The effects of quinoa bran dietary fiber on glucose and lipid metabolism and hepatic transcriptome in obese rats.

BACKGROUND: As a complex chronic metabolic disease, obesity not only affects the quality of human life but also increases the risk of various other diseases. Therefore, it is important to investigate the molecular mechanisms and therapeutic effects of dietary interventions that counteract obesity. RESULTS: In this study, we extracted soluble (SDF) and insoluble dietary fiber (IDF) from quinoa bran using an enzymatic method and further investigated their effects on lipid metabolism and blood lipid levels in obese rats. Quinoa bran dietary fiber showed significantly reduced body weight, blood glucose level, total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels compared to those in the model group of obese rats. Aspartate aminotransferase and alanine aminotransferase levels were significantly lower in the IDF group, demonstrating that IDF improved liver injury more significantly than SDF, which was consistent with the analysis of liver tissue sections. IDF supplementation significantly improved the oxidation resistance of obese rats by decreasing malondialdehyde and increasing superoxide dismutase and glutathione peroxidase levels compared to the high-fat diet group levels. Transcriptome analysis showed that IDF caused hepatic changes in genes (Ehhadh, PPARα, FADS, CPT1, CPT2, SCD-1, Acadm, and CYP7A1) related to fatty acid degradation, and this result coincided with that of the gene expression validation result. CONCLUSION: Overall, our research offers crucial data for the logical development of dietary fiber from quinoa bran with nutritional purposes. © 2023 Society of Chemical Industry.

Preparation, structure, and in-vitro hypoglycemic potential of debranched millet starch-fatty acid composite resistant starch.

Currently, the preparation methods and basic physicochemical properties of starch-FA complexes have been widely studied; however, no in-depth research on the regulatory mechanism of the digestive properties of debranched starch-unsaturated FA complexes has been conducted. Therefore, six fatty acids with different carbon chains and different degrees of unsaturation were complexed with de-branched millet starch in this research, using the microwave method. Microwave millet starch-linoleic acid complex (MPS-LOA) had the highest resistant starch (RS) content, and the structure and physicochemical properties of MPS-LOA were determined using various molecular techniques. The results indicate that MPS-LOA had a resistant starch (RS) content of 40.35% and the most notable fluorescence. The characteristic UV peaks of MPS-LOA were blue-shifted, and new IR peaks appeared. The crystalline structure changed to V-type crystals, the crystallinity increased, and the molecular weight decreased. The enthalpy and coagulability of MPS-LOA increased, and the swelling force decreased. Additionally, MPS-LOA showed enhanced α-glucosidase and α-amylase inhibition, and in-vitro hydrolysis kinetics analysis of MPS-LOA showed a hydrolysis index of 53.8 and an extended glycemic index (eGI)I of 54.6, indicating a low eGI food suitable for consumption by people with type II diabetes. These results provide a theoretical basis for the preparation of amylopectin- and starch-based foods with an anti-enzyme structure and a low glycemic index (GI).

Preparation of quinoa bran dietary fiber-based zinc complex and investigation of its antioxidant capacity in vitro.

In order to improve the economic utilization of quinoa bran and develop a safe and highly available zinc ion biological supplement. In this study, a four-factor, three-level response surface optimization of quinoa bran soluble dietary fiber (SDF) complexation of zinc was studied. The effect used four factors on the chelation rate was investigated: (A) mass ratio of SDF to ZnSO4.7H2O, (B) chelation temperature, (C) chelation time, and (D) pH. Based on the results of the single-factor test, the four-factor three-level response surface method was used to optimize the reaction conditions. The optimal reaction conditions were observed as mentioned here: the mass ratio of quinoa bran SDF to ZnSO4.7H2O was 1, the reaction temperature was 65°C, the reaction time was 120 min, and the pH of the reaction system was 8.0. The average chelation rate was 25.18%, and zinc content is 465.2 µg/g under optimal conditions. The hydration method rendered a fluffy quinoa bran SDF structure. The intramolecular functional groups were less stable which made the formation of the lone pairs of electrons feasible to complex with the added divalent zinc ions to form a quinoa bran soluble dietary fiber-zinc complex [SDF-Zn(II)]. The SDF-Zn(II) chelate had higher 2,2-diphenylpicrylhydrazyl (DPPH), ABTS+, hydroxyl radical scavenging ability, and total antioxidant capacity. Therefore, metal ion chelation in dietary fiber is of biological importance.

