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海底缺氧带甲烷氧化作用是一个重要的甲烷生物地球化学过程,已被许多地球化学现象所证实。甲烷缺氧氧化有效地减少了渗漏到海水和大气中的甲烷通量,但目前仅有的数据还不能很好地限定甲烷缺氧氧化在全球甲烷循环和全球碳循环中的作用。甲烷缺氧氧化的机理还存在争议,很可能是一个\"反甲烷生成\"过程。在许多天然气渗漏发育区域,由于甲烷缺氧氧化作用引起环境碱度的增加而沉淀冷泉碳酸盐岩,在海底表层沉积物中形成块状碳酸盐岩结壳。但冷泉碳酸盐岩生成所需的物理化学和生物地球化学条件在很大程度上还不清楚。数值计算表明,孔隙水中溶解足够量的甲烷、冷泉渗漏强度适中、较小的生物扰动作用有利于冷泉碳酸盐岩的生成,而过高的沉积速率则抑制冷泉碳酸盐岩结壳的生成。因此,海底发育冷泉碳酸盐岩可以指示天然气渗漏系统的演化特征。

Chromatin is not an inert structure, but rather an instructive DNA scaffold that can respond to external cues to regulate the many uses of DNA. A principle component of chromatin that plays a key role in this regulation is the modification of histones. There is an ever-growing list of these modifications and the complexity of their action is only just beginning to be understood. However, it is clear that histone modifications play fundamental roles in most biological processes that are involved in the manipulation and expression of DNA. Here, we describe the known histone modifications, define where they are found genomically and discuss some of their functional consequences, concentrating mostly on transcription where the majority of characterisation has taken place.

Dear Editor, Technologies to achieve specific and precise genome editing, such as knock-in and knock-out, are critical for deciphering the functions of a gene and for under- standing fundamental biological processes. Compared with the zinc finger nucleases （ZFN） and transcription activator-like effector nucleases （TALEN）, which have been used for genome editing [1], the Clustered Regu- larly Interspaced Short Palindromic Repeats （CRISPR）/ CRISPR-associated （Cas） system has emerged as a new powerful tool for genome modifications. It has recently been adopted for genome editing in human cell lines [2- 4], mouse [5], zebrafisb [6], C. elegans [7-12], and plants [13].

MicroRNAs（miRNAs） are small non-coding RNAs that regulate a variety of biological processes. miRNA expression often exhibits spatial and temporal specificity. However, genome-wide miRNA expression patterns in different organs during development of Arabidopsis thaliana have not yet been systemically investigated. In this study, we sequenced small RNA libraries generated from 27 different organ/tissue types, which cover the entire life cycle of Arabidopsis. Analysis of the sequencing data revealed that most miRNAs are ubiquitously expressed, whereas a small set of miRNAs display highly specific expression patterns. In addition, different miRNA members within the same family have distinct spatial and temporal expression patterns. Moreover, we found that some miRNAs are produced from different arms of their hairpin precursors at different developmental stages. This work provides new insights into the regulation of miRNA biogenesis and a rich resource for future investigation of miRNA functions in Arabidopsis.

Eukaryotic membrane proteins, many of which are key players in various biological processes, constitute more than half of the drug targets and represent important candidates for structural studies. In contrast to their physiological significance, only very limited number of eukaryotic membrane protein structures have been obtained due to the technical challenges in the generation of recombinant proteins. In this review, we examine the major recombinant expression systems for eukaryotic membrane proteins and compare their relative advantages and disadvantages. We also attempted to summarize the recent technical strategies in the advancement of eukaryotic membrane protein purification and crystallization.

Rather than random degradation products, the 18 to 40 nucleotides（nt） transfer RNA-derived small RNAs（tsRNAs） are RNA species generated specifically from pre-RNAs or mature tRNAs in archaea, bacteria and eukaryotes. Recent studies from animal systems have shown that tsRNAs are important non-coding RNAs that regulate gene expression at the transcriptional and/or post-transcriptional levels. They are involved in various biological processes, such as cell proliferation, tumor genesis, stress response and intergenerational epigenetic inheritance. In this review, we will summarize the discovery, biogenesis, and function of tsRNAs in higher plants. In addition, analysis on tsRNAs from lower plants is shown.

Objective： To provide a comprehensive literature review on roles of coagulation factor XIII （FXIII） in coagulation, wound healing, neoplasm, bone metabolism, and pregnancy. Data Sources： All articles in PubMed with key words ＂Coagulation factor XIII＂, ＂wound＂, ＂＇leukeraia＂, ＂tumor＂, ＂bone,＂ and ＂pregnancy＇＂ with published date from 2001 to 2016 were included in the study. Frequently cited publications before 2000 were also included. Study Selection： We reviewed the role of FXIll in biologic processes as documented in clinical, animal, and in vitro studies. Results： FXIII, a nlember of the transglutaminase （TG） family, plays key roles in various biological processes. Besides its well-known function in coagulation, the cross-linking of small molecules catalyzed by FXIII has been found in studies to help promote wound healing, improve bone metabolism, and prevent miscarriages. The study has also shown that FXIII concentration level differs in the blood of patients with leukemia and solid tumors and offers promises as a diagnostic indicator Conclusions： FXIII has many more biologic functions besides being known as coagulation factor. The TG activity of FXIII contributes to several processes, including wound healing, bone extracellular matrix stabilization, and the interaction between embryo and decidua of uterus. Further research is needed to elucidate the link between FXIII and leukemia and solid tumors.

In eukaryotes, epigenetic-based mechanisms are involved in almost all the important biological processes. Amongst different epigenetic regulation pathways, the dynamic covalent modifications on histones are the most extensively investigated and characterized types. The covalent modifications on histone can be ＂read＂ by specific protein domains and then subsequently trigger downstream signaling events. Plants generally possess epigenetic regulation systems similar to animals and fungi, but also exhibit some plant-specific features. Similar to animals and fungi, plants require distinct protein domains to specifically＂read＂ modified histones in both modification-specific and sequence-specific manners. In this review, we will focus on recent progress of the structural studies on the recognition of the epigenetic marks on histones by plant reader proteins, and further summarize the general and exceptional features of plant histone mark readers.

N^6-methyladenosine （m^6A） is the most common internal modification in eukaryotic mRNA. It is dynamically in- stalled and removed, and acts as a new layer of mRNA metabolism, regulating biological processes including stem cell pluripotency, cell differentiation, and energy homeostasis, m^6A is recognized by selective binding proteins; YTHDF1 and YTHDF3 work in concert to affect the translation of m^6A-containing mRNAs, YTHDF2 expedites mRNA decay, and YTHDC1 affects the nuclear processing of its targets. The biological function of YTHDC2, the final member of the YTH protein family, remains unknown. We report that YTHDC2 selectively binds m6A at its consensus motif. YTHDC2 enhances the translation efficiency of its targets and also decreases their mRNA abundance. Ythdc2 knock- out mice are infertile; males have significantly smaller testes and females have significantly smaller ovaries compared to those oflittermates. The germ cells of Ythdc2 knockout mice do not develop past the zygotene stage and according- ly, Ythdc2 is upregulated in the testes as meiosis begins. Thus, YTHDC2 is an m6A-binding protein that plays critical roles during svermatogenesis.