content of a single cell plays a vital role in ensuring precise investigations of cellular metabolism, and is a crucial aspect of lipidomic and proteomic studies. In addition, structural knowledge provides a better understanding of cell behavior as well as the cellular and subcellular mechanisms. However, single-cell analysis can be very challenging due to the very small size of each cell as well as the large variety and extremely low concentrations of substances found in individual cells. On account of its high sensitivity and selectivity, mass spectrometry holds great promise as an effective technique for single-cell analysis. Numerous mass spectrometric techniques have been developed to elucidate the molecular profiles at the cellular level, including electrospray ionization mass spectrometry (ESI-MS), secondary ion mass spectrometry (SIMS), laser-based mass spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). In this review, the recent advances in single-cell analysis by mass spectrometry are summarized. The strategies of different ionization modes to achieve single-cell analysis are classified and discussed in detail.

Oxidative C(sp3)-H functionalization of methyl-azaheteroarenes: a facile route to 1,2,4-triazolo[4,3-a]pyridines.

We herein describe an oxidative [4 + 1] annulation used to prepare 1,2,4-triazolo[4,3-a]pyridines in the presence of I2-DMSO. This protocol enables synthesis of triazolo[4,3-a]pyridine-quinoline linked diheterocycles via a direct oxidative functionalization of sp3 C-H bonds of 2-methyl-azaheteroarenes. The reaction shows a wide substrate scope and good functional group tolerance.

Docetaxel-loaded human serum albumin (HSA) nanoparticles: synthesis, characterization, and evaluation.

BACKGROUND: Docetaxel (DTX) is an anticancer drug that is currently formulated with polysorbate 80 and ethanol (50:50, v/v) in clinical use. Unfortunately, this formulation causes hypersensitivity reactions, leading to severe side-effects, which have been primarily attributed to polysorbate 80. METHODS: In this study, a DTX-loaded human serum albumin (HSA) nanoparticle (DTX-NP) was designed to overcome the hypersensitivity reactions that are induced by polysorbate 80. The methods of preparing the DTX-NPs have been optimized based on factors including the drug-to-HSA weight ratio, the duration of HSA incubation, and the choice of using a stabilizer. Synthesized DTX-NPs were characterized with regard to their particle diameters, drug loading capacities, and drug release kinetics. The morphology of the DTX-NPs was observed via scanning electron microscopy (SEM) and the successful preparation of DTX-NPs was confirmed via differential scanning calorimetry (DSC). The cytotoxicity and cellular uptake of DTX-NPs were investigated in the non-small cell lung cancer cell line A549 and the maximum tolerated dose (MTD) of DTX-NPs was evaluated via investigations with BALB/c mice. RESULTS: The study showed that the loading capacity and the encapsulation efficiency of DTX-NPs prepared under the optimal conditions was 11.2 wt% and 63.1 wt%, respectively and the mean diameter was less than 200 nm, resulting in higher permeability and controlled release. Similar cytotoxicity against A549 cells was exhibited by the DTX-NPs in comparison to DTX alone while higher maximum tolerated dose (MTD) with the DTX-NPs (75 mg/kg) than with DTX (30 mg/kg) was demonstrated in mice, suggesting that the DTX-NPs prepared with HSA yielded similar anti-tumor activity but were accompanied by less systemic toxicity than solvent formulated DTX. CONCLUSIONS: DTX-NPs warrant further investigation and are promising candidates for clinical applications.

Cholinergic Grb2-Associated-Binding Protein 1 Regulates Cognitive Function.

Grb2-associated-binding protein 1 (Gab1) is a docking/scaffolding molecule known to play an important role in cell growth and survival. Here, we report that Gab1 is decreased in cholinergic neurons in Alzheimer's disease (AD) patients and in a mouse model of AD. In mice, selective ablation of Gab1 in cholinergic neurons in the medial septum impaired learning and memory and hippocampal long-term potentiation. Gab1 ablation also inhibited SK channels, leading to an increase in firing in septal cholinergic neurons. Gab1 overexpression, on the other hand, improved cognitive function and restored hippocampal CaMKII autorphosphorylation in AD mice. These results suggest that Gab1 plays an important role in the pathophysiology of AD and may represent a novel therapeutic target for diseases involving cholinergic dysfunction.

A Low Molecular Weight Hyaluronic Acid Derivative Accelerates Excisional Wound Healing by Modulating Pro-Inflammation, Promoting Epithelialization and Neovascularization, and Remodeling Collagen.