The key micronutrient copper orchestrates broad-spectrum virus resistance in rice.

Copper is a critical regulator of plant growth and development. However, the mechanisms by which copper responds to virus invasion are unclear. We previously showed that SPL9-mediated transcriptional activation of miR528 adds a previously unidentified regulatory layer to the established ARGONAUTE (AGO18)-miR528-L-ascorbate oxidase (AO) antiviral defense. Here, we report that rice promotes copper accumulation in shoots by inducing copper transporter genes, including HMA5 and COPT, to counteract viral infection. Copper suppresses the transcriptional activation of miR528 by inhibiting the protein level of SPL9, thus alleviating miR528-mediated cleavage of AO transcripts to strengthen the antiviral response. Loss-of-function mutations in HMA5, COPT1, and COPT5 caused a significant reduction in copper accumulation and plant viral resistance because of the increased SPL9-mediated miR528 transcription. Gain in viral susceptibility was mitigated when SPL9 was mutated in the hma5 mutant background. Our study elucidates the molecular mechanisms and regulatory networks of copper homeostasis and the SPL9-miR528-AO antiviral pathway.

Effect of Fermentation Time on Molecular Structure and Physicochemical Properties of Corn Ballast Starch.

The effect of fermentation treatment on the surface morphology, crystal structure, molecular weight, chain length distribution, and physicochemical properties of corn starch was investigated using natural fermentation of corn ballast. The amylose content in corn ballast starch reduced at first after natural fermentation, then grew, following the same trend as solubility. There were certain erosion marks on the surfaces of fermented corn ballast starch granules. The crystalline structure of corn ballast starch remained the same, i.e., a typical A-type crystalline structure, at different fermentation times; however, the intensities of diffraction peaks were different. The weight-average molecular weight of starch first increased and then decreased after fermentation. The content of low-molecular-weight starch (peak 3) decreased from 25.59 to 24.7% and then increased to 25.76%, while the content of high-molecular-weight starch (peak 1) increased from 51.45 to 53.26%, and then decreased to 52.52%. The fermentation time showed a negative correlation with the viscosity of starch, and the pasting temperature first increased, and then decreased. Natural fermentation can be used as a technical means to produce corn starch products as a result of the experiments' findings, and future experiments will detect and analyze the bacterial structure of corn fermentation broth in order to better understand the molecular mechanism of natural fermentation affecting the structure and physicochemical properties of corn starch.

5,7,2,5-tetrahydroxy-8,6-dimethoxyflavone up-regulates miR-145 expression and inhibits proliferation of gastric cancer cells.

Introduction: Gastric cancer is a frequently detected malignancy, and its incidence has increased over the past decades in East Asia. The present study investigated the effect of 5,7,2, 5-tetrahydroxy-8,6-dimethoxyflavone (THDMF) on gastric cancer cells and explored the underlying mechanism. The study analysed cell viability changes, apoptotic features, and metastasis potential of treatment with THDMF. Material and methods: MTT colorimetric assay was used for measurement of MKN28, MKN45, and GES-1 cell proliferation and flow cytometry for the detection of apoptosis. Transwell and wound healing assays were used to observe the invasion and migration abilities of MKN28 cells. The expression of p21, MMP2/-9, PI3K, and c-Myc proteins was detected by western blotting. Results: The THDMF treatment significantly (p < 0.05) reduced MKN28 and MKN45 cell proliferation without changing GES-1 cell viability. A significant increase in apoptotic cell population on treatment with THDMF was observed. Treatment of MKN28 cells with THDMF increased the percentage of cells in the G1 phase. Exposure of MKN28 cells to THDMF caused a marked decrease in invasion and migration potential in comparison to control cells. The expression of miR-145 was markedly increased in MKN28 cells on treatment with THDMF. In MKN28 cells expression of c-Myc, PI3K, p-AKT, MMP-2, and MMP-9 was suppressed markedly on exposure to THDMF. The expression of p21 protein in MKN28 cells was markedly promoted on exposure to THDMF. Conclusions: THDMF exhibits anti-cancer effect on gastric cancer cells in vitro by activation of cell apoptosis and arrest of cell cycle. In addition, THDMF promoted miR-145 expression and down-regulation of PI3K/AKT signalling pathway in MKN28 cells. Therefore, THDMF may be utilised as a potential novel therapeutic agent for the treatment of gastric cancer.

