源自大黄鱼肠道柠檬酸杆菌的外切几丁质酶的特性分析（英文）北大核心CSCD

【目的】从饲喂富含几丁质饲料的大黄鱼肠道分离具有几丁质分解功能的菌株并分离鉴定新的几丁质酶。【方法】利用胶体几丁质平板分离饲喂杂鱼的大黄鱼肠道中的几丁质分解菌。对几丁质酶基因chi-X进行了克隆并在大肠杆菌中表达。对CHI-X的酶学性质进行了分析。【结果】从饲喂杂鱼的大黄鱼肠道内容物中分离出1株具有几丁质分解功能的费氏柠檬酸杆菌,其中的几丁质酶基因编码1个含493个氨基酸残基的蛋白,其中包含一个糖苷水解酶18家族催化域。CHI-X对胶体几丁质具有分解功能。最适p H和温度分别是4.0和60°C。CHI-X具有很强的pH稳定性,在pH 3.0–11.0的范围培育1 h仍保留90%左右的活性。Mn^(2+),Li^+和K^+可促进CHI-X酶活,Ag^+对CHI-X有抑制作用。CHI-X对蛋白酶和石斑鱼肠道内容物有较强的抗逆性。CHI-X可分解胶体几丁质为N-乙酰葡萄糖胺和N-乙酰葡萄糖胺二聚体,表明它是一个几丁质外切酶。最后,CHI-X和另一个几丁质酶Chi565表现出酶活性的加和效应。【结论】分离自肠道菌的CHI-X能很好适应海水鱼类的肠道环境,可以作为温水海水养殖鱼类的饲料添加剂使用。     

Birth weight and birth rate of heavy calves conceived by transfer of in vitro or in vivo produced bovine embryos

The aim of this study was to evaluate the difference in birth weight and gestation length between Japanese Black calves obtained from transfer of bovine embryos produced in vitro (IVP) and those developed in vivo (IVD). An additional objective was to clarify the sire effect on birth weight and gestation length and to examine the birth rate of heavier calves. Two Japanese Black bulls breed at our experimental station were used as a semen source for production of IVP and IVD embryos. Thirty-eight Japanese Black heifers and cows of various genetic backgrounds were used as embryo donors for IVD embryos. Ovaries for IVP embryos were collected at random at a local slaughterhouse from Japanese Black cattle of various genetic backgrounds. IVP embryos were produced using co-culturing with cumulus cells in 5% CS+TCM 199. Both the IVD and IVP embryos were transferred non-surgically to Holstein recipients on day 7+/-1 of estrous cycle. In this study, the birth weights and gestation lengths of half-sib single calves for bull A and B were analyzed.The numbers of single calves born by transfer of IVP and IVD embryos for bull A and B were 133 and 121, 243 and 465, respectively. The birth weight of the IVP calves was significantly higher (P<0.01) than that of the IVD (bull A: 31.0+/-0.4 kg versus 27.2+/-0.4 kg and bull B: 29.9+/-0.6 kg versus 26.6+/-0.2 kg). Gestation length of the IVP calves for bull A was significantly longer (P<0.01) than that of the IVD (291.9+/-0.9 days versus 283.6+/-0.5 days). However, for bull B, there were no differences in gestation length between the IVP and IVD calves (285.9+/-0.7 days versus 286.2+/-0.3 days). These results clearly indicated that IVP calves had heavier birth weights than IVD calves but that the average gestation length of IVP calves was not always longer than that of IVD calves. Furthermore, the birth rate of heavier calves and the incidence of stillbirth and perinatal mortality up to 48 h post partum in IVP calves (bull A: 11.3%, bull B: 7.8%) were greater (P<0.05) than those in IVD calves from both bulls (bull A: 4.1%, bull B: 3.7%).     

The plant glycosyltransferase clone collection for functional genomics

The glycosyltransferases (GTs) are an important and functionally diverse family of enzymes involved in glycan and glycoside biosynthesis. Plants have evolved large families of GTs which undertake the array of glycosylation reactions that occur during plant development and growth. Based on the Carbohydrate‐Active enZymes (CAZy) database, the genome of the reference plant Arabidopsis thaliana codes for over 450 GTs, while the rice genome (Oryza sativa) contains over 600 members. Collectively, GTs from these reference plants can be classified into over 40 distinct GT families. Although these enzymes are involved in many important plant specific processes such as cell‐wall and secondary metabolite biosynthesis, few have been functionally characterized. We have sought to develop a plant GTs clone resource that will enable functional genomic approaches to be undertaken by the plant research community. In total, 403 (88%) of CAZy defined Arabidopsis GTs have been cloned, while 96 (15%) of the GTs coded by rice have been cloned. The collection resulted in the update of a number of Arabidopsis GT gene models. The clones represent full‐length coding sequences without termination codons and are Gateway^® compatible. To demonstrate the utility of this JBEI GT Collection, a set of efficient particle bombardment plasmids (pBullet) was also constructed with markers for the endomembrane. The utility of the pBullet collection was demonstrated by localizing all members of the Arabidopsis GT14 family to the Golgi apparatus or the endoplasmic reticulum (ER). Updates to these resources are available at the JBEI GT Collection website http://www.addgene.org/ .     

