Enantioselective Synthesis of δ-Carbolinones via N-Heterocyclic Carbene Catalysis.

An enantioselective synthesis of δ-carbolinones was accomplished through N-heterocyclic carbene-catalyzed formal [3+3] annulation of 3-aminoindoles with 2-bromoenals. This protocol offers a rapid and efficient synthetic approach for accessing a wide range of enantioenriched structurally interesting δ-carbolinones under mild reaction conditions.

Loci and natural alleles for cadmium-mediated growth responses revealed by a genome wide association study and transcriptome analysis in rice.

BACKGROUND: Cadmium (Cd) is a toxic heavy metal that is harmful to the environment and human health. Cd pollution threatens the cultivation of rice (Oryza sativa L.) in many countries. Improving rice performance under Cd stress could potentially improve rice productivity. RESULTS: In this study, 9 growth traits of 188 different cultivated rice accessions under normal and Cd stress conditions were found to be highly variable during the seedling stage. Based on ~3.3 million single nucleotide polymorphisms (SNPs), 119 Cd-mediated growth response (CGR) quantitative trait loci (QTL) were identified by a genome-wide association study (GWAS), 55 of which have been validated by previously reported QTL and 64 were new CGR loci. Combined with the data from the GWAS, transcriptome analysis, gene annotations from the gene ontology (GO) Slim database, and annotations and functions of homologous genes, 148 CGR candidate genes were obtained. Additionally, several reported genes have been found to play certain roles in CGRs. Seven Cd-related cloned genes were found among the CGR genes. Natural elite haplotypes/alleles in these genes that increased Cd tolerance were identified by a haplotype analysis of a diverse mini core collection. More importantly, this study was the first to uncover the natural variations of 5 GST genes that play important roles in CGRs. CONCLUSION: The exploration of Cd-resistant rice germplasm resources and the identification of elite natural variations related to Cd-resistance will help improve the tolerance of current major rice varieties to Cd, as well as provide raw materials and new genes for breeding Cd-resistant varieties.

Effect of multimodal preemptive analgesia on postoperative gastrointestinal function and clinical outcome in patients undergoing laparoscopic colorectal surgery.

OBJECTIVE: This study aimed to investigate the effects of multimodal preemptive analgesia on postoperative gastrointestinal function and clinical outcomes in patients undergoing laparoscopic colorectal surgery. METHODS: This prospective study included a total of 108 patients undergoing elective laparoscopic colorectal surgery from June 2019 to June 2020. The patients were divided into the control group and the study group according to the random number table method. Patients in the study group were given flurbiprofen axetil and oxycodone before skin incision combined with bilateral transverse abdominis plane block (TAPB) before anaesthesia induction. In the control group, patients were given sufentanil and flurbiprofen axetil combined with bilateral TAPB in postanaesthesia care unit (PACU). The incidence of postoperative gastrointestinal dysfunction (POGD), I-FEED score, inflammatory factor levels, rehabilitation indicators, postoperative pain assessment and other organ complications were observed and compared between the two groups. RESULTS: The incidence of POGD in the study group was lower compared to the control group, and the difference was statistically significant (P < .05). The study group had lower total and mean scores of I-FEED at 24, 48, 72 and 96 hours after surgery; however, the differences were not statistically significant (P > .05). On the first and third day after operation, Lipopolysaccharide (LPS), C-reactive protein (CRP), Tumour necrosis factor (TNF-α) and Interleukins6 (IL-6) levels of the study group decreased significantly (P < .05). The reduction in inflammation factor levels from 1d to 3d was significantly greater than that of the control group (P < .05). CONCLUSION: The strategy of multimodal preemptive analgesia can effectively prevent the onset of POGD and may accelerate rehabilitation. In short, multimodal preemptive analgesia provides a novel prevention strategy for patients undergoing laparoscopic colorectal surgery.

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.

Natural variation in the promoter of OsHMA3 contributes to differential grain cadmium accumulation between Indica and Japonica rice.

Rice is a major source of cadmium (Cd) intake for Asian people. Indica rice usually accumulates more Cd in shoots and grains than Japonica rice. However, underlying genetic bases for differential Cd accumulation between Indica and Japonica rice are still unknown. In this study, we cloned a quantitative trait locus (QTL) grain Cd concentration on chromosome 7 (GCC7) responsible for differential grain Cd accumulation between two rice varieties by performing QTL analysis and map-based cloning. We found that the two GCC7 alleles, GCC7PA64s and GCC793-11 , had different promoter activity of OsHMA3, leading to different OsHMA3 expression and different shoot and grain Cd concentrations. By analyzing the distribution of different haplotypes of GCC7 among diverse rice accessions, we discovered that the high and low Cd accumulation alleles, namely GCC793-11 and GCC7PA64s , were preferentially distributed in Indica and Japonica rice, respectively. We further showed that the GCC7PA64s allele can be used to replace the GCC793-11 allele in the super cultivar 93-11 to reduce grain Cd concentration without adverse effect on agronomic traits. Our results thus reveal that the QTL GCC7 with sequence variation in the OsHMA3 promoter is an important determinant controlling differential grain Cd accumulation between Indica and Japonica rice.