Converting Poisonous Sulfate Species to an Active Promoter on TiO2 Predecorated MnOx Catalysts for the NH3-SCR Reaction.

MnOx-based catalysts possess excellent low-temperature NH3 selective catalytic reduction (NH3-SCR) activity, but the poor SO2/sulfate poisoning resistance and the narrow active-temperature window limit their application for NOx removal. Herein, TiO2 nanoparticles and sulfate were successively introduced into MnOx-based catalysts to modulate the NH3-SCR activity, and the active-temperature window (NO conversion above 80%, T80) was significantly broadened to 100-350 °C (SO42--TiO2@MnOx) compared to that of the pristine MnOx catalyst (ca. T80: 100-268 °C). Combined with advanced characterizations and control experiments, it was clearly shown that the poisonous effects of sulfate on the MnOx catalyst could be efficiently inhibited in the presence of TiO2 species due to the interaction between sulfate and TiO2 to form a solid superacid (SO42--TiO2) species as NH3 adsorption sites for the low-temperature process. Furthermore, such solid superacid (SO42--TiO2) species could weaken the redox ability to inhibit the excessive oxidation of NH3 and thus enhance the high-temperature activity significantly. This work not only puts forward the TiO2 predecoration strategy that converts sulfate to a promoter to broaden the active temperature window but also experimentally proves that the requirement of redox ability and acidity in the MnOx-based NH3-SCR catalyst was dependent on the reaction temperature range.

Effects of High-Temperature, High-Pressure, and Ultrasonic Treatment on the Physicochemical Properties and Structure of Soluble Dietary Fibers of Millet Bran.

OBJECTIVES: The effects of high-temperature, high-pressure, and ultrasonic treatment on the physicochemical properties and structure of soluble dietary fibers in millet bran were studied to provide a comprehensive reference for the utilization of millet bran. METHODS: Different physical methods were used to treat millet bran dietary fibers, and their microstructures and Fourier-transform infrared spectra before and after modification were compared. The physicochemical properties (water-holding capacity, swelling capacity, oil-holding capacity, fat-binding capacity, cation exchange capacity), total antioxidant capacity, and thermal characteristics were also analyzed. RESULTS: There were no significant changes in the chemical groups of millet bran's soluble dietary fibers after modification, but cracks appeared on the surface of the fibers and the structure became loose and porous. Fiber agglomeration was observed, as well as improved thermal stability. After modification, the water-holding capacity, swelling capacity, oil-holding capacity, fat-binding capacity, and cation exchange capacity of millet bran were improved. When compared to the original soluble dietary fibers, ultrasound-treated fibers showed the most substantial improvement in all four capabilities, with increases of 140, 50, 78.1, 65.7, and 37.8%, respectively, compared with the original soluble dietary fibers (P < 0.05). The total antioxidant capacity of the ultrasound-treated fibers was found to be higher than those of the fibers that underwent the other three treatments (P < 0.05). CONCLUSIONS: The physicochemical qualities and structural characteristics of the soluble dietary fibers in millet bran are affected by all three physical modification methods; however, the physicochemical properties of the ultrasound-treated fibers are most significantly improved.

Auxin response factors (ARFs) differentially regulate rice antiviral immune response against rice dwarf virus.

