"All in One" Strategy for Achieving Superprotonic Conductivity by Incorporating Strong Acids into a Robust Imidazole-Linked Covalent Organic Framework.

The fabrication of solid-state proton-conducting electrolytes possessing both high performance and long-life reusability is significant but challenging. An "all-in-one" composite, H3PO4@PyTFB-1-SO3H, including imidazole, sulfonic acid, and phosphoric acid, which are essential for proton conduction, was successfully prepared by chemical post-modification and physical loading in the rationally pre-synthesized imidazole-based nanoporous covalent organic framework (COF), PyTFB-1. The resultant H3PO4@PyTFB-1-SO3H exhibits superhigh proton conductivity with its value even highly up to 1.15 × 10-1 S cm-1 at 353 K and 98% relative humidity (RH), making it one of the highest COF-based composites reported so far under the same conditions. Experimental studies and theoretical calculations further confirmed that the imidazole and sulfonic acid groups have strong interactions with the H3PO4 molecules and the synergistic effect of these three groups dramatically improves the proton conductivity properties of H3PO4@PyTFB-1-SO3H. This work demonstrated that by aggregating multiple proton carriers into one composite, effective proton-conducting electrolyte can be feasibly achieved.

From Supramolecular Organic Cages to Porous Covalent Organic Frameworks for Enhancing Iodine Adsorption Capability by Fully Exposed Nitrogen-Rich Sites.

In order to overcome the limitations of supramolecular organic cages for their incomplete accessibility of active sites in the solid state and uneasy recyclability in liquid solution, herein a nitrogen-rich organic cage is rationally linked into framework systems and four isoreticular covalent organic frameworks (COFs), that is, Cage-TFB-COF, Cage-NTBA-COF, Cage-TFPB-COF, and Cage-TFPT-COF, are successfully synthesized. Structure determination reveals that they are all high-quality crystalline materials derived from the eclipsed packing of related isoreticular two-dimensional frameworks. Since the nitrogen-rich sites usually have a high affinity toward iodine species, iodine adsorption investigations are carried out and the results show that all of them display an enhancement in iodine adsorption capacities. Especially, Cage-NTBA-COF exhibits an iodine adsorption capacity of 304 wt%, 14-fold higher than the solid sample packed from the cage itself. The strong interactions between the nitrogen-rich sites and the adsorbed iodine species are revealed by spectral analyses. This work demonstrates that, utilizing the reticular chemistry strategy to extend the close-packed supramolecular organic cages into crystalline porous framework solids, their inherent properties can be greatly exploited for targeted applications.

Highly Enhancing CO2 Photoreduction by Metallization of an Imidazole-linked Robust Covalent Organic Framework.

Converting CO2 into value-added chemicals to solve the issues caused by carbon emission is promising but challenging. Herein, by embedding metal ions (Co2+ , Ni2+ , Cu2+ , and Zn2+ ) into an imidazole-linked robust photosensitive covalent organic framework (PyPor-COF), effective photocatalysts for CO2 conversion are rationally designed and constructed. Characterizations display that all of the metallized PyPor-COFs (M-PyPor-COFs) display remarkably high enhancement in their photochemical properties. Photocatalysis reactions reveal that the Co-metallized PyPor-COF (Co-PyPor-COF) achieves a CO production rate as high as up to 9645 µmol g-1 h-1 with a selectivity of 96.7% under light irradiation, which is more than 45 times higher than that of the metal-free PyPor-COF, while Ni-metallized PyPor-COF (Ni-PyPor-COF) can further tandem catalyze the generated CO to CH4 with a production rate of 463.2 µmol g-1 h-1 . Experimental analyses and theory calculations reveal that their remarkable performance enhancement on CO2 photoreduction should be attributed to the incorporated metal sites in the COF skeleton, which promotes the adsorption and activation of CO2 and the desorption of generated CO and even reduces the reaction energy barrier for the formation of different intermediates. This work demonstrates that by metallizing photoactive COFs, effective photocatalysts for CO2 conversion can be achieved.

Highly Effective Proton-Conductive Matrix-Mixed Membrane Based on a -SO3H-Functionalized Polyphosphazene.