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.

Fine mapping and candidate gene analysis of a major QTL for panicle structure in rice.

KEY MESSAGE: A gene not only control tiller and plant height, but also regulate panicle structure by QTL dissection in rice. An ideal panicle structure is important for improvement of plant architecture and rice yield. In this study, using recombinant inbred lines (RILs) of PA64s and 93-11, we identified a quantitative trait locus (QTL), designated qPPB3 for primary panicle branch number. With a BC3F2 population derived from a backcross between a resequenced RIL carrying PA64s allele and 93-11, qPPB3 was fine mapped to a 34.6-kb genomic region. Gene prediction analysis identified four putative genes, among which Os03g0203200, a previously reported gene for plant height and tiller number, Dwarf 88 (D88)/Dwarf 14 (D14), had three nucleotide substitutions in 93-11 compared with PA64s. The T to G substitution resulted in one amino acid change from valine in 93-11 to glycine in PA64s. Real-time PCR analysis showed expression level of D88 was higher in 93-11 than PA64s. The expression of APO1 and IPA1 increased, while GN1a and DST decreased in 93-11 compared with PA64s. Therefore, D88/D14 is not only a key regulator for branching, but also affects panicle structure.

Low-dose intramuscular dexmedetomidine as premedication: a randomized controlled trial.

BACKGROUND: Dexmedetomidine-induced bradycardia or hypotension has recently attracted considerable attention because of potentially grave consequences, including sinus arrest and refractory cardiogenic shock. A route other than intravenous injection or a low dose may help minimize cardiovascular risks associated with dexmedetomidine. However, few studies have addressed the clinical effects of low-dose intramuscular dexmedetomidine as premedication. MATERIAL AND METHODS: Forty American Society of Anesthesiologists physical status I adult patients undergoing suspension laryngoscopic surgery were randomized to receive intramuscular dexmedetomidine (1 µg·kg-1) or midazolam (0.02 mg·kg-1) 30 minutes prior to anaesthesia induction. The sedative, hemodynamic, and adjuvant anaesthetic effects of both premedications were assessed. RESULTS: The levels of sedation (Observer's Assessment of Alertness/Sedation scales) and anxiety (visual analog score) at pre-induction, and the times to eye-opening and extubation, were not different between the groups. The heart rate response following tracheal intubation and extubation, and mean arterial pressure responses after extubation, were attenuated in the dexmedetomidine group compared to the midazolam group. No bradycardia or hypotension was noted in any patients. Propofol target concentrations at intubation and at start and completion of surgery were decreased in the dexmedetomidine group, whereas no difference in respective remifentanil levels was detected. CONCLUSIONS: This study provides further evidence that dexmedetomidine premedication in low dose (1 µg·kg-1) by intramuscular route can induce preoperative sedation and adjuvant anaesthetic effects without clinically significant bradycardia or hypotension.

Synthetic apomixis: the beginning of a new era.

Apomixis is a process of asexual reproduction that enables plants to bypass meiosis and fertilization to generate clonal seeds that are identical to the maternal genotype. Apomixis has tremendous potential for breeding plants with desired characteristics, given its ability to fix any elite genotype. However, little is known about the origin and dynamics of natural apomictic plant systems. The introgression of apomixis-related genes from natural apomicts has achieved limited success. Therefore, synthetic apomixis, engineered to include apomeiosis, autonomous embryo formation, and autonomous endosperm development, has been proposed as a promising platform to effectuate apomixis in any crop. In this study, we have summarized recent advances in the understanding of synthetic apomixis and discussed the limitations of current synthetic apomixis systems and ways to overcome them.

NHC-Catalyzed Synthesis of α-Sulfonyl Ketones via Radical-Mediated Sulfonyl Methylation of Aldehydes.

An N-heterocyclic carbene (NHC)-catalyzed facile assembly of α-sulfonyl ketones has been successfully developed through a radical-mediated sulfonyl methylation of readily available aldehydes. This protocol involves the effective single-electron transfer reduction of α-iodosulfones by NHC-bound Breslow intermediates, thus allowing a subsequent radical-radical coupling to afford the target compounds. Moreover, the catalytic system was found to be equally effective for difunctionalization of styrenes and 1,3-enynes via a three-component radical relay process.

NHC-catalyzed radical acylation of cycloalkyl silyl peroxides to access 1,6-,1,7-, and 1,8-diketones.