There are 25 auxin response factors (ARFs) in the rice genome, which play critical roles in regulating myriad aspects of plant development, but their role (s) in host antiviral immune defense and the underneath mechanism remain largely unknown. By using the rice-rice dwarf virus (RDV) model system, here we report that auxin signaling enhances rice defense against RDV infection. In turn, RDV infection triggers increased auxin biosynthesis and accumulation in rice, and that treatment with exogenous auxin reduces OsIAA10 protein level, thereby unleashing a group of OsIAA10-interacting OsARFs to mediate downstream antiviral responses. Strikingly, our genetic data showed that loss-of-function mutants of osarf12 or osarf16 exhibit reduced resistance whereas osarf11 mutants display enhanced resistance to RDV. In turn, OsARF12 activates the down-stream OsWRKY13 expression through direct binding to its promoter, loss-of-function mutants of oswrky13 exhibit reduced resistance. These results demonstrated that OsARF 11, 12 and 16 differentially regulate rice antiviral defense. Together with our previous discovery that the viral P2 protein stabilizes OsIAA10 protein via thwarting its interaction with OsTIR1 to enhance viral infection and pathogenesis, our results reveal a novel auxin-IAA10-ARFs-mediated signaling mechanism employed by rice and RDV for defense and counter defense responses.

The effect of sorghum resistance resistant starch-mediated equol on the histological morphology of the uterus and ovaries of postmenopausal rats.

Equol is a metabolite of daidzein and has a higher biological activity than daidzein. Equol, combined with estrogen receptors, can reduce the incidence of diseases such as cardiovascular disease, osteoporosis, and breast cancer; more effectively alleviate the symptoms of perimenopausal syndrome; and improve age-related decline of the uterus and ovaries. Research has shown that food composition can greatly affect the formation of equol in the intestinal tract. In the intestines, the content of nonstarch polysaccharides that can stimulate fermentation is high, thereby allowing intestinal bacteria to quickly and completely transform the daidzein into equol. This study used Sprague Dawley (SD) rats as a model, where menopause was established through direct intragastric administration of formistan. In the 6-week-long experiment, intragastric administration of RS while feeding bean pulp reduced the body weight of postmenopausal rats, reduced the efficiency of feed utilization of rats, and increased the weight of organs such as the uterus and ovaries. Routine blood indexes showed that no adverse reactions were produced by intragastric administration of RS. 16s rDNA sequencing further verified Lactobacillus and Clostridium XIVa, as the bacteria that converted daidzein into equol.

Identification of the Metabolites in Rat Urine after Oral Administration and Elucidation of the Metabolic Process of Naozhenning Granule Using LC-MS.

Naozhenning (NZN) granule, a Chinese herbal formula, is widely used to treat craniocerebral trauma and promote functional recovery. In our previous study, the chemical components, as well as the serum metabolites in the male Sprague-Dawley rats of the NZN granule after oral administration were characterized. In this study, the urine metabolites in the male Sprague-Dawley rats were further investigated by ultrahigh-performance liquid chromatography-Q Exactive hybrid quadrupole-Orbitrap high-resolution accurate mass spectrometry. In order to identify the urine metabolites comprehensively, three sample preparation methods were used, including solid-phase extraction, protein precipitation method and solvent partition. Based on the accurate molecular weight and the fragmentation information from the MS spectra, a total of 76 urine metabolites were identified, which including 17 prototypes and 59 metabolites. The results showed that the detected urine metabolites were different for the different pretreatment methods, as some metabolites could only be detected in the particular pretreatment method. In addition, the metabolic processes of the components from NZN granule to the serum and urine were also elucidated and discussed. The results will provide useful information for further studying the relationship between the chemical components and pharmacological activity of NZN granule.

The resistant starch from sorghum regulates lipid metabolism in menopausal rats via equol.

Equol is a metabolite of daidzein and has a higher biological activity than daidzein. High levels of non-starch polysaccharides can stimulate fermentation in the intestine leading to rapid conversion of daidzein into equol that has great potential to reduce obesity in postmenopausal women. In the present study, female Sprague-Dawley rats were used to establish a menopausal model by oral administration of formestane and to compare the protective effect of resistant starch on lipid metabolism, with or without soybean feed. The resistant starch was found to effectively control body weight and adipose tissue quality, while increasing the high-density lipoprotein cholesterol (HDL-C) concentration and lowering the glycerol, triacylglycerols (TG), total cholesterol (TC), and low density lipoprotein cholesterol (LDL-C) concentrations with soybean feed. Equol inhibited the expression of SREBPC1 gene by inhibiting SHP in the liver via transcription factor FXR, thereby inhibiting the synthesis of triglyceride and fatty acid in the liver. PRACTICAL APPLICATIONS: Intake of a certain amount of resistant starch while eating the soy product can better regulate lipid metabolism in menopausal obese rats compared to consumption of resistant starch alone. Studies have shown that resistant starch converts daidzein to Equol by regulating the structure of the intestinal flora and acts as an estrogen in menopausal rats. This research will further expand the health applications of resistant starch and provide useful information for the food industry.

