GPR39-mediated ERK1/2 signaling reduces permethrin-induced proliferation of estrogen receptor α-negative cells.

Certain insecticides are known to have estrogenic effects by activating estrogen receptors through genomic transcription. This has led researchers to associate specific insecticide use with an increased breast cancer risk. However, it is unclear if estrogen receptor-dependent pathways are the only way in which these compounds induce carcinogenic effects. The objective of this study was to determine the impact of the pyrethroid insecticide permethrin on the growth of estrogen receptor negative breast cancer cells MDA-MB-231. Using tandem mass spectrometric techniques, the effect of permethrin on cellular protein expression was investigated, and gene ontology and pathway function enrichment analyses were performed on the deregulated proteins. Finally, molecular docking simulations of permethrin with the candidate target protein was performed and the functionality of the protein was confirmed through gene knockdown experiments. Our findings demonstrate that exposure to 10-40 µM permethrin for 48 h enhanced cell proliferation and cell cycle progression in MDA-MB-231. We observed deregulated expression in 83 upregulated proteins and 34 downregulated proteins due to permethrin exposure. These deregulated proteins are primarily linked to transmembrane signaling and chemical carcinogenesis. Molecular docking simulations revealed that the overexpressed transmembrane signaling protein, G protein-coupled receptor 39 (GPR39), has the potential to bind to permethrin. Knockdown of GPR39 partially impeded permethrin-induced cellular proliferation and altered the expression of proliferation marker protein PCNA and cell cycle-associated protein cyclin D1 via the ERK1/2 signaling pathway. These findings offer novel evidence for permethrin as an environmental breast cancer risk factor, displaying its potential to impact breast cancer cell proliferation via an estrogen receptor-independent pathway.

MiR-96-5p is involved in permethrin-promoted proliferation and migration of breast cancer cells.

MicroRNAs (miRNAs) are major players in cellular responses to xenobiotic compounds and toxins. However, the role of miRNAs in pyrethroid pesticide-induced cancer progression remains unclear. This study aimed to investigate the function of miR-96-5p in permethrin-induced proliferation and migration in breast cancer cells. In our study, the expression of miR-96-5p was upregulated in permethrin-treated MCF-7 cells. MiR-96-5p promoted MCF-7 cell proliferation and migration, accompanied bychanges in the expression of proteins involved in cell proliferation, migration, and apoptosis. Homeobox A5 (HOXA5) was identified as a direct target of miR-96-5p. HOXA5 silencing had the opposite effects with miR-96-5p inhibition. In conclusion, these results suggest that miR-96-5p is involved in permethrin-promoted proliferation and migration of breast cancer cells by targeting HOXA5.

The enhanced effect of magnetism on the thermoelectric performance of a CrI3 monolayer.

The effect of magnetism on the thermoelectric (TE) transformation efficiency has recently attracted a lot of attention. A CrI3 monolayer is a two-dimensional (2D) ferromagnetic (FM) semiconductor with a Curie temperature of 45 K. In this work, we employed first-principles calculations within the framework of density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method and Landauer-Buttiker theory to study the effect of magnetism on the TE performance of a CrI3 monolayer. The stability, electronic structures, density of states (DOS) and TE parameters of a CrI3 monolayer are calculated. Our calculation results indicate that the TE performance of a CrI3 monolayer in a FM state is superior to that in a non-magnetic (NM) state. Namely, magnetism is beneficial to improving the TE performance. To further investigate the physical mechanism, the phonon group velocity, the electronic and phonon transmission spectra and the effective mass of a CrI3 monolayer in FM and NM states are analyzed in detail. For a CrI3 monolayer in a NM state, the maximum ZT value at 40 K is 0.09 and 0.16 for p-type and n-type doping, respectively. Relative to that in a NM state, the maximum ZT of a CrI3 monolayer in a FM state is largely improved, and can reach 0.23 and 1.58 for p-type and n-type doping. Our research provides a valuable reference by showing that magnetism is a possible factor for improving the TE efficiency.

miR-96-5p attenuates malathion-induced apoptosis of human kidney cells by targeting the ER stress marker DDIT3.

