RNA-Seq Transcriptome Analysis and Evolution of OsEBS, a Gene Involved in Enhanced Spikelet Number per Panicle in Rice.

Spikelet number per panicle (SNP) is one of the most important yield components in rice. Rice ENHANCING BIOMASS AND SPIKELET NUMBER (OsEBS), a gene involved in improved SNP and yield, has been cloned from an accession of Dongxiang wild rice. However, the mechanism of OsEBS increasing rice SNP is poorly understood. In this study, the RNA-Seq technology was used to analyze the transcriptome of wildtype Guichao 2 and OsEBS over-expression line B102 at the heading stage, and analysis of the evolution of OsEBS was also conducted. A total of 5369 differentially expressed genes (DEGs) were identified between Guichao2 and B102, most of which were down-regulated in B102. Analysis of the expression of endogenous hormone-related genes revealed that 63 auxin-related genes were significantly down-regulated in B102. Gene Ontogeny (GO) enrichment analysis showed that the 63 DEGs were mainly enriched in eight GO terms, including auxin-activated signaling pathway, auxin polar transport, auxin transport, basipetal auxin transport, and amino acid transmembrane transport, most of which were directly or indirectly related to polar auxin transport. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis further verified that the down-regulated genes related to polar auxin transport had important effects on increased SNP. Analysis of the evolution of OsEBS found that OsEBS was involved in the differentiation of indica and japonica, and the differentiation of OsEBS supported the multi-origin model of rice domestication. Indica (XI) subspecies harbored higher nucleotide diversity than japonica (GJ) subspecies in the OsEBS region, and XI experienced strong balancing selection during evolution, while selection in GJ was neutral. The degree of genetic differentiation between GJ and Bas subspecies was the smallest, while it was the highest between GJ and Aus. Phylogenetic analysis of the Hsp70 family in O. sativa, Brachypodium distachyon, and Arabidopsis thaliana indicated that changes in the sequences of OsEBS were accelerated during evolution. Accelerated evolution and domain loss in OsEBS resulted in neofunctionalization. The results obtained from this study provide an important theoretical basis for high-yield rice breeding.

Rice Lesion Mimic Gene Cloning and Association Analysis for Disease Resistance.

Lesion mimic mutants refer to a class of mutants that naturally form necrotic lesions similar to allergic reactions on leaves in the absence of significant stress or damage and without being harmed by pathogens. Mutations in most lesion mimic genes, such as OsACL-A2 and OsSCYL2, can enhance mutants' resistance to pathogens. Lesion mimic mutants are ideal materials for studying programmed cell death (PCD) and plant defense mechanisms. Studying the genes responsible for the rice disease-like phenotype is of great significance for understanding the disease resistance mechanism of rice. In this paper, the nomenclature, occurrence mechanism, genetic characteristics, regulatory pathways, and the research progress on the cloning and disease resistance of rice lesion mimic mutant genes were reviewed, in order to further analyze the various lesion mimic mutants of rice. The mechanism lays a theoretical foundation and provides a reference for rice breeding.

A conserved clathrin-coated vesicle component, OsSCYL2, regulates plant innate immunity in rice.

Clathrin-mediated vesicle trafficking (CMVT) is a fundamental process in all eukaryotic species, and indispensable to organism's growth and development. Recently, it has been suggested that CMVT also plays important roles in the regulation of plant immunity. However, the molecular link between CMVT and plant immunity is largely unknown. SCY1-LIKE2 (SCYL2) is evolutionally conserved among the eukaryote species. Loss-of-function of SCYL2 in Arabidopsis led to severe growth defects. Here, we show that mutation of OsSCYL2 in rice gave rise to a novel phenotype-hypersensitive response-like (HR) cell death in a light-dependent manner. Although mutants of OsSCYL2 showed additional defects in the photosynthetic system, they exhibited enhanced resistance to bacterial pathogens. Subcellular localisation showed that OsSCYL2 localized at Golgi, trans-Golgi network and prevacuolar compartment. OsSCYL2 interacted with OsSPL28, subunit of a clathrin-associated adaptor protein that is known to regulate HR-like cell death in rice. We further showed that OsSCYL2-OsSPL28 interaction is mediated by OsCHC1. Collectively, we characterized a novel component of the CMVT pathway in the regulation of plant immunity. Our work also revealed unidentified new functions of the very conserved SCYL2. It thus may provide new breeding targets to achieve both high yield and enhanced resistance in crops.