A polyphosphazene with in-built -SO3H moieties (PP-PhSO3H) was facilely synthesized by the polymeric combination of hexachlorocyclotriphosphazene (HCCP) and sulfonate p-phenylenediamine. Characterization reveals that it is a highly stable amorphous polymer. Proton conductivity investigations showed that the synthesized PP-PhSO3H exhibits a proton conductivity of up to 6.64 × 10-2 S cm-1 at 353 K and 98% relative humidity (RH). This value is almost 2 orders of magnitude higher than the corresponding value for its -SO3H-free analogue, PP-Ph, which is 1.72 × 10-4 S cm-1 when measured under the same condition. Consequently, matrix-mixed membranes (labeled PP-PhSO3H-PAN) were further prepared by mixing PP-PhSO3H with polyacrylonitrile (PAN) in different ratios to test its potential application in the proton-exchange membrane (PEM) fuel cell. The analysis results indicate that when the weight ratio of PP-PhSO3H/PAN is 3:1 [named PP-PhSO3H-PAN (3:1)], its proton conductivity can reach up to 5.05 × 10-2 S cm-1 at 353 K and 98% RH, which is even comparable with those of proton-conductive electrolytes currently used in PEM fuel cells. Furthermore, the continuous test demonstrates that the PP-PhSO3H-PAN (3:1) has long-life reusability. This research reveals that by using phosphazene and sulfonated multiple-amine modules as precursors, organic polymers with excellent proton conductivity for the assembly of matrix-mixed membranes in PEM fuel cells can be easily synthesized by a simple polymeric process.

Facile construction of a highly proton-conductive matrix-mixed membrane based on a -SO3H functionalized polyamide.

Developing a facile strategy to construct low-cost and efficient proton-conductive electrolytes is pivotal in the practical application of proton exchange membrane (PEM) fuel cells. Herein, a polyamide with in-built -SO3H moieties, PA(PhSO3H)2, was synthesized via a simple one-pot polymeric acylation process. Investigations via electrochemical impedance spectroscopy (EIS) measurements revealed that the fabricated PA(PhSO3H)2 displays a proton conductivity of up to 5.54 × 10-2 S cm-1 at 353 K under 98% relative humidity (RH), which is more than 2 orders of magnitude higher than that of its -SO3H-free analogue PA(Ph)2 (2.38 × 10-4 S cm-1) under the same conditions. Therefore, after mixing with polyacrylonitrile (PAN) at different ratios, PA(PhSO3H)2-based matrix-mixed membranes were subsequently made and the analysis results revealed that the proton conductivity can reach up to 5.82 × 10-2 S cm-1 at 353 K and 98% RH when the weight ratio of PA(PhSO3H)2 : PAN is in 3 : 1 (labeled as PA(PhSO3H)2-PAN(3 : 1)), the value of which is comparable even to those of commercially available electrolytes that are used in PEM fuel cells. In addition, continuous testing shows that PA(PhSO3H)2-PAN(3 : 1) possesses long-life reusability. This work demonstrates that, utilizing the simple reaction of polymeric acylation with a sulfonated module as a precursor, highly effective proton-conductive membranes for PEM fuel cells can be achieved in a facile manner.

Highly Effective Proton-Conduction Matrix-Mixed Membrane Derived from an -SO3H Functionalized Polyamide.

Developing a low-cost and effective proton-conductive electrolyte to meet the requirements of the large-scale manufacturing of proton exchange membrane (PEM) fuel cells is of great significance in progressing towards the upcoming "hydrogen economy" society. Herein, utilizing the one-pot acylation polymeric combination of acyl chloride and amine precursors, a polyamide with in-built -SO3H moieties (PA-PhSO3H) was facilely synthesized. Characterization shows that it possesses a porous feature and a high stability at the practical operating conditions of PEM fuel cells. Investigations of electrochemical impedance spectroscopy (EIS) measurements revealed that the fabricated PA-PhSO3H displays a proton conductivity of up to 8.85 × 10-2 S·cm-1 at 353 K under 98% relative humidity (RH), which is more than two orders of magnitude higher than that of its -SO3H-free analogue, PA-Ph (6.30 × 10-4 S·cm-1), under the same conditions. Therefore, matrix-mixed membranes were fabricated by mixing with polyacrylonitrile (PAN) in different ratios, and the EIS analyses revealed that its proton conductivity can reach up to 4.90 × 10-2 S·cm-1 at 353 K and a 98% relative humidity (RH) when the weight ratio of PA-PhSO3H:PAN is 3:1 (labeled as PA-PhSO3H-PAN (3:1)), the value of which is even comparable with those of commercial-available electrolytes being used in PEM fuel cells. Additionally, continuous tests showed that PA-PhSO3H-PAN (3:1) possesses a long-life reusability. This work demonstrates, using the simple acylation reaction with the sulfonated module as precursor, that low-cost and highly effective proton-conductive electrolytes for PEM fuel cells can be facilely achieved.

