四川甘孜曲丝藻科硅藻中国新记录

在四川省甘孜藏族自治州进行硅藻多样性调查时,发现了单壳缝目硅藻中国新记录8种1变种(隶属于4属),分别为:原子曲丝藻Achnanthidium atomus Monnier,Lange-Bertalot&Ector、施特劳宾曲丝藻A.straubianum (Lange-Bertalot) Lange-Bertalot、亚显曲丝藻A. pseudoconspicuum (Foged) Jüttner&Cox、半孔曲丝藻A. semiapertum (Guermeur) Andresen,Stoermer&Kreis、阿雷塔斯真卵形藻Eucocconeis aretassii(Manguin) Lange-Bertalot、披针平面藻微小变种Planothidium lanceolatum var. minor Cleve、厄氏平面藻P.oestrupii (Cleve-Euler) Edlund、球囊沙生藻Psammothidium sacculus (Carter) Bukhtiyarova和双生沙生藻P.didymum (Hustedt) Bukhtiyarova&Round。利用光学显微镜(LM)及扫描电镜(SEM)对8种1变种进行观察,并对其形态特征和生境进行了详细描述。     

Seasonal and interannual variations of ecosystem photosynthetic characteristics in a semi-arid grassland of Northern China

北方半干旱草原生态系统光合参数的季节和年际变异 生态系统表观量子效率(α)、最大光合速率(P_max)和暗呼吸速率(R_d)不仅反映了生态系统水平 光合生理特征,同时也是碳循环模型中光合过程模拟的关键参数。气候和植被因子都会影 响光合参数的季节和年际变异,但二者在光合参数调控过程中的相对贡献和作用途径尚不清晰。本研究基于连续12年(2006–2017)的涡度相关观测数据,分析了内蒙古半干旱典型草原光合参数的季节和年际变化规律;利用回归分析和结构方程模型(SEM)方法明晰了环境和生理调控的作用途径及相对贡献。结果发现,光合参数(α、P_max和R_d)均表现出单峰的季节变化趋势,并呈现明显的年际波动。温度(T_a)和土壤含水量(SWC)的变化共同影响光合参数的季节变化,而SWC主导了其年际变异。α和R_d的变化主要由T_a决定,而Pmax的变化主要受SWC的影响。SEM模型分析表明,除了直接作用外,环境因子主要通过影响冠层水平气孔导度(gc)对光合参数和碳同化生理过程进行调控。此外,叶面积指数对光合参数特别是Pmax的季节和年际变异起主要调控作用。以上结果明确了环境和植被共同决定了生态系统水平光合参数的季节和年际变异,并强调了在水分受限的草原生态系统中,植被生理调控在光合碳同化能力和碳汇功能评估中的重要作用。     

Genomic insights into the adaptation and evolution of the nautilus,an ancient but evolving “living fossil”

The nautilus, commonly known as a “living fossil,” is endangered and may be at risk of extinction. The lack of genomic information hinders a thorough understanding of its biology and evolution, which can shed light on the conservation of this endangered species. Here, we report the first high-quality chromosome-level genome assembly of Nautilus pompilius. The assembled genome size comprised 785.15 Mb. Comparative genomic analyses indicated that transposable elements (TEs) and large-scale genome reorganizations may have driven lineage-specific evolution in the cephalopods. Remarkably, evolving conserved genes and recent TE insertion activities were identified in N. pompilius, and we speculate that these findings reflect the strong adaptability and long-term survival of the nautilus. We also identified gene families that are potentially responsible for specific adaptation and evolution events. Our study provides unprecedented insights into the specialized biology and evolution of N. pompilius, and the results serve as an important resource for future conservation genomics of the nautilus and closely related species.     

Protein thermostabilization requires a fine-tuned placement of surface-charged residues

Using the information from the genome projects, recent comparative studies of thermostable proteins have revealed a certain trend of amino acid composition in which polar residues are scarce and charged residues are rich on the protein surface. To clarify experimentally the effect of the amino acid composition of surface residues on the thermostability of Escherichia coli Ribonuclease HI (RNase HI), we constructed six variants in which five to eleven polar residues were replaced by charged residues (5C, 7Ca, 7Cb, 9Ca, 9Cb and 11C). The thermal denaturation experiments indicated that all of the variant proteins are 3.2-10.1 degrees C in Tm less stable than the wild proteins. The crystal structures of resultant protein variants 7Ca, 7Cb, 9Ca and 11C closely resemble that of E. coli RNase HI in their global fold, and several different hydrogen bonding and ion-pair interactions are formed by the mutations. Comparison of the crystal structures of these variant proteins with that of E. coli RNase HI reveals that thermal destabilization is apparently related to electrostatic repulsion of the charged residues with neighbours. This result suggests that charged residues of natural thermostable proteins are strictly posted on the surface with optimal interactions and without repulsive interactions.     

Plant regeneration via direct somatic embryogenesis in Panax japonicus

Panax japonicus is one of the important medicinal plants. Here, we established the protocol for plant regeneration of P. japonicus via direct somatic embryogenesis. Somatic embryos were directly obtained from the segments of zygotic embryos on MS medium with 4.4 μM 2,4-D. Thereafter, somatic embryos were produced by repetitive secondary somatic embryogenesis. The secondary somatic embryo formation was enhanced by plasmolyzing pretreatment (1.0 M mannitol for 10 h). Frequency of secondary somatic embryo formation from cotyledon segments was lowered by plasmolyzing pretreatment, but the number of somatic embryos per explants was greatly increased. Plasmolyzing pretreatment resulted in retardation of embryo growth and required subculture to fresh medium for further growth of embryos into cotyledonary stage. Without plasmolyzing pretreatment, cotyledonary embryos were obtained after 8 weeks of culture. All the cotyledonary somatic embryos germinated by 5 μM GA₃ treatment, but only 15.3% were germinated on hormone-free medium. After 2 months of culture on 1/2 strength WPM medium, plantlets produced flowers spontaneously. In the anthers of in vitro flowers, microsporogenesis occurred normally with low number of pollen grains.     