Recent knowledge of the cellular and molecular mechanisms underlying cutaneous wound healing has advanced the development of medical products. However, patients still suffer from the failure of current treatments, due to the complexity of healing process and thus novel therapeutic approaches are urgently needed. Previously, our laboratories produced a range of low molecular weight hyaluronic acid (LMW-HA) fragments, where a proportion of the glucosamine moieties were chemically N-acyl substituted. Specifically, N-butyrylation results in anti-inflammatory properties in a macrophage system, and we demonstrate the importance of N-acyl substituents in modulating the inflammatory response of LMW-HA. We have set up an inter-institutional collaborative program to examine the biomedical applications of the N-butyrylated LMW-HA (BHA). In this study, the potentials of BHA for dermal healing are assessed in vitro and in vivo. Consequently, BHA significantly promotes dermal healing relative to a commercial wound care product. By contrast, the "parent" partially de-acetylated LMW-HA (DHA) and the re-acetylated DHA (AHA) significantly delays wound closure, demonstrating the specificity of this N-acylation of LMW-HA in wound healing. Mechanistic studies reveal that the BHA-mediated therapeutic effect is achieved by targeting three phases of wound healing (i.e., inflammation, proliferation and maturation), demonstrating the significant potential of BHA for clinical translation in cutaneous wound healing.

N-Butyrylated hyaluronic acid ameliorates gout and hyperuricemia in animal models.

Context: Hyaluronic acid (HA) plays critical roles in the structural skeleton, joint lubrication, renal function and cell signaling. We previously showed that partially N-butyrylated, low molecular weight, hyaluronic acid (BHA) exhibited an anti-inflammatory effect in cultured human macrophage, where inflammation was induced either by a TL-4 agonist or the low molecular weight HA itself, in dose-dependent fashion. Objectives: To investigate the anti-inflammatory, antioxidative, and antihyperuricemic effects of BHA using animal models of acute gouty arthritis and hyperuricemia. Materials and methods: The anti-inflammatory effect of articular BHA (10 and 50 µg) injections was evaluated by measuring joint swelling and the serum levels of inflammatory cytokines in a model of acute gouty arthritis induced by intra-articular injection of monosodium urate crystals in Wistar rats (n = 10/group), in comparison to the control group with saline injection. Antioxidative and antihyperuricemic activities were investigated using intraperitoneal injections of oteracil potassium and yeast extract hyperuricemic Balb/C mice, which were treated with intraperitoneal injection of BHA at day 6-8 in the model. Results: In the gouty arthritis rat model, BHA at a higher dosage (50 µg) demonstrated a strong anti-inflammatory effect by reducing the degree of articular swelling and the serum levels of IL-1ß, IL-8, IFN-γ, and MCP-1 by 5.56%, 6.55%, 15.58% and 33.18%. In the hyperuricemic mouse model, lower dosage BHA (10 µg) was sufficient to provide antioxidative activities by significantly decreasing the ROS levels in both serum and liver by 14.87% and 8.04%, while improving liver SOD by 12.77%. Intraperitoneal injection of BHA suppressed uric acid production through reducing liver XO activity by 19.78% and decreased the serum uric acid level in hyperuricemic mice by 30.41%. Conclusions: This study demonstrated for the first time that BHA exhibits anti-inflammatory, antioxidative and antihyperuricemic effects in vivo, suggesting a potential therapeutic application of BHA in gouty arthritis and hyperuricemia.

Novel multimodal analgesia regimen improves post-TACE pain in patients with hepatocellular carcinoma.