Micro RNAs (miRNAs) are major players in cellular responses to xenobiotic compounds and toxins. However, their functions in organophosphate-induced cytotoxicity remain unclear. This study investigated the involvement of miR-96-5p in the non-cholinergic toxicity of malathion in normal human kidney cells (HK-2 cells). Malathion decreased HK-2 cell viability and the expression of miR-96-5p in a dose- and time-dependent manner. In addition, transfection with miR-96-5p mimics attenuated malathion-induced HK-2 cell apoptosis, whereas transfection with a miR-96-5p inhibitor increased HK-2 cell apoptosis. Luciferase assays indicated that miR-96-5p could bind directly to the 3'-untranslated region of DDIT3, a well-known marker of endoplasmic reticulum stress. Further analyses of the expression of apoptosis-related genes and proteins indicated that miR-96-5p may function to reduce malathion-induced HK-2 cell apoptosis via regulation of the DDIT3/B-cell lymphoma (BCL)-2/caspase-3 signaling pathway. In summary, the results of the present study indicate that miR-96-5p protects HK-2 cells from malathion-induced ER stress-dependent apoptosis by targeting DDIT3.

Monolayer Ti2C MXene: manipulating magnetic properties and electronic structures by an electric field.

Two-dimensional (2D) layered Ti2C MXene has been synthesized experimentally, and the magnetism of monolayer Ti2C MXene has been predicted theoretically. In this study, based on first-principles calculations, five magnetic configurations of monolayer Ti2C were constructed to predict the magnetic ground state. We have found that the antiferromagnetic (AFM) state has the lowest energy. By applying an external electric field, monolayer Ti2C changes from an AFM semiconductor to a ferrimagnetic (FIM) semiconductor, half-metal, magnetic metal, non-magnetic (NM) metal, and NM semiconductor. When the electric field increases beyond a certain value, the magnetic moments of Ti atoms sharply decrease. With the increase in the electric field, the effective masses decrease significantly, carrier mobility increases and conductivity increases. The magnetic anisotropy energies were calculated and the results showed that the out-of-plane direction was the magnetic easy axis. Using the mean-field approximation method, the Néel temperature of monolayer Ti2C is estimated to be 50 K. By applying an electric field, the Néel temperature significantly decreases, which shows that the electric field can effectively reduce the high Néel temperature. Therefore, our research suggests that the magnetic and electronic properties of 2D materials can be manipulated by an external electric field, which provides a feasible direction for the tuning of nanomagnetic devices.

Two novel triangular borophenes B3H and B6O: first-principles prediction.

By means of density functional theory calculations, we successfully predict two stable 2D triangular borophenes, namely B3H and B6O. Our results indicate that B3H is a Dirac material and its cone point is located at the K point of the Brillouin zone (BZ). B6O is identified as having a node-line ring and Dirac cones together. Its node-line ring formed by the intersection of the extended energy band from the two Dirac cones located on K point. This modified 2D borophene has great thermal and dynamic stability due to the electron transfer from the triangular boron lattice to the O atoms. The electronic structure of B6O nanofilm demonstrates novel properties such as two Dirac cones, more than 1.3 eV linear dispersion bands at some points of the BZ, as well as excellent transport properties for the extremely high mobility brought by the combination of the node-line semimetal and Dirac cones. Our study may motivate potential applications of 2D materials in nanoelectronics.

Gallium Thiophosphate: An Emerging Bidirectional Auxetic Two-Dimensional Crystal with Wide Direct Band Gap.

Two-dimensional (2D) materials with negative Poisson's ratio (NPR) attract considerable attention because of their exotic mechanical properties. We propose a new 2D material, monolayer GaPS4, which shows NPR for both in-plane (-0.033) and out-of-plane (-0.62) directions. Such coexistence of NPR in two distinct directions could be explained by its corner- and edge-shared tetrahedra pucker structure. GaPS4 has an ultralow cleavage energy of 0.23 J m-2 according to our calculation, such that exfoliation of the bulk material is feasible for the preparation of mono- and few-layer GaPS4. Direct wide band gap of 3.55 eV and moderate electron mobility have been revealed in monolayer GaPS4, while the direct gap feature is robust within a strain range of -6% to 6%. These findings render 2D GaPS4 a promising candidate for applications in nanoelectronics and low-dimensional electromechanical devices.

KTlO: a metal shrouded 2D semiconductor with high carrier mobility and tunable magnetism.

