Escherichia coli RecQ is a rapid, efficient, and monomeric helicase

RecQ family helicases play a key role in chromosome maintenance. Despite extensive biochemical, biophysical, and structural studies, the mechanism by which helicase unwinds double-stranded DNA remains to be elucidated. Using a wide array of biochemical and biophysical approaches, we have previously shown that the Escherichia coli RecQ helicase functions as a monomer. In this study, we have further characterized the kinetic mechanism of the RecQ-catalyzed unwinding of duplex DNA using the fluorometric stopped-flow method based on fluorescence resonance energy transfer. Our results show that RecQ helicase binds preferentially to 3'-flanking duplex DNA. Under the pre-steady-state conditions, the burst amplitude reveals a 1:1 ratio between RecQ and DNA substrate, suggesting that an active monomeric form of RecQ helicase is involved in the catalysis. Under the single-turnover conditions, the RecQ-catalyzed unwinding is independent of the 3'-tail length, indicating that functional interactions between RecQ molecules are not implicated in the DNA unwinding. It was further determined that RecQ unwinds DNA rapidly with a step size of 4 bp and a rate of approximately 21 steps/s. These kinetic results not only further support our previous conclusion that E. coli RecQ functions as a monomer but also suggest that some of the Superfamily 2 helicases may function through an "inchworm" mechanism.     

利用传递不平衡分析在多群体中鉴别猪脐疝易感基因

在本实验室前期利用白色杜洛克×二花脸F₂资源家系开展脐疝易感位点全基因组扫描定位的基础上,文章在7号染色体上的SWR1928和10号染色体上的SW830易感标记区域,结合脐疝发病机制在多群体中进行脐疝位置功能候选基因的筛选和易感位点的精细定位。在两个显著关联的微卫星位点区域搜寻到12个位置功能候选基因,采用比较测序法,选取12个候选基因内共计40个SNP位点在白色杜洛克×二花脸资源家系F₂/F₃脐疝群体中进行基因分型,利用Plink v1.07软件对基因型数据进行质量控制和传递不平衡(Transmission disequilibrium test,TDT)分析。结果表明,IL16(Interleukin 16)基因中的g.708C>T位点和CDC73(Cell division cycle 73)基因中的g.10664G>A位点与脐疝的关联性达到显著水平(P<0.05)。对这两个位点在西方商业猪种脐疝患病家系中进行基因分型和TDT验证分析,发现CDC73基因中的g.10664G>A位点仍与猪脐疝呈显著关联(P<0.05)。同时对CDC73基因中与资源家系脐疝呈弱相关的两个SNP位点g.10546A>G和g.10811A>G在西方商业猪种中进行TDT验证分析,发现这两个SNP位点与商业猪种脐疝发生的关联性达到极显著水平(P<0.01)。根据文章的分析结果,结合脐疝发生的生理机制及CDC73基因的生物学功能,推测CDC73基因可能为猪脐疝发生的易感基因。     

Effect of physiological factors on the flight ability of Calliptamus italicus L

Calliptamus italicus L. is a major migratory pest that often causes serious agricultural losses in the desert/semi‐desert steppe of Central Asia. The present study aims to understand the physiological factors that affect migration of C. italicus by examining the relationships between flight capacity, energy accumulation, ovarian development and Juvenile hormone (JH) titre. The results show that flight capacity decreases with age, being greatest among 2‐day‐old males and lowest among 13‐day‐old locusts. There is no significant correlation between energy accumulation and flight capacity, although JH titre is negatively correlated with flight capacity. Energy accumulation and flight capacity first increases then decreases in 1–13‐day‐old females. Glycogen accumulation is significantly correlated with flight speed, and triglyceride accumulation is significantly correlated with flight distance, duration and speed. Changes in JH titre in 1–13‐day‐old females show double titre peaks, which are negatively correlated with flight capacity. Seven‐day‐old C. italicus have the highest glycogen and triglyceride accumulation, greatest flight capacity, grade II ovarian development and lowest JH titre. By contrast, 13‐day‐old C. italicus have the lowest triglyceride accumulation, lowest flight capacity, grade IV ovarian development and lowest JH titre. Taken together, these findings demonstrate that there is a trade‐off between ovarian development and flight capacity of C. italicus.     

Development of insect-resistant transgenic indica rice with a synthetic cry1C* gene

Stemborers and leaffolders are two groups of lepidopteran pests that cause severe damage to rice in many areas of the world. In this study, a cry1C* gene encoding Bacillus thuringiensis (Bt) δ-endotoxin was synthesized by codon optimization as the first step towards gene stacking in our resistance management strategy of transgenic rice. Agrobacterium-mediated transformation of this gene into Minghui 63 (Oryza sativa L.), an elite indica CMS restorer line, produced 120 independently transformed plants, 19 of which had a single-copy transgene. Preliminary screening of T₁ families of these 19 transformants in the field identified five lines showing a high level of resistance to leaffolders (Cnaphalocrocis medinalis) and stemborers. Hybrids were produced by crossing these five lines with Zhenshan 97A, the male-sterile line for Shanyou 63, the most widely cultivated hybrid in China. These five lines and their hybrids were highly resistant to yellow stemborer (Tryporyza incertulas) as revealed by an insect bioassay. The content of Cry1C* protein varied considerably among the five lines as well as among the corresponding hybrids. T1c-19, a line showing the highest content of Cry1C* protein, and its hybrid were tested in the field for insect resistance and agronomic performance and found to be highly resistant to stemborers and leaffolders throughout the growth period, resulting in a significantly increased grain yield compared with the respective controls. These results indicate that T1c-19 can be used for production of insect-resistant hybrid rice and as a germplasm for gene stacking to produce rice plants with two toxins.     