A POMC-originated circuit regulates stress-induced hypophagia, depression, and anhedonia.

Chronic stress causes dysregulations of mood and energy homeostasis, but the neurocircuitry underlying these alterations remain to be fully elucidated. Here we demonstrate that chronic restraint stress in mice results in hyperactivity of pro-opiomelanocortin neurons in the arcuate nucleus of the hypothalamus (POMCARH neurons) associated with decreased neural activities of dopamine neurons in the ventral tegmental area (DAVTA neurons). We further revealed that POMCARH neurons project to the VTA and provide an inhibitory tone to DAVTA neurons via both direct and indirect neurotransmissions. Finally, we show that photoinhibition of the POMCARH→VTA circuit in mice increases body weight and food intake, and reduces depression-like behaviors and anhedonia in mice exposed to chronic restraint stress. Thus, our results identified a novel neurocircuitry regulating feeding and mood in response to stress.

High Enhancement in Proton Conductivity by Incorporating Sulfonic Acids into a Zirconium-Based Metal-Organic Framework via "Click" Reaction.

Taking a robust zirconium-based metal-organic framework, UiO-66, as a prototype, functional postmodification via the versatile Cu(I)-catalyzed azide-alkyne "click" reaction was carried out, and sulfonic acid groups were successfully grafted into its skeleton. Characterizations revealed that the MOF network was still well maintained after being treated by "clicked" modification. Investigations by electrochemical impedance spectroscopy measurements revealed that its proton conductivity increases exponentially up to 8.8 × 10-3 S cm-1 at 80 °C and 98% RH, while those of the UiO-66 and UiO-66-NH2 are only 6.3 × 10-6 and 3.5 × 10-6 S cm-1, respectively, at the same condition. Additionally, the continuous test shows it possesses long-life reusability. Such a remarkable enhancement on the proton conductivities and high performance in long-life reusability of the resultant MOF demonstrated that the "click" reaction is a facile reaction in postmodification of robust porous materials toward targeted applications, with which highly promising candidates of proton-conductive electrolytes for applying in proton-exchange-membrane (PEM) fuel cell can be achieved.

The false smut pathogen Ustilaginoidea virens requires rice stamens for false smut ball formation.

Rice false smut has emerged as a serious grain disease in rice production worldwide. The disease is characterized by the transformation of individual rice florets into false smut balls, which is caused by the fungal pathogen Ustilaginoidea virens. To date, little is known about the host factors required for false smut ball formation by U. virens. In this study, we identified histological determinants for the formation of false smut balls by inoculating U. virens into rice floral mutants defective with respect to individual floral parts. The results showed that U. virens could form mature false smut balls in rice floral mutants with defective pistils, but failed to develop false smut balls in the superwoman mutant lacking stamens, identifying that U. virens requires rice stamens to complete its infection cycle. Comparative transcriptome analysis indicated a list of candidate host genes that may facilitate nutrient acquisition by U. virens from the rice stamens, such as SWEET11, SWEET14 and SUT5, and genes involved in the biosynthesis of trehalose and raffinose family sugars. These data pinpoint rice stamens as the key target organ of U. virens infection and provide a valuable starting point for dissecting the molecular mechanism of false smut ball formation.

Genetic characterization of bovine ephemeral fever virus in southern China, 2013-2017.