Grain Size Associated Genes and the Molecular Regulatory Mechanism in Rice.

Grain size is a quantitative trait that is controlled by multiple genes. It is not only a yield trait, but also an important appearance quality of rice. In addition, grain size is easy to be selected in evolution, which is also a significant trait for studying rice evolution. In recent years, many quantitative trait loci (QTL)/genes for rice grain size were isolated by map-based cloning or genome-wide association studies, which revealed the genetic and molecular mechanism of grain size regulation in part. Here, we summarized the QTL/genes cloned for grain size and the regulation mechanism with a view to provide the theoretical basis for improving rice yield and breeding superior varieties.

Rice EARLY SENESCENCE 2, encoding an inositol polyphosphate kinase, is involved in leaf senescence.

BACKGROUND: Early leaf senescence influences yield and yield quality by affecting plant growth and development. A series of leaf senescence-associated molecular mechanisms have been reported in rice. However, the complex genetic regulatory networks that control leaf senescence need to be elucidated. RESULTS: In this study, an early senescence 2 (es2) mutant was obtained from ethyl methanesulfonate mutagenesis (EMS)-induced mutational library for the Japonica rice cultivar Wuyugeng 7 (WYG7). Leaves of es2 showed early senescence at the seedling stage and became severe at the tillering stage. The contents of reactive oxygen species (ROS) significantly increased, while chlorophyll content, photosynthetic rate, catalase (CAT) activity significantly decreased in the es2 mutant. Moreover, genes which related to senescence, ROS and chlorophyll degradation were up-regulated, while those associated with photosynthesis and chlorophyll synthesis were down-regulated in es2 mutant compared to WYG7. The ES2 gene, which encodes an inositol polyphosphate kinase (OsIPK2), was fine mapped to a 116.73-kb region on chromosome 2. DNA sequencing of ES2 in the mutant revealed a missense mutation, ES2 was localized to nucleus and plasma membrane of cells, and expressed in various tissues of rice. Complementation test and overexpression experiment confirmed that ES2 completely restored the normal phenotype, with chlorophyll contents and photosynthetic rate increased comparable with the wild type. These results reveal the new role of OsIPK2 in regulating leaf senescence in rice and therefore will provide additional genetic evidence on the molecular mechanisms controlling early leaf senescence. CONCLUSIONS: The ES2 gene, encoding an inositol polyphosphate kinase localized in the nucleus and plasma membrane of cells, is essential for leaf senescence in rice. Further study of ES2 will facilitate the dissection of the genetic mechanisms underlying early leaf senescence and plant growth.

Natural variation in the promoter of TGW2 determines grain width and weight in rice.

Understanding the genetic basis of natural variation in grain size among diverse rice varieties can help breeders develop high-yielding rice cultivars. Here, we report the discovery of qTGW2, a new semidominant quantitative trait locus for grain width and weight. The corresponding gene, TGW2, encodes CELL NUMBER REGULATOR 1 (OsCNR1) localized to the plasma membrane. A single nucleotide polymorphism (SNP) variation 1818 bp upstream of TGW2 is responsible for its different expression, leading to alteration in grain width and weight by influencing cell proliferation and expansion in glumes. TGW2 interacts with KRP1, a regulator of cell cycle in plants, to negatively regulate grain width and weight. Genetic diversity analysis of TGW2 in 141 rice accessions revealed it as a breeding target in a selective sweep region. Our findings provide new insights into the genetic mechanism underlying grain morphology and grain weight, and uncover a promising gene for improving rice yield.

Development of nutritious rice with high zinc/selenium and low cadmium in grains through QTL pyramiding.