A non-structural protein encoded by Rice Dwarf Virus targets to the nucleus and chloroplast and inhibits local RNA silencing.

RNA silencing is a potent antiviral mechanism in plants and animals. As a counter-defense, many viruses studied to date encode one or more viral suppressors of RNA silencing (VSR). In the latter case, how different VSRs encoded by a virus function in silencing remains to be fully understood. We previously showed that the nonstructural protein Pns10 of a Phytoreovirus, Rice dwarf virus (RDV), functions as a VSR. Here we present evidence that another nonstructural protein, Pns11, also functions as a VSR. While Pns10 was localized in the cytoplasm, Pns11 was localized both in the nucleus and chloroplasts. Pns11 has two bipartite nuclear localization signals (NLSs), which were required for nuclear as well as chloroplastic localization. The NLSs were also required for the silencing activities of Pns11. This is the first report that multiple VSRs encoded by a virus are localized in different subcellular compartments, and that a viral protein can be targeted to both the nucleus and chloroplast. These findings may have broad significance in studying the subcellular targeting of VSRs and other viral proteins in viral-host interactions.

Metabolomics coupled with SystemsDock reveal the protective effect and the potential active components of Naozhenning granule against traumatic brain injury.

ETHNOPHARMACOLOGICAL RELEVANCE: Naozhenning granule (NZN), a widely traditional Chinese medicine (TCM) prescription with a long history of clinical, which is mainly used in the treatment of concussion, cerebral post-traumatic syndrome, consists of Di Huang (Radix of Rehmannia glutinosa (Gaertn.) DC.), Dang Gui (Radix of Angelica sinensis (Oliv.) Diels), Chen Pi (Pericarpium of Citrus reticulata Blanco), Dan shen (Radix of Salvia Miltiorrhiza Bunge.), Di Long (Pheretima aspergillum (E. Perrier)), Mu Dan Pi (Cortex of Paeonia suffruticosa Andrews), Suan Zao Ren (Semen of Ziziphus jujuba Mill.), Chuan Xiong (Rhizoma of Ligusticum striatum DC.), Zhu Ru (Phyllostachys nigra (Lodd. Ex Lindl.) Munro), Bai Zi Ren (Semen of Platycladus orientalis (L.) Franco) and Fu Ling (sclerotium of Poria cocos (Schw.)Wolf). AIM OF THE STUDY: This study aimed to unravel the mechanism and material basis of NZN against traumatic brain injury. MATERIALS AND METHODS: In this study, a 1H nuclear magnetic resonance (NMR) based metabolomic approach combined with systemsDock was employed to study the protective effect of NZN against traumatic brain injury using a cerebral concussion rat model. The morris water maze test and biochemical indexes were used to evaluate the efficacy of NZN. RESULTS: The results of morris water maze test suggested NZN can improve the spatial learning and memory of model rats, and the superoxide dismutas (SOD) and malonyldialdehyde (MDA) level indicated that the effect of NZN was related with the regulation of oxidative stress. Multivariate analysis revealed that the effect of NZN was related with regulation of 18 brain metabolites, and the corresponding metabolic pathways were further revealed by MetPA analysis. 13 serum absorbed components were found to hit the targets both related with the metabolic regulation and cerebral trauma through systemsDock-aided molecular docking experiments, and these compounds might be served as the active compounds in NZN against cerebral trauma. CONCLUSION: 1H-NMR based metabolomics and molecular docking provided the insights for the synergistic mechanisms and the potential active compounds of NZN in treating cerebral trauma. However, the bioactive compounds and their synergistic effect need to be further validated.

Rice Dwarf Virus Small RNA Profiles in Rice and Leafhopper Reveal Distinct Patterns in Cross-Kingdom Hosts.

