Applications and roles of the CRISPR system in genome editing of plants

Genome editing is a valuable tool to target specific DNA sequences for mutagenesis in the genomes of microbes, plants, and animals. Although different genome editing technologies are available, the clustered regularly interspaced short palindromic repeats/Cas9 （CRISPR/ Cas9） system, which utilizes engineered endonucleases to generate a double-stranded DNA break （DSB） in the target DNA region and subsequently stimulates site-specific mutagenesis through DNA repair machineries, is emerging as a powerful genome editing tool for elucidating mecha- nisms of protection from plant viruses, plant disease resistance, and gene functions in basic and applied research. In this review, we provide an overview of recent advances in the CRISPR system associated genome editing in plants by focusing on application of this technology in model plants, crop plants, fruit plants, woody plants and grasses and discuss how genome editing associated with the CRISPR system can provide insights into genome modifications and functional genomics in plants.

Transcription's bubble under the influence of long-range interactions and helicoidal coupling

The influence of power-low long-range interactions （LRI） and helicoidal coupling （HC） on the properties of localized solitons in a DNA molecule when a ribonucleic acid polymerase （RNAP） binds to it at the physiological temperature is analytically and numerically investigated in this paper. We have made an analogy with the Heisenberg model Hamiltonian of an anisotropic spin ladder with ferromagnetic legs and anti-ferromagnetic rung coupling. When we limit ourselves to the second-order terms in the Taylor expansion, the DNA dynamics is found to be governed by a completely integrable nonlinear Schr？dinger （NLS） equation. In this case, results show that increasing the value of HC force or LRI parameter enhances the bubble height and reduces the number of base pairs which form the bubble. For the fourth-order terms in a Taylor expansion, results are closely resembling those of second-order terms, and are confirmed by numerical investigation. These results match with some experimental data and thus provide a better representation of the base pairs opening in DNA which is essential for the transcription process.

DNA-associated click chemistry

This review highlights the most recent advances in click chemistry associated with DNA.Cu[I]-catalyzed azides-alkynes Huisgen cycloadditions(CuAAC)and a strain-promoted alkyne-azide cycloaddition(SPAAC)are two popular click reactions that have great impact in DNA science.The simplicity,versatility,orthogonality,and high efficiency of click reaction along with a stable triazole product have been instrumental for the successful application of this reaction in the field of nucleic acid chemistry.CuAAC and SPAAC reactions have been widely used for DNA modification,including DNA labeling,metallization,conjugation,cross-linking,and ligation.Modified oligodeoxynucleotides obtained from click reaction have been extensively applied in the fields of drug discovery,nanotechnology,bio-conjugation,and material sciences,among others.The most recent advances in the synthesis and applications of clickable DNAs are discussed in detail in this article.

Characterization of the genes involved in nitrogen cycling in wastewater treatment plants using DNA microarray and most probable number-PCR

To improve nitrogen removal performance of wastewater treatment plants （WWTPs）, it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods：most probable number-polymerase chain reaction （MPN-PCR） and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional actwated sludge processes （CAS） are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern：the nitS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectivelv. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes （AO）, whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.

RPA functions as a platform for coupling of nucleosome assembly to DNA replication

Subject Code:C05 With the support by the National Natural Science Foundation of China,the research team led by Dr.Li Qing(李晴)at the State Key Laboratory of Protein and Plant Gene Research,School of Life Sciences and Peking-Tsinghua Center for Life Sciences,Peking University,Beijing,recently reported that