Enriching zinc (Zn) and selenium (Se) levels, while reducing cadmium (Cd) concentration in rice grains is of great benefit for human diet and health. Large natural variations in grain Zn, Se, and Cd concentrations in different rice accessions enable Zn/Se-biofortification and Cd-minimization through molecular breeding. Here, we report the development of new elite varieties by pyramiding major quantitative trait loci (QTLs) that significantly contribute to high Zn/Se and low Cd accumulation in grains. A chromosome segment substitution line CSSLGCC7 with the PA64s-derived GCC7 allele in the 93-11 background, exhibited steadily higher Mn and lower Cd concentrations in grains than those of 93-11. This elite chromosome segment substitution line (CSSL) was used as the core breeding material to cross with CSSLs harboring other major QTLs for essential mineral elements, especially CSSLGZC6 for grain Zn concentration and CSSLGSC5 for grain Se concentration. The CSSLGCC7+GZC6 and CSSLGCC7+GSC5 exhibited lower Cd concentration with higher Zn and Se concentrations in grains, respectively. Our study thus provides elite materials for rice breeding targeting high Zn/Se and low Cd concentrations in grains.

OsACL-A2 negatively regulates cell death and disease resistance in rice.

ATP-citrate lyases (ACL) play critical roles in tumour cell propagation, foetal development and growth, and histone acetylation in human and animals. Here, we report a novel function of ACL in cell death-mediated pathogen defence responses in rice. Using ethyl methanesulphonate (EMS) mutagenesis and map-based cloning, we identified an Oryza sativa ACL-A2 mutant allele, termed spotted leaf 30-1 (spl30-1), in which an A-to-T transversion converts an Asn at position 343 to a Tyr (N343Y), causing a recessive mutation that led to a lesion mimic phenotype. Compared to wild-type plants, spl30-1 significantly reduces ACL enzymatic activity, accumulates high reactive oxygen species and increases degradation rate of nuclear deoxyribonucleic acids. CRISPR/Cas9-mediated insertion/deletion mutation analysis and complementation assay confirmed that the phenotype of spl30-1 resulted from the defective function of OsACL-A2 protein. We further biochemically identified that the N343Y mutation caused a significant degradation of SPL30N343Y in a ubiquitin-26S proteasome system (UPS)-dependent manner without alteration in transcripts of OsACL-A2 in spl30-1. Transcriptome analysis identified a number of up-regulated genes associated with pathogen defence responses in recessive mutants of OsACL-A2, implying its role in innate immunity. Suppressor mutant screen suggested that OsSL, which encodes a P450 monooxygenase protein, acted as a downstream key regulator in spl30-1-mediated pathogen defence responses. Taken together, our study discovered a novel role of OsACL-A2 in negatively regulating innate immune responses in rice.

Genetic analysis for rice seedling vigor and fine mapping of a major QTL qSSL1b for seedling shoot length.

Seedling vigor is an important agricultural trait as direct-seeded rice technology becomes widely applied. In order to investigate the genetic mechanisms underlying seedling vigor in rice, seeds of 132 recombinant inbred lines (RILs) derived from 93-11 and PA64s, harvested from Lingshui and Hangzhou were cultivated in the nutrient solution, and four indices for seedling vigor were measured including seedling shoot length (SSL), seedling root length (SRL), seedling wet weight (SWW) and seedling dry weight (SDW). Significant correlations were observed among the indices, and also between 1000-seed weight (TSW) and SWW or SDW. Combined with a high-resolution genetic map generated from sequencing of the RILs, 65 quantitative trait loci (QTLs) were detected on all chromosomes with interval of 1.93 Mb on average. Among 57 QTLs for seedling vigor, 28 were detected from seeds harvested in both sites and 33 were first identified. With BC3F2 derived from 93-11 and a CSSL harboring segments from PA64s in 93-11 background, a major QTL for SSL, qSSL1b was fine mapped within 80.5 kb between two InDel markers. Our study provides a platform for further cloning of the QTL and dissecting the molecular basis for seedling vigor at early seedling stage in rice.

Unveiling the Genetic Basis Underlying Rice Anther Culturability via Segregation Distortion Analysis in Doubled Haploid Population.