BACKGROUD: Transarterial chemoembolization (TACE) is the primary palliative treatment for patients with unresectable hepatocellular carcinoma (HCC). However, it is often accompanied by postoperative pain which hinder patient recovery. This study was to examine whether preemptive parecoxib and sufentanil-based patient controlled analgesia (PCA) could improve the pain management in patients receiving TACE for inoperable HCC. METHODS: From June to December 2016, 84 HCC patients undergoing TACE procedure were enrolled. Because of the willingness of the individuals, it is difficult to randomize the patients to different groups. We matched the patients' age, gender and pain scores, and divided the patients into the multimodal group (n = 42) and control group (n = 42). Patients in the multimodal group received 40 mg of parecoxib, 30 min before TACE, followed by 48 h of sufentanil-based PCA. Patients in the control group received a routine analgesic regimen, i.e., 5 mg of dezocine during operation, and 100 mg of tramadol or equivalent intravenous opioid according to patient's complaints and pain intensity. Postoperative pain intensity, percentage of patients as per the pain category, adverse reaction, duration of hospital stay, cost-effectiveness, and patient's satisfaction were all taken into consideration when evaluated. RESULTS: Compared to the control group, the visual analogue scale scores for pain intensity was significantly lower at 2, 4, 6, and 12 h (all P < 0.05) in the multimodal group and a noticeably lower prevalence of post-operative nausea and vomiting in the multimodal group (31.0% vs. 59.5%). Patient's satisfaction in the multimodal group was also significantly higher than that in the control group (95.2% vs. 69.0%). No significant difference was observed in the duration of hospital stay between the two groups. CONCLUSION: Preemptive parecoxib and sufentanil-based multimodal analgesia regime is a safe, efficient and cost-effective regimen for postoperative pain control in HCC patients undergoing TACE.

Melatonin ameliorates hypoglycemic stress-induced brain endothelial tight junction injury by inhibiting protein nitration of TP53-induced glycolysis and apoptosis regulator.

Severe hypoglycemia has a detrimental impact on the cerebrovasculature, but the molecular events that lead to the disruption of the integrity of the tight junctions remain unclear. Here, we report that the microvessel integrity was dramatically compromised (59.41% of wild-type mice) in TP53-induced glycolysis and apoptosis regulator (TIGAR) transgenic mice stressed by hypoglycemia. Melatonin, a potent antioxidant, protects against hypoglycemic stress-induced brain endothelial tight junction injury in the dosage of 400 nmol/L in vitro. FRET (fluorescence resonance energy transfer) imaging data of endothelial cells stressed by low glucose revealed that TIGAR couples with calmodulin to promote TIGAR tyrosine nitration. A tyrosine 92 mutation interferes with the TIGAR-dependent NADPH generation (55.60% decreased) and abolishes its protective effect on tight junctions in human brain microvascular endothelial cells. We further demonstrate that the low-glucose-induced disruption of occludin and Caludin5 as well as activation of autophagy was abrogated by melatonin-mediated blockade of nitrosative stress in vitro. Collectively, we provide information on the detailed molecular mechanisms for the protective actions of melatonin on brain endothelial tight junctions and suggest that this indole has translational potential for severe hypoglycemia-induced neurovascular damage.

Reactive Oxygen Species Generated by NADPH Oxidases Promote Radicle Protrusion and Root Elongation during Rice Seed Germination.

Seed germination is a complicated biological process that requires regulation through various enzymatic and non-enzymatic mechanisms. Although it has been recognized that reactive oxygen species (ROS) regulate radicle emergence and root elongation in a non-enzymatic manner during dicot seed germination, the role of ROS in monocot seed germination remains unknown. NADPH oxidases (NOXs) are the major ROS producers in plants; however, whether and how NOXs regulate rice seed germination through ROS generation remains unclear. Here, we report that diphenyleneiodinium (DPI), a specific NOX inhibitor, potently inhibited embryo and seedling growth-especially that of the radicle and of root elongation-in a dose-dependent manner. Notably, the DPI-mediated inhibition of radicle and root growth could be eliminated by transferring seedlings from DPI to water. Furthermore, ROS production/accumulation during rice seed germination was quantified via histochemistry. Superoxide radicals (O2-), hydrogen peroxide (H2O2) and hydroxyl radicals (•OH) accumulated steadily in the coleorhiza, radicle and seedling root of germinating rice seeds. Expression profiles of the nine typical NOX genes were also investigated. According to quantitative PCR, OsNOX5, 7 and 9 were expressed relatively higher. When seeds were incubated in water, OsNOX5 expression progressively increased in the embryo from 12 to 48 h, whereas OsNOX7 and 9 expressions increased from 12 to 24 h and decreased thereafter. As expected, DPI inhibits the expression at predetermined time points for each of these genes. Taken together, these results suggest that ROS produced by NOXs are involved in radicle and root elongation during rice seed germination, and OsNOX5, 7 and 9 could play crucial roles in rice seed germination. These findings will facilitate further studies of the roles of ROS generated by NOXs during seed germination and seedling establishment and also provide valuable information for the regulation of NOX family gene expression in germinating seeds of monocot cereals.