Tumor spectrum, tumor latency and tumor incidence of the Pten-deficient mice

Background

Pten functionally acts as a tumor suppressor gene. Lately, tissue-specific ablation of Pten gene in mice has elucidated the role of Pten in different tumor progression models. However, a temporally controlled Pten loss in all adult tissues to examine susceptibility of various tissues to Pten-deficient tumorigenesis has not been addressed yet. Our goal was to explore the genesis of Pten-deficient malignancies in multiple tissue lineages of the adult mouse.

Methods and Findings

We utilized an inducible Cre/loxP system to delete Pten exon 5 in the systemic organs of ROSA26 (R26)-CreER^T;Pten^fx/fx mice. On reaching 45 weeks 4OHT-induced Pten loss, we found that the R26-CreER^T;Pten^fx/fx mice developed a variety of malignancies. Overall tumor mean latency was 17 weeks in the Pten-deficient mice. Interestingly, mutant females developed malignancies more quickly at 10∼11 weeks compared with a tumor latency of 21 weeks for mutant males. Lymphoma incidence (76.9% in females; 40.0% in males) was higher than the other malignancies found in the mutant mice. Mutant males developed prostate (20.0%), intestinal cancer (35.0%) and squamous cell carcinoma (10.0%), whereas the mutant females developed squamous cell carcinoma (15.4%) and endometrial cancer (46.1%) in addition to lymphomas. Furthermore, we tested the pharmacological inhibition of the PTEN downstream effectors using {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 on Pten-deficient prostate hyperplasia. Our data revealed that, indeed, the prostate hyperplasia resulting from the induced Pten loss was significantly suppressed by {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 (p = 0.007).

Conclusions

Through monitoring a variety of Pten-deficient tumor formation, our results revealed that the lymphoid lineages and the epithelium of the prostate, endometrium, intestine and epidermis are highly susceptible to tumorigenesis after the Pten gene is excised. Therefore, this R26-CreER^T; Pten^fx/fx mouse model may provide an entry point for understanding the role of Pten in the tumorigenesis of different organs and extend the search for potential therapeutic approaches to prevent Pten-deficient malignancies.     

伤胁迫对蚕豆叶片中茉莉酸分布的影响

在植物应对伤害等环境刺激的反应中,已知茉莉酸(JA)作为一种重要的信号分子在植物体内长距离运输,但目前对JA的细胞和亚细胞定位知之甚少。本研究用免疫荧光显微镜技术和免疫胶体金电镜技术证明茉莉酸分布在蚕豆叶片叶肉细胞的叶绿体、表皮细胞的细胞壁、保卫细胞的细胞壁、细胞质、叶绿体和细胞核上。其中保卫细胞的叶绿体和细胞核是JA分布的主要场所。叶片的局部灼伤可提高JA在质外体和气孔保卫细胞中的水平。由此推测,伤胁迫下JA分配的改变可能与植物体防御反应密切相关,并参与了对气孔运动的调控。     

Determination of triazines in infant nutrient cereal-based foods by pressurized microwave-assisted extraction coupled with high-performance liquid chromatography-mass spectrometry

A method for determining triazine herbicides in infant nutrient cereal-based foods by pressurized microwave-assisted extraction (PMAE), coupled with high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS), is described. The key parameters of PMAE, including extraction solvent, extraction time and temperature, were optimized. The isolation of the target compounds from the matrix was found to be efficient when 2 g of nutrient cereal samples was extracted with 20 mL of methanol for 10 min at 105 degrees C. Final determination was accomplished by HPLC-ESI/MS. The recoveries from 66.2 to 88.6% were obtained for three compounds at fortification levels (5-500 microg kg(-1)) with relative standard deviations (R.S.D.) 相似文献   

The Effect of Glycerol on Molecular Mobility in Amorphous Sucrose Detected by Phosphorescence of Erythrosin B

Luminescence from the triplet probe erythrosin B provides spectroscopic characteristics such as emission energy and lifetime that are sensitive to molecular mobility of the local solvent environment. This study investigated how variation in glycerol content influences the properties of an amorphous sucrose matrix by monitoring phosphorescence of erythrosin B over the temperature range from 5 to 100°C. Emission energy, lifetime, and red-edge excitation data revealed that glycerol affected the mobility of amorphous sucrose matrix primarily through plasticization when the mole ratio of glycerol/sucrose was above 0.27, resulting in a decrease in emission energy (ν _p), lifetime (τ) and energy difference (Δν _P) with excitation at the absorption peak and red edge and an increase in the nonradiative, collisional quenching rate k _TS0. At mole ratios ≤0.27 and at temperatures below the matrix T _g, glycerol exhibited an “antiplasticization” effect, as indicated by higher values of emission energy, lifetime, and energy difference and lower values of the matrix collisional quenching rate. Changes in the distribution of emission energy (emission bandwidth) and lifetime, and variation in the emission lifetime vs wavelength showed that glycerol reduced the spectral heterogeneity. These data illustrate the complex effect of a hydrogen bonding solute on the mobility of an amorphous, hydrogen bonded sugar matrix.