Anther culture (AC) is a valuable technique in rice breeding. However, the genetic mechanisms underlying anther culturability remain elusive, which has hindered its widespread adoption in rice breeding programs. During AC, microspores carrying favorable alleles for AC are selectively regenerated, leading to segregation distortion (SD) of chromosomal regions linked to these alleles in the doubled haploid (DH) population. Using the AC method, a DH population was generated from the japonica hybrid rice Shenyou 26. A genetic map consisting of 470 SNPs was constructed using this DH population, and SD analysis was performed at both the single- and two-locus levels to dissect the genetic basis underlying anther culturability. Five segregation distortion loci (SDLs) potentially linked to anther culturability were identified. Among these, SDL5 exhibited an overrepresentation of alleles from the female parent, while SDL1.1, SDL1.2, SDL2, and SDL7 displayed an overrepresentation of alleles from the male parent. Furthermore, six pairs of epistatic interactions (EPIs) that influenced two-locus SDs in the DH population were discovered. A cluster of genetic loci, associated with EPI-1, EPI-3, EPI-4, and EPI-5, overlapped with SDL1.1, indicating that the SDL1.1 locus may play a role in regulating anther culturability via both additive and epistatic mechanisms. These findings provide valuable insights into the genetic control of anther culturability in rice and lay the foundation for future research focused on identifying the causal genes associated with anther culturability.

Magnetic compression stricturoplasty in patients with severe stricture after simultaneous esophageal atresia and duodenal obstruction repair: A case report.

Combined esophageal atresia (EA), tracheoesophageal fistula (TEF) and duodenal obstruction result in various challenges in management, and a well-defined management protocol is still lacking. Esophageal stricture is the most common complication after EA repair. The use of magnetic compression alimentary tract anastomosis has been reported in children. By searching the literature, the present study reports the first case of simultaneous repair (EA repair followed by duodenal obstruction repair) and magnetic compression stricturoplasty for refractory esophageal stricture after EA repair in two male neonates. One of the neonates received delayed treatment of duodenal obstruction, and the other successfully underwent a simultaneous emergency operation of these combined anomalies. These two infants developed refractory strictures despite multiple endoscopic dilatation procedures during the postoperative follow-up period. Magnetic compression stricturoplasty procedures were successfully performed under fluoroscopic and endoscopic guidance without any leakage or complication. At the follow-up 10-months after stricturoplasty, the two patients achieved durable esophageal patency in the absence of dysphagia. Combination of early chest and abdominal X-ray detection is recommended to avoid a delayed diagnosis and treatment, as well as the synchronous operation for EA/TEF repair and duodenoduodenostomy in a single surgery for combined EA/TEF and duodenal obstructions. Therefore, magnetic compression stricturoplasty is a feasible and efficient method for establishing early patency of the esophagus in patients with refractory EA stricture.

CRISPR/Cas12a Coupled With Recombinase Polymerase Amplification for Sensitive and Specific Detection of Aphelenchoides besseyi.

Aphelenchoides besseyi (A. besseyi), a seed-borne parasitic nematode, is the causal agent of rice white tip disease (RWTD), which may result in a drastic loss of rice yield. Seed treatments are currently considered to be the most effective means of preventing the spread of RWTD. Therefore, the rapid, highly specific, and accurate detection of A. besseyi from rice seeds is crucial for the surveillance, prevention, and control of RWTD. Here, we describe a novel detection assay that combines recombinase polymerase amplification (RPA) and CRISPR/Cas12a to detect A. besseyi (termed RPA-Cas12a-Ab), with a low limit of detection (LOD) of 1 copy/µl of plasmid or 1:107 diluted DNA extracted from individual nematodes. To improve the user-friendliness, lateral flow strip assay (LFA) was adopted to visualize the detection result. The LOD of the RPA-Cas12a-Ab LFA assay was 1,000 copies/µl plasmid or 1:10 diluted DNA extracted from individual nematodes. The assay developed in this study was able to identify A. besseyi in 45 min with high accuracy and sensitivity without cross reaction with three closely related non-A. besseyi species. Thus, RPA-Cas12a-Ab is a rapid, sensitive, and specific detection system that requires no sophisticated equipment and shows promise for on-site surveillance of A. besseyi.

Magnetic compression anastomosis for rectal atresia following necrotizing enterocolitis: A case report.