Two-dimensional materials with high carrier mobility and tunable magnetism are in high demand for nanoelectronic and spintronic applications. Herein, we predict a novel two-dimensional monolayer KTlO that possesses an indirect band gap of 2.25 eV (based on HSE06 calculations) and high carrier mobility (450 cm2 V-1 s-1 for electrons and 160 cm2 V-1 s-1 for holes) by means of ab initio calculations. The electron mobility can be increased up to 26 280 cm2 V-1 s-1 and 54 150 cm2 V-1 s-1 for bilayer and trilayer KTlO, respectively. The KTlO monolayer has a calculated cleavage energy of 0.56 J m-2, which suggests exfoliation of the bulk material as a viable means for the preparation of mono- and few-layer materials. Remarkably, the KTlO monolayer demonstrates tunable magnetism and half-metallicity with hole doping, which are attributed to the novel Mexican-hat-like bands and van Hove singularities in its electronic structure. Furthermore, monolayer KTlO exhibits moderate optical absorption over the visible light and ultraviolet regions. The band gap value and band characteristics of monolayer KTlO can be substantially manipulated by biaxial and uniaxial strains to meet the requirement of various applications. All these novel properties make monolayer KTlO a promising functional material for future nanoelectronic and spintronic applications.

miR-513a-5p targets Bcl-2 to promote dichlorvos induced apoptosis in HK-2 cells.

miRNAs are crucially involved in cellular responses to exotic chemical toxins. However, the role of miRNAs in organophosphates induced cytotoxicity is poorly understood. In present study, we investigated the role of miR-513a-5p in dichlorvos induced cytotoxicity in human kidney cell line HK-2. We found that dichlorvos increased intracellular ROS level, upregulated miR-513a-5p expression and induced apoptosis in HK-2 cells. Moreover, overexpression of miR-513a-5p promoted apoptosis of HK-2 cells with or without exposure to dichlorvos while anti-miR-513a-5p partially suppressed dichlorvos induced apoptosis. Luciferase assay showed that miR-513a-5p could directly bind to the 3'-untranslated regions of Bcl-2. Furthermore, miR-513a-5p decreased the level of Bcl-2 and promoted dichlorvos induced apoptosis in HK-2 cells through the Bcl-2/Bax-Caspase-3 pathway. Taken together, our findings indicate that miR-513a-5p promotes dichlorvos induced apoptosis by targeting Bcl-2.

Analysis of alternative splicing events by RNA sequencing in the ovaries of Xiang pig at estrous and diestrous.

Alternative splicing (AS) is an important mechanism for controlling gene expression, which regulates multiple biological processes in higher organisms. Chinese indigenous Xiang pig has distinctive biological characteristics, such as small size, early sexual maturity, lower litter size and not very clear exhibition of estrous behaviors. To further understand how AS responds to estrous cycles in Xiang pig, the genome-wide analysis of AS events was performed by RNA-seq method in Xiang pig ovaries at diestrous and estrous. Using ASprofile program, we analyzed twelve basic AS events in Xiang pig ovaries and identified 68,775 AS events in 15,142 genes from diestrous ovaries and 69,493 AS events in 15,291 genes from the estrous ovaries with average 4.54 splicing events. 94.4-95.5% of expressed genes underwent alternative splicing in this tissues. The frequencies of AS events were similar to each other at diestrous and estrous. Transcription start site (TSS) was the predominant type of AS events, followed by transcription terminal site (TTS), and skipped exon (SKIP). The remaining type of AS events, e.g., intron retention (IR) and alternative exon ends (AE), showed the lower frequencies. Further comparison analysis of gene expression indicated that 4,433 genes had at least one splice variant differentially expressed during estrous, whereas only 2,382 of them were differentially expressed at gene level. Numerous genes involved in gonad development and hormone metabolism were differentially regulated through AS. Twelve genes with different types of alternatively splicing were validated by using RT-PCR method. The GO annotation and KEGG pathway analysis clearly revealed that a lot of DEGs (differentially expressed genes) and DSGs (differentially spliced genes) were involved in follicular development and ovarian steroid biosynthesis. A large number of DSGs, although not differentially expressed, were enriched in circadian rhythm and several signaling pathways. These pathways potentially regulated the female animal reproductive function in gene and/or AS level. Our results suggested that alternative splicing play an essential role in regulation of gene expression in female pigs during estrous. Numerous genes involved in gonad development, hormone metabolism, circadian rhythm were differentially regulated through alternative splicing.

Copy number variations of MTHFSD gene across pig breeds and its association with litter size traits in Chinese indigenous Xiang pig.