Bovine ephemeral fever virus (BEFV) can cause bovine ephemeral fever and is an economically important arbovirus of cattle. To expand the knowledge of the molecular epidemiology of BEFV in southern China, the complete surface glycoprotein G gene of BEFV was sequenced from samples collected in five restricted outbreaks from 2013 to 2017, namely 2013ZH, 2014HM, 2015GX, 11082-2016, and qy2017. It was noted that both 2014HM and 11082-2016 were detected in cattle regularly vaccinated with inactivated vaccine. Phylogenetic analysis demonstrated that all five strains grouped into cluster I. However, qy2017 was closer to the BEFV strains identified in Thailand, Japan, and Taiwan after 2000, while 2013ZH, 2014HM, 2015GX, and 11082-2016 were closer to the Chinese strains in 2011 and the Turkey strains in 2012. The analysis of antigenic sites indicated that several amino acid changes occurred between the five strains and the vaccine strain. Importantly, one novel amino acid mutation site was observed in the putative N-linked glycosylation sites of 2013ZH, 2014HM, 2015GX, and 11082-2016. Our study indicated novel genetic characteristics of the newly emerging BEFV strains in southern China and the necessity of updating the component of commercially available inactivated BEFV vaccines in China.

Development and application of a novel whole sediment toxicity test using immobilized sediment and Chlorella vulgaris.

The sediments of water bodies are not only pollutants sink but also sources of pollution. The assessment for the whole-sediment toxicity is still challenging research. Although the application of immobilized algal bead could overcome the practical difficulties in sediment toxicity assay, the weak growth and reduced sensitivity of algae inside the bead restricted its application. In this study, a sediment toxicity test was developed using immobilized sediment and Chlorella vulgaris. The immobilized sediment was prepared by mixing 2 g freeze-dried sediment and 15-mL 3% (w/v) alginate and hardened in a 4% (w/v) CaCl2 solution. Based on a C. vulgaris growth inhibition test and using the immobilized sediment, the median effective concentration value (EC50) of the spiked Cu and diuron was 506.23 and 2.37 mg/kg respectively, lower than that of using immobilized algae (719.62 and 3.12 mg/kg respectively). The Cu and diuron concentrations in the corresponding overlying water from the spiked immobilized and free sediment showed that sediment pollutants' diffusion capacity was not decreased after immobilization. By using the immobilized sediment in algae toxicity bioassay, the changes in the sediment toxicity of a polluted river before and after dredging was evaluated. The C. vulgaris growth inhibition in sediment A decreased from 81.94% to 8.43%; sediment B remained unchanged; sediment C stimulated the growth of C. vulgaris before dredging (-15.56%), but inhibited the algae growth after dredging (26.88%), and sediment D decreased growth inhibition from 32.66% to -12.60%.

Toxicity Changes of Heavily Polluted River Sediments on Daphnia magna Before and After Dredging.

Most of the pollutants discharged into the water will deposit at the bottom of the river and may cause biological toxicity. Daphnia magna-elutriate toxicity bioassay was usually applied to evaluate sediment toxicity. However, the loss of hydrophobic pollutants during the elutriating will lead to the underestimation of sediment toxicity. The purpose of this study is to apply the optimized immobilized sediments to D. magna test, so it can be directly exposed to the sediments and get accurate sediment toxicity results. The optimized immobilized sediment was prepared by mixing 1 g sediment with 7.5 mL 3% (w/v) alginate and hardened in a 4% (w/v) CaCl2 solution. Based on D. magna acute toxicity test, the median lethal concentration values (LC50) of the spiked Cu and diuron measured by using immobilized sediment were both lower than that of using the elutriate, in which the difference of Cu-LC50 reached a significant level. The toxicity changes of sediment in the polluted rivers before and after dredging were then be evaluated by using the immobilized sediment. The toxicity of the sediments at four sites decreased from acute-toxic (pro-dredging) to slight-acute-toxic and nontoxic (post-dredging).

Extracellular αB-crystallin modulates the inflammatory responses.

Neuroinflammation is considered a challenging clinical problem. Chronic inflammatory responses play important roles in the onset and progression of various neurodegenerative diseases, including multiple sclerosis (MS). Previous studies have shown that astrocytes express small heat shock protein αB-crystallin (CRYAB) which is capable of inhibiting inflammatory responses in astrocytes per se. However, the underlying mechanisms of CRYAB-induced modulation of neuroinflammation are still not fully understood. In the present study, we investigated the role of extracellular CRYAB in the interaction between microglia and astrocytes in the context of MS-associated neuroinflammation. We found that the expression of CRYAB was profoundly increased in EAE mice. CRYAB was preferentially expressed in astrocytes and could be secreted via exosomes. Levels of exosomal CRYAB secreted from astrocytes were markedly increased under stress conditions. Furthermore, incubation of immortalized astrocytes or microglia cell lines with CRYAB remarkably suppressed astrocytes and microglia-mediated inflammatory responses in both autocrine and paracrine manners. Our results reveal a novel function for extracellular CRYAB in the regulation of neuroinflammation. Targeting extracellular CRYAB-modulated neuroinflammation is a potential therapeutic intervention for MS.