RATIONALE: Rectal atresia caused by necrotizing enterocolitis (NEC) is a serious and rare complication in children. Magnetic compression anastomosis (MCA) has been effectively applied in children with congenital oesophageal atresia and biliary atresia. Herein, we reported a case of successfully application of MCA in an infant with rectal atresia following NEC. PATIENT CONCERNS: A 30 weeks premature birth female fetal infant was transferred to our neonatal intensive care unit due to premature delivery, low birth weight, and neonatal respiratory distress. On postpartum day 11, the infant developed abdominal distension and mucosanguineous feces. This infant was then clinically diagnosed as NEC. She underwent anesthesia and intestinal fistula operation on postpartum day 11 because of NEC. DIAGNOSIS: After 3 months, radiographic examination revealed rectal atresia and stricture. INTERVENTIONS: This infant was successfully treated with MCA following a cecum-rectal anastomosis and ileocecal valve was reserved. OUTCOMES: On postoperative day 9, she passed the 2 magnets per rectum. In addition, there were no difficult defecation or fecal incontinence or other short-term complications. After the 7-month follow-up, the patient had an excellent clinical outcome. LESSONS: MCA is a feasible and effective method for treating rectal atresia in infants.

Isolation of TSCD11 Gene for Early Chloroplast Development under High Temperature in Rice.

BACKGROUND: Chloroplasts are essential for photosynthesis and play key roles in plant development. High temperature affects structure of chloroplasts and metabolism in plants. The seryl-tRNA synthetase plays an important role in translation of proteins. Although seryl-tRNA synthetase has been widely studied in microbes and animals, few studies have reported about its role in chloroplast development under high temperature in rice. RESULTS: In this study, we isolated a novel temperature-sensitive chlorophyll-deficient 11 (tscd11) mutant by ethyl methane sulfonate (EMS) mutagenesis of japonica variety Wuyujing7. The tscd11 mutant developed albino leaves at the 3-leaf stage under high temperature (35 °C), but had normal green leaves under low temperature (25 °C). Consistent with the albino phenotype, impaired chloroplasts, decreased chlorophyll content and increased ROS accumulation were found in the tscd11 mutant at 35 °C. Fine mapping and DNA sequencing of tscd11 revealed a missense mutation (G to A) in the eighth exon of LOC_Os11g39670 resulted in amino acid change (Glu374 to Lys374). The TSCD11 gene encodes a seryl-tRNA synthetase localized to chloroplast. Complementation test confirmed that the point mutation in TSCD11 is responsible for the phenotype of tscd11. TSCD11 is highly expressed in leaves. Compared with the wild type (WT), mutation in TSCD11 led to significant alteration in expression levels of genes associated with chlorophyll biosynthesis, photosynthesis and chloroplast development under high temperature. CONCLUSIONS: TSCD11, encoding a seryl-tRNA synthetase localized to chloroplast, is vital to early chloroplast development at high temperature in rice, which help to further study on the molecular mechanism of chloroplast development under high temperature.

Genetic Analysis for Cooking and Eating Quality of Super Rice and Fine Mapping of a Novel Locus qGC10 for Gel Consistency.

Rice (Oryza sativa L.) is an important cereal that provides food for more than half of the world's population. Besides grain yield, improving grain quality is also essential to rice breeders. Amylose content (AC), gelatinization temperature (GT) and gel consistency (GC) are considered to be three indicators for cooking and eating quality in rice. Using a genetic map of RILs derived from the super rice Liang-You-Pei-Jiu with high-density SNPs, we detected 3 QTLs for AC, 3 QTLs for GT, and 8 QTLs for GC on chromosomes 3, 4, 5, 6, 10, and 12. Wx locus, an important determinator for AC and GC, resided in one QTL cluster for AC and GC, qAC6 and qGC6 here. And a novel major QTL qGC10 on chromosome 10 was identified in both Lingshui and Hangzhou. With the BC4F2 population derived from a CSSL harboring the segment for qGC10 from 93-11 in PA64s background, it was fine mapped between two molecular markers within 181 kb region with 27 annotated genes. Quantitative real-time PCR results showed that eight genes were differentially expressed in endosperm of two parents. After DNA sequencing, only LOC_Os10g04900, which encodes a F-box domain containing protein, has 2 bp deletion in the exon of PA64s, resulting in a premature stop codon. Therefore, LOC_Os10g04900 is considered to be the most likely candidate gene for qGC10 associated with gel consistency. Identification of qGC10 provides a new genetic resource for improvement of rice quality.