Copy number variation (CNV) is a major proportion of genetic variation, which changes the gene structure and dosage and affects gene expression and function. To validate the presence and the function of CNV in pig, we used real-time quantitative polymerase chain reaction (qPCR) method to validate a 496 kb CNV region comprising MTHFSD gene on chromosome 6 of Xiang pig detected by single nucleotide polymorphism (SNP) array. Then we investigated the distribution of the MTHFSD CNV in a total of 545 pigs in four breeds. About 46.2% and 32.7% individuals in the four pig breeds were detected to be types of loss and gain of MTHFSD locus. The relative copy numbers of MTHFSD gene showed the largest variation range (0-55 copies) in the Xiang pig population. The copy numbers of MTHFSD gene presented the positive correlations with the transcript level of MTHFSD gene in adult ovaries. Statistical analysis indicated that CNVs of MTHFSD gene was significantly changed the litter size traits of Xiang pigs, and the individuals with CNV gain showed more litter size than the CNV loss pigs. We have reasons to believe that the MTHFSD as RNA-binding protein play an important role in pig reproduction as a result of regulating MTHFS mRNA metabolism.

Three-Dimensional Resistive Metamaterial Absorber Loaded with Metallic Resonators for the Enhancement of Lower-Frequency Absorption.

Resistive patch array incorporating with metallic backplane provided an effective way to achieve broadband metamaterial absorbers (MAs) in microwave frequency, and the outstanding construction contributed more flexible and diversified broadband absorption. In this paper, we attempted to load metallic resonators (MRs) to three-dimensional resistive MA to further enhance the lower-frequency absorption performance. Simulation showed that the partial absorption peak was separated to the lower frequency, while the rest of broadband absorption was unaffected. Meanwhile, after combining multi-unit of the proposed MAs, the stair-stepping broadband absorption was also achieved. Finally, three samples were fabricated. The agreements between simulations and experimental results demonstrated that resistive MA loaded with MRs provided an effective way for further enhancement of lower-frequency absorption with almost no change of the absorbing structure and lightweight characteristic. Thus, it was worthy to expect a wide range of applications to emerge inspired from the proposed attempt.

Identification and profile of microRNAs in Xiang pig testes in four different ages detected by Solexa sequencing.

To further understand the role of microRNA (miRNA) during testicular development, we constructed four small RNA libraries from the testes of the Chinese indigenous Xiang pig at four different ages, which were sequenced using high-throughput Solexa deep sequencing methods. It yielded over 23 million high-quality reads and 1,342,579 unique sequences. At two and three months of age, the proportion which represented miRNAs was the most abundant class of small RNAs, but it was gradually replaced by the category that represented piRNAs in adult testes. We identified 543 known and homologous conserved porcine miRNAs and 49 potential novel miRNAs. There were 306 known miRNAs which were co-expressed in four libraries. Six miRNAs and three potential novel miRNAs were validated in testes and sperms of Xiang pig by RT-qPCR method. Many clusters of mature miRNA variants were observed, in which let-7 family was the most abundant one. After comparison among libraries, 204 miRNAs were identified as being differentially expressed and likely involved in the development and spermatogenesis of pig testes. This work presented a general genome-wide expression profile of the testes-expressed small RNAs in different ages of pig testes. Our results suggested that miRNAs performed a role in the regulation of mRNAs in puberty pig testes while piRNAs likely functioned mainly in sexually mature pig testes.

Inhibitory Effect of Propolis on Platelet Aggregation In Vitro.

Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was aimed to investigate the effects of different extracts of propolis and components of flavonoids on platelet aggregation. Platelet-rich plasma was prepared and incubated in vitro with different concentrations of the tested extracts and components of flavonoids. Platelets aggregation was induced by different agonists including adenosine diphosphate (ADP, 10 µM), thrombin receptor activator peptide (TRAP, 50 µM), and collagen (5 µg/mL). At 25 mg/L to 300 mg/mL, the water extract propolis (WEP) inhibited three agonists-induced platelet aggregations in a dose-dependent manner. The flavonoids isolated from the propolis also showed markedly inhibited platelet aggregation induced by collagen, ADP, and TRAP, respectively. The components including caffeic acid phenethyl ester (CAPE), galangin, apigenin, quercetin, kaempferol, ferulic acid, rutin, chrysin, pinostrobin, and pinocembrin and their abilities of inhibiting platelet aggregation were studied. It was concluded that propolis had an antiplatelet action in which flavonoids were mainly implicated.