circ_SEPT9, a newly identified circular RNA,promotes oral squamous cell carcinoma progression through miR‐1225/PKN2 axis

Circular RNAs (circRNAs) represent a newly discovered class of endogenous non‐coding RNAs which are widely expressed and play important roles in disease progression. However, the function of circRNAs in oral squamous cell carcinoma (OSCC) still remains largely unknown. In this research, we found that circ_SEPT9 was highly expressed in OSCC cell lines and tumour tissues. Results showed that circ_SEPT9 promoted OSCC proliferation and tumour growth. And, circ_SEPT9 also enhanced the migration and invasion of OSCC cells. Mechanically, we found that circ_SEPT9 acted as a sponge for miR‐1225 to rescue PKN2 expression in OSCC cells. Inhibition of circ_SEPT9/miR‐1225/PKN2 pathway could effectively block the proliferation and metastasis of OSCC cells. Our study provides strong evidence that circ_SEPT9/miR‐1225/PKN2 axis is a promising target for OSCC treatment.     

Suppressing Voltage Fading of Li‐Rich Oxide Cathode via Building a Well‐Protected and Partially‐Protonated Surface by Polyacrylic Acid Binder for Cycle‐Stable Li‐Ion Batteries

Li‐rich manganese based oxides (LRMOs) are considered an attractive high‐capacity cathode for advanced Li‐ion batteries; however, their poor cyclability and gradual voltage fading have hindered their practical applications. Herein, an efficient and facile strategy is proposed to stabilize the lattice structure of LRMOs by surface modification of polyacrylic acid (PAA). The PAA‐coated LRMO electrode exhibits only 104 mV of the voltage fading after 100 cycles and 88% capacity retention over 500 cycles. The structural stability is attributed to the carboxyl groups in PAA chains reacting with oxygen species on the surface of LRMO to form a uniform and tightly coated film, which significantly suppresses the dissolution of transition metal elements from the cathode materials into the electrolyte. Importantly, a H⁺/Li⁺ exchange reaction takes place between the LRMO and PAA, generating a proton‐doped surface layer. Density functional theory calculations and experimental evidence demonstrates that the H⁺ ions in the surface lattice efficiently inhibit the migration of transition metal ions, leading to a stabilized lattice structure. This surface modification approach may provide a new route to building a stable Li‐rich oxide cathode with high capacity retention and low voltage fading for practical Li‐ion battery applications.     

Dietary GABA induces endogenous synthesis of a novel imidazole peptide homocarnosine in mouse skeletal muscles

Amino Acids - Carnosine (β-alanyl-l-histidine) is an imidazole dipeptide present at high concentrations in skeletal muscles, where it plays a beneficial role. However, oral intake of carnosine...     

Mutation of the chloroplast‐localized phosphate transporter OsPHT2;1 reduces flavonoid accumulation and UV tolerance in rice

Phosphorus (P) is an essential macronutrient required for plant development and production. The mechanisms regulating phosphate (Pi) uptake are well established, but the function of chloroplast Pi homeostasis is poorly understood in Oryza sativa (rice). PHT2;1 is one of the transporters/translocators mediating Pi import into chloroplasts. In this study, to gain insight into the role of OsPHT2;1‐mediated stroma Pi, we analyzed OsPHT2;1 function in Pi utilization and photoprotection. Our results showed that OsPHT2;1 was induced by Pi starvation and light exposure. Cell‐based assays showed that OsPHT2;1 localized to the chloroplast envelope and functioned as a low‐affinity Pi transporter. The ospht2;1 had reduced Pi accumulation, plant growth and photosynthetic rates. Metabolite profiling revealed that 52.6% of the decreased metabolites in ospht2;1 plants were flavonoids, which was further confirmed by 40% lower content of total flavonoids compared with the wild type. As a consequence, ospht2;1 plants were more sensitive to UV‐B irradiation. Moreover, the content of phenylalanine, the precursor of flavonoids, was also reduced, and was largely associated with the repressed expression of ADT1/MTR1. Furthermore, the ospht2;1 plants showed decreased grain yields at relatively high levels of UV‐B irradiance. In summary, OsPHT2;1 functions as a chloroplast‐localized low‐affinity Pi transporter that mediates UV tolerance and rice yields at different latitudes.