Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C-H Functionalization.

The intermediacy of alkoxy radicals in cerium-catalyzed C-H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)-alkoxide complexes have been synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance and transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified alkoxy radicals as the sole heteroatom-centered radical species generated via ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom transfer (HAT) has been verified via kinetic analysis, density functional theory (DFT) calculations, and reactions under strictly chloride-free conditions. These experimental findings unambiguously establish the critical role of alkoxy radicals in Ce-LMCT catalysis and definitively preclude the involvement of chlorine radical. This study has also reinforced the necessity of a high relative ratio of alcohol vs Ce for the selective alkoxy-radical-mediated HAT, as seemingly trivial changes in the relative ratio of alcohol vs Ce can lead to drastically different mechanistic pathways. Importantly, the previously proposed chlorine radical-alcohol complex, postulated to explain alkoxy-radical-enabled selectivities in this system, has been examined under scrutiny and ruled out by regioselectivity studies, transient absorption experiments, and high-level calculations. Moreover, the peculiar selectivity of alkoxy radical generation in the LMCT homolysis of Ce(IV) heteroleptic complexes has been analyzed and back-electron transfer (BET) may have regulated the efficiency and selectivity for the formation of ligand-centered radicals.

MicroRNA-148a Controls Epidermal and Hair Follicle Stem/Progenitor Cells by Modulating the Activities of ROCK1 and ELF5.

Skin and hair development is regulated by complex programs of gene activation and silencing and microRNA-dependent modulation of gene expression to maintain normal skin and hair follicle development, homeostasis, and cycling. In this study, we show that miR-148a, through its gene targets, plays an important role in regulating skin homeostasis and hair follicle cycling. RNA and protein analysis of miR-148a and its gene targets were analyzed using a combination of in vitro and in vivo experiments. We show that the expression of miR-148a markedly increases during telogen (bulge and hair germ stem cell compartments). Administration of antisense miR-148a inhibitor into mouse skin during the telogen phases of the postnatal hair cycle results in accelerated anagen development and altered stem cell activity in the skin. We also show that miR-148a can regulate colony-forming abilities of hair follicle bulge stem cells as well as control keratinocyte proliferation/differentiation processes. RNA and protein analysis revealed that miR-148a may control these processes by regulating the expression of Rock1 and Elf5 in vitro and in vivo. These data provide an important foundation for further analyses of miR-148a as a crucial regulator of these genes target in the skin and hair follicles and its importance in maintaining stem/progenitor cell functions during normal tissue homeostasis and regeneration.

CsWAKL08, a pathogen-induced wall-associated receptor-like kinase in sweet orange, confers resistance to citrus bacterial canker via ROS control and JA signaling.

Citrus bacterial canker (CBC) is a disease resulting from Xanthomonas citri subsp. citri (Xcc) infection and poses a grave threat to citrus production worldwide. Wall-associated receptor-like kinases (WAKLs) are proteins with a central role in resisting a range of fungal and bacterial diseases. The roles of WAKLs in the context of CBC resistance, however, remain unclear. Here, we explored the role of CsWAKL08, which confers resistance to CBC, and we additionally analyzed the molecular mechanisms of CsWAKL08-mediated CBC resistance. Based on systematic annotation and induced expression analysis of the CsWAKL family in Citrus sinensis, CsWAKL08 was identified as a candidate that can be upregulated by Xcc infection in the CBC-resistant variety. CsWAKL08 can also be induced by the phytohormones salicylic acid (SA) and methyl jasmonic acid (MeJA) and spans the plasma membrane. Overexpression of CsWAKL08 resulted in strong CBC resistance in transgenic sweet oranges, whereas silencing of CsWAKL08 resulted in susceptibility to CBC. The peroxidase (POD) and superoxide dismutase (SOD) activities were significantly enhanced in the CsWAKL08-overexpressing plants compared to the control plants, thereby mediating reactive oxygen species (ROS) homeostasis in the transgenic plants. Moreover, the JA levels and the expression of JA biosynthesis and JA responsive genes were substantially elevated in the CsWAKL08 overexpression plants relative to the controls upon Xcc infection. Based on these findings, we conclude that the wall-associated receptor-like kinase CsWAKL08 positively regulates CBC resistance through a mechanism involving ROS control and JA signaling. These results further highlight the importance of this kinase family in plant pathogen resistance.