Identification of Tyrosine-9 of MAVS as Critical Target for Inducible Phosphorylation That Determines Activation

Background

Innate immunity to viruses involves receptors such as RIG-I, which senses viral RNA and triggers an IFN-β signaling pathway involving the outer mitochondrial membrane protein MAVS. However, the functional status of MAVS phosphorylation remains elusive.

Methodology/Principal Findings

Here we demonstrate for the first time that MAVS undergoes extensive tyrosine phosphorylation upon viral infection, indicating that MAVS phosphorylation might play an important role in MAVS function. A tyrosine-scanning mutational analysis revealed that MAVS tyrosine-9 (Y9) is a phosphorylation site that is required for IFN-β signaling. Indeed, MAVS Y9F mutation severely impaired TRAF3/TRAF6 recruitment and displayed decreased tyrosine phosphorylation in response to VSV infection compared to wild type MAVS. Functionally, MAVS Y9 phosphorylation contributed to MAVS antiviral function without interfering with its apoptosis property.

Conclusions/Significance

These experiments identify a novel residue of MAVS that is crucially involved in the recruitment of TRAF3/TRAF6 and in downstream propagation of MAVS signaling.     

Morphology and stress-strain properties along the small intestine in the rat

The stress-strain relationship is determined by the inherent mechanical properties of the intestinal wall, the geometric configurations, the loading conditions and the zero-stress state of the segment. The purpose of this project was to provide morphometric and biomechanical data for rat duodenum, jejunum and ileum. The circumferential strains were referenced to the zero-stress state. Large morphometric variations were found along the small intestine with an increase in the outer circumferential length and luminal area and a decrease in wall thickness in distal direction. The serosal residual strain was tensile and decreased in distal direction (P < 0.05). The mucosal residual strain was compressive and the absolute value decreased in distal direction (P < 0.001). The stress-strain experiments showed that the duodenum was stiffest. All segments were stiffest in longitudinal direction (P < 0.05). In conclusion, axial variation in morphometric and biomechanical properties was found in the small intestine. The zero-stress state must be considered in future biomechanical studies in the gastrointestinal tract.     

Toxicological and biochemical characterizations of GSTs in Liposcelis bostrychophila Badonnel (Psocop., Liposcelididae)

Abstract: The toxicological and biochemical characteristics of glutathione S‐transferases (GSTs) in the resistant and susceptible strains of Liposcelis bostrychophila were investigated. The two resistant strains were the dichlorvos‐resistant strain (DDVP‐R) and PH₃‐resistant strain (PH₃‐R), and the resistance factors were 22.36 and 4.51, respectively. Compared with their susceptible counterparts, the activities per insect and specific activities of GSTs in DDVP‐R and PH₃‐R were significantly higher. The apparent Michaelis–Menten constant values (K_m) for 1‐chloro‐2,4‐dinitrobenzene (CDNB) were obviously lower in DDVP‐R and PH₃‐R (i.e. lower K_m values, 1.5625 mm for DDVP‐R and 0.6230 mm for PH₃‐R) when compared with their susceptible counterpart (K_m = 3.5520), indicating a higher affinity to the substrate CDNB in resistant strains. In contrast, the catalytic activity of GSTs towards CDNB in the susceptible strain was significantly higher than those in resistant strains. It was noticeable that when reduced glutathione (GSH) was used as substrate, GSTs from resistant strains both indicated a significantly declined affinity. For the catalytic activity of GSTs towards GSH, only the V_max value in DDVP‐R increased significantly compared with that from the susceptible strain, suggesting an overexpression of GST in this resistant strain. The inhibition kinetics of insecticides to GSTs in vitro revealed that dichlorvos and paraoxon possessed excellent inhibition effects on GSTs. The susceptible strain showed higher sensitivity (I₅₀ = 0.9004 mm ) to dichlorvos than DDVP‐R and PH₃‐R (higher I₅₀s, 8.0955 mm for DDVP‐R and 9.3346 mm for PH₃‐R). As for paraoxon, there was a similar situation. The resistant strains both suggested a higher I₅₀ (1.8735 mm for DDVP‐R, and 0.4291 mm for PH₃‐R) compared with the susceptible strain (0.2943 mm ). These suggested that an elevated detoxification ability of GSTs developed in the resistant strains.     

西双版纳望天树林种子雨9年动态

种子雨是森林生态系统过程的重要组成部分。虽然国内外已有部分关于种子雨的研究, 但多数集中在温带和亚热带地区, 热带地区种子雨的长期监测研究仍显不足。为全面了解热带森林种子雨输入的数量动态和物种组成的长期规律, 本文对我国西双版纳望天树(Parashorea chinensis)林群落水平上9年(2008年5月至2017年4月)的种子雨输入进行了研究。9年共收集到木本植物的种子226种8,993,224粒, 其中大型种子(I-1型) 77种9,779粒; 中型种子(I-2型) 61种24,237粒; 小型种子(I-3型) 72种83,399粒; 粒状微小种子(II-1型) 13种1,215,235粒; 粒状极小种子(II-2型) 1种7,244,667粒; 细丝状种子(II-3型) 2种415,907粒。种子雨输入量排名前10位的优势种贡献了70%以上的种子数量。各类型种子的种子雨输入量均具有年际波动, 呈“大小年”的交替变化, 间隔期为1-2年, 物种组成也呈现一定的年际差异。持续9年的监测中, 每类型种子至少观察到了1次大年结实事件。