[Inhibitory effect of caveolin-1 on endoplasmic reticulum stress-induced apoptosis in macrophages via p38 MAPK pathway].

Endoplasmic reticulum (ER) stress occurs in macrophage-rich areas of advanced atherosclerotic lesions and contributes to macrophage apoptosis and subsequent plaque necrosis. The purpose of the present study was to investigate the effects of caveolin-1 (Cav-1) on ER stress-induced apoptosis in cultured macrophages and the underlying mechanisms. RAW264.7 cells were incubated with thapsigargin (TG) to establish ER stress model. And Cav-1 expression was detected by Western blot. After being pretreated with filipin(III), a caveolae inhibitor, RAW264.7 cells were assayed with flow cytometry and confocal laser scanning microscopy to detect cell apoptosis. Moreover, p38 mitogen-activated protein kinase (MAPK) phosphorylation and C/EBP homologous protein (CHOP) expression were detected with Western blot. The results showed that Cav-1 expression was markedly increased at early stage of TG treatment (P < 0.05) and then decreased with prolonged or high dose TG treatments. The increasing of Cav-1 expression induced by TG in RAW264.7 cells was abolished under inhibition of caveolae by filipin(III) (P < 0.05). The effect of TG on apoptosis of RAW264.7 cells was further augmented after pretreatment with filipin(III) (P < 0.05). Western blotting showed that MAPK phosphorylation induced by TG was inhibited by filipin(III) in RAW264.7 cells (P < 0.05), whereas CHOP remained unchanged (P > 0.05). These results suggest that Cav-1 may play a critical role in suppressing ER stress-induced macrophages apoptosis in vitro, and one of the mechanisms may be correlated with the activation of p38 MAPK prosurvival pathway.

microRNA and mRNA expression profiling analysis of dichlorvos cytotoxicity in porcine kidney epithelial PK15 cells.

Dichlorvos (DIC) is an organophosphate compound with cholinergic and noncholinergic neurotoxicity as well as non-neuronal cytotoxicity. Little is known about the mechanisms of DIC cytotoxicity in non-neuronal cells. In this study, we established a porcine kidney epithelial cell line (PK15) as a model to explore the mechanisms underlying DIC cytotoxicity based on miRNA and mRNA expression profiling analysis. We found that DIC inhibited the proliferation of PK15 cells in a dose- and time-dependent manner, which may result from apoptosis induced by DIC. Microarray analyses revealed that 16 and 14 miRNAs were significantly upregulated and downregulated in PK15 cells treated by 0.875 mM DIC for 8 h. Among the 30 differentially expressed miRNAs, 7 new miRNAs in pigs were predicted by homology-based searches. In addition, DIC upregulated 339 and downregulated 282 mRNA transcripts. A target prediction algorithm was used to analyze the pattern of differentially expressed miRNAs and mRNAs. Functional analysis indicated that these mRNAs belonged to different functional categories, forming a network participating in the DIC-induced apoptosis in PK15 cells. Therefore, our findings provide new insights into the role of miRNAs in the gene expression and function in DIC-related noncholinergic cytotoxicity.

Polymorphism in the first intron of follicle stimulating hormone beta gene in three Chinese pig breeds and two European pig breeds.

Follicle stimulating hormone (FSH) is a pituitary gonadotropin that plays a key role in the regulation of gonadal function in mammal. The gonadotropic hormones are composed of two subunits, the common alpha subunit and the hormone-specific beta subunit, which determine the binding to specific receptors and induction of biological response. The aim of this study was to investigate the polymorphism of the first intron of FSH-beta gene present in different pig breeds and its influence on the expression of FSH-beta gene. Genomic DNA was isolated from blood of three Chinese local pig breeds and two European pig breeds. The first intron of FSH-beta gene was amplified by polymerase chain reaction (PCR) and the PCR product was then determined by sequencing. The correlation between the expression level of FSH-beta gene and the sequence polymorphism was evaluated by RT-PCR using 29 heterozygous pig breeds. Three patterns of the PCR amplified fragments were observed in five different pig breeds. They are 500bp, 220bp, and 500/220bp in length representing three different genotypes with respect to the size of the first intron of FSH-beta gene. After sequencing the whole intron 1 of FSH-beta, we have found that the different size of the PCR amplified fragments was attributed to an insertion element, which was only found in the larger fragment. The insertion, specific in pig genome, showed high similarity to short interspersed nucleotide elements (SINE). Moreover, The Chinese pig breeds, Xiang, Nuogu and Kele pig, exhibited a statistically significant higher frequency of the allele with this SINE in FSH-beta gene than the European pig breeds did. To elucidate whether the SINE insertion affects the expression of FSH-beta gene, 29 heterozygous Chinese and European pig breeds were tested by RT-PCR. The results confirmed that the major transcript in the heterozygous pigs was from SINE- allele but not detected from SINE+ allele. These data suggested that the SINE insertion negatively regulated the expression of FSH-beta gene and the dominant character related to propagation was gained from the SINE- allele of FSH-beta locus in heterozygous breeds of pigs.