CitGVD: a comprehensive database of citrus genomic variations.

Citrus is one of the most important commercial fruit crops worldwide. With the vast genomic data currently available for citrus fruit, genetic relationships, and molecular markers can be assessed for the development of molecular breeding and genomic selection strategies. In this study, to permit the ease of access to these data, a web-based database, the citrus genomic variation database (CitGVD, http://citgvd.cric.cn/home) was developed as the first citrus-specific comprehensive database dedicated to genome-wide variations including single nucleotide polymorphisms (SNPs) and insertions/deletions (INDELs). The current version (V1.0.0) of CitGVD is an open-access resource centered on 1,493,258,964 high-quality genomic variations and 84 phenotypes of 346 organisms curated from in-house projects and public resources. CitGVD integrates closely related information on genomic variation annotations, related gene annotations, and details regarding the organisms, incorporating a variety of built-in tools for data accession and analysis. As an example, CitGWAS can be used for genome-wide association studies (GWASs) with SNPs and phenotypic data, while CitEVOL can be used for genetic structure analysis. These features make CitGVD a comprehensive web portal and bioinformatics platform for citrus-related studies. It also provides a model for analyzing genome-wide variations for a wide range of crop varieties.

Systematic Analysis and Functional Validation of Citrus XTH Genes Reveal the Role of Csxth04 in Citrus Bacterial Canker Resistance and Tolerance.

In this study, we performed a comprehensive survey of xyloglucan endotransglucosylase/hydrolase (XTH) and a functional validation of Citrus sinensis (Cs) XTH genes to provide new insights into the involvement of XTHs in Xanthomonas citri subsp. citri (Xcc) infection. From the genome of sweet orange, 34 CsXTH genes with XTH characteristic domains were identified and clustered into groups I/II, IIIA, and IIIB. Except for chromosome 9, the CsXTH genes were unevenly distributed and duplicated among all chromosomes, identifying a CsXTH duplication hot spot on chromosome 4. With Xcc induction, a group of citrus canker-related CsXTHs were detected. CsXTH04 was identified as a putative candidate gene, which is up-regulated in citrus bacterial canker (CBC)-resistant varieties and induced by exogenous treatment with salicylic acid (SA) and methyl jasmonate (MeJA). CsXTH04 overexpression conferred CBC susceptibility to transgenic citrus, while CsXTH04 silencing conferred CBC resistance. Taken together, the annotation of the CsXTH family provides an initial basis for the functional and evolutionary study of this family as potential CBC-susceptible genes. CsXTH04, validated in this study, can be used in citrus breeding to improve CBC resistance.

Cerium-Catalyzed Formal Cycloaddition of Cycloalkanols with Alkenes through Dual Photoexcitation.

We describe a synergistic utilization of cerium photocatalysis and photoinduced electron transfer catalysis that enables an atom- and step-economical ring expansion of readily available cycloalkanols. This operationally simple protocol provides rapid access to privileged and synthetically challenging bridged lactones. The mild catalytic manifold has been adapted to continuous flow for scale-up applications and employed for the concise synthesis of polycyclic core of nepalactones.

Selective functionalization of methane, ethane, and higher alkanes by cerium photocatalysis.

With the recent soaring production of natural gas, the use of methane and other light hydrocarbon feedstocks as starting materials in synthetic transformations is becoming increasingly economically attractive, although it remains chemically challenging. We report the development of photocatalytic C-H amination, alkylation, and arylation of methane, ethane, and higher alkanes under visible light irradiation at ambient temperature. High catalytic efficiency (turnover numbers up to 2900 for methane and 9700 for ethane) and selectivity were achieved using abundant, inexpensive cerium salts as photocatalysts. Ligand-to-metal charge transfer excitation generated alkoxy radicals from simple alcohols that in turn acted as hydrogen atom transfer catalysts. The mixed-phase gas/liquid reaction was adapted to continuous flow, enabling the efficient use of gaseous feedstocks in scalable photocatalytic transformations.

δ-Selective Functionalization of Alkanols Enabled by Visible-Light-Induced Ligand-to-Metal Charge Transfer.