RNA silencing has evolved as a widespread antiviral strategy in many eukaryotic organisms. Antiviral RNA silencing is mediated by virus-derived small RNAs (vsiRNAs), created by the cleavage of double-stranded viral RNA substrates by Dicer (Dcr) in animals or Dicer-like (DCL) proteins in plants. However, little is known about how the RNA silencing mechanisms of different hosts respond to the same virus infection. We performed high-throughput small RNA sequencing in Nephotettix cincticeps and Oryza sativa infected with Rice dwarf phytoreovirus and analyzed the distinct accumulation of vsiRNAs in these two hosts. The results suggested a potential branch in the evolution of antiviral RNA silencing of insect and plant hosts. The rice vsiRNAs were predominantly 21 and 22 nucleotides (nt) long, suggesting that OsDCL4 and OsDCL2 are involved in their production, whereas 21-nt vsiRNAs dominated in leafhopper, suggesting the involvement of a Dcr-2 homolog. Furthermore, we identified ~50-fold more vsiRNAs in rice than in leafhoppers, which might be partially attributable to the activity of RNA-dependent RNA polymerase 6 (RDR6) in rice and the lack of RDR genes in leafhoppers. Our data established a basis for further comparative studies on the evolution of RNA silencing-based interactions between a virus and its hosts, across kingdoms.

A novel strategy and kinetics analysis of half-fractional high cell density fed-batch cultivation of Zygosaccharomyces rouxii.

Zygosaccharomyces rouxii is an important microorganism for aroma production in traditional fermented foods. Using Z. rouxii as the original strain, the batch was split after glucose depletion in the culture medium. Half of the volume of the culture medium was released, and fresh culture medium was fed in. The exponential culture kinetics and the formula for the half-fractional fed-batch cultivations were determined to achieve a new strategy for high cell density culturing of Z. rouxii. Based on a full cultivation, three half-fractional fed-batch cultivations were performed after every 10 hr of culture. The specific growth rates of Z. rouxii at the different stages were in the order µ X0>µ X1>µ X2>µ X3 (0.525 to 0.229 hr-1). The glucose substrate consumption rates gradually decreased following the order µ S0>µ S1>µ S2>µ S3 (-1.165 to -0.722, g/g). The equation models for cell growth and glucose substrate consumption showed typical exponential behavior. The total cell yield was 1.78-fold higher than the yield from a full cultivation, and this continuous subculture strategy also indicated a higher efficiency than traditional full cultivation. A new strategy for highly efficient culturing of Z. rouxii was achieved in a pilot scale. A foundation with data support for the production and application of Z. rouxii was developed.

A viral protein promotes host SAMS1 activity and ethylene production for the benefit of virus infection.

Ethylene plays critical roles in plant development and biotic stress response, but the mechanism of ethylene in host antiviral response remains unclear. Here, we report that Rice dwarf virus (RDV) triggers ethylene production by stimulating the activity of S-adenosyl-L-methionine synthetase (SAMS), a key component of the ethylene synthesis pathway, resulting in elevated susceptibility to RDV. RDV-encoded Pns11 protein specifically interacted with OsSAMS1 to enhance its enzymatic activity, leading to higher ethylene levels in both RDV-infected and Pns11-overexpressing rice. Consistent with a counter-defense role for ethylene, Pns11-overexpressing rice, as well as those overexpressing OsSAMS1, were substantially more susceptible to RDV infection, and a similar effect was observed in rice plants treated with an ethylene precursor. Conversely, OsSAMS1-knockout mutants, as well as an osein2 mutant defective in ethylene signaling, resisted RDV infection more robustly. Our findings uncover a novel mechanism which RDV manipulates ethylene biosynthesis in the host plants to achieve efficient infection.

Rice stripe virus NS3 protein regulates primary miRNA processing through association with the miRNA biogenesis factor OsDRB1 and facilitates virus infection in rice.