An unprecedented N-heterocyclic carbene (NHC)-catalyzed radical acylation of cycloalkyl silyl peroxides was developed using readily available aldehydes as the acylating agents. This protocol provides an exceptionally useful method for the efficient and rapid synthesis of long-chain 1,6-/1,7-/1,8-diketones, especially unsymmetrical ones. This strategy also has the advantages of mild conditions, good functional group compatibility, and potential applications in the late-stage functionalization of aldehydes with bioactive fragments and in the construction of long-chain complex bioactive molecules.

Mitigating cadmium accumulation in rice without compromising growth via modifying the regulatory region of OsNRAMP5.

Cadmium (Cd) intake poses a significant health risk to humans, and the contamination of rice grains with Cd is a major concern in regions where rice is a staple food. Although the knockout of OsNRAMP5, which encodes a key transporter responsible for Cd and manganese (Mn) uptake, can significantly reduce Cd accumulation in rice grains, recent studies have revealed that this knockout adversely affects plant growth, grain yield, and increases vulnerability to abiotic and biotic stresses due to reduced Mn accumulation. In this study, we employed CRISPR/Cas9 technology to modify the regulatory region of OsNRAMP5 with the aim of reducing Cd accumulation in rice grains. Our findings demonstrate that mutations in the regulatory region of OsNRAMP5 do not impact its expression pattern but result in a reduction in translation. The decreased translation of OsNRAMP5 effectively decreases grain Cd accumulation while leaving Mn accumulation and important agronomic traits, including yield, unaffected. Thus, our study presents a practical and viable strategy for reducing Cd accumulation in rice grains without compromising Mn accumulation or overall rice production.

Synthetic apomixis enables stable transgenerational transmission of heterotic phenotypes in hybrid rice.

In hybrid plants, heterosis often produces large, vigorous plants with high yields; however, hybrid seeds are generated by costly and laborious crosses of inbred parents. Apomixis, in which a plant produces a clone of itself via asexual reproduction through seeds, may produce another revolution in plant biology. Recently, synthetic apomixis enabled clonal reproduction of F1 hybrids through seeds in rice (Oryza sativa), but the inheritance of the synthetic apomixis trait and superior heterotic phenotypes across generations remained unclear. Here, we propagated clonal plants to the T4 generation and investigated their genetic and molecular stability at each generation. By analyzing agronomic traits, as well as the genome, methylome, transcriptome, and allele-specific transcriptome, we showed that the descendant clonal plants remained stable. Unexpectedly, in addition to normal clonal seeds, the plants also produced a few aneuploids that had eliminated large genomic segments in each generation. Despite the identification of rare aneuploids, the observation that the synthetic apomixis trait is stably transmitted through multiple generations helps confirm the feasibility of using apomixis in the future.

Comparative Metabolomics Combined with Physiological Analysis Revealed Cadmium Tolerance Mechanism in Indica Rice (Oryza sativa L.).

Cadmium (Cd) pollution reduces rice production and quality, putting food security and human health at risk. We conducted comparative physiology and metabolomic analyses in two indica rice ('NH199' and 'NH224') to elucidate the Cd-tolerance mechanism. Cd hampered rice growth, induced oxidative stress, and changed the metabolomics profiling of the root. The biochemical and physiological analysis demonstrated that NH224 exhibited a more potent Cd-tolerance ability than NH199. Cd was primarily distributed in root, and NH224 had a lower Cd translocation factor than NH199 by about 24%. The metabolomic analysis revealed 180 and 177 differentially accumulated metabolites between Cd-stressed seedlings and the controls in NH224 and NH199, respectively. In NH224, amino acids biosynthesis, hormone metabolism, lipids-related metabolism, phenylalanine metabolism, and phenylpropanoid biosynthesis pathways were more active and highly associated with antioxidant defense system, biosynthesis of the cell wall and phytochelatins, and maintenance of plasma membrane stability. These findings provide insights into the metabolic profiles of rice following Cd stress and the screening and breeding of Cd-tolerant rice varieties.

Concurrent Disruption of Genetic Interference and Increase of Genetic Recombination Frequency in Hybrid Rice Using CRISPR/Cas9.

Manipulation of the distribution and frequency of meiotic recombination events to increase genetic diversity and disrupting genetic interference are long-standing goals in crop breeding. However, attenuation of genetic interference is usually accompanied by a reduction in recombination frequency and subsequent loss of plant fertility. In the present study, we generated null mutants of the ZEP1 gene, which encodes the central component of the meiotic synaptonemal complex (SC), in a hybrid rice using CRISPR/Cas9. The null mutants exhibited absolute male sterility but maintained nearly unaffected female fertility. By pollinating the zep1 null mutants with pollen from indica rice variety 93-11, we successfully conducted genetic analysis and found that genetic recombination frequency was greatly increased and genetic interference was completely eliminated in the absence of ZEP1. The findings provided direct evidence to support the controversial hypothesis that SC is involved in mediating interference. Additionally, the remained female fertility of the null mutants makes it possible to break linkage drag. Our study provides a potential approach to increase genetic diversity and fully eliminate genetic interference in rice breeding.

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.