Two-factor ANOVA of SSH and RNA-seq analysis reveal development-associated Pi-starvation genes in oilseed rape.

MAIN CONCLUSION: The 5-leaf-stage rape seedlings were more insensitive to Pi starvation than that of the 3-leaf-stage plants, which may be attributed to the higher expression levels of ethylene signaling and sugar-metabolism genes in more mature seedlings. Traditional suppression subtractive hybridization (SSH) and RNA-Seq usually screen out thousands of differentially expressed genes. However, identification of the most important regulators has not been performed to date. Here, we employed two methods, namely, a two-round SSH and two-factor transcriptome analysis derived from the two-factor ANOVA that is commonly used in the statistics, to identify development-associated inorganic phosphate (Pi) starvation-induced genes in Brassica napus. Several of these genes are related to ethylene signaling (such as EIN3, ACO3, ACS8, ERF1A, and ERF2) or sugar metabolism (such as ACC2, GH3, LHCB1.4, XTH4, and SUS2). Although sucrose and ethylene may counteract each other at the biosynthetic level, they may also work synergistically on Pi-starvation-induced gene expression (such as PT1, PT2, RNS1, ACP5, AT4, and IPS1) and root acid phosphatase activation. Furthermore, three new transcription factors that are responsive to Pi starvation were identified: the zinc-finger MYND domain-containing protein 15 (MYND), a Magonashi family protein (MAGO), and a B-box zinc-finger family salt-tolerance protein. This study indicates that the two methods are highly efficient for functional gene screening in non-model organisms.

Water-Binding-Mediated Gelation/Crystallization and Thermosensitive Superchirality.

Determination of molecular structural parameters of hydrophobic cholesterol-naphthalimide conjugates for water binding capabilities as well as their moisture-sensitive supramolecular self-assembly were revealed. Water binding was a key factor in leading trace water-induced crystallization against gelation in apolar solvent. Ordered water molecules entrapped in self-assembly arrays revealed by crystal structures behave as hydrogen-bonding linkers to facilitate three-dimensional growth into crystals rather than one-dimensional gel nanofibers. Water binding was also reflected on the supramolecular chirality inversion of vesicle self-assembly in aqueous media via heating-induced dehydration. Structural parameters that favor water binding were evaluated in detail, which could help rationally design organic building units for advancing soft materials, crystal engineering, and chiral recognition.

A Triazole-Containing Metal-Organic Framework as a Highly Effective and Substrate Size-Dependent Catalyst for CO2 Conversion.

A highly porous metal-organic framework (MOF) incorporating both exposed metal sites and nitrogen-rich triazole groups was successfully constructed via solvothermal assembly of a clicked octcarboxylate ligand and Cu(II) ions, which presents a high affinity toward CO2 molecules clearly verified by gas adsorption and Raman spectral detection. The constructed MOF featuring CO2-adsorbing property and exposed Lewis-acid metal sites could serve as an excellent catalyst for CO2-based chemical fixation. Catalytic activity of the MOF was confirmed by remarkably high efficiency on CO2 cycloaddition with small epoxides. When extending the substrates to larger ones, its activity showed a sharp decrease. These observations reveal that MOF-catalyzed CO2 cycloaddition of small substrates was carried out within the framework, while large ones cannot easily enter into the porous framework for catalytic reactions. Thus, the synthesized MOF exhibits high catalytic selectivity to different substrates on account of the confinement of the pore diameter. The high efficiency and size-dependent selectivity toward small epoxides on catalytic CO2 cycloaddition make this MOF a promising heterogeneous catalyst for carbon fixation.

Bimetallic Metal-Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion.