We demonstrate the application of ligand-to-metal charge transfer (LMCT) excitation to the direct catalytic generation of energetically challenging alkoxy radicals from alcohols through a coordination-LMCT-homolysis process with an abundant and inexpensive cerium salt as the catalyst. This catalytic manifold provides a simple and efficient way to utilize the characteristic reactivity and selectivity of transient alkoxy radicals for δ-selective C-H bond functionalization. Under mild redox-neutral conditions without the need for prefunctionalization, this method provides a versatile platform to access molecular complexity from simple and abundant alcohols.

Photocatalytic C-C Bond Cleavage and Amination of Cycloalkanols by Cerium(III) Chloride Complex.

A general strategy for the cleavage and amination of C-C bonds of cycloalkanols has been achieved through visible-light-induced photoredox catalysis utilizing a cerium(III) chloride complex. This operationally simple methodology has been successfully applied to a wide array of unstrained cyclic alcohols, and represents the first example of catalytic C-C bond cleavage and functionalization of unstrained secondary cycloalkanols.

[Correlation of HLA-DRB1 gene polymorphism and aplastic anemia in Xinjiang Han people].

OBJECTIVE: To investigate the correlation between the human leukocyte antigen (HLA) DRB1 and the aplastic anemia (AA). METHODS: A total of 243 Han ethnic people in Xinjiang were enrolled for this study. Among them, 43 people were diagnosed as AA and the other 200 were healthy controls. All the blood samples of the 243 people were tested by polymerase chain reaction-sequence specific primer (PCR-SSP) DNA typing techniques. Then their allele frequencies were compared by the statistical analysis of x(2); test to study the correlation between the HLA-DRB1 gene polymorphism and the AA in Xinjiang. RESULTS: The HLA-DRB1 allele frequency distributions in AA patients and healthy controls were similar, that was, DRB1*15 allele frequency was highest, while DRB1*4, DRB1*7, DRB1*9, DRB1*12 expressions were higher, and the lowest frequency was DRB1*17. The frequency of HLA-DRB1*8 allele in the AA group (13.73%) was significantly higher than that in healthy controls (6.99%) (OR=2.202, P<0.05). The frequency of HLA-DRB1*12, DRB1*14 alleles were lower in AA group than in healthy control group, but the difference was not statistically significant (P>0.05). However, compared with the healthy control group, the female AA patients had a lower frequency of HLA-DRB1*12 allele (5.41% vs 10.00%, OR=0.2079, P<0.05) and the male AA cases had a lower HLA-DRB1*14 allele (2.11% vs 7.53%, OR=0.1403, P<0.05); The frequency of HLA-DRB1*15 allele in female AA patients was significantly higher than that in healthy control group (27.45% vs 14.56%, OR=2.433, P<0.05). CONCLUSION: The HLA-DRB1*8 could be a susceptibility allele for AA. The HLA-DRB1*12 and the HLA-DRB1*14 could be the antagonistic alleles for female and male AA patients, respectively. The HLA-DRB1*15 could be a susceptibility allele for the female AA patients.

[Pleomorphism of the myelin-like bodies in the hepatocytes of patients with Dubin-Johnson syndrome complicated with chronic hepatitis B].

OBJECTIVE: To explore characteristics of the myelin-like bodies in the hepatocytes of patients with Dubin-Johnson syndrome (DJS) complicated with chronic hepatitis B (CHB). METHODS: 11 cases of DJS complicated with CHB and 5 cases DJS without CHB were studied clinicopathologically. The hepatocyte ultrastructure was observed with transmission electron microscope and taken photos. The data were compared and analyzed using Fisher's Exact Test. RESULTS: Deposition of myelin-like bodies can be observed in the hepatocytes of DJS patients with CHB but can not in DJS patients without CHB. The morphology of pigment varys. The electron density and volume of pigment in DJS patients with CHB can be classified into five types: brights (2/11,18.2%), reticulation (1/11, 9.1%), punctiform (6/11, 54.5%), abnormity (1/11, 9.1%) and primary type (1/11, 9.1%). The myelin-like bodies in the hepatocytes of patients with DJS are high density and round with membrance (we named it as primary type) (5/5, 100%). CONCLUSIONS: The myelin-like bodies in the hepatocytes of DJS patients with CHB possess special pleomorphism and may have important diagnostic value.