MicroRNAs (miRNAs) are small regulatory RNAs processed from primary miRNA transcripts, and plant miRNAs play important roles in plant growth, development, and response to infection by microbes. Microbial infections broadly alter miRNA biogenesis, but the underlying mechanisms remain poorly understood. In this study, we report that the Rice stripe virus (RSV)-encoded nonstructural protein 3 (NS3) interacts with OsDRB1, an indispensable component of the rice (Oryza sativa) miRNA-processing complex. Moreover, the NS3-OsDRB1 interaction occurs at the sites required for OsDRB1 self-interaction, which is essential for miRNA biogenesis. Further analysis revealed that NS3 acts as a scaffold between OsDRB1 and pri-miRNAs to regulate their association and aids in vivo processing of pri-miRNAs. Genetic evidence in Arabidopsis showed that NS3 can partially substitute for the function of double-stranded RNA binding domain (dsRBD) of AtDRB1/AtHYL1 during miRNA biogenesis. As a result, NS3 induces the accumulation of several miRNAs, most of which target pivotal genes associated with development or pathogen resistance. In contrast, a mutant version of NS3 (mNS3), which still associated with OsDRB1 but has defects in pri-miRNA binding, reduces accumulation of these miRNAs. Transgenic rice lines expressing NS3 exhibited significantly higher susceptibility to RSV infection compared with non-transgenic wild-type plants, whereas the transgenic lines expressing mNS3 showed a less-sensitive response. Our findings revealed a previously unknown mechanism in which a viral protein hijacks OsDRB1, a key component of the processing complex, for miRNA biogenesis and enhances viral infection and pathogenesis in rice.

Rice Dwarf Virus P2 Protein Hijacks Auxin Signaling by Directly Targeting the Rice OsIAA10 Protein, Enhancing Viral Infection and Disease Development.

The phytohormone auxin plays critical roles in regulating myriads of plant growth and developmental processes. Microbe infection can disturb auxin signaling resulting in defects in these processes, but the underlying mechanisms are poorly understood. Auxin signaling begins with perception of auxin by a transient co-receptor complex consisting of an F-box transport inhibitor response 1/auxin signaling F-box (TIR1/AFB) protein and an auxin/indole-3-acetic acid (Aux/IAA) protein. Auxin binding to the co-receptor triggers ubiquitination and 26S proteasome degradation of the Aux/IAA proteins, leading to subsequent events, including expression of auxin-responsive genes. Here we report that Rice dwarf virus (RDV), a devastating pathogen of rice, causes disease symptoms including dwarfing, increased tiller number and short crown roots in infected rice as a result of reduced sensitivity to auxin signaling. The RDV capsid protein P2 binds OsIAA10, blocking the interaction between OsIAA10 and OsTIR1 and inhibiting 26S proteasome-mediated OsIAA10 degradation. Transgenic rice plants overexpressing wild-type or a dominant-negative (degradation-resistant) mutant of OsIAA10 phenocopy RDV symptoms are more susceptible to RDV infection; however, knockdown of OsIAA10 enhances the resistance of rice to RDV infection. Our findings reveal a previously unknown mechanism of viral protein reprogramming of a key step in auxin signaling initiation that enhances viral infection and pathogenesis.

OsRDR6 plays role in host defense against double-stranded RNA virus, Rice Dwarf Phytoreovirus.

RNAi is a major antiviral defense response in plant and animal model systems. RNA-dependent RNA polymerase 6 (RDR6) is an essential component of RNAi, which plays an important role in the resistance against viruses in the model plants. We found previously that rice RDR6 (OsRDR6) functioned in the defense against Rice stripe virus (RSV), and Rice Dwarf Phytoreovirus (RDV) infection resulted in down-regulation of expression of RDR6. Here we report our new findings on the function of OsRDR6 against RDV. Our result showed that down-regulation of OsRDR6 through the antisense (OsRDR6AS) strategy increased rice susceptibility to RDV infection while over-expression of OsRDR6 had no effect on RDV infection. The accumulation of RDV vsiRNAs was reduced in the OsRDR6AS plants. In the OsRDR6 over-expressed plants, the levels of OsRDR6 RNA transcript and protein were much higher than that in the control plants. Interestingly, the accumulation level of OsRDR6 protein became undetectable after RDV infection. This finding indicated that the translation and/or stability of OsRDR6 protein were negatively impacted upon RDV infection. This new finding provides a new light on the function of RDR6 in plant defense response and the cross-talking between factors encoded by host plant and double-stranded RNA viruses.