A highly porous metal-organic framework (MOF) incorporating two kinds of second building units (SBUs), i.e., dimeric paddlewheel (Zn2 (COO)4 ) and tetrameric (Zn4 (O)(CO2 )6 ), is successfully assembled by the reaction of a tricarboxylate ligand with Zn(II) ion. Subsequently, single-crystal-to-single-crystal metal cation exchange using the constructed MOF is investigated, and the results show that Cu(II) and Co(II) ions can selectively be introduced into the MOF without compromising the crystallinity of the pristine framework. This metal cation-exchangeable MOF provides a useful platform for studying the metal effect on both gas adsorption and catalytic activity of the resulted MOFs. While the gas adsorption experiments reveal that Cu(II) and Co(II) exchanged samples exhibit comparable CO2 adsorption capability to the pristine Zn(II) -based MOF under the same conditions, catalytic investigations for the cycloaddition reaction of CO2 with epoxides into related carbonates demonstrate that Zn(II) -based MOF affords the highest catalytic activity as compared with Cu(II) and Co(II) exchanged ones. Molecular dynamic simulations are carried out to further confirm the catalytic performance of these constructed MOFs on chemical fixation of CO2 to carbonates. This research sheds light on how metal exchange can influence intrinsic properties of MOFs.

Ruthenium-Catalyzed Oxidative Homocoupling of Arylboronic Acids in Water: Ligand Tuned Reactivity and Mechanistic Study.

Molecular catalysts based on water-soluble arene-Ru(II) complexes ([Ru]-1-[Ru]-5) containing aniline (L1), 2-methylaniline (L2), 2,6-dimethylaniline (L3), 4-methylaniline (L4), and 4-chloroaniline (L5) were designed for the homocoupling of arylboronic acids in water. These complexes were fully characterized by (1)H, (13)C NMR, mass spectrometry, and elemental analyses. Structural geometry for two of the representative arene-Ru(II) complexes [Ru]-3 and [Ru]-4 was established by single-crystal X-ray diffraction studies. Our studies showed that the selectivity toward biaryls products is influenced by the position and the electronic behavior of various substituents of aniline ligand coordinated to ruthenium. Extensive investigations using (1)H NMR, (19)F NMR, and mass spectral studies provided insights into the mechanistic pathway of homocoupling of arylboronic acids, where the identification of important organometallic intermediates, such as σ-aryl/di(σ-aryl) coordinated arene-Ru(II) species, suggested that the reaction proceeds through the formation of crucial di(σ-aryl)-Ru intermediates by the interaction of arylboronic acid with Ru-catalyst to yield biaryl products.

Troponate/Aminotroponate Ruthenium-Arene Complexes: Synthesis, Structure, and Ligand-Tuned Mechanistic Pathway for Direct C-H Bond Arylation with Aryl Chlorides in Water.

A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products.

Multiple rice microRNAs are involved in immunity against the blast fungus Magnaporthe oryzae.

MicroRNAs (miRNAs) are indispensable regulators for development and defense in eukaryotes. However, the miRNA species have not been explored for rice (Oryza sativa) immunity against the blast fungus Magnaporthe oryzae, the most devastating fungal pathogen in rice production worldwide. Here, by deep sequencing small RNA libraries from susceptible and resistant lines in normal conditions and upon M. oryzae infection, we identified a group of known rice miRNAs that were differentially expressed upon M. oryzae infection. They were further classified into three classes based on their expression patterns in the susceptible japonica line Lijiangxin Tuan Hegu and in the resistant line International Rice Blast Line Pyricularia-Kanto51-m-Tsuyuake that contains a single resistance gene locus, Pyricularia-Kanto 51-m (Pikm), within the Lijiangxin Tuan Hegu background. RNA-blot assay of nine of them confirmed sequencing results. Real-time reverse transcription-polymerase chain reaction assay showed that the expression of some target genes was negatively correlated with the expression of miRNAs. Moreover, transgenic rice plants overexpressing miR160a and miR398b displayed enhanced resistance to M. oryzae, as demonstrated by decreased fungal growth, increased hydrogen peroxide accumulation at the infection site, and up-regulated expression of defense-related genes. Taken together, our data indicate that miRNAs are involved in rice immunity against M. oryzae and that overexpression of miR160a or miR398b can enhance rice resistance to the disease.