Development of Three Sets of High-Throughput Genotyped Rice Chromosome Segment Substitution Lines and QTL Mapping for Eleven Traits.

BACKGROUND: Detecting and mapping chromosomal regions that are related to quantitative phenotypic variation in chromosome segment substitution lines (CSSLs) provides an effective means to characterize the genetic basis of complex agronomic trait. CSSLs are also powerful tools for studying the effects of quantitative trait loci (QTLs) pyramiding and interaction on phenotypic variation. RESULTS: Here, we developed three sets of CSSLs consisting of 81, 55, and 61 lines, which were derived from PA64s × 9311, Nipponbare × 9311 and PA64s × Nipponbare crosses, respectively. All of the 197 CSSLs were subjected to high-throughput genotyping by whole-genome resequencing to obtain accurate physical maps for the 3 sets of CSSLs. The 3 sets of CSSLs were used to analyze variation for 11 major agronomic traits in Hangzhou and Shenzhen and led to the detection of 71 QTLs with phenotypic effect that ranged from 7.6% to 44.8%. Eight QTLs were commonly detected under two environments for the same phenotype, and there were also 8 QTL clusters that were found. Combined with GWAS on grain length and expression profiles on young panicle tissues, qGL1 detected in CSSLs was fine mapped within a 119 kb region on chromosome 1 and LOC_Os01g53140 and LOC_Os01g53250 were the two most likely candidate genes. CONCLUSIONS: Our results indicate that developing CSSLs genotyped by whole-genome resequencing are powerful tools for basic genetic research and provide a platform for the rational design of rice breeding. Meanwhile, the conjoint analysis of different CSSLs, natural population and expression profiles can facilitate QTL fine mapping.

The indica nitrate reductase gene OsNR2 allele enhances rice yield potential and nitrogen use efficiency.

The indica and japonica rice (Oryza sativa) subspecies differ in nitrate (NO3-) assimilation capacity and nitrogen (N) use efficiency (NUE). Here, we show that a major component of this difference is conferred by allelic variation at OsNR2, a gene encoding a NADH/NADPH-dependent NO3- reductase (NR). Selection-driven allelic divergence has resulted in variant indica and japonica OsNR2 alleles encoding structurally distinct OsNR2 proteins, with indica OsNR2 exhibiting greater NR activity. Indica OsNR2 also promotes NO3- uptake via feed-forward interaction with OsNRT1.1B, a gene encoding a NO3- uptake transporter. These properties enable indica OsNR2 to confer increased effective tiller number, grain yield and NUE on japonica rice, effects enhanced by interaction with an additionally introgressed indica OsNRT1.1B allele. In consequence, indica OsNR2 provides an important breeding resource for the sustainable increases in japonica rice yields necessary for future global food security.

Variation in the Abundance of OsHAK1 Transcript Underlies the Differential Salinity Tolerance of an indica and a japonica Rice Cultivar.