The immunogenicity of fusion protein linking the carboxyl terminus of the B subunit of Shiga toxin 2 to the B subunit of E. coli heat-labile enterotoxin.

To augment the immunogenicity of the subunit B of Shiga toxin (Stx2e B) produced by Escherichia coli and protect piglets from edema disease in china, a fusion gene was constructed consisting of Stx2e B genetically linked at the N-terminus of the B subunit of heat-labile enterotoxin (LTB) in a translational fusion. After being induced with IPTG, the expressed fusion protein of Stx2e B-LTB was about 8.8% of total proteins, approximately 13 microg/ml of the bacteria culture. The Stx2e B-LTB fusion protein was found to be nontoxic to Vero cells at the dose higher than 1 microg/ml and to mice less than 100 microg/ml. Antibody titer against the fusion protein Stx2e B-LTB was 1:76,800, much higher than that of the recombinant Stx2e B protein (1:12,800) alone. All of the mice immunized with the Stx2e B-LTB fusion protein survived when challenged with a lethal dose (LD) of Stx2e toxin. The results showed that the poor immunogenicity of Stx2e B was overcome by conjugating the stx2e B to ltB. The immunogenicity of the constructed fusion protein Stx2e B-LTB in the present study was highly qualified to protect animals against Shiga toxin produced from Shiga toxin-producing Escherichia coli (STEC). The fusion protein of Stx2e B-LTB could be a candidate for a vaccine against edema disease and post-weaning diarrhea simultaneously in piglets.

Identification and function of the growth hormone gene in Rongjiang pig of China.

Growth of animal is largely regulated by growth hormone (GH). In this study, the GH gene was isolated and cloned from the genomic DNA library from Rongjiang pig, a Chinese local swine, using polymerase chain reaction technique. The complete nucleotide sequence of a 1.903 kb genomic fragment containing Rongjiang swine GH gene has been determined. The GH gene contained five exons and four introns similar to the GH genes of other mammalians and exhibited 97%~99% identity to the GH genes of the four western meat-type breeds and nine Chinese local pigs. Polymorphism of GH genes was analyzed by using the restriction enzymes Dde I, Nar I and BsmN I in four western meat-type breeds and ten Chinese local pigs. Five polymorphic restriction sites, with Dde I at the base 622 (G/A) in exon 2 and 274 (T/C) in 5o-flank, with Nar I at 631 (G/A) in exon 2, and with BsmN I at the base 841 (T/C) in intron 2 and 1358 (A/G) in exon 4, were identified. The polymorphic restriction site at 1358 (A/G) leaded to the GH mature protein of Rongjiang pig differing from that of four western meat-type breeds and eight Chinese local breeds at the residue Val108 substituted by Ile108. According to the crystal structure of human GH mature protein, this Ile108 substitution might result in a lower affinity of GH for its receptor in Rongjiang breed.

Identification of 20 microRNAs from Oryza sativa.

MicroRNAs (miRNAs) are present in both plant and animal kingdoms and represents a growing family of non-coding RNAs. These tiny RNAs act as small guides and direct negative regulations usually in the process of development through sequence complementarity to target mRNAs. Although a large number of miRNAs have been identified from various animals, so far plant miRNA studies have focused mainly on Arabidopsis. Here we describe the identification of 20 miRNAs from a rice cDNA library. All the miRNAs were presumably processed from precursors with stem-loop structures and were positively detected in rice cells from at least one tissue, some of which showed tissue-specific expression. Twenty-three unique rice genes were identified to be feasible targets for seven rice miRNAs, including four members of Scarecrow-like transcription factor, the targets of miR-39 that had been characterized in Arabidopsis. Lacking long complementarity, the regulatory targets of 13 miRNAs remain to be further investigated. A possible mechanism of translational repressor for plant miRNAs that lack perfect complementarity to target mRNAs is discussed.