Salinity imposes a major constraint over the productivity of rice. A set of chromosome segment substitution lines (CSSLs), derived from a cross between the japonica type cultivar (cv.) Nipponbare (salinity sensitive) and the indica type cv. 9311 (moderately tolerant), was scored using a hydroponics system for their salinity tolerance at the seedling stage. Two of the CSSLs, which share a ∼1.2 Mbp stretch of chromosome 4 derived from cv. Nipponbare, were as sensitive to the stress as cv. Nipponbare itself. Fine mapping based on an F2 population bred from a backcross between one of these CSSLs and cv. 9311 narrowed this region to 95 Kbp, within which only one gene (OsHAK1) exhibited a differential (lower) transcript abundance in cv. Nipponbare and the two CSSLs compared to in cv. 9311. The gene was up-regulated by exposure to salinity stress both in the root and the shoot, while a knockout mutant proved to be more salinity sensitive than its wild type with respect to its growth at both the vegetative and reproductive stages. Seedlings over-expressing OsHAK1 were more tolerant than wild type, displaying a superior photosynthetic rate, a higher leaf chlorophyll content, an enhanced accumulation of proline and a reduced level of lipid peroxidation. At the transcriptome level, the over-expression of OsHAK1 stimulated a number of stress-responsive genes as well as four genes known to be involved in Na+ homeostasis and the salinity response (OsHKT1;5, OsSOS1, OsLti6a and OsLti6b). When the stress was applied at booting through to maturity, the OsHAK1 over-expressors out-yielded wild type by 25%, and no negative pleiotropic effects were expressed in plants gown under non-saline conditions. The level of expression of OsHAK1 was correlated with Na+/K+ homeostasis, which implies that the gene should be explored a target for molecular approaches to the improvement of salinity tolerance in rice.

Characterization of a major QTL for manganese accumulation in rice grain.

Some diets lack sufficient manganese (Mn), an essential mineral. Increasing Mn in grain by biofortification could prevent Mn deficiency, but may increase levels of the toxic element cadmium (Cd). Here, we investigated Mn in rice (Oryza sativa) grains in recombinant inbred lines (RILs) from the cross of 93-11 (low grain Mn) with PA64s (high grain Mn). Quantitative trait locus (QTL) analysis to identify loci controlling grain Mn identified a major QTL, qGMN7.1, on the short arm of chromosome 7; qGMN7.1 explained 15.6% and 22.8% of the phenotypic variation in the RIL populations grown in two distinct environments. We validated the QTL with a chromosome segment substitution line (CSSL), CSSL-qGMN7.1, in the 93-11 background harboring qGMN7.1 from PA64s. Compared to 93-11, CSSL-qGMN7.1 grain had increased Mn and decreased Cd concentrations; CSSL-qGMN7.1 roots also showed enhanced Mn uptake. Fine mapping delimited qGMN7.1 to a 49.3-kb region containing OsNRAMP5, a gene responsible for Mn and Cd uptake. Sequence variations in the OsNRAMP5 promoter caused changes in its transcript level, and in grain Mn levels. Our study thus cloned a major QTL for grain Mn concentration in rice, and identified materials for breeding rice for high Mn and low Cd concentrations in the grain.

miR-451 acts as a suppressor of angiogenesis in hepatocellular carcinoma by targeting the IL-6R-STAT3 pathway.

Hepatocellular carcinoma (HCC) is a highly vascularized tumor and the third ranking contributor of tumor-associated death. Our previous study corroborated the inhibitory roles of miRNA-451 (miR-451) in HCC cell growth and invasion. However, its effect on angiogenesis in HCC remains poorly elucidated. In this study, overexpression of miR-451 clearly attenuated the promoting effects of HCC cells on cell proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs). Importantly, ectopic expression of miR­451 also attenuated tumor growth and angiogenesis in nude mice. In vitro, the expression of IL­6 receptor (IL­6R) was reduced and identified as a direct target of miR­451 by bioinformatics and a dual­firefly luciferase reporter assay. Moreover, upregulation of IL­6R strikingly ameliorated the inhibitory function of conditioned medium from miR­451­transfected HCC cells in HUVEC proliferation, migration and tube formation. Further mechanistic assay substantiated that miR­451 restrained vascular endothelial growth factor (VEGF) production of HCC cells by targeting IL­6R­STAT3 signaling as evidenced that IL­6R upregulation induced the increase in VEGF levels and interrupting signal transducer and activator of transcription 3 (STAT3) signaling with ectopic expression of dominant-negative STAT3 (STAT3D) markedly decreased VEGF expression. Additionally, conditioned medium of miR-451-overexpressed HCC also impaired the VEGF receptor 2 (VEGFR2) signaling in HUVECs. Accordingly, miR-451 may function as a potential suppressor of tumor angiogenesis in HCC by targeting IL-6R-STAT3-VEGF signaling, suggesting a promising therapeutic avenue for managing HCC.